VSEBINA – CONTENTS
Materiali in tehnologije – 40 let
Materials and technology – 40 years
F. Vodopivec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Prvi urednik revije – Jo`a Arh
F. Vodopivec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Laudation in honour of professor dr. Franc Vodopivec on the occasion of his 75th birthday
M. Jenko . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
75 let Franca Vodopivca
L. Kosec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Marin Gabrov{ek – 80 let
F. Vodopivec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
PREGLEDNI ZNANSTVENI ^LANKI – REVIEW ARTICLES
Zgodovina serijske publikacije Materiali in tehnologije / Materials and technology
Historical overview of the scientific journal Materiali in tehnologije / Materials and technology
N. Jamar, J. Jamar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Theoretical calculation of the lubrication-layer thickness during metal drawing
Teoreti~ni izra~un debeline plasti maziva pri vle~enju kovin
D. ]ur~ija, I. Mamuzi} . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
IZVIRNI ZNANSTVENI ^LANKI – ORIGINAL SCIENTIFIC ARTICLES
The notch effect on the fatigue strength of 51CrV4Mo spring steel
VPliv zareze na trajno nihajno trdnost vzmetnega jekla 51CrV4Mo
B. [u{tar{i~, B. Sen~i~, B. Arzen{ek, P. Jodin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
An integrity analysis of washing-machine holders
Analiza celovitosti nosilca kadi v pralnem stroju
N. Gubeljak, M. Mejac, J. Predan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
The effect of a material’s heterogeneity on the stress and strain distribution in the vicinity of a crack front
Vpliv heterogenosti materiala na porazdelitev napetosti in deformacije v bli`ini konice razpoke
D. Kozak, N. Gubeljak, J. Vojvodi~ Tuma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
The numerical solution of strain wave propagation in elastical helical spring
Numeri~na re{itev propagacije deformacijskega vala v elasti~ni spiralni vzmeti
S. Ayadi, E. Hadj-Taïeb, G. Pluvinage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
[tudij notranje oksidacije v naoglji~enih hitrostrjenih trakovih Cu
The study of the internal oxidation in internally carbonised Cu ribbons
R. Rudolf, L. Kosec, I. An`el, L. Gusel, M. Poharc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA – DOCTOR'S, MASTER'S AND DIPLOMA DEGREES . . . . . . . . . . . 59
ISSN 1580-2949
UDK 669+666+678+53 MTAEC9, 41(1)1–64(2007)
MATER.
TEHNOL.
LETNIK
VOLUME 41
[TEV.
NO. 1
STR.
P. 1–64
LJUBLJANA
SLOVENIJA
JAN.-FEB.
2007

MATERIALI IN TEHNOLOGIJE – 40 LET
MATERIALS AND TECHNOLOGY – 40 YEARS
^e ocenjujemo po zgledu znanstvenih in strokovnih
revij, ki se tiskajo v dr`avah, ki so tehnolo{ko in indu-
strijsko bolj razvite od Slovenije, {tiridesetletnica izha-
janja ni posebno visok jubilej. Je pa pomemben, ker se je
v tem obdobju v Sloveniji metalurgija, `e stoletja
uveljavljena industrijska proizvodnja, utrdila tudi kot
in`enirska stroka in postala in`enirska veda. Obdobje
konec 90. let prej{nega stoletja je bilo kriti~no za meta-
lur{ko industrijo, saj je precej{en del politike, ki je
sku{al premalo premi{ljeno uveljaviti nove gospodarske
in ekolo{ke poglede, zavra~al obnovo metalur{kih proiz-
vodnih naprav. Na sre~o te ideje niso dobile ve~inske
podpore, metalurgiji jekla in aluminija pa sta se z inve-
sticijami v nove proizvodne naprave pribli`ali standar-
dom ekolo{ke sprejemljivosti tehnologije, ki jih zago-
varja zbornik ''The State on the World'', ki ga vsako leto
tiska The Worldwatch Institute iz Washingtona, ZDA.
Od vseh industrijskih panog je v Sloveniji meta-
lurgija najbolje prenesla tranzicijsko obdobje. To
dokazuje dvoje: bila je bolje kot druge industrijske veje
tehnolo{ko usposobljena za prehod v nove tr`ne razmere
in, nasprotno od prerokovanja mnogih, poraba in
proizvodnja kovin in zlitin se v novem tiso~letju nista
zmanj{ali, temve~ sta celo zelo zrastli. Manj{i tehnolo{ki
zaostanek metalurgije za najbolj razvitimi okolji je bil
brez dvoma tudi rezultat ustvarjalnega sodelovanja
tehnologov in raziskovalcev v industrijskih podjetjih z
raziskovalci v akademskih ustanovah.
Prav okrepitev in raz{iritev ter seznanjanje javnosti z
dose`ki raziskovalno-razvojnega sodelovanja so bili
najmo~nej{a opora ideji o za~etku tiskanja nove revije,
namenjene objavam znanstvenih in strokovnih del,
namenjenim obravnavi prakti~nih in z njimi povezanih
teoretskih dose`kov pri raziskavah zgradbe, vedenju
kovin in zlitin pri predelavi v uporabno obliko in
lastnosti pri uporabi. Te`i{~e je bilo na jeklu, kjer je bilo
tedaj najve~ dobro organiziranega raziskovanja. Zato je
nova revija dobila naziv @elezarski zbornik. Izhajala je
~etrtletno in v njej so bila tiskana mnoga kakovostna
znanstvena in strokovna dela, dokaz ustvarjalnosti in
trdega dela {tevilnih posameznikov, ki so pogosto pri{li
do pomemebnih izvirnih dose`kov z inventivnim
metodolo{kim na~inom na podlagi izsledkov preizkusov
in analiz na rutinski laboratorijski in analitski opremi.
Kakovost raziskovalno-razvojnega dela, posebno s
stali{~a bolj{ega poznanja dogajanja med procesi v talini
in v trdnem, je zrastla zaradi dognanj, ki jih je
omogo~ala nova raziskovalna oprema v podjetjih in na
akademskih institucijah.
Materiali in tehnologije / Materials and technology 41 (2007) 1, 3–5 3
Compared to some journals in countries that are more
developed in terms of technology and industry than
Slovenia, 40 years of publication is not a particularly
significant anniversary. It is, however, very important, as
during this period of time metallurgy, an industrial
activity with centuries of tradition in Slovenia, matured
as an independent engineering profession and became an
engineering science. The period up until the end of the
1990s was a critical one for the metallurgical industry, as
there was strong political opposition to the refurbishment
of metallurgical production facilities based on ill-consi-
dered economic and ecological measures. However, the
attempt did not receive sufficient support and so the steel
and aluminium industries were able to invest sufficient
funds in new production facilities and approach the
acceptable ecological standards recommended in the
survey ''The State of the World'', published by The
Worldwatch Institute, Washington, USA.
Of all the branches of industry in Slovenia,
metallurgy was the must successful in getting through
the transition period. This suggests that it was better
technologically qualified to access new markets than
other branches of industry, and contrary to expectations,
production levels began to increase in the 21st century.
The reason why metallurgy did not lag behind as much
as other branches of industry in Slovenia was at least
partly due to the fruitful cooperation in research and
development between researchers from academic
institutions and those from industry.
It was the cooperation between scientists working on
the problems of improving technologies and developing
new alloys that was at the heart of the decision to publish
a new journal, some 40 years ago. In this way, the
achievements of scientific investigations on practical and
related theoretical topics, such as the melting of alloys,
their structure and their behaviour when processing
finished products and their properties during use, would
be made known to the to public. The accent was on
steels, since this was the field with the most organised
research and development, and so the name of the
journal was chosen as @elezarski Zbornik. Professional
and scientific articles presenting new findings, often
based on the inventive use of routine testing methods,
were published quarterly. The quality of the articles
increased significantly, especially for processes and
properties related to the microstructure and homogeneity
of alloys, when new scientific facilities were set up in
academic institutions and in industrial laboratories.
Focused scientific research helped to close the gap on
Del zaslug za la`jo prilagoditev na nove tr`ne
razmere po osamosvojitvi Slovenije ima gotovo tudi
ve~ja u~inkovitost raziskovanja in razvoja. Zato sta
tehnologija in proizvodi tudi tam, kjer oboje ni bilo
odvisno od velikih investicij, zaostajala najve~ nekaj let
za najbolj razvitimi okolji. V delih, ki so bila objavljena
v reviji @elezarski zbornik lahko dobro spremljamo rast
znanja o strjevanju zlitin, razvoj tehnologije desoksi-
dacije in raz`veplanja jeklene taline, izoblikovanje
mikrostrukture med vro~im in hladnim preoblikovanjem,
izbolj{anje racionalnosti porabe energije, razvoj
proizvodov z lastnostmi za specifi~ne pogoje uporabe,
razvoj raziskovalne metodike, tudi rezultate postopnega
zmanj{anja obremenitve okolja in {e marsikaj, kar se
lahko razbere iz naslovov v bibliografski {tevilki, ki je
bila tiskana ob 40-letnici izhajanja. Med avtorji objav-
ljenih del najdemo najpomembnej{e raziskovalce iz
doma~ega okolja, laureate dr`avnih nagrad in vidna
imena iz tujine. Posebna odlika revije je veliko {tevilo
avtorjev iz industrijskih okolij in prav takim gre zasluga,
da se je revija izognila nevarnosti, da bi se metalurgija
kot veda v Sloveniji preve~ oddaljila od metalurgije kot
industrijske tehnologije.
Jugoslavija je bila v obdobju ekonomske krize `e po
letu 1986, tej krizi se je v Sloveniji pridru`ila po letu
1989 {e tranzicijska kriza, katere vzrok je bila izguba
dotedanjih trgov za industrijske proizvode. Politika ni
bila posebno u~inkovita pri pomo~i industriji pri prema-
govanju krize, zato se je, nasprotno kot v razvitih oko-
ljih, zmanj{al obseg raziskovanja in razvoja v industriji
in posledi~no tudi obseg raziskovanja v akadenskih
institucijah. Tudi revija je pri{la v krizo, ki se je {e
pove~ala zaradi fina~nih te`av izdajatelja.
S spremembo naslova revije v Kovine Zlitine Tehno-
logije je bil leta 1992 napravljen prvi korak k raz{iritvi
vsebinske podlage revije na raziskovanje in razvoj
najpomembnej{ih in`enirskih materialov: kovin in zlitin,
keramike, gradbenih materialov in polimerov ter z njimi
povezanih tehnologij, tudi vakuuma in tehnologij
oplemenitenja povr{ine, vlogo izdajatelja pa je prevzel
In{titut za kovinske materiale in tehnologije. Uredni{ki
odbor je bil dopolnjen in vanj so bili vklju~eni razisko-
valci iz drugih podro~ij in procesov. Postopoma so bili
pridobljeni tudi soizdajatelji, ki so poskrbeli za mate-
rialno podporo izhajanja. Ukrepi so se pokazali kot zelo
u~inkoviti, saj je skokoma mo~no zrastlo {tevilo avtorjev
in {tevilo tiskanih del ter tematika, ki je bila v njih
predstavljena.
Kot samoumevno se je zato pokazalo ponovno
preimenovanje revije v dana{ji naziv Materiali in tehno-
logije (Materials and Technology) in ponovna dopolnitev
uredni{kega odbora. S predlogom, da se vsebina revije
obogati s predstavitvami novih doktorjev znanosti s
podro~ja raziskovanja materialov in najmodernej{ih
tehnolo{kih dose`kov v podjetjih, {e ni dosegla pri~ako-
vanega uspeha.
Po letu 2000 se je uradna politika pri oceni kakovosti
objavljenih raziskovalnih dose`kov popolnoma naslonila
na objave del po uvrstitvi revije v indeksu citiranosti SCI
4 Materiali in tehnologije / Materials and technology 41 (2007) 1, 3–5
the more advanced countries to just a few years,
especially for cases when the progress was not related to
large industrial investments. For this reason, in @ele-
zarski Zbornik it is possible to follow the increased use
of knowledge related to the solidification of alloys, the
progress in the de-oxidation and de-sulphurisation
processing of steels, the evolution of microstructure and
properties during hot and cold working, the decrease of
energy consumption, the development of analytical and
investigation methodology, the improvements in
ecology, and other topics, as indicated by the titles of the
articles in the issue of the journal giving the bibliography
for 40 years of publication. As for the authors, many are
distinguished scientists from different fields of research
and development, from both Slovenia and abroad. The
fact that a number of these authors came from industrial
companies is considered a positive attribute and
indicates that metallurgy as a science did not separate
too much from metallurgy as an industrial technology in
Slovenia.
The economic crisis in Yugoslavia was made worse
in Slovenia after 1989 because of the loss of traditional
markets for industrial products. The politics did not help
industry in overcoming the crisis, the amount of research
and development in industry was reduced, as was the
amount of research in academic institutions. The journal
suffered too, principally because of the editor's financial
difficulties.
With the change of the journal's name to Metals
Alloys Technologies in 1992 the first steps towards
broadening the contents base were made with the
inclusion of topics related to the research and develop-
ment of the most important engineering materials: metals
and alloys, ceramics, polymers and building materials.
The journal also included vacuum and surface techno-
logies, and a new publisher was found. The number of
members of the editorial board was increased with the
association of researchers working in new fields.
Gradually, new publishers were also associated and the
material base of the publishing was enlarged. The effect
of the changes was a sharp increase in the number of
authors, the number of manuscripts submitted for publi-
cation and the number of topics presented. Another
change of name to Materials and Technology and a new
editorial board were, for this reason, a natural step
forward.
After 2000 the official methodology of evaluating the
quality of the articles changed significantly with the
classification of the journal according to the Science
Citation Index (SCI) of the Institute of Scientific
Information (ISI), which is based mostly on the scientific
merit of the articles. Still today, however, the signifi-
cance of the articles' findings for the growth of
knowledge for technology and the development of new
products relevant to Slovenian industry has not been
assessed. This probably explains the decline in the
number of submitted manuscripts, which still, however,
remained above the number of articles printed in other
journals edited in Slovenia. Also, the fact that the journal
(Science Citation Index), katerega osnova je pomen
objavljenih dose`kov za znanost. Premalo je cenjena
vsebinska ocena objave, v kateri bi bila upo{tevana tudi
vrednost dose`ka za rast znanja, ki ga potrebuje
slovensko okolje za tehnolo{ko in produktno rast. To je
bil verjetno glavni razlog, da se je {tevilo objavljenih del
postopoma zmanj{alo, vendar se je ohranilo nad {tevilom
izvirnih del, ki so objavljena v drugih revijah, ki se
tiskajo v Sloveniji. Razvrednotena je bila tudi citiranost
revije v 15 mednarodnih sekundarnih bazah podatkov, ki
po pomenu za razvoj tehnologije in novih materialov ter
njihove uporabe v industriji in gradbeni{tvu gotovo
presegajo indeks SCI. Za tega pa celo izdajatelj ISI
(Institute of Scientific Informations) iz Filadelfije v ZDA
na svoji internetni strani pi{e, da je ve~ citatov na o`jih
raziskovalnih podro~jih. In`enirskih materialov, ki so
osnova sodobne civilizacije, prav gotovo ne moremo
uvrstiti med taka, ozka raziskovalno-razvojna podro~ja.
Ni dvoma tudi, da je manj{a mo`nost, da bi bila neka
znanstvena revija vklju~ena v indeks SCI, ~e ne izhaja
izklju~no ali prete`no v angle{~ini, s ~imer zanemari
enega od temeljnih poslanstev, tj. razvoja znanstvenega
in tehni{kega izrazoslovja v nacionalnem jeziku. Vendar
odlo~itev o tej dilemi ni stvar uredni{ke politike, temve~
raziskovalne politike dr`ave kot celote, ki finan~no
podpira izdajanje {tevilnih revij. Ne glede na te pomi-
sleke, se je spremenila uredni{ka politika in v zadnjih
letih je dele` tiskanih znanstvenih del prevladal nad
dele`em strokovnih, npr. v letu 2006 je bilo objavljeno
86 % znanstvenih del.
Revija Materiali in tehnologije je po obsegu in
vsebini na nivoju ali celo presega periodi~ne publikacije,
ki se tiskajo v Sloveniji. Zato je bil v letu 2005 na seji
uredni{kega odbora sprejet sklep, da se odpravijo
formalne pomanjkljivosti, in da {tevilke izhajajo redno
dvomese~no. To je bilo v letniku 2006 uresni~eno in ni
zadr`kov, da ne bi bilo tako tudi naprej. Uredni{tvo
lahko izbolj{a svoje delo, ne more pa izbolj{ati vsebine
objavljenih del in citiranja revije, oboje je odvisno od
avtorjev rokopisov in od ~lanov uredni{kega odbora.
Zato vabim vse raziskovalce, ki se ukvarjajo z razli~nimi
problemi materialov in problemi povezanimi z materiali,
da objavijo svoja dela tudi v reviji Materiali in
tehnologije, in da v njej objavljena dela citirajo v svojih
delih, ki so tiskane v drugih dr`avah. Predvsem od
njihovega odziva bo odvisna nadaljnja rast kakovosti in
ugleda revije ter v njej tiskanih del.
Ljubljana, januar 2007
Glavni urednik
Franc Vodopivec
Materiali in tehnologije / Materials and technology 41 (2007) 1, 3–5 5
is cited in 15 international databases which are
significant for the development of technology and new
products became of secondary importance. It is useful to
remember that in the instructions of the ISI, the publisher
of the SCI, it is explained that the number of citations is,
on average, larger for specialised research fields. It
would, of course, be absurd to classify the field of
engineering materials, the basis of modern technological
civilisation, as specialised. It is probably also the case
that there is a smaller possibility for inclusion in the SCI
for journals that are not printed mostly, or exclusively, in
English. The use of English, however, hinders the
realisation of two tasks of the journal: the understanding
of the articles by local readers and the development of
domestic technical terminology. The answer to both
these questions is for the national agency that supports
the publication of a number of journals. In spite of these
considerations, the publishing policy was changed and
the number of scientific articles increased gradually up
to a share of 86 % in 2006.
In terms of quality and the number of articles the
journal Materials and Technology is at the same level or
even above that for other periodicals printed in Slovenia.
In 2005 the editorial board decided that, gradually, other
formal obstacles that are important for inclusion in the
SCI should be overcome. In 2006 all the ISI criteria for
inclusion in the SCI were fulfilled. The fulfilment of
other criteria, for example, the citation of articles printed
in Materials and Technology, is solely the decision of
authors also publishing in international journals.
Improving the reputation of the journal depends on the
number and the quality of the manuscripts submitted to
the journal. For this reason, potential authors are kindly
invited to submit manuscripts for publication. The
editors and referees will be happy to assist in improving
the manuscripts in terms of presentation and language.
The editor and the editorial board very much
appreciate the material support of the publisher and of
the associate publishers, the Ministry of Higher
Education, Science and Technology of the Republic of
Slovenia, as well as all the authors and referees, who are
primarily responsible for the quality of printed articles.
Thanks also go to the refferees for Slovenian and
English, and to the journal's technical staff.
Ljubljana, January 2007
Editor-in-chief
Franc Vodopivec
PRVI UREDNIK REVIJE – JO@A ARH
Ne bi bilo prav, ~e se ob 40. obletnici ne bi spomnili
prvega urednika revije @elezarski Zbornik, kajti brez
za~etka tudi 40-letnice ne bi praznovali. Brez posebnih
izku{enj in z veliko voljo se je J. Arh, ustvarjalen
raziskovalec jeklarske teorije in tehnologije, pogumno
spoprijel z novim in zahtevnim projektom na novem
podro~ju dejavnosti, prevzemom obveznosti, da bo revija
za`ivela in obstala kot resna, kakovostna periodi~na
publikacija. V majhnem okolju, tako je slovensko okolje
v fizi~nem in v duhovnem obsegu, se vse preve~ pogosto
dogodi, da odmevni polo`itvi temeljnega kamna ne sledi
tako `ivljenje projekta, kot so njegovi o~etje pri~akovali.
^e ho~e biti resna in dobra, mora periodi~na publikacija
vsako leto javnosti predstaviti neko primerno {tevilo
dobrih strokovnih in znanstvenih del. ^e je fond avtorjev
dovolj velik, to ni problem, ~e pa je fond avtorjev
majhen, brez dvoma je tak tudi bil, ko je J. Arh prevzel
projekt, postane naloga glavnega urednika mnogo te`ja
in njegova prva naloga ni, da izmed predlo`enih del
izbere tista, ki ustrezajo po vsebini in po kakovosti in
poskrbi, da se predstavijo javnosti v primerni obliki,
temve~ da animira potencialne avtorje, sicer za objavo ni
predlo`eno dovolj del, da bi bila selekcija primernih
sploh mogo~a. Z vztrajnostjo in iznajdljivostjo, ki ju je
pokazal `e kot odgovoren za realizacijo razvojnih
projektov, katerih cilj je bil napredek v tehnologiji in
osvajanje novih proizvodov v mati~nem podjetju, je bil
J. Arh kos vsem problemom. Revija je postopoma za`i-
vela, z njeno rastjo je rasel fond avtorjev in vsako leto je
bilo tiskano ve~ del, ki bi se jih ne sramovale revije, ki
`e desetletja izhajajo v mnogo bolj razvitih okoljih. S
svojim delom je J. Arh ne samo polo`il kamen temu, kar
danes je, ampak z iznajdljivostjo in vztrajnostjo na{el
re{itve tudi tedaj, ko bi mnogi obupali in odstopili.
Po diplomi na Univerzi v Ljubljani se je J. Arh
zaposlil v @elezarni Jesenice in ji ostal zvest do
upokojitve. Vse znanje, ustvarjalnost in delo je posvetil
tehnologiji izdelave jekla, {e posebej kakovosti
proizvodnje in osvajanju novih proizvodov. V vsem, kar
je delal, je zapustil trajno sled, tako pomembno, da so
ga proizvajalci jeklarske opreme iz tujine ve~krat
anga`irali kot svetovalca pri zagonu novih proizvodnih
agregatov v evropskih in v neevropskih dr`avah, {e
posebej, ~e so se pri tem pojavili problemi, ali je bilo
potrebno postopek dopolniti tako, da je bila dose`ena
ve~ja kakovost oziroma izdelana nova vrsta jekla.
O svojem raziskovalnem in izvedenskem delu je
poro~al v reviji, ki jo je urejeval, na doma~ih in tujih
strokovnih in znanstvenih konferencah, o njem in
njegovem delu pa so poro~ali tudi v tovarni{kem glasilu
in v dnevnikih. Kidri~eva nagrada za delo pri razvoju
postopka za izdelavo jekel, legiranih s svincem za
obdelavo na avtomatih, Pantzova nagrada za dose`ke v
mati~nem podjetju pri razvoju jeklarske tehnologije in
diploma zaslu`nega ~lana Zveze in`enirjev in tehnikov
Slovenije so dokaz, da so njegovo delo cenili mnogi in
mu dali tudi pomembna javna priznanja.
Vsi, ki nadaljujemo delo J. Arha pri reviji Materiali
in tehnologije, ki se zaradi bolj razvitega okolja in
ve~jega fonda avtorjev sre~ujemo z druga~nimi problemi
rednega izhajanja revije, znamo {e posebej ceniti
pionirsko delo J. Arha.
Glavni urednik
Franc Vodopivec
6 Materiali in tehnologije / Materials and technology 41 (2007) 1, 6
LAUDATION IN HONOUR OF PROFESSOR DR. FRANC
VODOPIVEC ON THE OCCASION OF HIS 75th BIRTHDAY
Professor Dr. Franc Vodopivec, scientific councillor
and former director of Institute of Metals and Tech-
nology and former member of the State Council of
Republic Slovenia, is celebrating his 75th birthday. This
birthday is the occasion to look at the background and
the development of this well known scientist and at the
influence which his research work has in the field of
elaboration, transformation and use of metals and alloys
in Slovenia and abroad.
Professor Franc Vodopivec was born in Rakitnik, on
8th October 1931. After finishing with distinction the
secondary school education, he studied Metallurgy at the
University of Ljubljana. In 1956 he joined Metallurgical
Institute, present Institute of Metals and Technology in
Ljubljana directed by founder Professor Ciril Rekar. In
1959 he received through the International Agency of
Atomic Energy in Vienna a scholarship from the French
Government. Working in the Institute de Recherché de la
Siderurgie, in St.Germain en Laye, France from 1960 to
1962 he prepared his doctor thesis and graduated in 1962
at the University of Paris, Paris, France with the thesis
Study of the behaviour of arsenic and phosphorous by
selective oxidation of iron alloys with low contents of
both elements.
He returned in 1962 to the Metallurgical Institute and
founded the Laboratory for Metalography, 1972 he
became head of Technology Department to 1978,
assistant director to 1990 and director from 1990 to April
1996 when he retired. In 1992, Professor Vodopivec was
elected for the first time in the Council State of Republic
Slovenia by the community of researchers and engineers
and in 1997 for the second time.
He is editor in chief of Slovenian scientific journal
Metals Alloys Technologies since 1996.
Professor Vodopivec is full of development spirit and
creative ideas. He has been doing research work on the
behaviour of metals in oxidative atmosphere, micro-
structure characterization of metals by optical and
electron microscopy, electron probe analysis, mechanical
testing; behaviour of material in use at medium and high
temperature, hot and cold working of metals, recovery,
recrystallization and grain growth. His present research
interest include: ductile permanent magnet alloys, non
oriented electrical steel sheets, grain growth induced by
selective surface segregation, topology of microstructure
and behaviour of metals in use.
Professor Vodopivec has published over 250 papers
in international journals and conferences and 320 papers
in Slovenian journals and conferences on topics of
science, technology and use of metals and alloys.
Professor Vodopivec has been supervisor to several
Ph.D. and Master Degree students at the Universities of
Ljubljana, Maribor, Belgrade and Zagreb. He is also
very active in the international academic field. He was a
chairman of international scientific conferences and
project evaluator in EU actions of COST.
He is still president of Slovenian Society of
Materials, member of executive council of Slovenian
Vacuum Society, member of Slovenian Electron and
Microelectronics Society, Slovenian Society of Che-
mistry, Historical Society of Ljubljana, chairman of the
R&D group of the Slovenian Association of Engineers,
chairman of annual Conferences on Materials and
Technologies from 1990 to 1996 and was member of
Vacuum Metallurgy scientific division of International
Union for Vacuum Science, Technique and Applications
– IUVSTA from 1992–1995. He is one of the founders
of Slovenian Academy of Engineering Sciences. He
wrote in Slovenian newspapers several tens of articles of
industrial and research policy. In 1978 he received the
Boris Kidri~ Foundation Award and in 1984 the Boris
Kidri~ Award for science.
His many projects were supported by 21 industrial
societies and associations in Slovenia and the former
Yugoslavia from Metallurgy over mechanical energy to
power stations as well as the Slovenian and the Yugoslav
governments. He was involved also in the projects of
international cooperations EU RD actions and USA-
Slovenia projects.
He prepared forensic analysis of several industrial
failures which qualified Slovenian societies to win
arbitration for retributions of damages from foreign
companies suppliers of industrial equipment.
In 2004 he received state award – Zois award for his
life work from the Republic of Slovenia.
His colleagues hope very much that he will instead of
his retirement, take part in discussions, lectures and
publications. Most of all we would like to wish him and
his family many years to come in good health.
Monika Jenko
Materiali in tehnologije / Materials and technology 41 (2007) 1, 7 7
75 LET FRANCA VODOPIVCA
Slovenska strokovna literatura za podro~je meta-
lurgije in in`enirskih materialov je nekaj desetletij nazaj
tesno povezana z imenom prof. dr. Franca Vodopivca. Je
avtor {tevilnih originalnih ~lankov s podro~ja fizikalne
metalurgije, in`enirskih materialov, razvoja, karakteri-
zacije in uporabe materialov ter raziskav po{kodb strojev
in naprav na razli~nih podro~jih tehnike, posebej v
energetiki in procesni industriji. Svoje delo je postavil na
ogled in oceno mednarodni strokovni javnosti, z enako
zavzetostjo in veseljem je objavljal tudi v doma~ih
strokovnih revijah, kar je imel za svojo nacionalno
dol`nost in obveznost raziskovalca.
Njegov namen in odlo~nost obve{~ati strokovno
javnost o aktualnih problemih stroke in gospodarstva sta
`iva `e od za~etkov njegovega raziskovalnega dela na
Metalur{kem in{titutu, posebej pa od njegove vrnitve z
in{tituta IRSID v Franciji. Od takrat je v njegovem
najbolj plodovitem raziskovalnem obdobju iz notranje
potrebe objavil {tevilne znanstvene ~lanke. Svoje
sodelavce je opozarjal na pomen publiciranja razisko-
valnih dose`kov in napovedoval ~as, ko je to postalo
eksisten~na nuja raziskovalne srenje. Prof. dr. Franc
Vodopivec ni bil med privilegiranimi raziskovalci tudi
takrat ne, ko so se pre{tevali v desetinah ali stotinah.
Najve~ raziskav je naredil za slovensko industrijo jekla.
Trdil je in tudi ves ~as dokazoval, da je v vsakem
na~rtovanem in dobro vodenem raziskovalnem delu
dovolj vsebine za publiciranje v priznanih mednarodnih
revijah. Tu se velja spomniti zanimive in raz{irjene
problematike jekla za krogli~ne le`aje, evolucije mikro-
strukture in lastnosti pri vro~i predelavi razli~nih jekel,
raziskovanja mehko- in trdomagnetnih materialov in
razvoja raziskovalne metodologije. Z relativno malo
raziskovalne opreme je uspe{no tekmoval, posebej na
podro~ju forenzi~nih raziskav, z laboratoriji, ki so si jih
`e takrat lahko privo{~ile velike industrijske korporacije.
Prof. dr. Franc Vodopivec je {e vedno aktiven,
predvsem kot vir idej in programiranega na~rtovanja
raziskovalnega dela, vsestranski mentor in svetovalec
raziskovalcem vseh stopenj. Brez hrupa je `e dobro
desetletje urednik revije Materiali in tehnologije, katere
predhodnika sta bila @elezarski zbornik in Kovine
Zlitine Tehnologije.
[iroka razgledanost in obilica znanja mu omogo~ata
najti hiter in u~inkovit stik z avtorji zelo razli~nih vsebin.
Zato jim lahko pomaga in svetuje pri predstavitvi
njihovega dela strokovni javnosti in jih spodbuja pri
njihovem delu in napredku. @elimo mu, da bi {e naprej
tako uspe{no in plodovito vodil to revijo.
Ladislav Kosec
8 Materiali in tehnologije / Materials and technology 41 (2007) 1, 8
MARIN GABROV[EK – OB JUBILEJU
Osebnosti, ki pustijo trajen pe~at v dru`bi kot celoti
ali v enem od njenih segmentov, se pojavijo, ko so
razmere kriti~ne in zrele za velike spremembe. Marin
Gabrov{ek spada med take osebnosti. Bil je med prvimi,
ki so spoznali, da metalurgija v Sloveniji ne bo pre-
`ivela, ~e se ne bo hitro spremenila iz prete`no mojstrske
dejavnosti v tehni~no stroko in znanstveno vedo.
Zna~ilnost mojstrstva je, da so dela na osnovi receptov,
ki so plod dolgoletne prakse, stroka in veda pa postane
tedaj, ko se za~no v razumevanje in obvladovanje
procesa proizvodnje kovin in zlitin vklju~evati tudi
termodinami~ne in kineti~ne zakonitosti reakcij, ki se
dogajajo v staljeni in v trdni kovini in zaradi katerih
gradivo dobi neke, vnaprej predvidene lastnosti. K tej
spremembi je prispeval veliko, ker je z eno nogo stal
trdno v industriji kot vodja raziskovalno-razvojnega
oddelka v velikem industrijskem podjetju, z drugo pa
trdno v akademski sferi: u~il je na univerzi ter aktivno
sodeloval in materialno podpiral raziskovalne in
razvojne projekte na univerzah in in{titutih. Kjerkoli je
delal, je pustil pe~at ~loveka, ki spo{tuje vse, ki pri delu
dose`ejo nekaj koristnega, in nikdar ni {tedil besed, ko je
bilo komu treba povedati, da se da nekaj narediti tudi
bolj{e, kot je bilo narejeno.
V rekordnem ~asu je diplomiral za in`enirja
metalurgije na Univerzi v Ljubljani leta 1952 in se
zaposlil v tedanji @elezarni Jesenice. Hitro se je z delom
in prodornostjo uveljavil; po njegovi zaslugi je v `ele-
zarni postopoma nastal raziskovalni oddelek, v katerem
so razvili {tevilne nove proizvode in vpeljali nove
tehnolo{ke poti. Danes ni prav mnogo tistega v proiz-
vodnem programu dedi~a @elezarne Jesenice, podjetja
Acroni, d.o.o., kar ni bilo `e razvito v ~asu, ko je Marin
Gabrov{ek v upravi podjetja odgovarjal za razvoj in
neposredno vodil raziskovalni oddelek. Veliko {tevilo let
je vodil tudi Odbor za raziskave v okviru Zdru`enega
podjetja Slovenske `elezarne in tedaj se je svoj vpliv
raz{iril tudi na podro~je ne`elezne metalurgije in
livarstva. Enaki principi so ga vodili, ko je delal kot ~lan
razli~nih delovnih teles v Jugoslaviji in bil zato povsod
spo{tovan in upo{tevan kot ~lovek z znanjem, na
katerega besedo se je bilo mogo~e zanesti.
Po kratkem sta`u na Institutu de Recherches de la
Sidérurgie v Franciji je na Univerzi v Ljubljani dokto-
riral. V disertaciji je posredno dokazal nekaj, kar je bilo
mogo~e razlo`iti {ele ve~ kot desetletje kasneje, ko so
bile razvite nove metode za natan~ne analize kemi~ne
sestave povr{ine kristalnih zrn v jeklih. M. Gabrov{ek je
avtor in soavtor {tevilnih strokovnih del internega
zna~aja ter avtor in soavtor strokovnih in znanstvenih
del, ki so bila objavljena v tedanji Jugoslaviji in v
{tevilnih tujih dr`avah. Zna~ilno zanj je bilo, da ga ni
bilo lahko prepri~ati, da se vklju~i in celo podpre neki
razvojni ali raziskovalni projekt, ko pa se je odlo~il, je
postal gonilna sila njegove realizacije. Za svoje delo je
dobil velika priznanja, med njimi Pantzovo nagrado
mati~nega podjetja in Krajgherjevo nagrado GZ
Slovenije, oboje za uspehe pri razvoju proizvodov in
tehnologije.
Marin Gabrov{ek spada med tiste posameznike,
katerih slika bi morala viseti na ~astnem mestu v
podjetju, kjer je opravil toliko dela, ki je bilo tako dobro,
da je podjetje pre`ivelo tranzicijsko krizo in je danes
poslovno uspe{no. Zato je bil in je {e lahko zgled
mlaj{im generacijam, kaj se lahko dose`e, ~e je trdna
volja in se smotrno uporabi ustvarjalnost ljudi v podjetju
in zunaj njega, ki imajo ideje in so pripravljeni delati.
Da bi uveljavil podjetje in metalurgijo, se je vklju~eval v
razli~ne gremije, tudi take, ki so odlo~ali o tem, katere
projekte je smiselno podpreti iz javnih sredstev in se ni
obotavljal pri tem uporabiti argument, da je za projektom
stvarni interes nekega delujo~ega industrijskega podjetja.
Dosledno je zagovarjal prepri~anje, da je v vseh seg-
mentih dejavnosti potrebno ve~ znanja, posebno pa je
potrebno ve~ tistega znanja, ki ga je mogo~e uporabiti v
slovenskem industrijskem okolju. Danes, ko so razmere
take, da po pravilniku Javne agencije za raziskovalno
dejavnost RS dobi raziskovalec za objavljeno delo v
prvovrstni tuji reviji oceno od 80 do 100 to~k, za
podeljen evropski patent oceno 10 to~k in za uresni~eno
inovacijo oceno 2 to~ki, {e posebej potrebujemo take
ljudi, kot je bil M. Gabrov{ek. Mogo~e bi politika, ki
deli javni denar za raziskave in razvoj, upo{tevala tako
osebnost, ~e bi dovolj glasno povedali, da je treba denar
najpreje zaslu`iti in ga {ele nato deliti in tako razmi{ljati
tudi pri odlo~itvah o javni podpori raziskovalnim projek-
tom. Marin Gabrov{ek je intuitivno vedel, da razisko-
valci ne prispevajo k rasti blaginje ljudi, ~e ne ustvarjajo
tudi ali predvsem znanja, ki ga nek prostor potrebuje za
rast, kajti prepoznavnost dr`ave in naroda {irijo
materialni in nematerialni proizvodi bolj kot znanost, ki
ne ~uti potrebe, da bi morala ustvarjati tudi za ljudi.
Z Marinom Gabrov{kom sem imel mnogo slu`benih
stikov in postopoma se je med nama razvila posebna
oblika prijateljstva, ki je imela podlago v zelo podobnem
pogledu na dogajanja v prostoru in dru`bi. Pri njem sta
mi bila posebno v{e~ neposrednost in ostrina razgovora o
nekem strokovnem ali znanstvenem problemu, za
Materiali in tehnologije / Materials and technology 41 (2007) 1, 9–10 9
katerega sva oba iskala odgovor. Imponirala mi je
samozavest, s katero se je pogovarjal s predstavniki strok
in ved, ki so bile bolj presti`ne v javnosti, v~asih samo
zato, ker jim je nasedel vrh politike. V razgovorih in
razpravah je znal postavljati vpra{anja, na katera z
lepore~jem ni bilo mogo~e odgovoriti. Sam ni lepore~ja
uporabljal nikdar, nasprotno, bil je tako kratek in
neposreden, da bi bil lahko kdo, ki ga ni poznal, osebno
prizadet. ^e bo kdo kdaj pisal o zgodovini raziskovanja
v Sloveniji, ne bo mogel mimo pregleda dose`kov
raziskovalnega dela v preteklem letu ali dveh z oceno
industrijske vrednosti dose`enega, ki ga je pripravil za
vsakoletno konferenco metalurgov v Portoro`u. To je
zagotavljalo, da so se sredstva javnih skladov za razisko-
vanje in razvoj uporabila smotrno, kolikor so razmere
omogo~ale, za rast znanja, ki se je uporabilo v prostoru,
kjer je bilo ustvarjeno, bolj ambicioznim posameznikom
pa omogo~alo, da se njihovo ime pojavlja tudi v
uglednih tujih znanstvenih revijah. Bil je med pobudniki
usstanovitve revije @elezarski zbornik, s katero se je
metalurgija uveljavila kot enakovredna stroka in veda v
slovenskem in jugoslovanskem prostoru. [e danes kot
~lan izdajateljskega sveta revije vnukinje Materiali in
tehnologije bedi nad tem, da kljub zelo spremenjenim
razmeram revija ne zanemari preve~ svojega temeljnega
poslanstva, ki je {irjenje in poglabljanje znanja o
kovinah in zlitinah in o njihovi smotrni uporabi.
Poznam mnogo ljudi, ki so imeli delovne ali slu`bene
stike s slavljencem, vendar nikogar, ki bi nanj ohranil
slab spomin, ~etudi razgovori z njim o slu`benih
zadevah pogosto niso potekli v najbolj prijaznem tonu.
Kot ni {tedil sebe, ni {tedil tudi drugih, ~e niso naredili
vsega, kar so na~rtovali.
Marin, v imenu {tevilnih iz moje generacije in
mlaj{ih Ti zagotavljam, da si z osebnim zgledom,
dose`ki dela in odgovornostjo zanj v slovenski metalur-
giji v Sloveniji in {e posebej v podjetju, v katerega
razvoj si vlo`il `ivljenjsko delo, zapustil trajne sledove.
V imenu vseh, ki smo te poznali osebno, in mlaj{ih, ki so
o Tebi in Tvojem delu samo sli{ali, Ti `elim, da bi ostal
pri dobrem zdravju in nas {e kdaj s trezno besedo
opomnil, da se kaj da narediti tudi bolje, kot smo
naredili, in da ni resni~nega napredka brez znanja in
trdega ustvarjalnega dela.
V imenu vseh, ki smo se trudili in se {e trudimo, da
bi slovenski metalurgiji kot stroki in vedi ohranili ugled,
pri nastanku katerega je Tvoje delo imelo tako pomebno
vlogo.
Franc Vodopivec
10 Materiali in tehnologije / Materials and technology 41 (2007) 1, 9–10


N. JAMAR, J. JAMAR: ZGODOVINA SERIJSKE PUBLIKACIJE MATERIALI IN TEHNOLOGIJE
ZGODOVINA ZNANSTVENE SERIJSKE PUBLIKACIJE
MATERIALI IN TEHNOLOGIJE / MATERIALS AND TECHNOLOGY
HISTORICAL OVERVIEW OF THE SCIENTIFIC JOURNAL
MATERIALI IN TEHNOLOGIJE / MATERIALS AND TECHNOLOGY
Nina Jamar1, Jana Jamar2
1Lipce 10, 4273 Blejska Dobrava, Slovenija
2Uredni{tvo serijske publikacije Materiali in tehnologije, In{titut za kovinske materiale in tehnologije, Lepi pot 11, 1000 Ljubljana, Slovenija
nina.jamar@telemach.net
Podan je zgodovinski pregled 40-letnega izhajanja serijske publikacije Materiali in tehnologije (pred tem @elezarski zbornik in
Kovine zlitine tehnologiej) in prikazani statisti~ni podatki za obdobje od leta 2000 do leta 2006. Opisan je tudi potek izhajanja
omenjene serijske publikacije v elektronski obliki in vpliv objave polnih besedil ~lankov v elektronski obliki na odmevnost in
citiranost serijske publikacije v svetu. Prikazan je tudi diagram poteka izdajateljske dejavnosti po ISO 9000. Zaklju~ek pa je
namenjen pogledu na prihodnost serijske publikacije Materiali in tehnologije.
Klju~ne besede: znanstvena serijska publikacija, @elezarski zbornik, Kovine zlitine tehnologije, Materiali in tehnologije,
zgodovinski pregled, statisti~ni podatki, elektronsko zalo`ni{tvo, ISO 9000
The article describes the history of scientific publication Materiali in tehnologije / Materials and Technology (before @elezarski
zbornik / Iron and Steel Journal and Kovine zlitine tehnologije / Metals Alloys Technologies). There are some statistical data for
the years 2000-2006. The article also deals with electronic form of the mentioned serial publication and the influence of online
publishing on the recognition and citation of Materiali in tehnogije / Materials and Technology over the world. It is also shown
how scientific serial publication in the process of publishing considers ISO 9000. At the end of the articles it is described how
Materiali in tehnologije will develop in future.
Key words: scientific serial publication, Iron and Steel Journal, Metals Alloys Technologies, Materials and Technology,
historical overview, statistical data, electronic publishing, ISO 9000.
MATERIALI IN TEHNOLOGIJE
(@ELEZARSKI ZBORNIK ® KOVINE ZLITINE TEHNOLOGIJE → MATERIALI IN TEHNOLOGIJE)
ISSN: 1580-2949 (tiskana verzija) ; 1580-3414 (elektronska verzija)
UDK: 669+666+678+53
1 @ELEZARSKI ZBORNIK (1967–1991)
Periodi~na publikacija @elezarski zbornik (ISSN
0372-8633) je bila strokovno glasilo Slovenskih `elezarn
in Metalur{kega in{tituta, Ljubljana. Izhajala je v letih
1967–1991 kot ~etrtletnik. V prvem letniku so iz{le le tri
{tevilke. Od leta 1967 dalje so bili strokovni ~lanki
vsebinsko klasificirani po univerzalni decimalni
klasifikaciji, kasneje {e po klasifikaciji ASM/SLA (od
1967–3 dalje). ^lanku so sledili povzetki v angle{kem,
nem{kem in od leta 1968 tudi v ruskem jeziku. Od leta
1975 dalje je revija objavljala avtorske izvle~ke v
slovenskem, nem{kem, angle{kem in ruskem jeziku. Od
drugega letnika dalje je bilo v zadnji {tevilki letnika
oziroma v prvi {tevilki naslednjega letnika objavljeno
letno kronolo{ko kazalo. Periodi~na publikacija je
obsegala podro~je kovinskih in deloma nekovinskih
materialov. Odgovorni urednik je bil dipl. ing. Jo`e Arh,
@elezarna Jesenice (1967/1–1991/4). Uredni{ki odbor so
do leta 1984 sestavljali trije ~lani: Jo`e Rodi~, Barbori~
in Aleksander Kveder. Nato se je {tevilo ~lanov Ured-
ni{kega odbora postopoma ve~alo. Tehni~ni uredniki so
bili: Edo @agar (1967/1–1980/4), Darko Brada{kja
(1981/1–1987/2), Jana Jamar (1987/1–1991/4). Ob dvaj-
setletnici izhajanja te periodi~ne publikacije je bila
izdelana in izdana bibliografija ~lankov za obdobje od
1967 do 1986. Iz{la je kot posebna {tevilka @elezarskega
zbornika 1987/5. Oprema in zunanja oblika revije se v
dvajsetih letih nista bistveno spreminjali.
2 KOVINE ZLITINE TEHNOLOGIJE (1992–1999)
Leta 1992 je periodi~na publikacija @elezarski zbor-
nik spremenila svoje ime v Kovine zlitine tehnologije
(ISSN 1318-0010). Preimenovala se je zaradi vsebinske
raz{iritve. Obsegala je podro~ja kovinskih materialov in
anorganskih materialov, polimerov in materialov, ki se
uporabljajo v vakuumski tehniki. Do leta 1994 je
izhajala v {tirih {tevilkah na leto, od leta 1995 dalje pa je
imela {est {tevilk na leto. Avtorji prispevkov so bili
poleg slovenskih tudi uveljavljeni tuji strokovnjaki.
Zadnja {tevilka letnika je vsebovala letno kazalo, ki je
bilo razdeljeno na kronolo{ko, avtorsko in vsebinsko.
Leta 1997 je iz{la prva izredna {tevilka te periodi~ne
publikacije (1997/5).
Izdajatelj je bil In{titut za kovinske materiale in
tehnologije, Ljubljana. Soizdajatelji so bili: ACRONI,
Materiali in tehnologije / Materials and technology 41 (2007) 1, 13–19 13
UDK 050:6(497.4) ISSN 1580-2949
Pregledni znanstveni ~lanek/Review scientific article MTAEC9, 41(1)13(2007)
Jesenice, IMPOL, Slovenska Bistrica, Kemijski in{titut,
Ljubljana, Koncern Slovenske `elezarne, Metal, Ravne
na Koro{kem, Talum, Kidri~evo, Fakulteta za stroj-
ni{tvo, Ljubljana, Institut "Jo`ef Stefan", Ljubljana in
Slovensko dru{tvo za tribologijo, Ljubljana. Izdajanje je
sofinanciralo Ministrstvo za znanost in tehnologijo
Republike Slovenije. Glavni in odgovorni uredniki so
bili: dipl. ing. Jo`e Arh (1992/1–1994/3), mag. Ale{
Lagoja (1994/4–1995/6) in prof. dr. Franc Vodopivec
(1996/1–1999/6). Uredni{ki odbor se je raz{iril na sedem
~lanov. O uredni{ki politiki je soodlo~al Izdajateljski
svet in mednarodni pridru`eni ~lani Uredni{kega odbora.
Tehni~no urejanje je vodila Jana Jamar (1992/1–1999/6).
V letu 1998 so v uredni{tvu periodi~ne publikacije na
predlog Ministrstva za znanost in tehnologijo poskrbeli
za kategorizacijo in razvrstitev ~lankov po tipologiji
dokumentov za vodenje bibliografij in vnos podatkov v
COBISS. Za obdobje 1996/1999 je bilo vneseno 436
zapisov ~lankov.
Na svetovnem spletu je bila periodi~na publikacija
Kovine zlitine tehnologije dosegljiva na naslovu
http://www.ctk.uni-lj.si/kovine/. Objavljena so bila
kazala posameznih {tevilk, naslovi in avtorji ~lankov,
povzetki in klju~ne besede v slovenskem in angle{kem
jeziku. Od leta 1998 dalje so bili vsi ~lanki, ki so bili
objavljeni v tej serijski publikaciji, na svetovnem spletu
dosegljivi v polnem tekstu. V letu 1999 je bila izdelana
strategija iskanja po ~lankih (avtor, klju~ne besede,
naslov ~lanka …).
Periodi~na publikacija je bila citirana v devetih
mednarodnih sekundarnih publikacijah in bazah podat-
kov: Metals Abstracts, Engineered Materials Abstracts,
Business Alert Abstracts (Steels, Nonferrous, Polymers,
Ceramics, Composites), Chemical Abstracts, Aluminium
Industry Abstracts, Referativnyj `urnal Metallurgija,
Metadex, Inside Conferences, DOMA.
V serijski publikaciji Kovine zlitine tehnologije so
bili objavljeni redni prispevki in izbrani recenzirani
prispevki, predstavljeni na Konferencah o materialih in
tehnologijah, ki vsako leto potekajo v Portoro`u.
Prispevki v posameznih {tevilkah so bili izdani v
skladu z mednarodnimi standardi ISO in po navodilih
Ministrstva za visoko {olstvo, znanost in tehnologijo.
Periodi~na publikacija je ustrezala mednarodnim
informacijskim zahtevam, kar vklju~uje ISSN, stan-
dardno terminologijo, mednarodne merske enote,
izvle~ek, klju~ne besede, za~etek ~lanka na neparni
strani in na isti strani podatki o avtorju in serijski
publikaciji. Naslovi ~lankov, povzetki in klju~ne besede
so bili objavljeni v slovenskem in angle{kem jeziku. Od
leta 1998 dalje je postala ustaljena tudi praksa navedbe
datuma prejema rokopisa in sprejema prispevka za
objavo.
Leta 1999 je bila izdelana: Bibliometrijska analiza
in primerjava serijskih publikacij @elezarski zbornik
1967/68 in Kovine zlitine tehnologije 1996/97 (Jamar,
Ba{, Ju`ni~, 2000). Rezultati so pokazali razvoj perio-
di~ne publikacije in velik kakovostni skok v teh letih.
Bibliometrijsko so bile ugotovljene naslednje spremem-
be:
• pove~alo se je {tevilo avtorjev pri posameznem
~lanku in {tevilo ustanov, iz katerih so prihajali;
• raz{irilo se je podro~je, ki ga obravnavajo objave iz
periodi~ne publikacije;
• periodi~na publikacija je iz strokovne periodi~ne
publikacije prerasla v znanstveno.
3 MATERIALI IN TEHNOLOGIJE (2000 ®)
Periodi~na publikacija Materiali in tehnologije
(ISSN 1580-2949) je za~ela izhajati leta 2000. Raz-
{irjena je bila njena vsebina. Podro~je kovin in zlitin se
je raz{irilo na druge materiale (polimeri, anorganski
materiali, materiali, ki se uporabljajo v vakuumski
tehniki) in dalje na kompozitne, gradbene materiale,
nanomateriale ter njihove tehnologije in materiale za
fuzijo. Postala je vodilna periodi~na publikacija za
podro~je materialov v Sloveniji. S spremembo imena naj
bi {e bolj jasno opredeljevala svojo vsebino. Njen cilj je
raz{iriti interesno podro~je na ~im ve~ materialov, dose~i
prepoznavnost in ve~jo citiranost v tujih referatnih
publikacijah in bazah podatkov. S postopno rastjo kako-
vosti in vklju~itvijo v nove mednarodne baze podatkov si
periodi~na publikacija prizadeva dose~i citiranost v
Science Citation Index-u, kar bi pomenilo, da bi imeli
slovenski raziskovalci ve~ji interes za objavljanje svojih
znanstvenih in strokovnih ~lankov tudi v slovenski reviji.
Revija izhaja v {estih {tevilkah letno, od leta 2006 dalje
vsaka {tevilka kot samostojni zvezek. Zadnja {tevilka
letnika vsebuje letno kazalo: kronolo{ko, avtorsko in
vsebinsko. Glavni in odgovorni urednik je prof. dr.
France Vodopivec, pomo~nica glavnega in odgovornega
urednika doc. dr. Monika Jenko. ^lani Uredni{kega
odbora, Izdajateljskega sveta in mednarodni pridru`eni
~lani Uredni{kega odbora sodelujejo pri usmeritvah
uredni{ke politike revije in pri odlo~itvah o recenziranju
~lankov. Tehni~no urejanje vodi Jana Jamar.
Na svetovnem spletu je periodi~na publikacija
Materiali in tehnologije dosegljiva na naslovu
http://www.imt.si/materiali-tehnologije (ISSN 1580-
3414). Izdajanje periodi~ne publikacije poteka po ISO
90001 (Diagram 1).
Prve ideje o digitalizaciji periodi~ne publikacije
Kovine zlitine tehnologije so se popolnoma spontano
porodile v drugi polovici leta 1995. ^lani uredni{tva so
se po premisleku odlo~ili, da bi izdelali spletno stran, ki
bi vsebovala osnovno predstavitev periodi~ne publi-
kacije, kazala po {tevilkah, letna kazala ter izvle~ke
prispevkov. Del spletne strani je bil namenjen avtorjem
prispevkov (navodila avtorjem, podatki o indeksiranju
prispevkov v mednarodnih sekundarnih virih, na~ini
komuniciranja z uredni{tvom, roki oddaje ~lankov).
Dostopna je bila na URL-naslovu http://www.ctk.
uni-lj.si/kovine/. Razmi{ljanja o dostopnosti ~lankov v
N. JAMAR, J. JAMAR: ZGODOVINA SERIJSKE PUBLIKACIJE MATERIALI IN TEHNOLOGIJE
14 Materiali in tehnologije / Materials and technology 41 (2007) 1, 13–19
N. JAMAR, J. JAMAR: ZGODOVINA SERIJSKE PUBLIKACIJE MATERIALI IN TEHNOLOGIJE
Materiali in tehnologije / Materials and technology 41 (2007) 1, 13–19 15
Diagram 1: Izdajanje revije Materiali in tehnologije – potek izdajateljske dejavnosti po ISO 9000
polnem besedilu pa so se ustavila pri tehni~no zapleteni
izdelavi datotek v programskem jeziku Hypertext
Markup Language (HTML). Programski jezik HTML
(HTML 2) je bil v takratni razvojni stopnji {e zelo
okoren in ni vseboval nekaterih mo`nosti, ki so se
pojavile kasneje.
V naslednjih dveh letih, 1997 in 1998, so se s poja-
vom novih programskih okolij razmere za oblikovanje
hiperteksta korenito spremenile. HTML 3.2 in HTML 4
sta omogo~ila {tevilne nove re{itve. Microsoft Office 97
je omogo~il enostavno pretvorbo dokumentov iz okolja
Office v hipertekst. To je ponovno spodbudilo idejo o
polnem besedilu znanstvenih in strokovnih prispevkov v
elektronski verziji. S porastom elektronskih serijskih
publikacij s polnimi besedili prispevkov na svetovnem
spletu je bilo mo`no primerjati datote~ne oblike, v
katerih so se polna besedila pojavljala na svetovnem
spletu, predvsem periodi~ne publikacije s podro~ja
naravoslovja in tehnike, re{itev grafi~nih elementov v
prispevkih: npr. grafikoni in slike, in re{itve zapletenih
tekstovnih delov, kot so matemati~ne izpeljave in
kemijske formule.
Na spletno stran je bilo postavljeno enostavno
iskalno orodje, s katerim je bilo omogo~eno iskanje po
kazalih in hipertekstovnih sklopih prispevkov (podatki o
avtorju, izvle~ek v sloven{~ini in angle{~ini, klju~ne
besede v sloven{~ini in angle{~ini). Hipertekstovni deli
dokumentov so bili izdelani z uporabo orodij MS Office
in FrontPageExpress.
S spremembo naslova Kovine zlitine tehnologije v
Materiali in tehnologije je tudi spletna stran dobila novo
oblikovno in vsebinsko podobo. Nov URL-naslov
elektronske verzije revije je http://www.imt.si/materiali-
tehnologije. Z uporabo iskalnega orodja PICO SEARCH
je bila poenostavljena mo`nost iskanja po prispevkih.
Izdelan je bil neke vrste portal za podro~je naravoslovnih
ved in tehnike. Cilj spletne strani je ~im ve~ja dostopnost
naj{ir{emu krogu uporabnikov. Svetovni splet omogo~a
bolj interaktiven odnos med bralci in uredni{tvom. S
spremljanjem novih tehnologij v elektronskem zalo`ni-
{tvu in z dodatnim izobra`evanjem, s {e bogatej{o zbirko
uporabnih povezav, s postavitvijo elektronskih forumov,
z obve{~anjem uporabnikov o novih mo`nostih pridobi-
vanja informacij s tega podro~ja znanosti (spremljanje
razvoja in dostopnosti novih podatkovnih zbirk in
standardov, obve{~anje o konferencah in mo`nostih
izobra`evanja, spremljanje zakonodaje) je upati, da bo to
postalo prijazno in uporabno spletno mesto za razisko-
valce, {tudente in druge, ki jih zanima to podro~je
znanosti.2
Prednosti izdajanja periodi~ne publikacije v elek-
tronski obliki so:
• urejenost ~lankov v enostavno podatkovno zbirko
omogo~a tematsko poizvedovanje po vsebini ~lan-
kov;
• enostavnej{i stiki med avtorji in uredni{tvom;
• trajen in enostaven dostop do polnotekstovnih for-
matov prispevkov, ne glede na kraj in ~as;
• elektronska periodi~na publikacija je dosegljiva pred
tiskano obliko;
• la`ja, hitrej{a, skoraj brezmejna dostopnost do gra-
diva v kateremkoli ~asu;
• {ir{a odmevnost, opaznost in vidnost v mednarodnem
prostoru;
• razli~ne mo`nosti iskanja (po kazalih, izvle~kih,
klju~nih besedah);
• mo`nosti povezovanja s citiranimi in drugimi sorod-
nimi ~lanki;
• omogo~a avtorjem teko~e in hitre informacije
uredni{kega odbora: navodila avtorjem, obvestila;
• mo`nosti prevzemanja celotnih ~lankov;
• omogo~a sledljivost ~lanka (zgodovina ~lanka na
enem mestu);
• informacije so cenej{e od tiskane oblike.
V letu 2001 je bilo izdelano diplomsko delo Biblio-
metrijsko-bibliografska primerjava znanstvene
periodi~ne publikacije MATERIALI IN TEHNOLO-
GIJE (2000) in MATERIALS SCIENCE AND
TECHNOLOGY (2000). Delo je bilo posve~eno 35.
obletnici izdajanja revije MATERIALI IN TEHNO-
LOGIJE.
Rezultati bibliometri~ne analize periodi~ne publi-
kacije Materiali in tehnologije (2000) so v primerjavi s
serijsko publikacijo Materials Science and Technology
(2000) pokazali, da bi avtorji (raziskovalci) in uredniki
periodi~ne publikacije Materiali in tehnologije morali
posve~ati ve~ pozornosti naslednjim merilom:
• pove~ati {tevilo objavljenih ~lankov, kar bi pomenilo
ve~je {tevilo citatov in s tem ve~jo mo`nost prido-
bitve dejavnika vpliva;
• spodbujati skupinsko delo raziskovalnih skupin in s
tem pove~ati povpre~no {tevilo avtorjev na ~lanek,
saj se dela kolektivnih avtorjev pogosteje citirajo;
• pove~ati mednarodnost avtorjev glede na priporo~ila
Institute for Scientific Information za vklju~itev
serijskih publikacij v Science Citation Index;
• ve~je sodelovanje kadrov, zaposlenih na univerzah;
pri tem se postavlja vpra{anje zanimanja zaposlenih
na univerzah za objavljanje v serijski publikaciji brez
dejavnika vpliva, ker so pri svojih reelekcijah najbolj
vezani na periodi~ne publikacije, ki so indeksirane v
Science Citation Indexu;
• citiranje literature ~lankov iz periodi~ne publikacije
Materiali in tehnologije v serijskih publikacijah z
visokim dejavnikom vpliva.
V zvezi z diplomskim delom je bila izdelana in izve-
dena tudi ANKETA O ZADOVOLJSTVU AVTOR-
JEV Z UREDNI[TVOM IN KVALITETO
PERIODI^NE PUBLIKACIJE MATERIALI IN
TEHNOLOGIJE TER O CITIRANI LITERATURI.
N. JAMAR, J. JAMAR: ZGODOVINA SERIJSKE PUBLIKACIJE MATERIALI IN TEHNOLOGIJE
16 Materiali in tehnologije / Materials and technology 41 (2007) 1, 13–19
Pomanjkljivosti, ki so bile opa`ene pri rezultatih
ankete o zadovoljstvu avtorjev z uredni{tvom in kvali-
teto periodi~ne publikacije Materiali in tehnologije:
• preslaba informativnost naslovov ~lankov in iz-
vle~kov;
• ni debatnega dela v serijski publikaciji, s ~imer bi se
pove~ala komunikacija med avtorji, ~eprav sami
avtorji menijo, da debatnega dela ne pogre{ajo;
• uporaba periodi~ne publikacije Materiali in tehno-
logije v elektronski obliki je premajhna;
• premajhna prepoznavnost periodi~ne publikacije
Materiali in tehnologije v tujini.
• Pozitivne ugotovitve, ki so bile opa`ene pri rezultatih
ankete o zadovoljstvu avtorjev z uredni{tvom in kva-
liteto periodi~ne publikacije Materiali in tehnologije:
• hitrost objave prispevkov je ustrezna;
• delo lektorjev je zelo pozitivno;
• razdelitev ~lankov po tipologiji dokumentov na stro-
kovne, znanstvene in pregledne ~lanke je ustrezna;
• kvaliteta papirja, slik in fotografij je dobra;
• uredni{ka politika zadovoljuje uporabnike (avtorje
prispevkov in druge uporabnike).
Pohvalno je, da `elijo avtorji (drugi del ankete) bolj
kot povzemati dosedanje dose`ke na raziskovalnem
podro~ju poudariti originalne ugotovitve na podro~ju
dela, presene~a pa nas sklicevanje na avtoritete na
dolo~enem znanstvenem podro~ju. Ve~ina avtorjev
velikokrat, pa verjetno {e premalo, pregleda seznam
citatov avtorjev, ki objavljajo ~lanke z njihovega pod-
ro~ja dela in ta citirana dela velikokrat uporabijo pri
svojem nadaljnjem delu. Zanimivo je, da tudi avtorji, ki
sicer malokrat pregledajo seznam citatov avtorjev, ki
objavljajo ~lanke z njihovega podro~ja dela, ta dela
velikokrat uporabljajo pri svojem nadaljnjem delu.
Avtorji malokrat osebno poznajo avtorje del, ki jih
citirajo, in malokrat citirajo ~lanke, objavljene v serijski
publikaciji Materiali in tehnologije. Na njihovo citiranje
pa mo~no vpliva dostopnost dolo~ene literature, zato je
pomembna ustrezna nabavna politika knji`nic, kjer
avtorji informacijske vire pregledujejo (Jamar, 2001).
4 PREGLED / MATERIALI IN TEHNOLOGIJE:
2000–2006
Tabela 1: MIT 2000–2006 : Fizi~ni obseg
[tevilka
revije
[tevilo
strani
[tevilo
~lankov
Avtorske
pole
2000 / 1–6 452 79 28,30
2001 / 1–6 500 72 31,25
2002 / 1–6 492 71 30,75
2003 / 1–6 420 67 26,50
2004 / 1–6 + p. {. 491 67 30,70
2005 / 1-6 334 30 20,30
2006 / 1-6 354 44 22,15
Skupaj 3043 430 189,95
Tabela 2: MIT 2000–2006: Pregled prispevkov po tipologiji doku-
mentov
^lanki 2000 2001 2002 2003 2004 2005 2006 Skupaj
Pregledni
znanstveni ~l.
6 4 6 8 6 5 8 43
Izvirni
znanstveni ~l.
43 44 50 35 42 18 30 262
Strokovni
~lanki
30 24 15 24 19 7 6 125
Tabela 3: MIT 2000–2006 : Analiza jezika ~lankov
Leto Slovenski jezik % Angle{ki jezik %
2000 84,81 15,19
2001 72,20 27,80
2002 69,00 31,00
2003 58,00 42,00
2004 53,75 46,25
2005 31,67 68,33
2006 20,45 79,55
Tabela 4: MIT 2000–2006: Razmerje med objavljenimi znanstvenimi
in strokovnimi ~lanki
Leto Strokovni
prispevki, %
Znanstveni
prispevki, %
2000 38,00 62,00
2001 33,00 67,00
2002 21,00 79,00
2003 36,00 64,00
2004 28,35 71,65
2005 26,70 73,30
2006 13,65 86,35
Tabela 5: MIT 2000–2006 : Analiza po avtorjih
Leto [tevilo
vseh
avtorjev
[tevilo
razli~nih
avtorjev
[tevilo
~lankov
[tevilo
avtorjev
na ~lanek
2000 222 174 79 2,81
2001 222 156 72 3,08
2002 216 169 71 3,05
2003 194 163 67 2,90
2004 243 193 67 3,60
2005 109 89 30 3,60
2006 147 130 44 3,34
Tabela 6: MIT 2000–2006 : Mednarodnost avtorjev / razli~ni avtorji
Leto Slovenija, % Tujina, %
2000 85,06 14,94
2001 85,14 14,86
2002 80,10 19,90
2003 73,20 26,80
2004 62,15 37,85
2005 69,72 30,28
2006 52,40 47,60
N. JAMAR, J. JAMAR: ZGODOVINA SERIJSKE PUBLIKACIJE MATERIALI IN TEHNOLOGIJE
Materiali in tehnologije / Materials and technology 41 (2007) 1, 13–19 17
Tabela 7: MIT 2000–2006 : Vsebinski pregled ~lankov
Podro~je 2000 2001 2002 2003 2004 2005 2006
Kovinski materiali 51,90 68,06 71,85 67,15 71,67 70,00 68,20
Anorganski materiali 31,64 11,11 12,65 7,45 11,95 23,30 9,10
Vakuumska tehnika 8,90 12,50 7,05 10,45 7,45 0,00 4,55
Polimeri 6,30 6,94 7,05 3,00 3,00 3,35 13,60
Gradbeni materiali 0,00 0,00 0,00 7,45 5,95 3,35 4,55
Informatika 1,26 0,00 1,40 0,00 0,00 0,00 0,00
Raziskovalna politika 0,00 1,39 0,00 0,00 0,00 0,00 0,00
Raziskave in razvoj 0,00 0,00 0,00 1,50 0,00 0,00 0,00
Standardizacija 0,00 0,00 0,00 1,50 0,00 0,00 0,00
Metodologija 0,00 0,00 0,00 1,50 0,00 0,00 0,00
Tabela 8: MIT 2000–2006 : Citiranje literature
Leto [tevilo ~lankov z dolo~enim {tevilom citatov (%)
0 cit. 1–4 cit.5–9 cit. 10–14
cit.
15–19
cit.
20–29
cit.
30 in
ve~ cit.
2000 1,27 15,19 39,24 26,58 8,86 7,59 1,27
2001 0,00 13,88 40,28 23,61 6,95 12,50 2,78
2002 0,00 11,30 33,80 28,15 12,70 11,25 2,80
2003 1,50 14,90 41,80 26,90 3,00 5,95 5,95
2004 1,50 10,45 43,25 22,35 14,95 6,00 1,50
2005 0,00 3,35 50,00 16,65 13,35 6,65 10,00
2006 0,00 18,18 34,10 22,72 13,63 4,54 6,81
Tabela 9: MIT 2000–2006 : Povpre~no {tevilo citatov na ~lanek
Leto [t. citatov [t. ~lankov [t. ~lankov
brez cit.
[t. citatov/
~lanek
2000 797 79 1 10,09
2001 807 72 0 11,20
2002 848 71 0 11,95
2003 775 67 1 11,55
2004 734 67 0 10,95
2005 530 30 0 18,30
2006 576 44 0 13,10
Statisti~ni pregled revije Materiali in tehnologije ka`e
nekaj zanimivih ugotovitev:
• {tevilo ~lankov upada: 79 ~lankov (leto 2000), 44
~lankov (leto 2006)
• {tevilo znanstvenih ~lankov se pove~uje v razmerju s
strokovnimi ~lanki: 62 % (leto 2000), 86 % (leto
2006)
• analiza jezika ~lankov ka`e, da se je ekstremno
pove~alo {tevilo ~lankov, objavljenih v angle{kem
jeziku: 15,19 % (leto 2000), 79,55 % (leto 2006)
• poudarek je na timskem delu raziskovalcev: 2,81
avtorja na ~lanek (leto 2000), 3,34 avtorja na ~lanek
(leto 2006)
• mednarodnost avtorjev in povezovanje slovenskih
avtorjev s tujimi se pove~uje: 14,94 % tujih avtorjev
(leto 2000), 47,60 tujih avtorjev (leto 2006)
• pove~uje se {tevilo citatov na ~lanek: 10,09 citatov
na ~lanek (leto 2000), 13,10 citatov na ~lanek (leto
2006)
Tabela 10: Pregled po letih izhajanja
Letnik Leto Število zvezkov in {tevilk
Znan-
stveni in
strokovni
~lanki
Tehni~ne
novice
@ELEZARSKI ZBORNIK
1 1967 3 (3) 27
2 1968 4 (4) 25
3 1969 4 (4) 24
4 1970 4 (4) 25
5 1971 4 (4) 24
6 1972 4 (4) 21
7 1973 4 (4) 22 2
8 1974 4 (4) 22 3
9 1975 4 (4) 23 1
10 1976 4 (4) 18 4
11 1977 4 (4) 17 10
12 1978 4 (4) 14 3
13 1979 4 (4) 15 3
14 1980 3 (4 – 1 dvojna {tevilka) 22 4
15 1981 4 (4) 27
16 1982 4 (4) 15 2
17 1983 4 (4) 15 2
18 1984 4 (4) 17 2
19 1985 4 (4) 20 3
20 1986 4 (4) 12 4
21 1987 5 (5 – 1 bibliografija) 19 4
22 1988 4 (4) 18 2
23 1989 4 (4) 17 6
24 1990 4 (4) 22 4
25 1991 4 (4) 16 2
KOVINE ZLITINE TEHNOLOGIJE
26 1992 3 (4 – 1 dvojna {tevilka) 69 1
27 1993 3 (4 – 1 dvojna {tevilka) 58 5
28 1994 3 (4 – 1 dvojna {tevilka) 118 3
29 1995 3 (6 – 3 dvojna {tevilka) 124
30 1996 4 (6 – 2 dvojna {tevilka) 110
31 1997 5 (7 – 2 dvojna {t, 1 posebna
{t.)
104 5
32 1998 4 (6 – 2 dvojna {tevilka) 107 4
33 1999 4 (6 – 2 dvojna {tevilka) 95 1
MATERIALI IN TEHNOLOGIJE
34 2000 4 (6 – 2 dvojna {tevilka) 75 3
35 2001 4 (6 – 2 dvojna {tevilka) 72
36 2002 4 (6 – 2 dvojna {tevilka) 69 2
37 2003 4 (6 – 2 dvojna {tevilka) 66 1
38 2004 5 (6 – 2 dvojna {t., 1 posebna
{t.)
67
39 2005 5 (6 – 1 dvojna {tevilka) 30
40 2006 6(6) 44
1–40 1967–2006 160 (185) 1664 86
SKUPAJ 1750
V letnikih 1–40 (1967–2006) je iz{lo 160 zvezkov oz. 185 {tevilk
revije vklju~no z dvojnimi {tevilkami, s 1664 znanstvenimi in
strokovnimi ~lanki, 86 tehni~nimi novicami, skupaj 1750 objavljenimi
prispevki.
N. JAMAR, J. JAMAR: ZGODOVINA SERIJSKE PUBLIKACIJE MATERIALI IN TEHNOLOGIJE
18 Materiali in tehnologije / Materials and technology 41 (2007) 1, 13–19
5 MATERIALI IN TEHNOLOGIJE /
PRIHODNOST
• Materiali in tehnologije so vodilna periodi~na
publikacija za podro~je materialov v slovenskem
prostoru, za kar se bo uredni{ki odbor trudil tudi v
prihodnje.
• [tevilo prispevkov v angle{kem jeziku naj bi se v
prihodnje pove~alo, ~eprav se tu pojavlja dilema:
"Kdo bo skrbel za slovensko tehni{ko besedo na
podro~ju materialov, ~e bodo vsi prispevki angle{ki?"
Torej bo treba najti kompromis, da bodo angle{ki
~lanki prevladujo~i, nekaj pa jih bo ostalo v sloven-
skem jeziku, predvidoma bodo v sloven{~ini pred-
vsem prispevki avtorjev, zaposlenih v industriji.
Obstaja tudi mo`nost, da bi vse ~lanke prevedli v
angle{~ino, kar pa bo te`ko izvedljivo zaradi previ-
sokih stro{kov izdajanja periodi~ne publikacije.
• Periodi~na publikacija Materiali in tehnologije
obravnava podro~ja, kjer so slike mikrostruktur in
diagrami zelo pomembni, zato se mora ohraniti ~im
bolj{a kvaliteta tiskanja.
• Uredni{ki odbor namerava pridobiti ve~ mednarodno
priznanih avtorjev.
• Pove~ati bi bilo treba citiranje periodi~ne publikacije
Materiali in tehnologije v serijskih publikacijah z
visokim dejavnikom vpliva.
• Treba bi bilo poiskati podporo priznanih tujih
strokovnjakov za uvrstitev periodi~ne
publikacije Materiali in tehnologije v
Science Citation Index.
• Trajno in a`urno izdajanje elektronske
oblike periodi~ne publikacije Materiali
in tehnologije na najmanj sedaj dose-
`enem kakovostnem nivoju.
• Elektronska verzija periodi~ne publi-
kacije Materiali in tehnologije naj bi
za`ivela kot spletno mesto, kjer bi
uporabnik poleg ~lankov periodi~ne publikacije v
polnem tekstu na{el {e {tevilne druge servise s
strokovnih podro~ij, ki jih periodi~na publikacija
obsega (imenski katalog spletnih povezav, novice,
zanimivosti za raziskovalce).
• Serijsko publikacijo Materiali in tehnologije naj bi
intenzivno vklju~evali v razvoj potencialnega skup-
nega informacijskega servisa slovenskih znanstvenih
in strokovnih publikacij.
• Pridobitev dejavnika vpliva
• ^lanki v reviji Materiali in tehnologije 2007/1 dalje
bodo opremljeni z DOI (Digital Object Identifier)
identifikatorji. V Sloveniji bo revija Materiali in
tehnologije ena prvih, ki bo prevzela sistem za
ozna~evanje avtorsko pravno za{~itenih del na
internetu (DOI).
• ^lanki revije Materiali in tehnologije od 2007/1 dalje
bodo indeksirani tudi v:
DOAJ (Directory of Open Access Journals)
GOOGLE SCHOLAR
SCIRUS
• Leta 2007/2 bo iz{la posebna {tevilka revije Materiali
in tehnologije. Objavljena bo Bibliografija ~lankov
1967–2006. Ob tej prilo`nosti bo izdan tudi po{tni
`ig : 40 let izdajanja serijske publikacije Materiali
in tehnologije.
6 LITERATURA
1 N. Jamar, Bibliometrijsko-bibliografska primerjava
znanstvene serijske publikacije Materiali in tehno-
logije (2000) in Materials Science and Technology
(2000) : diplomsko delo, [N. Jamar], Jesenice 2001
2 M. Pu{nik: Elektronska oblika revije Materiali in
tehnologije, Vloga specialnih knji`nic pri pospe-
{evanju dru`benega in gospodarskega razvoja.
Izgradnja knji`ni~nih zbirk: pridobivanje in izlo~anje
gradiva: zbornik referatov, Ljubljana, Narodna in
univerzitetna knji`nica, 2000, 163–172
N. JAMAR, J. JAMAR: ZGODOVINA SERIJSKE PUBLIKACIJE MATERIALI IN TEHNOLOGIJE
Materiali in tehnologije / Materials and technology 41 (2007) 1, 13–19 19

D. ]UR^IJA, I. MAMUZI]: THEORETICAL CALCULATION OF THE LUBRICATION-LAYER THICKNESS ...
THEORETICAL CALCULATION OF THE
LUBRICATION-LAYER THICKNESS DURING METAL
DRAWING
TEORETI^NI IZRA^UN DEBELINE PLASTI MAZIVA PRI
VLE^ENJU KOVIN
Du{an ]ur~ija, Ilija Mamuzi}
University of Zagreb, Faculty of Metallurgy, 44103 Sisak, Croatia
plutonijanac21@net.hr
Prejem rokopisa – received: 2005-09-15; sprejem za objavo – accepted for publication: 2006-10-25
The calculation of the lubricant-layer thickness using a fluid-mechanics approach is shown for the case of the cold drawing of
metals. Examples of the calculation for a solid lubricant layer and a different geometry of the die entering angle are shown. The
calculation of the effect of inertial force with a high drawing speed on the lubricant-layer thickness is also presented.
Key words: lubrication, Reynolds equation, mathematical modelling, Couett flowing, lubricant inertia
Predstavljen je izra~un debeline plasti maziva je za vle~enje kovin na podlagi mehanike fluidov in primeri izra~una za trdno
mazivo ter razli~no geometrijo vhoda v matrico. Predstavljen je tudi primer izra~una vpliva sile vztrajnosti na debelino mazivne
plasti pri veliki hitrosti vle~enja.
Klju~ne besede: mazanje, Reynoldsova ena~ba, matemati~no modeliranje, Couettov tok, inercija maziva
1 INTRODUCTION
During the cold working of metals the presence of a
lubricant on the surface ensures a lower extrusion force,
less die wear and a reduction in the energy consumed1.
The lubricant layer enables a greater per-pass reduction,
a better surface quality and an increase in the operational
stability of working devices2,3. It also increases the
drawing speed by 50 % and the yield by 20 %3. In the
drawing process for low and middle carbon steels,
expensive industrial lubricants are substituted with soap
powders4. The functional quality of the lubricants for
drawing depends on:
• the metal drawing temperature (thermal decompo-
sition lowers the lubricant capacity and the antifric-
tion properties),
• the adhesive force to the covered metal surface,
• the resistance to its expulsion from the deformation
area,
• the corrosion properties.
Furthermore, the lubricant should be free of com-
pounds that have a harmful effect on human skin, an
unpleasant smell or a low flash point. For metal
extrusion and drawing the following lubricants are used:
• solid lubricants derived from animals, such as cattle
and sheep’s tallow and synthetic powders,
• liquid lubricants (machine oils and plant fats),
• emulsion oils and emulsions,
• glass lubricants5.
For wire drawing the following lubricants are used:
• powders of calcium and sodium soaps with the
addition of molybdenum disulfide powder,
• mineral oils,
• emulsions based on flour, soap and sulphuric acid,
• water dispersions of colloidal graphite.
For the drawing of tubes with a non-circular profile
an iodine solution in dibutylphtalate is used as a
lubricant. After working, the lubricant residue is
removed by washing in hot water, and the tubes are
passivated in a water solution of calcined soda and
trisodiumphophate6.
This lubricant is deposited on a phosphate base with
the immersion of tubes in the solution7 at a temperature
of 70 °C to 90 °C. Also, the combined processes of the
deposition of phosphate and lubricant were developed,
and an improvement to the wetting angle was achieved
by combining zinc phosphate and sodium soap in the
water solution 8. The immersion time was 5 min to 10
min. With longer immersion times the technological
properties of the solution are impaired because of the
reaction:
6R0Na + Zn3(Po4)2 →3R02Zn + 2Na3PO4 (1)
where R0 is the radical of the fatty acid. Also, the
following reactions can occur:
2C17H35COOONa + H2SO4 →
→ 2C17H35COOH + Na2SO4 (2)
R02Zn + H2SO4 → 2R0N + ZnSO4 (3)
The stability of the solution is increased with the
addition of a solution of caustic of soda with a pH ≈ 8.
For the drawing of silver and precious-metal alloys
paraffin wax and other waxes are used.
Materiali in tehnologije / Materials and technology 41 (2007) 1, 21–27 21
UDK 621.778:519.8 ISSN 1580-2949
Review scientific article/Pregledni znanstveni ~lanek MTAEC9, 41(1)21(2007)
2 FLUID MECHANICS DURING LUBRICANT
DRAWING
2.1 Calculation of the layer thickness for a liquid lubri-
cant
For this calculation, Pradtl adapted the Reynolds
hydrodynamic equation9, 9/1, 9/2 and the solution
dp/dx = 6 µv0 (h0 – h)/h
3 (4)
is used for the calculation of the lubricant layer thick-
ness. In the equation the inertial forces are neglected
and the lubricant is treated as a Newtonian fluid10.
Furthermore, the absence of any effect of external
forces, the constant pressure over the section of the
metal and the large ratio of curvature of the metals
surface over the lubricant layer thickness are assumed11.
The tool (matrix) geometry has a strong influence on the
drawing process12. A scheme of the drawing with the
lubricant corresponding to Equation (4) is shown in
Figure 1.
The dynamic viscosity of the lubricant depends on
the pressure according to the Barussa13 law:
η = η 0 exp (γp)
For a linear change of shape in the matrix gap Ψ in
Figure 1, the lubricant layer thickness (height) is:
h = h0 – x tanα (5)
The change of pressure in the lubricant layer is:
∆p = – (1/γ) ln[1 – 3µ0 γ v0(2 – h0/h)/h tan α] (6)
For p = p0 and h = h0, the lubricant layer height
(thickness) in the entry gap of the deformation zone is
deduced as:
h0 = (3µ0γv0)/[(1 – exp(–γp0)] tan α] (7)
This solution was developed by Mizuno1 and later
confirmed by Grudev and Kolmogorov13,14. Also, the
solution can be used:
h0v = (9µ0γv0)/[4(1 – exp(–γpv)] tan α] (8)
where pv = σt0 – σ0 and σt0 = 1.15 σt (9)
The hydrodynamic friction was first investigated by
Kameron,15 and his findings were later confirmed by
Christopherson and Naylor15/1,15/2, 15/3.
In the modified scheme of die drawing16 in Figure 2
the Descartes system is shifted17 in comparison to Figure
1. For the same die, the Descartes system can also be
placed according to Figure 318.
For Figure 3 the Reynolds equation written in cylin-
drical coordinates is:
1/r[∂/∂r(r∂vz/∂r)] = (1/µ) ∂p/∂z (10)
∂p/∂r = 0 (11)
According to Figure 2 and assuming z = z0, the
maximal pressure in the lubricant layer is obtained with
the solution of Equation (10) for the proper boundary
conditions:
pmax = – 6µu{1–2ε0/(Rw–a)[1– ε0/2(Rw–a)]}/
/Tε0 : Rw = tanαLp=TLp (12)
By analogy, the maximal pressure in the lubricant
layer according to Figure 3 is:
pmax= – (6µu) [1–z0/lb]
2 /(Tt–Top)∆ : z0(Tt–Top) = ∆;
Tt–Top = tan α1 – tan α (13)
The solutions according to Figure 2 and 3 have
some common factors. The lubricant’s rheological
D. ]UR^IJA, I. MAMUZI]: THEORETICAL CALCULATION OF THE LUBRICATION-LAYER THICKNESS ...
22 Materiali in tehnologije / Materials and technology 41 (2007) 1, 21–27
Figure 3: Scheme of drawing for the case of metal and die surfaces
forming the lubricant wedge
Slika 3: Shema vle~enja za primer, ko povr{ini kovine in matrice
oblikujeta klinasti sloj maziva
Figure 1: Scheme of die drawing with lubricant
Slika 1: Shema vle~enja z mazivom
Figure 2: Modified scheme of die drawing with lubricant
Slika 2: Modificirana shema vle~enja z mazivom skozi matrico
properties are characterized by the dynamic viscosity, µ,
the kinematics with the drawing speed, v, the shape of
the die with the tangent (α) of the angle of the lubricant
layer, Tt–Top, and the thickness of the lubricant layer, ε0
and ∆. The processing is isothermal and the effect of
temperature on the lubricant viscosity can be considered
to be included in the calculation of Barussa’s equation.
The drawing scheme19 for the drawing with a die of
more complex design is shown in Figure 4.
In the Descartes system the hydrodynamic lubri-
cation is described with the simplified Reynolds
differential equation:
∂p/∂x = µ ∂2vx /∂y2 (14)
∂p/∂y = 0 (15)
With the boundary conditions:
vxy=0 = v0 + ∆v(x/lp)2
vx½y=h = h0 – x tan α = 0 (16)
For the simplification of the analysis the die shown in
Figure 5 is separated into two parts relative to the line
A-A and the ordinate 0 – y in Figure 5B is the section
line A –A in Figure 4A.
The pressure gradient in the lubricant layer according
to Figure 5A is:
∂p/∂x = 6µ {[v0 + ∆v(x/lp)2] (h0 – xtanα*) – 2v1h2}/
(h0 – xtan α*)
3 (17)
By analogy, the gradient of the pressure for the
scheme in Figure 5B is deduced by considering the
boundary conditions:
vxy=0 = v1
vxy=h1 = 0
∂p/∂x = 6µv1(h1 – 2h2)/h13 (18)
It is sufficient to know the solution of the differential
equation for one side of the line A-A because both sides
are related with the equation:
h2 = h1/2 + h1
3 [1 – exp(–γp0)]/(12µ0γv1lK) (19)
The effect of inertial forces in the drawing processes
is described by the equation:
∂p/∂x = 6µv0/h2 +C1µ/h3 +
+ [tan α ρ/120h3](16v0
2h2 – C1
2) (20)
with
C1 = k/2 – [k2/4 + 2v0h0(8v0h0 + 3k)]1/2 (21)
and
k = 120ν/tan α (22)
The lubricant inertia forces20 increase with the
drawing angle and the drawing speed and decrease with
a greater dynamic viscosity of the lubricant.
Besides the presented solutions of the differential
equations, mathematical modelling is also applied to
deduce the lubricant layer thickness21, especially for
rough surfaces22. The following four functions j must be
considered for the correct calculation:
ε/Ras = 7,72·10
-2 ϕ1(Rapop) ϕ2(Rauz) ϕ3(stuz) ϕ4(stpop) (23)
where Ras is the average roughness, Rapop and Rauz are
the longitudinal and transverse average roughness, and
stuz and stpop are the roughness reference length. It is
assumed that the anisotropy of the micro-relief does not
affect the wear for a liquid lubricant. Empirical
investigations have shown for soap powders that the
ratio ε/Ras has values in the range 0.4 to 12.7 and 1.7 to
3.2 for the industrial oil I-8A, according to the Russian
standard. These figures show that the industrial oil
ensures a better regime of liquid lubrication and friction
if the surface roughness is greater than the lubricant
layer thickness, ε, and the orientation of the roughness
affects the frictional force.
D. ]UR^IJA, I. MAMUZI]: THEORETICAL CALCULATION OF THE LUBRICATION-LAYER THICKNESS ...
Materiali in tehnologije / Materials and technology 41 (2007) 1, 21–27 23
(A)
(B)
Figure 5: Two sections of Figure 4: a) Linear gap for lubricant flow,
b) Square gap for lubricant flow
Slika 5: Dva dela slike 4
Figure 4: Drawing scheme for a complex die
Slika 4: Shema vle~enja skozi kompleksno votlico
2.2 Calculation for a solid lubricant
According Figure 6, the distribution of the tangential
forces9/2 in a solid lubricant can be calculated from the
solution of the equation for scheme I in Figure 6:
τ1 = –τ0 – dp/dx(h2–y) (24)
In the equation it is assumed that the lubricant
conforms to the rheological law for a plastic sub-
stance9/2,9/3:
τ = τ0 + K |γ0|m–1 · γ0 (25)
The distribution of the lubricant flow speed for case
II conforms to the equation22/1:
v
h y
c K
p
x
c c
=
−
+




+( )2
1
1
1 d
d
(26)
The flow of solid lubricant shown in Figure 6 for a
cold drawn tube is similar to the flow of fluid in between
two parallel plates, known as Couette flow. For the
calculation of the lubricant layer the thickness in the
entry section of the deformation zone Kolmogorova and
[evljakova23/1 devised the following analytical solution
of Equation (26) assuming that, according to Figure 6,
above the height h1 the lubricant is a cooling liquid and
below it is a solid lubricant:
–K(1––h1)[
–h 2
2 (3+3–h1–2
–h2)+
–K(1––h1)
3] – (27)
–2δ〈3–q[–h 2
2 ––K(1––h1)
2]––h 2
3 +–K(1––h1)
2(2+–h1)〉 = 0
2[2–q–h 2
2 (3–h1–
–h2)+
–K–h1(1–
–h1)
3––h1
–h 2
3 ]·
·[–K(1––h10)+
–h10]–
–h10
–h0·[2
–K(1––h10)+
–h10]· (28a)
·[–h 2
2 (3+3–h1–2
–h2)+
–K(1––h1)
3] = 0
2(1––h1)〈–q[3–h 2
2 +–K(1––h1)
2]––K–h1(1–
–h1)
2––h 2
3 〉·
·[–K(1––h10)+
–h10]–
–h0
–K(1––h10)
2· (28b)
·[–h 2
2 (3+3–h1–2
–h2)+
–K(1––h1)
3] = 0
With – q
q
v h
=
0
; – h
h
h1
1= ; – h
h
h2
2= ; – h
h
h0
0= ;
– h
h
h10
10= ; – K K=
µ
; δ
τ
=
Kv
h
0
0
The solution for the case of the solid lubricant
according to schemeI in Figure 6 is:
[ ]2
1
1 22
1
1
1
12
2
12 1 21 1
c
c c z c
c
h h h h h h
+
− − − − − −− + − + − − + −( ) (σ σ λ 12 2
− ⋅)a
·( ) ( )2 021 12 2 21 2 12 21 122 2 2− + − =
− − − − − −h h h h h ha a aδ λ (28c)
[ ]2
1
1
2
1 1
2
2
2
2
1
12 12
c
c c c z
c
c
c
h h h h h
+
+
+
− + + +− + − + − + − −( )
+ − + − − − −− − − + − − −σ δ λ( ) ( ) ( )(q h h h h h hz c a1 12 1 21 1 12 21 12 2 11
− − +)h a12 2
+ − ⋅ =− − − − −δ λ2 21 2 12 21 1 122 1 0( )h h h h h
a a
q
q
v h
− =
0
; σ
τ
=






v
h
K
c
0
0
; h
h
h1
1− = ; h
h
h2
2= ; λ
τ
τ1 0
1= s ;
λ
τ
τ2 0
2= s ; δ
τ 0
1
1
1
2
=
−
+
b K
k h
c z a
n n
; δ
τ 0
2
2
1
2
=
−
+
b K
k h
c z a
n n
h h h12 1 2
− − −= − ; h h h21 1 2
− − −= + ; z a a c= + + −1 1 2 (28d)
In modern investigations of the plastic working of
metals and the use of lubricants tribological principles
are increasingly used24. Frequently, emulsions are used
in combination with solid lubricants25. Also, the effects
of decorative26 and corrosion-protection coatings are
investigated using fluid-mechanics principles. Of special
practical importance is the fast development of cold
drawing27 and, as shown in this study, improvements are
looked for in suitable solutions of basic fluid-mechanics
equations and mathematical modelling28 in cases when
adequate solutions for the basic equations are not yet
found. Polymer lubricants are being introduced because
of the possibility to tailor their properties29 and because
high-speed wire drawing30 is increasingly being used.
With the development of new lubricants, special care
should be given to the ecology of use and to their
biological decomposition processes31.
2.3 Examples of calculations
The drawing scheme in Figure 2 makes it possible to
model the matrix entry gap and select a determined layer
thickness eA in the gap Ψ ahead of e0, the starting section
of the metal deformation. In Table 1 an example of a
calculation is given for the case of the gap angle a = 0.02
rad and the value of the technological parameter:
A = (1 – exp(–γp0))/6µγv0 = 1965512 m
–1 (29)
The lubricant layer thickness in the die gap is cal-
culated according to Equation (5).
If the geometry of the enter gap Ψ, and the geometry
of the die opening according to Figure 5B is modelled
assuming the cubic polynomial:
ε(x) = ε0 – ax + x
2/2RM – ax
3/2R2M (30)
D. ]UR^IJA, I. MAMUZI]: THEORETICAL CALCULATION OF THE LUBRICATION-LAYER THICKNESS ...
24 Materiali in tehnologije / Materials and technology 41 (2007) 1, 21–27
Figure 6: Scheme of the flowing of solid lubricant during cold
drawing
Slika 6: Shema toka trdnega maziva pri hladnem vle~enju
With RM = 0.2 m, α = 0.2 rad and the technological
parameter according to Equation (29) and Ψ deduced as
a function of vo, the curve in Figure 7 is obtained. The
curve series 1 is the solution of Equation (18), while the
curve Poly (series 1) is obtained by using the
interpolation of the polynomial (30).
Table 1: Effect of the matrix gap opening Ψ (possible entry lubricant
layer thickness εA) on ε0 (lubricant layer thickness at the start of the
plastic deformation)
Tabela 1: Vpliv oblike odprtine matrice Ψ (mo`na debelina plasti
maziva εA) na ε0 (debelina plasti maziva na za~etku plasti~ne defor-
macije)
εA/m ε0/m
1.26E-05 9.98E-06
1.56E-05 1.17E-05
2.02E-05 1.41E-05
4.54E-05 2.25E-05
5.55E-05 2.45E-05
9.75E-05 2.92E-05
1.25E-04 3.07E-05
5.48E-04 3.48E-05
7.25E-03 3.54E-05
9.25E-03 3.54E-05
0.01 3.54E-05
If the lubricant is in excess ahead of the matrix gap
entry section, as in Figure 1, there is no influence of εA
on ε0. However, if εA is lowered below 5.48E-4 m, ε0
will also be lowered significantly. The influence of εA on
ε0 commences for a critical entry gap size. This is shown,
for a drawing angle limited to 0.02 rad in Figure 7. As it
is critical, the enter gap Ψ is assumed, for which the
value εA lowers ε0 by about 5 %. The increase of the
drawing speed shifts the critical gap size to greater
values of εA and, for this reason, the effect of drawing
speed is greater for smaller drawing angles. For the
correct modelling of the entering gap size of the drawing
die, good results were achieved using Equation (5). For
an optimal modelling radius, the effect of εA on ε0 is
lower. In other words, for a constant εA, ε0 will be
lowered more for a smaller drawing angle, while the
grating of the lubricant will be greater.
In Figure 8 the effect of the inertia index is shown
for the initial section of the metal deformation zone as
the solution of equations (20) and (18), with the
dependence on the dynamic viscosity for a liquid
lubricant and the drawing speed vo. The index of the
inertia increases with the increase of the drawing speed
and the lowering of the lubricant’s dynamic viscosity.
For η = 1 P, the index of the inertia is negligible, as
established by the previously cited authors, G. L. Kol-
mogorov, V. L. Kolmogorov, V. I. Mele{ko, V. L.
Mazur and others.
D. ]UR^IJA, I. MAMUZI]: THEORETICAL CALCULATION OF THE LUBRICATION-LAYER THICKNESS ...
Materiali in tehnologije / Materials and technology 41 (2007) 1, 21–27 25
Figure 8: Effect of drawing speed on the index of inertia of the
lubricant
Slika 8: Vpliv hitrosti vle~enja na indeks vztrajnosti maziva
v
y xx
C
ri
tic
al
di
e
ga
p,
Drawing speed,
Figure 7: Effect of the drawing speed on the critical size of Ψ (section
of change of ε0 by 5 %)
Slika 7: Vpliv hitrosti vle~enja na kriti~no velikost Ψ (prerez, ker se
ε0 spremeni za 5 %)
Figure 9: Calculated distribution of the speed of two liquid lubricants
in the tube shaped entry die gap according to Equations (28a) and
(28b) for v0 = 16 m/s
Slika 9: Izra~unana porazdelitev hitrosti po ena~bah (28a) in (28b) v
cevnem vhodu votlice za dve teko~i mazivi
In the case of the calculation for two emulsions with
a different volume density and assuming –K = 10; d = 2.05;
–q = 0.5; –h1 = 0.9, the results –h2 = 0.7251, –h0 = 0.4529,
–h10 = 0.8759 were obtained,23 in good agreement with
earlier data in ref.I. The lubricant speed at the level h1 in
Figure 6 is of 0.41 v0. The results of these calculations
are in good agreement with calculations based on
Equations (28a) and (28b) given in several references for
the case of two liquid lubricants of different specific
density separated at the height –h1, as shown approxi-
mately in Figure 9.
In Table 2 the results of the calculation for a fat
lubricant are shown as a solution of the Equations (28c)
and (28d) for the conditions equal to those in23/1,23/2: s1 =
0; s2 = 0; m = 1; c = 1; z = 2; a1 = a2 = 0.
Table 2: Calculations for a fat lubricant and total lubricant sticking
Tabela 2: Izra~un na trdno mazivo (mast) in popolno oprijetost
maziva
δ h h1 2
− −−
7 0.686296 – 0.641544 = 0.044752
6 0.68923 – 0.637575 = 0.0516
5 0.693 – 0.632 = 0.061
4.5 0.696097 – 0.628717 = 0.06734
4 0.699336 – 0.624449 = 0.0748
3 0.708732 – 0.612105 = 0.0966
2.5 0.71572 – 0.60273 = 0.11299
2 0.72556 – 0.589477 = 0.1361
According to these results, the thickness of the solid
lubricant layer 3 in Figure 6 decreases with the increase
of δ.
3 CONCLUSION
In the article a short survey of the theory of the
application of lubricants for the cold-drawing processes
of metals is given. The dies are presented in different
coordinate systems with the aim of more easily finding
the analytical solutions for the basic fluid mechanics
differential equations necessary for the calculation of the
lubricant-layer thickness. The solutions of the basic
equations are shown for liquid and solid lubricants, and
the combination of both, and the calculation of the
change of lubricant layer thickness in the section of the
deformation zone in the entry section of the working die.
For the case of the laminar flow of non-compressible
lubricants, the analytical solutions of Reynolds diffe-
rential equations give acceptable results. For the case of
insufficiently lubricated surfaces with a greater
roughness and hydrodynamic lubrication, it is not yet
possible to use analytical solutions of Reynolds
equations, and for this reason, mathematical modelling is
used32. Also, the effect of lubricant inertia forces is
considered for high drawing speeds used to increase the
angle significantly 33.
Symbols not explained in the text
Symbol Unity Significance
A m–1 Technological parameter
pH number Negative log of the concentration of
hydrogen ions
R0 – Radical of fat acids
Rw, RM m Parameter of the deformation zone and
die radius
p, p0 Pa Pressure in the lubricant layer and in
the entering section of the deformation
zone
x, y, z, r m Descartes coordinates and cylindrical
coordinates
µ, µ0 Pa s Lubricant dynamic viscosity for the
pressures p and p0
v0, vz m/s Metal drawing speed with movement
along the longitudinal axis z
h0, h m Lubricant thickness on the entering
section of the deformation zone and in
the die gap
γ m2/N Piezo-coefficient of the lubricant
viscosity
exp, tan 2.718... Basis of the natural log and tangent of
the metal-drawing die
hov m Lubricant layer thickness determined
using the variation calculation
σt0, σ0 N/m2 Metal yield stress and tensile strength
ν m2/s Kinematic viscosity
q m2/s Lubricant volume consumption per
length of the drawn metal
ρ kg/m3 Fluid density
εA m Lubricant layer thickness ahead of the
die entry gap
α, α∗ rad Drawing angle (a∗ is the rotated angle
related to a)
Ψ m Die gap that can be filled with
lubricant (difference between the
diameter of the die opening and the
sum of the rod + the lubricant
thickness
a m Initial tube size
b m b = a + eA
vz, u m/s Speed along the longitudinal axis z
and the metal drawing speed
z0 m Distance of the lubricant layer with
the thickness D from the initial point
lp, lK m Design characteristics of the die in the
deformation zone
τ Pa Tangential stress
τ0, K, m Grease rheological constants
γ0 Gliding speed
∆ m Lubricant layer thickness in Figure 3
θ m Ordinate of rupture of the lubricant
wedge
Translation from Croatian: prof. dr. Franc Vodopivec
4 REFERENCES
1 Pe{i} M., Milenkovi} V., Hladno izvla~enje `ica, {ipki i cevi,
Tehni~ka knjiga, Beograd 1965, 191–192
2 Mol~anov M. M, Nosov V. A., Romanec V. A., Metallurg 26 (1981)
7, 38–40
D. ]UR^IJA, I. MAMUZI]: THEORETICAL CALCULATION OF THE LUBRICATION-LAYER THICKNESS ...
26 Materiali in tehnologije / Materials and technology 41 (2007) 1, 21–27
3 ^ekmarev A. P., Mele{ko V. I., Mazur V. L., Stalj 39 (1969) 12,
1108–1111
4 Tra~ak S. V., Ka~ur V. I., Hohlova M. P., Stalj 49 (1979) 10,
789–791
5 Mamuzi} I., Drujan V. M., Teorija materijali tehnologija ~eli~nih
cijevi, Hrvatsko metalur{ko dru{tvo, Zagreb, 1996, 214
6 Jakovliev V. V., Semeljnickij B. L., Baljavin V. A., Stalj 42 (1972)
6, 82
7 [tanko V. M., Novikov V. G., Lipkin Ja. N., Stalj 41 (1971) 10, 933
8 Greben{}ikova A. Z., Stalj 29 (1959) 10, 932
9 Ivu{i} V., Tribologija, HMDT ISBN 96038-3-8, Zagreb 1998
Kolmogorov G. L., Gidrodinami~eskaja smazka pri obrabotke
metallov davlenniem, Moskva, Metallurgija 1986, 168
Kolmogorov V. L., Orlov V. L., Kolmogorov G. L., Gidrodinami-
~eskaja poda~a smazki, Moskva, Metallurgija 1975, 256
10 Zikov Ju. S., Izvestija ^ernaja metallurgija 30 (1987) 4, 52–53
11 Zikov Ju. S., Teorija prokati, teoreti~eskie problemi prokatnogo
proizvodstva, Metallurgija, Moskva 1975
12 Iharo{ B., Metalurgija 11 (1972) 3–4, 3
Iharo{ B., Metalurgija 12 (1973) 1, 31
Iharo{ B., Metalurgija 12 (1973) 2, 21
13 Kolmogorov G. L., Izveszija ^ernaja metallurgija 26 (1983) 10, 68
14 Mizuno T., Japon J. Soc. Techn. Plast 7 (1966) 6, 383–389
15 Christopherson D. G., Naylor H., Wire Ind., 22 (1955) 7, 260
Christopheron D. G., Naylor H., Proc. Inst. Mech. Engrs., (1955) 8,
169
Christopheron D. G., Naylor H., Wire Production 4 (1955) 5
16 Nedovizij I. N., Trudi konferenci po metiznomu proizvodstve 15–21
marta 1959. CBTI ^eljabinskogo sovnarhoza
17 Perlin I. L., [apiro V. Ja., [koljnikov E. L., Izvestija Cvetnaja
metallurgija 6 (1963) 5, 130–137
18 Kolmogorov V. L., Sb., In`inernie metodi ras~eta tehnologi~eskih
procesov obrabotki metallov davleniem, Metallurgizdat, Sverdlovsk,
1961
19 Kolmogorov G. L., Izvestija ^ernaja metallurgija 16 (1973) 8, 76
20 Kolmogorov G. L., Sjanov S. P., Izvestija ^ernaja metallurgija 30
(1987) 10, 35
21 Jurkovi} M., Hrie{ik A., Jurkovi} Z., Vitez I., Metalurgija 37 (1988)
3, 159–163
22 Grudev A. P., Dol`anskij A. M., Sigalov B. Ju., Kovalev V. S., Izve-
stija ^ernaja metallurgija 31 (1988) 2, 52–54
23 [evljakov V. Ju., Kolmogorov G. L., Izvsetija ^ernaja metallurgija
31 (1988) 10, 67–70
[evljakov V. Ju., Prevad~uk V. P., Izvestija ^ernaja metallurgija 31
(1988) 5, 61–65
Prevad~uk V. P., [evljakov V. Ju., Izvestija ^ernaja metallurgija 27
(1984) 11, 74–77
24 Kolmogorov V. L., Fedotov A. V., J. Mater. Process. Technol., 95
(1999) 1–3, 55–64
Kuznetsov S. A., Vinogradov S. I., Semenov S. Y., Graber E. A.,
Proizvod. Prokata July (1999) 7, 26–28
25 Belosevich V. K., Ionov S. M., Proizvod. Prokata August (1999) 8,
3–6
26 Mamuzi} I., Drujan V. M., Teorija materijali tehnologija ~eli~nih
cijevi, Hrvatsko metalur{ko dru{tvo, Zagreb 1996, 444
Sukurai M., Hiraya A., Hashimoto S., Techn. Rev., 80 (1999), 71–77
27 Zaccone D. C., Bodnar J. J., Elko R. G., Grivna J. M., J. M. Trans. J.
Mater. Manuf., 107 (1998), 26–24
Me D. M., Liu S. P., Zheng J. F., Met. Form. Technol. 20 (2002) 5,
29–32
Bao P., Cheu X. P., Jiany N. M., Met. Form. Technol. 20 (2002) 2,
8–10
Keun Y. T., Lee B. H., Wagoner R. H., J. Mater. Process. Technol.
130 (2002), 60–63
28 Liu Y. J., Tieu A. K., J. Mater. Process. Technol. 130 (2002),
202–207
Kim B. M., Kim D. H., Jeong D. J., Key Eng. Mater., (2003),
233–236, (Part I) 377–382
29 Blanchourd C. R., Crowinshield R. D., Johanson T. S., Laurent M.
P., Wear, 255 (2003) 1, 780–784
30 Artemov V. V., Demyanova V. I., Frolov V. I., Grunko B. N., Stal
73 (2003) 5, 59–63
31 Kr`an B., Vi`intin J., Biorazgradivo mazivo za duboko izvla~enje na
osnovu biljnih ulja, XXXVI Stru~no-znanstveni simpozij, Maziva
2003, Rovinj, Croatia, 22–24. 10. 2003
32 Kolmogorov V. L., Computers and Structures, 44 (1992) 1–2,
419–424
33 ]ur~ija D., Mamuzi} I., Metalurgija 44 (2005) 2, 113–117
D. ]UR^IJA, I. MAMUZI]: THEORETICAL CALCULATION OF THE LUBRICATION-LAYER THICKNESS ...
Materiali in tehnologije / Materials and technology 41 (2007) 1, 21–27 27

B. [U[TAR[I^ ET AL.: THE NOTCH EFFECT ON THE FATIGUE STRENGTH OF 51CrV4Mo SPRING STEEL
THE NOTCH EFFECT ON THE FATIGUE STRENGTH OF
51CrV4Mo SPRING STEEL
VPLIV ZAREZE NA TRAJNO NIHAJNO TRDNOST VZMETNEGA
JEKLA 51CrV4Mo
Borivoj [u{tar{i~1, Bojan Sen~i~2, Boris Arzen{ek1, Philippe Jodin3
1Institute of Metals and Technology, Lepi pot 11, 10000 Ljubljana, Slovenia
2[tore Steel, @elezarska cesta 3, 3220 [tore, Slovenia
3ENIM, University of Metz, France
borivoj.sustarsic@imt.si
Prejem rokopisa – received: 2006-05-17; sprejem za objavo – accepted for publication: 2006-11-27
Standardized and technological testing of the fatigue strength of spring steels is a complex and time-consuming, and therefore
expensive, task. The determination of Woehler’s (S-N) curves using a resonant pulsator is relatively fast and simple. In this
investigation the test is performed using standard Charpy V-notched specimens with the aim to obtain an appropriate
comparison with the results of technological tests on real springs. The steel springs were made of high-quality flat steel with a
smooth shot-peened surface, free of notches and with no large microstructure or surface defects. The performed investigation
can help with quality control and improvements to the properties of the steel springs. The paper presents a determination of the
fatigue strength of 51CrV4Mo spring steel using a resonant pulsator. The notch effect, the influence of the microstructure and
the surface quality are also discussed.
Keywords: fatigue strength, S-N curves, notch effect, resonant pulsator, spring steel
Standardizirani postopki dolo~evanja trajne nihajne trdnosti vzmetnih jekel in tehnolo{ko preizku{anje vzmeti so zahtevni, dragi
in dolgotrajni. Dolo~evanje Woehlerjevih (S-N) krivulj z resonan~nim pulzatorjem je relativno hitro in enostavno. V pri~ujo~i
raziskavi smo izdelali S-N-krivulje vzmetnega jekla 51CrVMo4 na standardnih Charpyjevih preizku{ancih z V-zarezo zato, da
bi ugotovili, ali je mo`na ustrezna primerjava z rezultati, dobljenimi z dragim in zamudnim dinami~nim preizku{anjem vzmeti.
Listnate vzmeti razli~nih oblik in dimenzij se izdelujejo iz plo{~atih profilov visokokvalitetnega vzmetnega jekla, ki imajo po
izdelavi gladko peskano povr{ino brez ve~jih geometrijskih ali mikrostrukturnih napak. Zato, da bi lahko ocenili pravo trajno
nihajno trdnost preiskovanega jekla, smo morali upo{tevati vpliv koncentracije napetosti, ki nastaja, ker imajo preizku{anci
V-zarezo. Uvajanje te preiskovalne metode v redno kontrolo kvalitete bi lahko pripomoglo k izbolj{anju kvalitete in razvoju
novih vrst vzmetnih jekel.
V ~lanku predstavljamo dolo~evanje trajne nihajne trdnosti vzmetnega jekla 51CrV4Mo z uporabo resonan~nega pulzatorja.
Predstavljen je na~in vrednotenja vpliva geometrijske zareze na trajno nihajno trdnost, kakor tudi vpliv mikrostrukture in
kvalitete povr{ine jekla.
Klju~ne besede: trajna nihajna trdnost, S-N krivulje, vpliv zareze, resonan~ni pulzator, vzmetno jeklo
1 INTRODUCTION
The [tore Steel plant is one of the largest European
producers of spring steels for heavy-duty trucks and
other automotive applications. Spring manufacturers use
different types of spring steels in different strength
levels, from 1300 MPa up to 1800 MPa. Parabolic
mono-leaf springs are situated at the highest strength,
quality and safety level, which is normally interesting for
all spring steel producers. For the required high quality
level the best spring steel with an appropriate fine-
grained microstructure, without segregations and large
inclusions, as well as surface defects is necessary.
Generally, spring manufacturers produce springs from
steel in the as-delivered (flat/round hot-rolled) condition.
The springs are then heat treated and tested. It is a
typical technological (structural) dynamic (fatigue) test,
based on a statistical safety analysis, performed directly
with the springs. A typical testing load is (760 ± 440)
MPa for parabolic springs and (800 ± 650) MPa for
high-quality springs in the frequency range 1–2 Hz.
Also, some other additional mechanical investigations
are usually performed, i.e., a determination of the
Vickers or Rockwell hardness, a Charpy impact test and
a standard tensile test.
However, the fatigue testing of springs after
manufacturing is a time-consuming and expensive task.
It is also too late to provide information to the steel
producer, who needs timely and appropriate information
about the steel’s quality in the production from batch to
batch. Standard fatigue-strength testing is performed on
smooth cylindrical or flat specimens. This can be
performed in the tension-compression, bend or torsion
modes. It is also expensive and time-consuming work,
acceptable as appropriate only for the research and
development of new types of steels. Often, steel
producers do not have the appropriate mechanical
servo-hydraulic fatigue-testing machine. However, they
need fast and reliable data about the produced spring
steel prior to delivery. Therefore, alternative solutions
are required. One of them is a determination of the
fatigue bend strength on Charpy V-notched specimens
with a high-frequency pulsator 1.
Materiali in tehnologije / Materials and technology 41 (2007) 1, 29–34 29
UDK 539.42:669.14.018.252 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 41(1)29(2007)
The fatigue strength depends on the loading mode
(tension, bend etc.), the variable loading magnitude
(amplitude, ratio R = Flower/Fupper or Mmin/Mmax), the shape
of the dynamic cycle, the frequency, the testing
conditions (temperature, atmosphere etc.), the surface
roughness and the notch effects. The dynamic structural
spring tests that simulate the spring’s real-load spectrum
are the most reliable, but also the most expensive and
time consuming task. The aim of this research was to
analyze the possibility of assessing a real spring’s life
and to transfer the results of high-frequency pulsator
testing on the spring’s real behavior.
The final quality of the manufactured spring does not
depend only on the quality of the steel. It also depends
significantly on the spring’s manufacturing procedure
(hot forming, i.e., rolling, bending, punching, eye
making), the final heat treatment and the shot peening.
Therefore, high-quality steel does not necessarily mean a
high-quality spring. The steel’s properties can be
significantly degraded during the manufacturing of the
spring if the spring’s manufacturing procedure is not
properly carried out. However, the overall spring quality
is evaluated on the basis of the final dynamic testing of
samples with a definite statistical probability. The steel
producer has to guarantee that the delivered spring steel
has the appropriate quality. Therefore, it must possess its
own well-documented in-process and final independent
quality control, including dynamic testing to be able to
define the phase in which the steel production is critical
regarding the quality in the event of a customer
complaint.
In this paper the testing of the fatigue strength of the
selected spring steel, 51CrV4Mo, with a resonant
pulsator is presented. The notch effect, the influence of
the microstructure and the surface quality are also
considered. The results are compared with the dynamic
testing of real commercial leaf springs made of the same
steel quality.
2 DETERMINATION OF S-N CURVES WITH A
HIGH-FREQUENCY PULSATOR
The testing was performed with a Cracktronic 70
(Rumul, Switzerland) high-frequency pulsator 1 at the
Institute of Metals and Technology, Ljubljana, Slovenia
(Figure 1). It is based on the accommodated loading
frequency for the investigated material (resonance). For
this reason it is also called a resonant pulsator. It can
serve for the simple fatigue of the specimen until its
fracture or for the much more sophisticated monitoring
of crack growth. In the latter case the specimen must be
equipped with a transducer technology sensor (KRAK-
gauges), which can determine the crack initiation and
follow the crack growth based on the cracking of a thin
foil adhered to the specimen. The sensor provides a
DC-voltage output proportional to the crack length. This
gauge method is appropriate for ductile structural steels,
Al and Ti alloys, when the elastic deformation is
followed by plastic yielding, and a steady transition from
stable to unstable crack growth is expected. In the case
of a hard and brittle material, such as tool, high-speed
and spring steels, when the fracture only occurs after
elastic deformation, with negligible yielding, crack
initiation is connected with fast, sudden unstable crack
propagation. In this case only the appropriate bending-
moment ratio (R = Mmin/Mmax) should be selected for the
applied Charpy V specimen and the number of cycles to
its fracture should be recorded. Using this approach the
so-called Woehler’s or S-N curve (stress S vs. number of
cycles N) can be determined 2. The resonant pulsator can
also serve for the formation of a fatigue crack of definite
size (length) to produce precracked specimens for the
determination of the fracture-mechanics parameters
(plain-strain fracture toughness KIc, the J integral or the
crack-opening displacement COD).
The Cracktronic 70 high-frequency pulsator is
designed for the dynamic bending of a standard Charpy
V-notched (CVN) specimen (Figure 2). The variable
bending moment is generated by an electromagnetically
driven resonator with a maximum swing angle of 2°
(± 1°). The maximum moment is 70 Nm (± 35 Nm)
acting in the range of S = 2l = 40 mm. The resonant
(working) frequency is approximately 180 Hz in the case
of steel. The pulsator is connected to a personal
computer (PC) and a Fractomat device, which serve for
the set up, the data acquisition and the control of the
loading conditions (Figure 1).
The dimensions of the CVN specimens are: total
length lt = 55 mm, width a = 10 mm, and height h = 8
mm. A standard V-notch with 2-mm depth, opening
angle 45° and root radius 0.25 mm was applied (see
Figure 2). The resistance Wx of a given cross-section is:
W
a h
x =
⋅ = ⋅
2 2
6
10 8
6
= 106.67 mm2 (1)
B. [U[TAR[I^ ET AL.: THE NOTCH EFFECT ON THE FATIGUE STRENGTH OF 51CrV4Mo SPRING STEEL
30 Materiali in tehnologije / Materials and technology 41 (2007) 1, 29–34
Figure 1: Cracktronik 70 resonant pulsator with the equipment for set
up, control, data acquisition, registration and recording of fatigue and
crack-growth tests
Slika 1: Resonan~ni pulzator Cracktronik 70 s pripadajo~o opremo za
registracijo, prenos in obdelavo podatkov
The net-bending stress for the applied dynamic
moment is then:
σ n
x
M
W
M
a h
= =
⋅
⋅
dyn dyn6
2
(2)
and the static moment is calculated according to:
Mstat = [Mdyn + (R·Mdyn)]/2 (3)
with the loading ratio R = Mmin/Mmax = 0.1 applied in
the performed experiments. The corresponding ampli-
tude is Ma:
Ma = Mdyn + Mstat (4)
For example, for the applied Mdyn= 60 Nm and R =
0.1 the static moment is Mstat = 33 Nm and the amplitude
Ma = 27 Nm, respectively. Conversely, with moments
one can express these with the nominal stresses: σdyn =
562.5 MPa, σstat = 309.4 MPa and σa = 253.1 MPa.
The fatigue strength σf is the largest stress deviation
for the stress amplitude value σa from a mean value σsr,
for which the material can last for an infinitely long time
(mandatory, more than 107 cycles) without plastic
deformation:
sf = σsr ± σa (5)
Fatigue strength is dramatically reduced if the
material contains a geometrical stress concentrator, such
as a notch, a hole or a large reduction of the area. CVN
specimens applied for testing the fracture toughness
using the Cracktronic 70 have a sharp V notch.
Therefore, it must be taken into consideration whether
one can assess the real fracture toughness of the spring
steel and the lifetime of the manufactured springs.
However, it also necessary to consider the influence of
metallurgical (inclusions, pores, decarburisation layer,
residual stresses, segregations etc.) and mechanical
factors (in-rolled scale, residuals of casting powder,
surface roughness, hard white layer etc.), which can also
act as stress concentrators and crack initiators, resulting
in a drastic reduction of the fatigue strength. The ratio
between the maximum σmax and nominal stress σn applied
to the real structure is called the theoretical elastic stress
concentration kt. It is also called the geometrical or shape
factor:
k t
n
=
σ
σ
max (6)
The theoretical calculations of kt are very complex,
possible only for simple geometries, and can be found in
the appropriate literature 7. Therefore, nowadays kt is
calculated exclusively by the FEM for more complex
geometries and loading configurations. The reduction of
fracture toughness due to the notch is experimentally
evaluated by a determination of the S-N curves of
notched and un-notched specimens. The fracture-
toughness reduction factor kf is then given by the ratio
between the fracture toughness of un-notched σf and the
notched specimens σfn:
k f
f
fn
=
σ
σ
(7)
It depends on the shape and the size of the notch, the
material and the load configuration. Neuber 2 improved
the calculation of the notch sensitivity by taking into
consideration these factors with the following equation:
k
k
r
f
f
fn
t= = +
−
+
σ
σ ρ
1
1
1 '/
(8)
where ρ' is a material constant that depends on the
material’s tensile strength and r is the radius of the
notch tip. The material’s notch sensitivity during fatigue
can then be finally expressed by the so-called
notch-sensitivity factor q:
q
k
k
=
−
−
f
t
1
1
(9)
3 PREPARATION OF THE CVN SPECIMENS
Standard CVN specimens (10 × 10 × 55) mm were
cut out and machined from flat (90 × 32) mm spring
steel, 51CrV4 type, in the as-delivered (hot-rolled)
condition, with Rockwell hardness HRc ≈ 30 and tensile
strength Rm ≈ 900 MPa. The fatigue of the V-notched
strength with the Cracktronic 70 was determined in the
as-delivered, and also in the as-heat-treated condition
with the specimens machined in two ways: by rough
milling only and with an additional fine grinding. A heat
treatment corresponding to the material’s highest
strength level of 1800 MPa was selected: austenitization
860 °C for 20 min, oil quenching and tempering at 350
°C for 60 min. The average values of the tensile proper-
ties were as follows: tensile strength Rm = 1810 MPa,
yield strength Rp0.2 = 1714 MPa, elongation A = 8 % and
B. [U[TAR[I^ ET AL.: THE NOTCH EFFECT ON THE FATIGUE STRENGTH OF 51CrV4Mo SPRING STEEL
Materiali in tehnologije / Materials and technology 41 (2007) 1, 29–34 31
a)
b)
Figure 2: Standard CVN specimen (a) and its positioning in the
Cracktronik pulsator (b)
Slika 2: Standardni Charpyjev preizku{anec z V-zarezo (a) in njegova
namestitev v ~eljusti resonan~nega pulzatorja Cracktronik (b)
reduction of area Z = 43 %. The Rockwell hardness was
HRc ≈ 50 and the Charpy impact energy 8 J to 9 J.
4 RESULTS AND DISCUSSION
Figure 3 shows the S-N curve of the investigated
steel in the as-delivered condition. The surface of the
specimens was only rough honed and not fine grinded.
The crack initiation and the fracture of the specimens
were clearly distinguished during the testing by the
gradual drop of the working frequency. The notch
fatigue strength is approximately 235 MPa. The obtained
value is very low and almost four times lower than the
tensile strength of steel in the as-delivered condition
(approximately 900 MPa). Usually, the fatigue strength
has to be 50–60 % of the tensile strength, and in this case
it was only 26 %. This difference can be mainly
attributed to the effect of the stress concentration caused
by the V-notch.
The next series of ten specimens was heat treated in
the above-mentioned conditions. The heat treatment was
performed before machining. However, the specimens
were only rough honed and not fine grinded. They were
then fatigued with the Cracktronic 70 and the S-N curve
was determined. The obtained notched fatigue strength is
extremely low (approximately 95 MPa), almost 20-times
lower than the tensile strength of the heat-treated steel
(approximately 1800 MPa). This is proof that, in
addition to the notch effect, the surface quality
(roughness) contributes significantly to the decrease of
the fatigue strength. It is especially important if the
samples are in the heat-treated condition, when a high
strength level of the spring steel is obtained. The
detrimental influence of the surface roughness on the
fatigue strength is well known 2-5, but such a large
influence was not expected. The SEM investigations
revealed the formation of an oxidation/decarburisation
layer during the heat treatment (Figure 4), indicating
that the very low fatigue strength cannot be attributed
only to the notch effect and the surface roughness, but
also to this layer. In order to clarify the effect of this
layer, the next ten specimens were machined with a
supplement of 0.2 mm, which was removed by fine flat
(surface roughness approximately Ra ≈ 0.3–0.5 µm and
profile (V-notch) grinding after the heat treatment. In
this way, the oxidation-decarburisation layer that was
eventually formed during the heat treatment was
removed.
The next step was the determination of the S-N curve
with the Cracktronic 70. Figure 5 shows the S-N curve
of the investigated steel in the heat-treated condition,
indicating the fatigue strength of about 310 MPa. The
obtained value is still approximately six times lower than
the tensile strength of the steel in the heat-treated
condition, but at the expected level if the notch effect is
considered.
To better understand the effect of stress concentration
caused by the notch on the fatigue strength a finite
element method (FEM) was applied in this investigation
to simulate three-point bending in the elastic loading
regime. However, this is only a rough approximation to
the real conditions of the experiment. The FEM
simulation, performed by CASTEM 6, has shown that the
net-stress concentration factor kt is between 3.8 and 3.9,
depending on the number of nodes applied at the notch
B. [U[TAR[I^ ET AL.: THE NOTCH EFFECT ON THE FATIGUE STRENGTH OF 51CrV4Mo SPRING STEEL
32 Materiali in tehnologije / Materials and technology 41 (2007) 1, 29–34
a
b
Figure 4: Micrographs of a heat-treated CVN specimen: a) SEM
fracture surface in the root of the V-notch and the surface of the
notched region, magnification 120 times, b) root of V-notch, visible in
the cross-section under a light microscope, magnification 100 times
Slika 4: Mikroskopska posnetka toplotno obdelanega CVN-preiz-
ku{anca: a) SEM-preloma v korenu V-zareze in povr{ina podro~ja v
zarezi; pove~ava 120-krat, b) koren V-zareze v prerezu, viden pod
opti~nim mikroskopom: pove~ava 100-krat
σ
σ
σ
m
a
x
Figure 3:Woehler’s curve of the investigated spring steel, 51CrV4, in
the as-delivered condition.
Slika 3: Woehlerjeva krivulja preiskovanega jekla 51CrV4 v izhod-
nem (vro~e valjanem) stanju.
root. It means that the maximum stress at the notch root
is approximately 3.85-times larger than the mean value.
This value of the stress-concentration factor is similar to
an experimentally verified value for standard CVN
specimens 7,8. If the experimentally obtained notch
fatigue strength is multiplied by this factor one can
predict the fatigue strength of a smooth (un-notched)
specimen of spring steel:
sf = kf · sfn » kt · σfn =3.85 · 310 = 1193.5 MPa (10)
The performed dynamic testing of the manufactured
springs at (760 ± 440) MPa and (800 ± 650) MPa (σf =
1200 MPa and 1450 MPa) and a frequency of 1 Hz
showed that the springs last from 7.9 · 104 to 1.2 · 105
cycles and 4.0 ⋅ 104 to 6.8 · 104 cycles, respectively.
Most frequently it was the second leaf of the springs near
eyes or holes that was broken by fatigue. One can
calculate from Figure 5 that the selected spring steel will
fracture for this number of cycles if the notched material
is exposed to a dynamic load from 312 MPa to 351 MPa.
Taking into account the notch effect, this corresponds
effectively from 1250 MPa to 1350 MPa, which agrees
very well with the performed dynamic testing of the
manufactured springs. For high-quality springs the re-
quired fatigue fracture limit is from 2.25 · 105 to 5.5 · 105
cycles at a higher loading level (σt = 1450 MPa). This
means that the steel quality has to be improved by
approximately 20 %, to σfn = 375 MPa (see Figure 5).
A relatively good agreement of the above
calculations with the results of the structural testing of
the real springs was obtained. This simple calculation
did not take into consideration the influence of the
material’s strength, the residual stresses, the size of the
inclusions and other effects. Therefore, a better and more
detailed analysis based on the FEM local-stress concept
and extreme value statistics 9,10 will be performed in the
future.
5 MICROSTRUCTURE INVESTIGATION AND
FRACTOGRAPHY
Microstructure investigations under light (LM) and
scanning electron (SEM) microscopes were also
performed. Standard metallographic specimens were
made and the microstructures were observed at different
magnifications in the rolling and perpendicular
directions. Figures 6a and 6b show a typical
ferrite-pearlite microstructure of the spring steel in the
as-delivered condition. However, the steel has a fine
structure of tempered martensite with clearly visible
segregations of the main alloying elements (Cr and Mo)
after the heat treatment (Figures 7a and 7b). Some
sulphide (MnS), alumo-silicate and other hard inclusions
were also found (Figure 7b). All these defects can
significantly contribute to lower fatigue strength of the
steel.
Due to the significantly higher depth resolution the
SEM is much more appropriate for observing the
fractured surfaces than the LM. Figures 8a and 8b show
SEM micrographs of typical fractured surfaces of the
CVN specimens after fatigue testing with the
Cracktronic 70 device. The final fracture is quasi-ductile.
The fractured surfaces are striated due to the fatiguing of
the material. The cracks also spread perpendicularly to
the notch tip and are initiated on the larger hard particles
(Figure 8b).
B. [U[TAR[I^ ET AL.: THE NOTCH EFFECT ON THE FATIGUE STRENGTH OF 51CrV4Mo SPRING STEEL
Materiali in tehnologije / Materials and technology 41 (2007) 1, 29–34 33
Figure 5:Woehler’s curve of the investigated spring steel, 51CrV4, in
the as-heat-treated condition; fine grinded specimens
Slika 5:Woehlerjeva krivulja preiskovanega vzmetnega jekla 51CrV4
v pobolj{anem stanju; fino bru{eni preizku{anci
a
b
Figure 6: Microstructure of investigated spring steel, 51CrV4, in
as-delivered condition: a) magnification 100 times and b) magnifi-
cation 200 times; LM, etched in nital
Slika 6: Mikrostruktura preiskovanega vzmetnega jekla 51CrV4 v
vro~e valjanem stanju: a) pove~ava 100-krat in b) pove~ava 200-krat;
opti~ni mikroskop, jedkano v nitalu
6 CONCLUSIONS
The results of the performed investigations showed
that it is possible to determine the fatigue strength of
spring steels with a resonant pulsator using Charpy V
test specimens. They must be properly prepared with a
fine flat and profile grinding after the heat treatment.
From the obtained S-N curves and the determined
notched fatigue strength one can simply predict the real
fatigue strength of the spring steel by the application of
the corresponding stress-concentration factor.
The significance of the notch and the surface
roughness for the results is clearly demonstrated by the
performed investigations. However, other defects, such
as an oxidation/decarburisation layer, segregations and
inclusions can also significantly decrease the fatigue
strength of the steel and the manufactured spring. The
influence of the segregations and the inclusions in this
type of steel, as well as the influence of residual stresses
caused by the machining and shot-peening of the springs
will be analyzed and evaluated in the near future.
7 REFERENCES
1 Rumul: Operating Instructions, 7.0 kN.cm resonant testing machine
Cracktronic, Russenberger Prüfmaschinen AG, CH, 1992 and web
page: (http://www.rumul.ch/)
2 G. E. Dieter: Mechanical Metallurgy, Second and third Edition,
McGraw-Hill Book Co., NY, 1976/1986
3 A. Kveder et al: Metalur{ki priro~nik, Tehni{ka zalo`ba Slovenije,
Ljubljana, 1972
4 B. Kraut: Strojni{ki priro~nik, Tehni{ka knjiga Zagreb, 1964
5 G. Pluvinage, M. Gjonaj: Notch Effects in Fatigue and Fracture,
NATO Science Series, Vol.11, 2001
6 CASTEM, FEM code, home page address: http://www-cast3m.
cea.fr/cast3m/index.jsp
7 P. Jodin, C. Cera: Asymmetrical notches in plates, Mater. Tehnol.,
37 (2003) 6, 341–346
8 F. Vodopivec, B. Arzen{ek, D. Kmeti~, J. V. Tuma: On the Charpy
Fracturing Process, Mater. Tehnol., 37 (2003) 6, 317–326
9W. Eichlseder: Fatigue analysis by local stress concept based on
finite element results, Computers and Structures, 80 (2002),
2109–2113
10 E. Joossens: Extreme Value Statistics: Second-Order Models and
Applications to Metal Fatigue, Ph. D. Thesis, Leuven, Belgium, 2006
B. [U[TAR[I^ ET AL.: THE NOTCH EFFECT ON THE FATIGUE STRENGTH OF 51CrV4Mo SPRING STEEL
34 Materiali in tehnologije / Materials and technology 41 (2007) 1, 29–34
a
b
Figure 7: Microstructure of investigated spring steel, 51CrV4, in
heat-treated condition: a) magnification 100 times and b) magnifi-
cation 200 times; LM, etched in nital
Slika 7: Mikrostruktura preiskovanega vzmetnega jekla 51CrV4 v
pobolj{anem stanju: a) pove~ava 100-krat in b) pove~ava 200-krat;
opti~ni mikroskop, jedkano v nitalu
a
b
Figure 8: SEM micrograph of fractured surface of investigated spring
steel in the as-heat-treated condition: a) magnification 100 times and
b) magnification 6500 times
Slika 8: SEM-posnetek prelomne povr{ine po utrujanju CVN-preiz-
ku{anca iz preiskovanega vzmetnega jekla 51CrV4 v pobolj{anem
stanju: a) pove~ava 100-krat in b) pove~ava 6500-krat
N. GUBELJAK ET AL.: AN INTEGRITY ANALYSIS OF WASHING-MACHINE HOLDERS
AN INTEGRITY ANALYSIS OF WASHING-MACHINE
HOLDERS
ANALIZA CELOVITOSTI NOSILCA KADI V PRALNEM STROJU
Nenad Gubeljak1, Matej Mejac2, Jozef Predan1
1University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia
2Diploma student employed at Gorenje, gospodinjski aparati, d. d., Partizanska 12, 3320 Velenje, Slovenia
nenad.gubeljak@uni-mb.si
Prejem rokopisa – received: 2006-05-17; sprejem za objavo – accepted for publication: 2006-11-13
This paper deals with a structure-integrity analysis of a holder designed to carry the cross of a washing machine. Premature
fracture of the holder occurred during mechanical tests of the washing machine in the factory. In order to prevent fracture, the
task was to determine the causes of the premature fracture of the holder and estimate the suitability of a new design of holder
cross in the washing machine. The input data for the structure-integrity analysis were obtained from mechanical testing of the
materials used. A stress-and-strain analysis of the holder’s limit load was performed using finite-element modelling of the
holder. Dynamic tests of holders with two different thicknesses were made on a servo-hydraulic machine in order to find
dynamically the strength and endurance of the holder. The fracture behaviour of the holders is defined by the initiation and
propagation of a crack. The determined behaviour confirmed that a new design of holders (with thickness t = 2.5 mm instead of
t = 1.5 mm) reduces the stress concentration in the critical region. Consequently, the new holder, subjected to the same dynamic
load, can last for more cycles until it breaks. The total number of cycles exceeded the requirements set for industrial testing.
Key words: structure-integrity assessment, fracture-toughness testing, high-cycle fatigue, washing-machine holder
V ~lanku je predstavljena analiza celovitosti kri`nega nosilca kadi pralnega stroja. Pred~asna poru{itev nosilca je nastopila med
mehanskim preizku{anjem pralnega stroja v podjetju. Z namenom, da se prepre~i pred~asna poru{itev nosilca, so bili raziskani
vzroki za poru{itev in ocenjena je bila primernost nove zasnove nosilca kri`a kadi pralnega stroja. Vhodni podatki za oceno
celovitosti so bili dobljeni na osnovi mehanskih preizkusov materialov. Napetostna in deformacijska analiza nosilca pri mejnem
stanju obremenitve je bila opravljena z numeri~nim modeliranjem in izra~unom po metodi kon~nih elementov. Dinami~ni
preizkusi dveh nosilcev z razli~nima debelinama ob enakem vpetju, kot je to v pralnem stroju, so bili opravljeni na
servohidravli~nem preizku{evalnem stroju. Na osnovi opravljenih preizkusov je bila dolo~ena dinami~na trdnost in vzdr`ljivost
nosilcev. Lomno vedenje nosilcev je bilo ocenjeno glede na lomno `ilavost materiala med utrujenostno rastjo razpoke kot tudi
glede na iniciacijo kon~nega, nestabilnega loma nosilca. Dobljeni rezultati potrjujejo, da nova zasnova nosilca z debelino t = 2,5
mm namesto t = 1,5 mm ob posledi~no spremenjenem polmeru zakrivljenosti zmanj{a koncentracijo napetosti v kriti~nem delu.
Tako je pokazano, da novi nosilec pod enako obratovalno obremenitvijo prestane ve~je {tevilo ciklov do kon~ne poru{itve, kot
je predpisano za preizkuse pri preverjanju kontrole kakovosti v podjetju.
Klju~ne besede: ocena celovitosti konstrukcij, preizku{anje lomne `ilavosti, visokocikli~no utrujanje, nosilec kadi pralnega
stroja
1 INTRODUCTION
Holders for carrying the cross of a washing
machine’s drum are dynamically loaded components, see
Figure 1. The premature fracture of the holder can cause
severe damage to other mechanical and electrical parts in
the housing of the washing machine. Therefore, the
integrity of the holder is essential for the safe and
reliable service of the whole washing machine.
The mechanical testing of a washing machine with an
eccentric load was performed in the factory. The results
showed that the number of cycles without fracture or
crack formation is insufficient for the quality-control
requirements. A failure analysis and inspection of the
fractured parts showed that the initial fracture occurred
in the central holders of the cross, while the fracture of
the outer holders occurred at the end, when the inner
holder was already broken, see Figure 2. Therefore, the
aim of this study was to carry out a stress-strain analysis
and a structure-integrity analysis of the inner holders of a
washing machine’s drum.
Materiali in tehnologije / Materials and technology 41 (2007) 1, 35–40 35
UDK 539.55:620.17:669.14 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 41(1)35(2007)
Figure 1: Holder cross welded on the drum of a washing machine
Slika 1: Kri`ni nosilec kadi bobna pralnega stroja
2 MECHANICAL PROPERTIES
The mechanical testing was performed on a steel
sheet of the same material and the same thickness as
used for the inner holders of the cross of the
washing-machine drum. The nominal parent metal is
DC03. The tensile mechanical properties were measured
on flat tensile specimens with geometries according to
the DIN10125 standard. The obtained mechanical
properties are shown in Table 1.
Fatigue-crack growth and fracture-mechanics testing
were performed on a middle-cracked tensile specimen,
M(T) 1, with the geometry shown in Figure 3. The initial
notch of 0.5 mm in the hole was made with a razor
blade. The growth of the fatigue crack was followed on
both sides of the central hole. The fatigue loading of the
sheets (t = 2.5mm) was performed in load control with a
ratio R = Fmin/Fmax = 0.21 and frequency 20 Hz, Fmax =
25.4 kN. The Paris-Erdogan relationship 2 was used to
describe the fatigue-crack growth law, as shown in
Figure 4.
The fracture-toughness measurement 3 was per-
formed on cracked specimens with measurements of
crack-mouth opening displacement (CMOD) in the
specimen’s symmetry loading line, as shown in Figure
N. GUBELJAK ET AL.: AN INTEGRITY ANALYSIS OF WASHING-MACHINE HOLDERS
36 Materiali in tehnologije / Materials and technology 41 (2007) 1, 35–40
Figure 2: Broken outer holder without fatigue-crack propagation
Slika 2: Zlomljeni zunanji nosilci brez vidne utrujenostne rasti
razpoke
Table 1: Obtained tensile mechanical properties for the parent material (DC03)
Tabela 1: Dobljeni rezultati za mehanske lastnosti za osnovni material (po oznaki DC03)
Thickness, t = 2.0 mm Thickness, t = 2.5 mm Standard
prescription01 02 01 02
(R0,005/Rp0,2)/MPa 152/203 184/217 135/188 123/188 Rp0.2 max = 240
Rm/MPa 300 306 284 286 270-370
E/MPa 201012 202516 188284 159913 210000
Table 2: Obtained fracture-toughness values for parent material (DC03)
Tabela 2: Dobljeni rezultati za lomno `ilavost za osnovni material (DC03)
t/mm W/mm a/mm σp0.2/MPa σy/MPa KI,i/MPa m1/2 Fi/kN CTODpl,m/mm CTODm/mm KI,mat/MPa m1/2
2.0 140 34.1 210 180 11.23 18.5 0.595 0.599 145.61
2.5 140 34.6 188 130 17.918 33.6 0.995 1.004 205.86
( )/
Figure 4: Results of fatigue-crack growth rate for left- and right-side
measurements (specimens with t = 2.5mm)
Slika 4: Rezultati hitrosti utrujenostne rasti razpoke za meritev na levi
in desni strani izvrtine v preizku{ani plo{~i z debelino t = 2,5 mm
Figure 3: Middle-cracked tensile specimen (t = 2.5 mm)
Slika 3: Plo{~a s sredinsko razpoko ob izvrtini za natezni preizkus (t =
2,5 mm)
5. During the test compliance the unloading method was
used to observe stable crack-growth extension. The
recorded data are plotted in Figure 6. The results of the
fracture mechanics testing are listed in Table 2.
3 TENSILE AND FATIGUE TEST
Tensile and fatigue tests were performed on the same
holder (thickness and geometry) as was tested in the
factory. The holder was welded with eight spot welds, as
with the washing drum, but in the laboratory case this
was on a pad for testing, as shown in Figure 7. The
holder was tested statically with tensile pulling until
fracture, as shown in Figure 8. A graph of load vs.
stroke was recorded, as shown in Figure 9.
The fatigue pull testing of both holders (with t = 1.5
mm and t = 2.5 mm) was performed with the same
N. GUBELJAK ET AL.: AN INTEGRITY ANALYSIS OF WASHING-MACHINE HOLDERS
Materiali in tehnologije / Materials and technology 41 (2007) 1, 35–40 37
CMOD /mm
F
/k
N
Figure 6: Measured data load vs. CMOD (t = 2.5 mm)
Slika 6: Izmerjeni podatki v odvisnosti obremenitve in odpranja ustja
razpoke (t = 2,5 mm)
a b c
Figure 5:Measurement of CMOD values for middle-cracked tensile specimen (t = 2.5 mm); a) start of test b) stable crack initiation c) end of test
Slika 5: Meritev odpiranja ustja razpoke (ang. CMOD) med nateznim obremenjevanjem plo{~e s sredinsko razpoko (t = 2,5 mm); a) za~etek
preizkusa, b) za~etek stabilne rasti, razpoke c) konec preizkusa
F
/k
N
, /mml
Figure 9: Load vs. stroke during static pulling test of holder
Slika 9: Obremenitev v odvisnosti od pomika, ki je posneta med
stati~nim trgalnim preizkusom nosilca
Figure 7: Holder welded by spots on pad for testing
Slika 7: Nosilec, zavarjen s to~kovnimi zvari na podlago za preiz-
ku{anje
Figure 8: Static pulling test of holder
Slika 8: Stati~ni trgalni preizkus nosilca, ki je zavarjen na podlago za
preizku{anje
equipment. Since the fatigue-behaviour analysis was
performed only to compare two holders (different in
thickness and root radius), the same fatigue load was
chosen (Fmax = 2 kN, R = –1). The fatigue crack appeared
in the holder (t = 1.5 mm) in the expected region, like
during the washing-machine test. The fatigue crack did
not appear in the holder (t = 2.5 mm) after 1 million load
cycles. As a result, a higher maximum fatigue load (Fmax
= 3.5 kN) was used and the fatigue crack appeared in
same region, as shown in Figure 10.
The fatigue-crack growth sensitivity was estimated
for both holders by using fatigue-crack growth rate
testing results, e.g., from Figure 4 for t = 2.5 mm.
The range of the fatigue stress-intensity factor was
determined using
∆K K Kmax max min= − (1)
since the loading ratio corresponds to the range of the
fatigue stress-intensity factor is
∆K Kmax max= 2 (2)
A finite-element calculation shows that in the root
region of the holder both tension stress and shear stress
appear. The relevant maximum stress-intensity factor is
K K Kmax = +I II
2 2 (3)
where KI and KII are determined using equations 6:
K aI = σ π (4)
where s is the maximum tensile stress determined by FE
analysis, a is the initial crack length in the holder (e.g.,
a = 1 mm).
K II = − +( . .4886 11383
2ξ ξ +28.198ξ −38.563ξ3 4
+20.555ξ )(τ5 πa ) (5)
t is the maximum shear stress in the crack plane; it is
also determined by FE analysis and x is the ratio
between the crack length and the thickness.
Calculated values (Table 3) show that for the same
tensile loading of the screw at the holder the SIFs are
more than three times lower for the holder with thickness
t = 2.5mm than for the holder with t = 1.5 mm.
4 NUMERICAL MODELLING
The numerical modelling and the calculation using
the finite-element method was carried out for the inner
holder. In order to determine the stress-strain profile
along the crack propagation line in the holder a
numerical analysis was performed, Figure 12. The
stress-strain analysis in the direction perpendicular to the
fatigue crack front was performed using Pro/Mechanica
software (a module of the Pro/Engineer software). An
additional contact surface on the 3D solid model was
defined under the head’s screw. The boundary conditions
and the finite-element mesh with tetra-elements 5 is
shown in Figure 13. The stress fields (von Mises) for the
same applied pressure on the contact surface are shown
in Figure 14. It is clear that the stress profile and the
stress peak depend on the radius of the holder. The stress
distribution along the fatigue-crack propagation line is
shown in Figure 15, where the most critical value is
N. GUBELJAK ET AL.: AN INTEGRITY ANALYSIS OF WASHING-MACHINE HOLDERS
38 Materiali in tehnologije / Materials and technology 41 (2007) 1, 35–40
σy
σy
τxy
τxy
Root direction, /mmlR
(
,
)
/M
P
a
σ
τ
Figure 11: Maximum tensile and shear stress along the uncracked
root of the holder calculated using the FEM
Slika 11: Porazdelitev osnih in stri`nih napetosti vzdol` kriti~nega
upognjenega dela nosilca
Figure 10: Fatigue crack at root region of holder (t = 1.5 mm)
Slika 10: Med dinami~nim utrujenostnim obremenjevanjem nosilca se
je pojavila razpoka v kriti~nem upognjenem delu nosilca (t = 1,5 mm)
Table 3: Stress-intensity factor values for the holder
Tabela 3: Vrednosti faktorja intezivnosti napetosti v kriti~nem upognjenem delu nosilca
Material
data
Load Stress intensity factors at holder
t/mm KIm at/MPa m1/2 ∆Kcrit/MPa m1/2 σy/MPa τ/MPa a/mm KI/MPa m1/2 KII/MPa m1/2 ∆Kmax/MPa m1/2
1.5 145.61 291.22 165 165 1.0 9.24 15.19 35.56
2.5 205.86 411.72 65 65 1.0 3.64 4.23 11.16
achieved for the model with thickness t = 1.5 mm and
root radius R = 0.5 mm. It is obvious that the specimen
with t = 2.5 mm and root radius R = 2 mm has the lowest
stress values along the fatigue-crack growth path.
5 DETERMINATION OF THE FAILURE LOAD
Determining the fatigue load of the holder that
appears in the washing machine during the test is
difficult. It was only known that a fatigue crack appeared
and the entire holder was broken when the critical
N. GUBELJAK ET AL.: AN INTEGRITY ANALYSIS OF WASHING-MACHINE HOLDERS
Materiali in tehnologije / Materials and technology 41 (2007) 1, 35–40 39
Figure 14: Calculated stress (von Mises) at the surface of the
numerical model
Slika 14: Izra~unane primerjalne napetosti (von Mises) na povr{ini
numeri~nega modela
Figure 15: Distribution of stresses (von Mises) along the crack path in
the root of the holder
Slika 15: Porazdelitev napetosti (von Mises) vzdol` upognjenega
dela, v katerem je napredovala razpoka
(a)
(b)
Figure 13: Boundary conditions and finite-element mesh with
tetra-elements; a) boundary condition, loading and symmetry line; b)
detail of mesh with tetra elements
Slika 13: Robni pogoji in umre`enje nosilca za izra~un po metodi
kon~nih elementov; a) robni pogoji, obremenitev in simetrijska
ravnina za numeri~ni izra~un, b) detajl mre`e s tetraedrskimi elementi
Figure 12: Critical path for fatigue-crack growth on the inner holder
Slika 12: Napredovanje utrujenostne razpoke vzdol` kriti~nega dela
nosilca
fatigue-crack length was achieved after a certain number
of cycles. In this case the number of cycles contains an
initiation stage and a fatigue-crack propagation stage.
The longest critical crack length in the holder tested in
the factory was measured in the fractured surface of the
holder (acrit = 20.9 mm).
The difference between the fatigue-crack surface and
the final ductile failure was obvious. In order to
determine the failure load the SINTAP procedure (level
1) was performed by using our own software 6,7. The
calculation shows that the final failure of a single holder
appeared at the moment Mcrit = 4.9 N m. The result is
shown in Figure 16; it corresponds to a tensile load in
the screw of 198 N. Figure 16 shows that failure
occurred with significant plasticity of the non-fractured
ligament of the holder. This confirms the assumption
that failure occurs under plane-stress conditions. The
failure occurred at a low stress-intensity factor value
(low loading ratio, Kr).
6 CONCLUSION
The inner holder of a washing machine is a critical
part. This holder is subjected to dynamic loading with
R = –1. The critical part of the holder is the root region,
which is deformed with a different radius, depending on
the thickness of the metal sheet. In the first prototype of
the washing machine the holder had a thickness of t =
1.5 mm and a root radius of R = 0.5 mm. The premature
fracture of the holder occurred in the factory. The
replacement holder had a thickness t = 2.5 mm and a root
radius R = 2 mm. In the paper the analyses of the stress
concentration were performed in order to determine the
fatigue durability of the holder. On the basis of the
experimental results of the material testing, the fatigue
and fracture mechanics parameters and also the
finite-element analysis of the critical part of holder, it is
possible to assess the SIF, and on the basis of the critical
crack length in the holder the failure load that occurred
in the holder during the washing-machine testing in the
company.
However, the new holder subjected to the same
dynamic load can survive a larger number of cycles until
failure, where the total number of cycles exceeds the
industrial testing requirements.
7 REFERENCES
1 ASTM E 647-99. Measurements of Fatigue Crack Growth Rates,
1999
2 Paris, P., Erdogan, F., A Critical Analysis of Crack Propagation
Laws, Journal Basic Engineering, (1963), 528–534
3 Schwalbe, K-H., Neale B. K., Heerens J. The GKSS test procedure
for determining the fracture behaviour of materials, EFAM GTP 94,
Geesthacht, 1994
4 Carpinteri A., Brighenti R., Huth H-J, Vantabori S.: Fatigue growth
of surface crack in welded T – joint. International Journal of Fatigue
(2005)
5 La{ V., Vacek V., Rehounek L.: Void model-numerical simulation
and comparison with experiment. 41st International Conference
Experimental Stress Analysis 2003, Milovy 2003, Czech Republic
6 Gubeljak N., Valh T.: SINTAP-Software for Engineering Structure
Integrity Analysis, 2004
7 SINTAP: Structural integrity assessment procedure. Final Report.
EU-Project BE 95-1462. Brite Euram Programme, Brussels, 1999
N. GUBELJAK ET AL.: AN INTEGRITY ANALYSIS OF WASHING-MACHINE HOLDERS
40 Materiali in tehnologije / Materials and technology 41 (2007) 1, 35–40
Figure 16: Determination of critical loading of washing machine’s holder
Slika 16: Dolo~itev kriti~ne obremenitve kri`nega nosilca kadi pralnega stroja po postopku SINTAP
D. KOZAK ET AL.: THE EFFECT OF A MATERIAL’S HETEROGENEITY ...
THE EFFECT OF A MATERIAL’S HETEROGENEITY ON
THE STRESS AND STRAIN DISTRIBUTION IN THE
VICINITY OF A CRACK FRONT
VPLIV HETEROGENOSTI MATERIALA NA PORAZDELITEV
NAPETOSTI IN DEFORMACIJE V BLI@INI KONICE RAZPOKE
Dra`an Kozak1, Nenad Gubeljak2, Jelena Vojvodi~ Tuma3
1University of Osijek, Mechanical Engineering Faculty, Trg I. Brli}-Ma`urani} 2, 35000 Slavonski brod, Croatia
2University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia
3Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana, Slovenia
1dkozak@sfsb.hr, 2nenad.gubeljak@uni-mb.si, 3jelena.tuma@imt.si
Prejem rokopisa – received: 2006-05-17; sprejem za objavo – accepted for publication: 2006-11-27
In this investigation a high-strength low-alloyed (HSLA) steel of the 700-MPa strength class was used as a base material. A
butt-welded joint with X grooves was produced with an overmatched weld metal that had a yield strength 23 % greater than that
of the base material. Three-point bending B × 2B test specimens (thickness B = 36 mm) were extracted from the welded joints.
The straight crack front (a0 = 35,571 mm) crosses different microstructures through the thickness of the specimen.
Both fracture-mechanics tests and a 3D finite-element analysis were performed. The CTOD parameter of the fracture toughness
was measured and calculated numerically. The loading level at which stable crack growth occurred was also determined. The
comparison of the experimental and numerical values of the CTOD (d5) displacements showed good agreement. The principal
stress, σy, the Mises equivalent stress, σeq, and the plastic equivalent strain, εpl, eq, at the moment of crack initiation were studied
for six equidistant layers from the surface to the mid-thickness of the specimen. The dependence of the crack-opening stress
(denoted as σx in this paper) on the local fracture-toughness value was considered as the parameter which determines the
direction of the crack-front propagation. The results show that the lower strength of the base metal contributes to the crack-path
deviation in the mid-thickness of the specimen. Both the crack-path deviation and the higher toughness of the base metal
increase the critical fracture toughness value of the welded joint.
Key words: strength overmatched welded joint, crack, stress and strain distribution, finite element analysis
V tej raziskavi je bilo kot osnovni material uporabljeno visokotrdno malolegirano jeklo (HSLA) s trdnostjo 700 MPa za ~elni
zvar z X-`lebovi je bil pripravljen in uporabljen deponirani material z mejo plasti~nosti, ki je bila za 23 % ve~ja kot pri
osnovnem materialu. Tri-to~kovni upogibni preizku{anci B × 2B (debelina B = 36 mm) so bili izrezani iz zvarjenega spoja. ^elo
ravne razpoke (a0 = 35,571 mm) seka skozi debelino preizku{anca razli~ne mikrostrukture. Opravljeni so bili lomnomehanski
preizkusi in analiza 3D kon~nih elementov. CTOD-parameter mehanike loma je bil izmerjen in numeri~no izra~unan. Dolo~en
je bil tudi nivo obremenitve, pri katerem je nastala stabilna rast razpoke. Primerjava eksperimentalnih in numeri~nih vrednosti
za CTOD (d5)-premike je pokazala dobro ujemanje. Glavna napetost σy, ekvivalentna Mises-napetost σeq in ekvivalentna
plasti~na deformacija εok-eq so bile opredeljene za 6 med seboj enako oddaljenih plasti od povr{ine do sredine preizku{anca.
Odvisnost med napetostjo odprtja razpoke (ozna~eno z σx v tem ~lanku) in lokalno vrednostjo za `ilavost loma je upo{tevana
kot parameter, ki dolo~a smer propagacije ~ela razpoke. Rezultati ka`ejo, da manj{a trdnost osnovnega materiala povzro~i
deviacijo poteka razpoke v sredini preizku{anca. Deviacija poti razpoke in ve~ja `ilavost osnovnega materiala pove~ata `ilavost
loma zvarnega spoja.
Klju~ne besede: trdnost spoja z ve~jo trdnostjo vara, razpoka, porazdelitev napetosti in deformacije, analiza kon~nih elementov
1 INTRODUCTION
The heterogeneity of the materials in a welded joint
on the macroscopic level has been made possible by
modern joining techniques such as laser welding and
electron-beam welding 1. Such inhomogeneity in the
materials can also be intentional, for example, when
using functionally graded materials 2. If a component
made from such dissimilar materials has defects, it
should be assessed from the fracture-mechanics point of
view. The knowledge of the stress distribution can be
very useful for calculating the fracture-mechanics
parameters as part of the SINTAP defect-assessment
procedure 3. It also helps to determine numerically the
yield load solution 4. To evaluate the fracture toughness
and the mechanicsms of failure, the stress-strain field at
cracks located in the joint must be understood 5. An
asymmetry in the distribution of the stresses in the
vicinity of the crack tip could influence the crack-path
deviation from its original direction. The usual failure
criterion for a homogeneous material is that the crack
grows in a direction perpendicular to the maximum
principal stress. In a multiphase material, the fracture
criterion based on the ratio of the crack opening stress to
the material toughness distributed in front of the crack
tip is proposed for determining the direction of the crack
propagation of a mixed-mode fracture problem in 6.
Therefore, the stress-strain distribution near the crack
front due to the increasing load is very important for the
better understanding of the whole fracture process.
Experimental methods applied to follow the strain fields
(e.g., the object grating method) are very accurate, but
Materiali in tehnologije / Materials and technology 41 (2007) 1, 41–46 41
UDK 539.42:621.791.05:669.14 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 41(1)41(2007)
limited to the visible surface of the specimen 7. As a
result a finite-element analysis becomes very useful.
Although many factors influence the yielding in
cracked welded components 8, the aim of this paper is to
show how the yield strength of overmatched weld metal
affects the stress and strains fields. To do this a B × 2B
three-point bend specimen with an X-weld cracked
through the thickness of the specimen was considered.
Both 3D finite-element calculations and experiments
were performed.
2 TESTING OF FRACTURE-TOUGHNESS
SPECIMENS
B × 2B three-point-bend fracture-toughness speci-
mens (thickness B = 36 mm) were extracted from the
welded plate (Figure 1) and prepared for fracture-
mechanics testing. HSLA steel with yield strength of 676
MPa was used as the base material (BM). The X-welded
joint was produced using an overmatched weld metal
(WM) with a yield strength of 833 MPa. In this case the
yield-strength mismatch factor, defined as the ratio M =
Rp0,2
WM /Rp0,2
BM , was equal to M = 833/676 = 1.23. The
straight crack front passed over the overmatched weld
metal near the surfaces, while the base metal of lower
strength was located in the middle of the specimen
(Figure 2).
During the CTOD (δ5) fracture-toughness testing
unstable crack propagation occurred after some initial
stable crack growth. Fractographic and metallographic
analyses showed that the crack path started to deviate in
the mid-thickness of the specimen, where the crack front
passes from the heat-affected zone (HAZ) to the softer
base metal. For this reason, the finite-element calculation
was performed to provide an insight into the state of the
stresses and strains at the moment of onset of the stable
crack growth.
3 FINITE-ELEMENT ANALYSIS
The geometry of the weld with the specified location
of the crack is depicted in Figure 3. The finite-element
calculation was performed on a solid numerical model.
D. KOZAK ET AL.: THE EFFECT OF A MATERIAL’S HETEROGENEITY ...
42 Materiali in tehnologije / Materials and technology 41 (2007) 1, 41–46
Figure 3: Geometry of the weld
Slika 3: Geometrija zvara
Figure 2: B × 2B fracture-toughness specimen
Slika 2: B × 2B-preizku{anec za `ilavost loma
Figure 1: Welded plate from which specimens were extracted
Slika 1: Zvarjena plo{~a, iz katere so bili izdelani preizku{anci
Figure 4: FE mesh of the weld part
Slika 4: FE-mre`a zvarjenega dela
Taking into account the thickness symmetry of the
specimen, only one half is modelled. A standard 20-node
structural solid element from the ANSYS 9 library was
used. Commercial programs specialised in modelling
crack fronts, e.g., Zencrack or FEA Crack, were not
applied. The free-meshing technique was applied, with a
size of 100 µm for the first fan of elements (Figure 4).
The nodes, a distance of 2.5 mm from both sides of the
crack tip, should be foreseen so as to be able to calculate
the CTOD (δ5) parameter of the fracture toughness for
each load up to the load at which stable crack growth
occurs. The load is applied incrementally as the pressure
on the two rows of mid-plane elements. The total
numbers of elements and nodes were 5450 and 24384,
respectively. Both materials in the joint were modelled
as isotropic elastic-plastic with their own yield laws.
Because of its minimal influence on the results, the
modelling of the HAZ as a particular material in the joint
was omitted.
4 RESULTS AND DISCUSSION
The opening displacements measured at the crack
mouth (CMOD) are in very good agreement with those
determined numerically. On the other hand, the
finite-element results for the CTOD (δ5) displacements
are lower than the experimentally measured values
(Figure 5). This proves that it is much more difficult to
really simulate the local fracture behaviour of the
material than the global behaviour. It is also evident that
a crack-tip opening displacement calculated by the
finite-element method deviates significantly as the
loading is increased.
The stress σy caused by the force acting in the
y-direction, the Mises equivalent stress, σeq, and the
plastic equivalent strain, εpl, eq, at the moment of the
crack initiation are presented for the six equidistant
layers from the surface to the mid-thickness of the
specimen (Figure 6). In addition, the variation of the
plastic equivalent strain, εpl, eq, during the load increase is
presented in Figure 7.
5 DISCUSSION AND CONCLUSIONS
The effect of the yield strength of the overmatched
weld metal on the stress and strain distribution in the
case of a B × 2B fracture-toughness specimen cracked in
the middle was studied experimentally and numerically.
The crack front passes over the different materials
through the thickness of the specimen, which tends to
complicate the finite-element analysis.
The numerical values of the global fracture-
toughness parameters, such as the load-line displacement
or the crack-mouth opening displacement are in very
good agreement with the experiment up to the moment
of the crack initiation. On the other hand, the
finite-element results for the local toughness parameters,
such as the CTOD (δ5) displacement, are lower than the
experimentally measured values.
The magnitude of the σy stress is significantly greater
in the mid-thickness of the specimen than on the surface,
which is the opposite of the effective stress, σeff. A
characteristic asymmetry of the stress and strain field
due to material’s heterogeneity in the joint occurred in
the vicinity of the crack front. It is evident from the
effective stress distribution that higher values of the
stresses are present in the weld material that has a higher
yield strength, which is in accordance with the theory.
The peak of the highest stress is shifted from the crack
tip point, depending on the local material toughness
parameter. In contrast to the effective stress distribution,
the higher values of the equivalent plastic strain, εpl, eq,
spread to the softer base metal with an increase in the
loading.
The crack-opening stress (σx in this case) divided by
the local fracture-toughness value can be considered as
the parameter that determines the direction of the
crack-front propagation. The results show that the
presence of a low-strength base metal contributes to the
crack path deviation in the mid-thickness of the
specimen. Both the crack-path deviation and the higher
toughness of base metal increase the critical fracture
toughness value of the welded joint.
D. KOZAK ET AL.: THE EFFECT OF A MATERIAL’S HETEROGENEITY ...
Materiali in tehnologije / Materials and technology 41 (2007) 1, 41–46 43
0
20
40
60
80
100
120
140
0,00 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08 0,09 0,10 0,11 0,12
δ5 /mm
L
o
a
d
,
EXP
FEM
F
/k
N
Figure 5: F-CTOD (δ5) diagram
Slika 5: F-CTOD (δ5)-diagram
D. KOZAK ET AL.: THE EFFECT OF A MATERIAL’S HETEROGENEITY ...
44 Materiali in tehnologije / Materials and technology 41 (2007) 1, 41–46
Figure 6: Stress and strain fields near the crack tip at the moment of crack initiation (F = 134.2 kN)
Slika 6: Polje napetosti in deformacije v bli`ini konice razpoke v trenutku za~etka razpoke (F = 134,2 kN)
D. KOZAK ET AL.: THE EFFECT OF A MATERIAL’S HETEROGENEITY ...
Materiali in tehnologije / Materials and technology 41 (2007) 1, 41–46 45
Figure 7: Spreading of the equivalent plastic strain fields in the vicinity of the crack front as the loading increases
Slika 7: Raz{iritev ekvivalentnega polja plasti~ne deformacije v bli`ini vrha razpoke pri pove~anju obremenitve
6 REFERENCES
1 G. Çam, S. Erim, Ç. Yeni, M. Koçak, Determination of mechanical
and fracture properties of laser beam welded steel joints, Welding
Research, Welding Research Supplement (1999), 193–201
2W. Pompe, H. Worch, M. Epple, W. Friess, M. Gelinsky, P. Greil, K.
Hempel, D. Scharnweber, K. Schulte, Functionally graded materials
for biomedical applications, Materials Science and Engineering A,
362 (2003) 1–2, 40–60
3 Y.-J. Kim, M. Koçak, R. Ainsworth, U. Zerbst, SINTAP defect
assessment procedure for strength mismatched structures,
Engineering Fracture Mechanics, 67 (2000), 529–546
4 Y.-J. Kim, K.-H. Schwalbe, Compendium of yield load solutions for
strength mis-matched DE(T), SE(B) and C(T) specimens, Engi-
neering Fracture Mechanics, 68 (2001), 1137–1151
5 F. Matejicek, N. Gubeljak, D. Kozak, M. Koçak, Stress-strain state at
the vicinity of the crack tip in strength mis-match welded joint,
Proceedings of the 13th European Conference on Fracture on CD
Rom, San Sebastian, 2000, Paper reference 1U.6
6 Y. Chen, J. D. Lee, M. S. Oskard, A. Eskandarian, Meshless analysis
of crack propagation in multiphase material, Proceedings of the XI.
International Conference on Fracture on CD Rom, Turin, 2005
7 N. Gubeljak, D. Semenski, N. Drvar, J. Predan, D. Kozak, M. Oblak,
Object grating method application in strain determination on CTOD
tests, Strain, 42 (2006), 81–87
8 D. Kozak, J. Vojvodi~ Tuma, N. Gubeljak, D. Semenski, Factors
influencing the yielding constraint for cracked welded components,
Mater. Tehnol., 39 (2005), 29–36
9 ANSYS 10.0 Release, User’s manual, 2005
D. KOZAK ET AL.: THE EFFECT OF A MATERIAL’S HETEROGENEITY ...
46 Materiali in tehnologije / Materials and technology 41 (2007) 1, 41–46
S. AYADI ET AL.: THE NUMERICAL SOLUTION OF STRAIN WAVE PROPAGATION ...
THE NUMERICAL SOLUTION OF STRAIN WAVE
PROPAGATION IN ELASTICAL HELICAL SPRING
NUMERI^NA RE[ITEV PROPAGACIJE DEFORMACIJSKEGA
VALA V ELASTI^NI SPIRALNI VZMETI
Sami Ayadi1, Ezzeddine Hadj-Taïeb1, Guy Pluvinage2
1Unité de Recherche : Mécanique des fluides appliquée et modélisation, ENIS, B.P. W, 3038 Sfax, Tunisie
2Laboratoire de Fiabilité Mécanique, ENIM, Ile du Saulcy, 57045 Metz, France
samya@netcourrier.com
Prejem rokopisa – received: 2006-05-17; sprejem za objavo – accepted for publication: 2006-11-10
When a helical spring is subjected to a rather large impact loading, significant axial and rotational oscillations can occur in the
spring. A mathematical formulation is presented to describe non linear dynamic response of impacted helical springs. The
governing equations for such motion are two coupled non-linear, hyperbolic, partial differential equations of second order. The
axial and rotational strains and velocities are considered as principal dependent variables. Since the governing equations are
non-linear, the solution of the system of equations can be obtained only by some approximate numerical technique. When the
strains are small, the equations of motion are rendered linear. The numerical technique employed in this paper is the method of
characteristics for, both, linear and non-linear wave propagation problems. In order to resolve the non-linear problem of the
dynamic response of helical spring, the non-1inear characteristics method is used. The compatibility equations are integrated
along the characteristics and written in difference form. Thus, the unknown values of the axial strain, rotational strain, axial
velocity and rotational velocity at any point of the spring, can be determined by resolving a system of four simultaneous
equations. For this system, the values of the coefficients and the known variables are computed by interpolation and integration
along non-linear characteristic lines. The procedure must be slightly modified when the end points of the spring are involved. At
both ends, in order to determine the unknown variables values, use is made of only two characteristics. The numerical results
are obtained for helical spring under axial impact. The dynamic responses are computed and plotted for some sections of the
spring.
Key words: helical spring, dynamic response, strains, method of characteristics, non linear behaviour
Ko je spiralna vzmet sunkovito mo~no obremenjena, lahko nastanejo v njej osna in rotacijsko nihanje. Predstavljena je
matemati~na re{itev za opis nelinearnega odgovora obremenjene vzmeti. Ta odgovor lahko predstavimo z dvema povezanima
nelinearnima portalnima hiperboli~nima diferencialnima ena~bama druge stopnje. Kot glavni spremenljivki so upo{tevane osne
in rotacijske deformacije. Ena~be niso linearne, zato so re{ljive le s pribli`no numeri~no tehniko. Pri majhnih deformacijah so
ena~be nihanja linearne. Uporabljena numeri~na tehnika je metoda karakteristik za oboje, linearno in nelinearno propagacijo
valovanja. S ciljem, da se najde re{itev za nelinearni problem, dinami~nega odgovora vzmeti, je uporabljena linearna
karakteristika. Ena~be kompatibilnosti so integrirane vzdol` karakteristik in napisane v obliki diferenc. Tako na~in je mogo~e
dolo~iti neznane vrednosti za aksialno in rotacijsko deformacijo in hitrost v vsaki to~ki vzmeti z re{itvijo sistema iz simultanih
ena~b. Za ta sistem so vrednosti koeficientov in znanih spremenljivk izra~unane z interpolacijo in integracijo vzdol`
nekarakteristi~nih linij. Proceduro je potrebno modificirati pri kon~nih to~kah vzmeti. Za re{itev za ti dve to~ki in za dolo~itev
vrednosti neznanih spremenljivk sta uporabljeni le dve spremenljivki. Numeri~ni rezultati so dolo~eni za spiralno vzmet pri osni
obremenitvi. Dinami~ni odgovori so izra~unani in grafi~no prikazani za nekatere prereze vzmeti.
Klju~ne besede: spiralna vzmet, dinami~ni odgovor, deformacije, metoda karakteristik, nelinearno vedenje
1 INTRODUCTION
The dynamic behaviour of helical springs is an
important engineering problem. In practice, helical
springs are commonly used as structural elements in
many mechanical applications (suspension systems,
motor valve springs,…). The primary functions of
springs are to absorb energy, to apply a definite force or
torque, to support moving masses or isolate vibration,…
To simplify the analysis, it is generally assumed that
the material is elastic. The design of helical springs
requires two stages, the static and dynamic. The
analytical solution to the static equations of cylindrical
helical springs subjected to large deflections was
obtained by Love 1.
In many research papers, the dynamic response of
elastic material springs is investigated using various
models. When a helical spring is subjected to a rather
large impact loading, significant torsional oscillations
can occur in the spring. The equations of motion,
governing this behaviour, are derived in an article by
Phillips and Costello 2. Stokes 3 conducted an analytical
and experimental program to investigate the radial
expansion of helical springs due to longitudinal impact.
The significance of torsional oscillations on the radial
expansion of helical springs is presented in the work of
Costello 4. In this work a linear theory was presented and
the analytical solution, obtained by the Laplace trans-
form, did indicate rather large radial expansion under
impact. Sinha and Costello 5 used a finite difference
technique and the method of linear characteristics to
solve numerically the non-linear partial differential
equations in the time domain.
Mottershead 6 developed special finite element for
solving the differential equations. Yilderim 7 developed
an efficient numerical method based on the stiffness
Materiali in tehnologije / Materials and technology 41 (2007) 1, 47–52 47
UDK 539.3:62-27 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 41(1)47(2007)
transfer matrix for predicting the natural frequencies of
cylindrical helical spring. Becker et al. 8 also used the
matrix transfer method to produce the natural frequen-
cies of helical springs. Dammak et al. 9 developed an
efficient two nodes finite elements with six degrees of
freedom per node to model the behaviour of helical
spring.
In this paper we extend the work of Sinha and
Costello 5 to investigate numerically the non-linear beha-
viour of impacted springs using non linear characteristics
method and to compare the results with linear theory.
The numerical results of linear theory are obtained by
the method of characteristics and by the Lax Wendroff
finite differences method (Ayadi and Hadj-Taïeb 10).
2 MATHEMATICAL MODEL
The equations which describe non linear one-dimen-
sional dynamic behaviour of helical springs can be
adapted from the analytical model developed by Phillips
and Costello 2. Applying the theory of dimensional
analysis and the momentum equations, to an element of
spring between two sections x and x+dx (Figure 1a),
submitted to axial force F and torque T, yields the
following equations of spring motion:
a
u
x
b
x
e
u
t
∂
∂
∂
∂
∂
∂
2
2
2
2
2
2
+ =υ (1)
b
u
x
c
x
e
t
∂
∂
∂
∂
∂
∂
2
2
2
2
2
2
+ =υ υ (2)
where u is the axial displacement of the spring, υ = rθ is
the rotational displacement of the spring, r is the radius
of the spring helix in the unstretched position, x is the
axial co-ordinate along the spring and t is time.
The coefficients a, b, c and e, occurring in equations
(1) and (2), are given by the expressions:
a
r
EI
F
x= ⋅ = + ⋅
2 ∂
∂ε
υ α α α( sin cos )(sin )
[ ]
⋅ − + +
− −


ν
1+ν
υ α α α
α
α
( sin cos )(sin )
cos
( ) sin
/x
xu
2
2 2 3 21 1






(3)
b
r
EI
F r
EI
T u
u
x
x
= ⋅ = ⋅ = +
− +
2
2
2
2 2
1
1 1
∂
∂
∂
∂β ε
α
α
sin
( )cos
( ) sin[ ]α 1 2/




−
−
+
−
+
+ 

cos
( )( sin cos
α
ν
ν
ν
υ α + α)
1
2
1
1 ux x (4)
c
r
EI
T
ux= ⋅ = +




∂
∂ε
α 1−
ν
1+ν
αsin ( ) sin1 2 2 (5)
e
Mr
EIh
=
2
(6)
where h is the length of the spring in the unstretched
position, E is Young’s modulus of the spring material,
M is the total mass of the spring, I is the moment of
inertia of the wire cross section, n is Poisson’s ratio of
the spring material and α is the helix angle of the spring
in the unstretched position. Thus, it is seen that the
coefficients a, b, c and e are functions of ε = ux = ∂u/∂x
and b = ux = ¶u/¶x and hence, the governing equations
of motion are non-linear.
It can be seen from equations (3), (4) and (5) that
when the strains are small, i.e., IuxI << 1 and IuxI << 1
the coefficients have the approximate values:
a = −
+




1
1
2ν
ν
α αcos sin
b = −
+
ν
ν
α α
1
2sin cos (7)
c = −
+




1
1
2ν
ν
α αsin sin
If these values are employed in place of the actual
non-constant coefficients, the equations of motion are
rendered linear.
3 NUMERICAL SOLUTION
The numerical solution of the initial boundary value
problem governed by the equations (1) and (2) may be
obtained by the method of characteristics (Abbott 11,
S. AYADI ET AL.: THE NUMERICAL SOLUTION OF STRAIN WAVE PROPAGATION ...
48 Materiali in tehnologije / Materials and technology 41 (2007) 1, 47–52
Figure 1: Helical spring description. a) Free body diagram of spring
element, b) Static deflection of helical spring
Slika 1: Opis spiralne vzmeti; a) prostotelesni diagram elementa
vzmeti; b) stati~ni upogib spiralne vzmeti
Chou and Mortimer 12, Hadj-Taïeb and Lili 13). The
method of characteristics, which is based on the
propagation of the waves, is applied to obtain ordinary
differential equations. In principle, it is not a numerical
but an analytical solution method. However some of the
necessary integrations are generally done numerically.
Equations (1) and (2) can be converted into a set of
first order partial differential equations. Since ¶ux/¶t =
∂ut/∂x, ∂ux/∂t = ∂
t/∂x and (∂ux/∂x)dx + (∂ux/∂t)dt = dux
etc., the above set of equations (1) and (2), in matrix
form, can be written as:
a b
b c
x t
x
0 0 0 1 0 0
0 0 0 0 0 1
0 1 0 0 1 0 0 0
0 0 0 1 0 0 1 0
0 0 0 0 0 0
0 0
−
−
−
−
d d
d d
d d
d d
t
x t
x t
0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
























∂ ∂
∂ ∂
∂ ∂
∂ ∂
∂ ∂
∂ ∂
∂ ∂
∂ ∂
u x
u t
x
t
u x
u t
x
t
x
x
x
x
t
t
t
t
/
/
/
/
/
/
/
/
υ
υ
υ
υ
























=








0
0
0
0
d
d
d
d
u
u
x
x
t
t
υ
υ
















(8)
The characteristic directions are determined by
setting the determinant of the coefficient matrix of
equation (8) equal to zero. Hence the following equation
results:
( ) ( )ac b
dt
dx
a c
dt
dx
− 



− + 



+ =2
4 2
1 0 (9)
The above equation has four roots which are:
dt
dx
a c a c b
ac b




= + + − +
−







1 2
2 2
2
1 2
4
2,
/
( ) ( )
( )
m
and
dt
dx
a c a c b
ac b




= − + ± − +
−







3 4
2 2
2
1 2
4
2,
/
( ) ( )
( )
(10)
When linear theory is used, we obtain:
dx
dt
c
EIh
Mr e




= ± = ± = ±
1 4
2
,
sin
sin
f α
α
and
dx
dt
c
EIh
Mr e




= ± = ±
+
= ±
+2 3 2 1 1,
sin sin
(
s
α
ν
α
ν)
(11)
cf is the fast speed of rotational waves (υx, υt) and cs is
the small speed of axial waves (ux, ut).
The four roots defined equations (10) or (11) are real
and, hence, the system is hyperbolic. The canonical form
of a hyperbolic system along the characteristics (some-
times called either 'Compatibility equations' or 'Riemann
Invariant equations') can be determined by replacing any
column of the coefficient matrix in equation (8) by the
right-hand side column vector and setting the deter-
minant equal to zero. The following equation results:
1
2 2
− 









+ 









−c t
x
u b
t
x
x x
d
d
d
d
d
dυ
– 1
2 3
− 













+ 







c
t
x
t
x
u b
t
x
t
d
d
d
d
d
d
d


=dυ t 0 (12)
In difference form, equation (12) becomes:
1
2 2
− 









+ 









−c t
x
u b
t
x
x x
d
d
d
d
∆ ∆υ
– 1
2 3
− 













+ 







c
t
x
t
x
u b
t
x
t
d
d
d
d
d
d
∆ 

=∆υ t 0 (13)
Thus, the unknown values of (ux, υx, ut and υt), at any
point L, as shown in Figure 2, can be determined by
knowing their values at the points P, Q, R and S lying on
the four characteristics passing through L and then
solving four simultaneous equations obtained from
equation (13). Although the characteristics are curved
due to the non-linearity of equations (1) and (2), it will
be assumed that LP, LQ, LR and LS are straight lines.
Hence, equation (13) yields:
1
2
1
− 











− + 



c
t
x
u u b
t
xx x
d
d
d
d1, P
L P
P
2
( )
,






− −(υ υx xL P )
– 1
2
− 















− +c t
x
t
x
u u bt t
d
d
d
d
d
1, P 1, P
L P( )
t
x t td P
3
L P










− =
1
0
,
)(υ υ
S. AYADI ET AL.: THE NUMERICAL SOLUTION OF STRAIN WAVE PROPAGATION ...
Materiali in tehnologije / Materials and technology 41 (2007) 1, 47–52 49
Figure 2: Method of characteristics. a) Non-linear theory, b) Linear
theory
Slika 2:Metoda karakteristik; a) nelinearna teorija; b) linearna teorija
where uxL, υxL, utL and υtL are the unknown values at the
point L; uxP, υxP, utP and υtP are the known values at the
point P; and (dt/dux)1,P is the slope of the characteristics
of family 1 passing through P. Three similar equations
can be written for the points Q, R and S. By solving the
four simultaneous equations obtained from equation
(13), the values of uxL, υxL, utL and υtL can be obtained
at any point L. It should be noted that the values at the
points P, Q, R and S, are computed by non-linear inter-
polation.
Figure 2b shows the characteristics in the case of
linear theory where the wavespeeds cf and cs are con-
stant.
4 NUMERICAL RESULTS FOR IMPACTED
SPRING
Consider the hypothetical spring system shown by
Figure 3. The parameters of the spring are: the original
length of spring h = 48.26 cm, the helix angle α =
0.141815 rd, the radius of the spring r = 17.932 cm, the
number of coils n = 3, the Poisson’s ratio ν = 0.29, the
wire radius rf = 1.509 cm, the Young’s modulus E =
20.685·106 N/cm2, the initial compression ∆ = 16.51 cm
and the mass of the spring M = 19.146 kg.
Initial conditions
The initial conditions are:
ux(x,0) = –D/h and ux(x,0) = 0 (14)
ut(x,0) = 0 and 
t(x,0) = 0 (15)
Boundary conditions
The dynamic response studied here is due to a given
velocity at the impacted end of the spring x = 0 (see
Figure 4). The boundary conditions are:
ut(0,t) = f1(t), ut(0,t) = 0, ut(h,t) = 0, ut(h,t) = 0 (16)
φ1(t) is defined by the values given in Table 1.
Table 1: Axial velocity at x = 0
Time, t/ms 0 3.375 27.75 50.625
Axial velocity, /(m/s) 0 9.062 1.165 -0.3
The spring is divided into equidistant sections in the
x direction: ∆x = h/N. Two separate FORTRAN pro-
grams were run on a PC computer. The problem has
been solved by the method of characteristics using N =
180 grid points for both linear and non-linear theories. In
the case of linear theory the same problem has also been
solved by the finite difference Lax-Wendroff method
using N = 1000 grid points [Ayadi and Hadj-Taïeb
(2006)].
The computed results by the method of characte-
ristics for the linear and non-linear theories are shown in
Figures 5 and 6. The axial and rotational strains are at
the impacted end (x = 0).
As pointed by Phillips and Costello, the results of the
plots show the necessity of solving the non-linear
equations of motion for the spring under this type of
loading. The linear theory is adequate for predicting the
axial force in the spring but can lead to erroneous results
in predicting the axial twisting moment and radial
expansion of the spring (see Table 2).
S. AYADI ET AL.: THE NUMERICAL SOLUTION OF STRAIN WAVE PROPAGATION ...
50 Materiali in tehnologije / Materials and technology 41 (2007) 1, 47–52
Figure 4: Axial velocity at the impacted end of the spring (x = 0)
Slika 4: Osna hitrost na sunkovito obremenjenem koncu vzmeti (x =
0)
Figure 3: Helical spring boundaries
Slika 3: Meja spiralne vzmeti
Figure 6: Rotational strain at the impacted end (x =0).
Slika 6: Rotacijska deformacija na sunkovito obremenjenem koncu (x
= 0)
Figure 5: Axial strain at the impacted end (x = 0).
Slika 5: Osna deformacija na sunkovito obremenjenem koncu (x = 0)
Table 2: Axial force, axial moment and radial expansion at x = 0 and t
= 0.0346 sec
Time
t/(ms)
Axial force
(N)
Axial moment
(mN)
Radial
expansion
(mm)
Linear theory -11100 540.5 -0.950
Non linear
theory
-11167.1 1155.4 -2.8194
It should be pointed out that once the axial and
rotational strains are known, the stresses can be
computed from the elementary strength of material
formula. Generally, the most significant stresses
occurring in a helical spring are due to the torsional
moment acting on the wire cross section. Since the
torsional moment on a cross section is due mainly to the
S. AYADI ET AL.: THE NUMERICAL SOLUTION OF STRAIN WAVE PROPAGATION ...
Materiali in tehnologije / Materials and technology 41 (2007) 1, 47–52 51
t /ms
t /ms
t /ms
t /ms
t /ms
Figure 8: Rotational strains in the spring
Slika 8: Rotacijske deformacije v vzmeti
t /ms
t /ms
t /ms
t /ms
t /ms
Figure 7: Axial strains in the spring
Slika 7: Osne deformacije v vzmeti
axial force in the spring, the linear theory is felt to be
quite adequate for ca1culating the stresses in this
example.
Figures 7 and 8 show the computed strain curves at
some sections of the spring (x = 0, x = h/4, x = h/2, x =
3h/4 and x = h). It illustrates the phenomenon we are
dealing with in the case of linear and non-linear spring
dynamic responses. Due to the non-linearity of equations
(1) and (2), the wave speeds are not constant and the
characteristics lines are curved. Hence, the strain wave
fronts are smoothly running. The computed strain results
of the linear equations of motion presented in Figures 7
and 8 are obtained by finite difference Lax-Wendroff
scheme.
Figure 9 shows the characteristics lines for linear
theory. At time t = 0, the spring is impacted and two
waves, fast rotational strain wave and slow axial strain
wave, travel the spring until they reach the other end x =
h. The behaviour of characteristic paths of rotational
wave differs from those of the axial one. The strain
evolution would result from the velocity function applied
at the impacted spring end, x = 0, and from the wave
reflections at the two ends of the spring. It should be
noted that the axial strain wave has an effect on the
rotational strain. As it can be seen from the curves of
Figures 7 and 8, the reflected rotational strain wave
travelling from the end of the spring causes rotational
strain to rise. But the reflected axial wave attenuates and
limits the values of rotational strain. The process is
repeated and indicated the influence of axial strain wave
on the behaviour of rotational strain.
5 CONCLUSION
The numerical solution of the spring dynamic
response has been presented in this paper. The solution is
obtained with coupled two non-linear partial differential
equations of the hyperbolic type. The two numerical
methods employed are the method of curved
characteristics and the finite-difference conservative
method of Lax-Wendroff. The non-linear characteristics
method requires the use of non-linear interpolation
method to compute the strains evolution at any interior
section of the spring.
The finite difference method is more practical and
simulates correctly the strain waves propagation when
the linear equations of motion are considered. Computed
results obtained by this method agree favourably well
with the numerical results based upon the characteristics
method. The developed program has been applied to the
large deformation analysis of helical springs under axial
loading. It can be seen from the calculated results that
the linear theory is reasonably accurate, as far as, the
axial strain is concerned but is in considerable error for
investigating the rotational strain.
6 REFERENCES
1 A. E. H. Love, A treatise on the mathematical theory of elasticity,
4th Editions Dover, 1927
2 J. W. Phillips, G. A. Costello, Large deflections of impacted helical
springs, Journal of the Acoustical Society of America, 51 (1972),
967–972
3 V. K. Stokes, On the dynamic radial expansion of helical springs due
to longitudinal impact, Journal of Sound and Vibration, 35 (1974),
77
4 G. A. Costello, Radial expansion of impacted helical springs, Journal
of Applied Mechanics, Trans. ASME, 42 (1975), 789–792
5 S. K. Sinha, G. A. Costello, The numerical solution of the dynamic
response of helical springs, International Journal for Numerical
Methods in Engineering, 12 (1978), 949–961
6 J. E. Mottershead, The large displacements and dynamic stability of
spring using helical finite elements, International Journal of
Mechanical Sciences, 24 (1982 )9, 547–558
7 V. Yildirim, An efficient numerical method for predicting the natural
frequencies of cylindrical helical springs, International Journal of
Mechanical Sciences, 41 (1999), 919–939
8 L. E. Becker, G. G. Chassie, W. L. Cleghorn, On the natural
frequencies of helical compression springs, International Journal of
Mechanical Sciences, 44 (2002), 825–841
9 F. Dammak, M. Taktak, S. Abid, A. Dhieb, M. Haddar, Finite
element method for the stress analysis of isotropic cylindrical helical
spring, European Journal of Mechanics A/Solids 24, 12 (2005),
1068–1078
10 S. Ayadi, E. Hadj-Taieb, Simulation numérique du comportement
dynamique linéaire des ressorts hélicoïdaux, Transactions The
Canadian Society of Mechanical Engineering, 30 (2006) 2, 191–208
11 M. B. Abott, An introduction to the method of the characteristics,
American Elsevier New York, 1966
12 P. C. Chou, R. W. Mortimer, Solution of one dimensional elastic
wave problems by the method of characteristics, J. Appl. Mech.,
Trans. ASME, 34 (1967), 745–750
13 E. Hadj-Taieb, T. Lili, The numerical solution of the transient
two-phase flow in rigid pipelines, International Journal for Nume-
rical Methods in fluids, 29 (1999), 501–514
S. AYADI ET AL.: THE NUMERICAL SOLUTION OF STRAIN WAVE PROPAGATION ...
52 Materiali in tehnologije / Materials and technology 41 (2007) 1, 47–52
Figure 9: Characteristic lines for helical spring linear response
dynamic
Slika 9: Karakteristi~ne linije za linearni dinami~ni odgovor spiralne
vzmeti
R. RUDOLF ET AL.: [TUDIJ NOTRANJE OKSIDACIJE V NAOGLJI^ENIH HITROSTRJENIH TRAKOVIH Cu
[TUDIJ NOTRANJE OKSIDACIJE V NAOGLJI^ENIH
HITROSTRJENIH TRAKOVIH Cu
THE STUDY OF THE INTERNAL OXIDATION IN INTERNALLY
CARBONISED Cu RIBBONS
Rebeka Rudolf1, Ladislav Kosec2, Ivan An`el1, Leo Gusel1, Mojmir Poharc3
1Univerza v Mariboru, Fakulteta za strojni{tvo, Smetanova 17, 2000 Maribor, Slovenija
2Univerza v Ljubljani, Naravoslovnotehni{ka fakulteta, A{ker~eva 12, 1000 Ljubljana, Slovenija
3Zlatarna Celje, d. d., Celje, Kersnikova 19, 3000 Celje, Slovenija
rebeka.rudolf@uni-mb.si
Prejem rokopisa – received: 2006-02-20; sprejem za objavo – accepted for publication: 2006-11-27
V prispevku predstavljamo kompozit z nanometrsko velikostjo plinskih por, ki so nastale pri notranji oksidaciji (NO) fino
dispergiranih nanometrskih delcev grafita. Za izhodno mikrostrukturo so bili izbrani notranje oglji~eni hitro strjeni trakovi
~istega bakra, kjer je bila v Cu-matici dose`ena zelo enakomerna disperzija grafitnih delcev velikosti nekaj 100 nm. Pri procesu
NO predhodno notranje oglji~enih hitro strjenih trakov je nastala kemijska reakcija nanometrskih grafitnih delcev z
raztopljenim kisikom. Pri tem so nastali plinski produkti CO oz. CO2, ki so zavzeli volumen nekdanjega trdnega delca in se niso
mogli raztopiti v kristalni mre`i bakra ter so posledi~no ostali ujeti v prostoru, kjer je bil pred reakcijo trden grafit. Tako nastali
plinski produkti ustvarjajo zaradi mnogo ve~jega specifi~nega volumna od trdnega grafita tla~ne napetosti na okoli{ko
Cu-matico in posledi~no povzro~ajo t. i. napetostno utrjanje. Po drugi strani pa tako nastala napetostna polja lahko reagirajo z
drse~imi dislokacijami in jim prepre~ijo nadaljnje gibanje, s ~imer pri~akujemo izbolj{anje mehanskih lastnosti tak{nega
kompozita.
Klju~ne besede: notranja oksidacija, kompozit, Cu-trakovi, mikrostruktura
In this paper we present the composite with the fine dispersion of nano-sized bubbles, which can be formed by the internal
oxidation of fine dispersed graphite particles. For this purpose the initial pure Cu ribbons were internally carbonised to obtain
very fine some 100 nm sized graphite particles homogeneously distributed in the Cu matrix. By the internal oxidation process
the reaction of dissolved oxygen with graphite yields the gas products (CO, CO2), which cannot be dissolved in crystal lattice of
the metal. The gas products are meshed in the space previously occupied by graphite and they have a greater specific volume
than solid graphite, thus establishing the compressive stresses in the metallic matrix and consequently causing the strengthening
effect. On the other hand, such stress field can react with sliding dislocation, whereby they impede the dislocation motion and
consequently it would expect that the composite mechanical properties would be improved.
Key words: internal oxidation, composite, Cu ribbons, microstructure
1 UVOD
Za izdelavo najbolj zahtevnih disperzijsko utrjenih
zlitin (DUZ) se danes uporabljata kombinaciji tehnologij
izdelave mehanskega legiranja in notranje oksidacije. Pri
tem je prednost notranje oksidacije predvsem v mo`nosti
doseganja zelo drobnih in enakomerno porazdeljenih
disperznih delcev. V DUZ so drobno dispergirani delci
ovire za gibanje dislokacij tudi v razmerah (visoke
temperature), ko se utrjevalni u~inek drugih mo`nih ovir:
raztopljeni atomi, izlo~ki in podmeje zrn idr., mo~no
zmanj{a. Dodatna zunanja napetost, ki je potrebna, da
dislokacija v DUZ pri visokih temperaturah zaobide
nekoherentne delce in postane znova gibljiva, je
povezana z energijo potrebno za plezanje dislokacijskega
segmenta preko delca, in z energijo, potrebno za
odcepljanje dislokacijskega segmenta od delca. V fazi
plezanja (vzpenjanje na delec) nastane podalj{anje
dislokacije, dodatna energija pa se porabi za tvorbo
novega dela dislokacijske ~rte. Obenem poteka pri
gibanju dislokacije tudi relaksacija deformacijskega
polja okoli dela dislokacijske ~rte, ki je v stiku z delcem
(dislokacija se tako reko~ vpne na delec, pri tem se
linijska energija dislokacije zni`a od polne vrednosti v
matici do ~asovno odvisne ni`je vrednosti na mejni
povr{ini delec/matica). Zato je v fazi spu{~anja
dislokacije z delca potrebna dodatna energija za t. i.
odcepljanje dela dislokacijskega segmenta od delca
oziroma za ponovno ustvarjanje deformacijskega polja
(zvi{anje linijske energije dislokacije do polne vrednosti)
okoli dela dislokacijske ~rte, ki delec zapu{~a. Pri tem je
drsenje dislokacije pri povi{anih temperaturah kontro-
lirano s tistim delnim procesom (plezanje, odcepljanje),
za katerega je potrebna ve~ja dodatna energija. Kot
ka`ejo rezultati nedavnih1 raziskav, postane `e pri
relativno majhnem zni`anju linijske energije dislokacije
med plezanjem (» 6 %) drsenje dislokacij pri povi{anih
temperaturah kontrolirano s fazo odcepljanja. Tako velja,
da je utrjevalni u~inek disperzoidov pri povi{anih tempe-
raturah odvisen predvsem od velikosti sprostitve linijske
energije dislokacij na mejni povr{ini delec/matica med
gibanjem dislokacije preko delca. Ker poteka sprostitev
dislokacijske energije s prerazporeditvijo atomov in z
difuzijo vzdol` mejne povr{ine, omogo~ajo nekohe-
rentne, kemijsko {ibko vezane mejne povr{ine najve~je
sprostitve dislokacijske energije in maksimalno utrjanje.
Materiali in tehnologije / Materials and technology 41 (2007) 1, 53–58 53
UDK 669.3:66.094.3:620.18 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 41(1)53(2007)
Teoreti~ne raziskave2 poka`ejo, da bi po tej teoriji bile
najprimernej{e ovire za drsenje dislokacij t. i. prazninski
delci nanometrske velikosti. Skladno s to teorijo je bil
namen na{ega raziskovalnega dela osredinjen na sintezo
kompozita z nanometrsko disperzijo plinskih por, ki bi
lahko nastale pri notranji oksidaciji fino dispergiranih
delcev grafita v Cu-matici.
Preliminarne {tudije izdelave diskontinuirnega kom-
pozita Cu-C s kombinacijo mehanskega legiranja in
sintranja niso pripeljale do zahtevane nanodisperzije
C-delcev3, zato smo v nadaljevanju raziskav izkoristili
znano dejstvo, da atomi ne~isto~ (O, N, S, C) segregirajo
na kristalnih defektih. Teorija raztapljanja tujih atomov v
kristalni mre`i osnovne kovine namre~ pravi, da je
maksimalna koncentracija raztopljenih atomov odvisna
od velikosti atomov legirnega elementa ali ne~isto~e,
velikosti intersticij (pri intersticijski trdni raztopini) in s
tem povzro~enimi napetostmi v kristalni mre`i, od
sorodnosti kristalnih mre` (pri substitucijski trdni
raztopini), od valence, kemijskega potenciala in
elektro-negativnosti atomov itd. V praksi pa lahko
privzamemo, da je maksimalna topnost atomov ne~isto~
odvisna od dose`ene koncentracije defektov v kristalni
mre`i. Med mo`ne postopke, ki omogo~ajo nastanek
mikrostrukture z visoko koncentracijo defektov, spada
tudi hitro strjevanje. Na podlagi tega smo postavili
hipotezo, da lahko diskontinuirni kompozit Cu-C z
nanometrsko velikostjo grafitnih delcev izdelamo s
kombinacijo hitrega strjevanja in notranjega oglji~enja.
V naslednji stopnji pa smo z notranjo oksidacijo
predhodno notranje oglji~enih hitro strjenih trakov
povzro~ili potek kemijske reakcije grafitnih delcev z
raztopljenim kisikom. Pri tem so nastali plinski produkti
CO oz. CO2, ki so zavzeli volumen nekdanjega trdnega
C-delca in so plinske pore. Dejstvo, da nastanejo pri
notranji oksidaciji sistema Cu-C z drobno disperzijo
C-delcev plinske pore nanometrske velikosti4, je v na{ih
{tudijah idejna re{itev za izdelavo materiala z nano-
metrsko disperzijo plinskih por.
2 EKSPERIMENTALNO DELO
Hitro strjeni trakovi ~istega Cu so bili izdelani iz
elektrolizno ~istega bakra (99,97 %) na laboratorijski
napravi Melt Spinner M-10 (slika 1) na Naravoslovno-
tehni{ki fakulteti v Ljubljani. 400 gramske zatehte zlitin
smo indukcijsko stalili v grafitnem talilnem loncu z
notranjim premerom 48 mm in pravokotno izlivno
odprtino 0,8 mm v argonovi atmosferi. S kontroliranim
nadtlakom argona 0,2–0,3 bar v talilnem loncu smo
omogo~ili stacionaren tok taline skozi izlivno odprtino
ter pri obodni hitrosti bobna 23 m/s izdelali kontinuirno
neprekinjene hitro strjene trakove debeline od 60 µm do
100 µm in {irine od 2,5 mm do 3,5 mm. Parametre litja
pri hitrem strjevanju (velikost izlivne odprtine, nadtlak
argona, obodna hitrost bobna) smo izbrali na osnovi
rezultatov predhodnih lastnih raziskav5. Iz hitro strjenih
trakov smo izrezali kraj{e trakove dol`ine » 4 cm, ki
smo jih na povr{ini mehansko spolirali in o~istili z
ultrazvokom. Posamezne vzorce hitro strjenih trakov
smo obdali z nanometrskim amorfnim ogljikovim
prahom in jih nato izostatsko stisnili v tabletke. Izdelane
tabletke smo vstavili v kremenovo epruveto in nato v
cevno pe~. Eksperimente notranjega oglji~enja smo
naredili v za{~itni atmosferi Ar 5.0, pri temperaturi 873
K in ~asu 1 h. Slika 2 shematsko prikazuje zgradbo
vzorca za preizkus notranjega oglji~enja.
Notranje oglji~ene hitro strjene trakove ~istega Cu
smo nato notranje oksidirali (NO) pri T = 1173 K pri
razli~no dolgih ~asih (7, 15, 30, 45) min, s ~imer smo
`eleli raziskati kinetiko in mehanizem NO ter posledi~no
s tem nastalo mikrostrukturo. ^ase smo izbrali na
podlagi teoreti~nega izra~una povpre~ne difuzijske
dol`ine, ki jo opravijo atomi kisika v ~isti Cu matici (po
~asu t = 15 min pri T = 1173 K je le-ta x = 1,8 mm).
Preskuse NO smo izvedli tako, da smo vzorce trakov
vstavili v kremenovo epruveto, v katero smo predhodno
nasuli me{anico prahov Cu/Cu2O v razmerju 1:1
(Rhinessova kopel – slika 3). Tako smo prepre~ili
zunanjo oksidacijo osnovne kovine in na povr{ini
bakrene stene dosegli maksimalno topnost kisika pri
R. RUDOLF ET AL.: [TUDIJ NOTRANJE OKSIDACIJE V NAOGLJI^ENIH HITROSTRJENIH TRAKOVIH Cu
54 Materiali in tehnologije / Materials and technology 41 (2007) 1, 53–58
1 – Talilni lonec, 2 – Plin pod tlakom (Ar, N2), 3 – Raztaljena kovina, 4 – [oba,
5 – Curek taline, 6 – Kapljica taline, ki oblikuje trak, 7 – Hlajen vrte~i se valj, 8
– Trak amorfne kovine, 9 – Strgalo, 10 – Induktor, ϑ – Kot nalivanja
Slika 1: Postopek izdelave tankih kovinskih trakov11
Figure 1: Chill-Block-Melt-Spinning process11
Slika 2: Shemati~en prikaz vzorca za preizkuse notranjega oglji~enja
Figure 2: Schematic presentation of internal carbonisation process
temperaturi `arjenja (pri T = 1173 K je maksimalna
topnost [O] v bakru C0max » 0,00621 %).
Mikrostrukturne preiskave izhodnih in NO-vzorcev
trakov smo izvedli z razli~nimi mikroskopskimi tehni-
kami: s svetlobno mikroskopijo (Nikon Epiphot 300,
opremljen s sistemom za digitalno analizo slike), z
vrsti~no elektronsko mikroskopijo (Jeol JSM 840A z
EDX-Link Analytical AN 1000) in s transmisijsko
elektronsko mikroskopijo (Philips CM20 200 kV z
LaB6-katodo, opremljen z analizatorji EELS (Electron
Energy-Loss Spectrometry), ki omogo~a izvajanje analiz
elementov od Li do U v kombinaciji z informacijo vrste
vezave pri resuluciji 1 nm) in EFTEM (Energy-Filtering
TEM, ki omogo~a izvajanje analiz porazdelitev elemen-
tov v tankih plasteh z resolucijo 1 nm).
3 REZULTATI IN DISKUSIJA
Zna~ilna izhodna mikrostruktura pre~nega prereza
notranje oglji~enih hitro strjenih Cu-trakov je prikazana
na sliki 4. S slike je razvidna po volumnu zrn enako-
merna razporejenost delcev. Gostota izlo~enih delcev na
mejah kot v notranjosti zrn je primerljivo enaka. Kva-
litativna mikrokemi~na analiza teh delcev z energijsko
disperzijskim spektrometrom EDS je pokazala, da
vsebujejo grafit. Z dodatnimi preiskavami na TEM
mikroskopu je bilo ugotovljeno, da imajo delci velikost
med 100 nm in 500 nm (slika 5a). Dobljena uklonska
slika na delcih pa je tudi potrdila, da so le-ti grafitni
precipitati (slika 5b). Rezultati izmerjenih medmre`nih
razdalj namre~ ustrezajo podatkom JCPDS-4609436 in
JCPDS-4609447, ki so zna~ilni za grafit.
Metalografske preiskave pre~nih prerezov vzorcev
notranje oksidiranih hitro strjenih trakov Cu-C so
pokazale, da je po delni notranji oksidaciji dobljena
mikrostruktura sestavljena iz dveh razli~nih con, in sicer
iz: (i) cone notranje oksidacije in (ii) neoksidiranega
dvofaznega podro~ja (slika 6). ^elo cone notranje
oksidacije je vidno kot meja med svetlim zunanjim -
oksidiranim in temnej{im notranjim - {e neoksidiranim
podro~jem z grafitnimi delci. Cona NO je sestavljena iz
Cu matice in oksidiranih delcev – plinskih por.
Razporeditev plinskih por je podobna razporeditvi
C-delcev v {e neoksidiranem dvofaznem obmo~ju, sicer
pa so plinske pore ve~inoma bolj okrogle in nekoliko
ve~je kot C-delci, njihovo {tevilo pa je po volumnu
nekoliko manj{e. Ta dejstva nakazujejo, da so plinske
pore po vsej verjetnosti nastale z direktno oksidacijo
C-delcev. Da bi potrdili prisotnost plinskih por, smo
R. RUDOLF ET AL.: [TUDIJ NOTRANJE OKSIDACIJE V NAOGLJI^ENIH HITROSTRJENIH TRAKOVIH Cu
Materiali in tehnologije / Materials and technology 41 (2007) 1, 53–58 55
Slika 5: A) TEM-mikroposnetek grafitnega delca in B) uklonska slika
del~ka in okoli{kega podro~ja
Figure 5: A) TEM image of the graphite particle and B) Diffraction
pattern taken the particle and the surrounding area
Slika 3: Shematski prikaz vzorca za preizkus oksidacije grafita v
Cu-matici
Figure 3: Schematic presentation of internal oxidation of graphite in
Cu-matrix
Slika 6: Mikrostruktura Cu-C-traku: (A) po delni in (B) po popolni
notranji oksidaciji
Figure 6: Microstructure of the Cu-C ribbons after: (A) partial and
(B) complete internal oxidation
Slika 4: Zna~ilna mikrostruktura notranje oglji~enega hitro strjenega
traku Cu (T = 873 K, 1 h)
Figure 4: Typical microstructure of internally carbonised Cu rapidly
solidified ribbon (T = 873 K, 1 h)
izvedli natan~nej{e preiskave cone NO v pre~nem
prerezu traku s presevno elektronsko mikroskopijo. Za ta
namen smo vzorec notranje oksidiranega Cu-C-traku
stanj{ali v okoljskem vrsti~nem mikroskopu Quanta 200
3D, opremljenim z ionsko pu{ko in sistemom za
nana{anje platine. Na posameznih mestih vzorca smo po
postopku tanj{anja z ionsko pu{ko dobili presevna
podro~ja z debelino, manj{o od 50 nm. Vzorec smo nato
vstavili v presevni elektronski mikroskop, kjer smo po
jedkanju z ioni Ar+ v presevnem podro~ju z analiza-
torjem EFTEM izvedli mikrokemi~no analizo. Porazde-
litev elementov Cu, O in C v zrnu, kjer smo opazili
plinske pore, je prikazana na sliki 7. Iz dobljene
porazdelitve elementov lahko sklepamo, da so v
obmo~ju plinskih por tik pod povr{ino le kisikovi atomi,
medtem ko je vsebnost elementov Cu in C prakti~no
zanemarljiva. Da bi ugotovili tip vezave kisika v plinskih
porah, smo opravili tudi EELS-analizo. EELS-spekter za
kisik O K je bil posnet v obmo~ju plinske pore pod
povr{jem in primerjalno {e za kisik v obmo~ju okoli{ke
Cu-matice. Rezultati so prikazani na sliki 8. S slike 8A
je razvidno, da ima spekter O K za kisik, ki se nahaja v
plinski pori, maksimalno vi{ino vrha pri 540 eV, oblika
in lega krivulje sta zna~ilni za molekulski kisik, medtem
ko ima spekter O K v obmo~ju matice zna~ilnosti za
kisik, ki je vezan v Cu(II)O-oksid – zunanja oksidacija
(slika 8B). Na podlagi tega lahko sklepamo, da se v
plinski pori kisik nahaja v obliki plina.
Preiskave pre~nih prerezov NO vzorcev so pokazale,
da so plinske pore nastale kot posledica selektivne
oksidacije grafitnih delcev nanometrske velikosti. Pri
tem je pri reakciji raztopljenega kisika z grafitnimi delci
pri{lo do nastanka plinov CO in CO2, ki se niso mogli
raztopiti v kristalni Cu-mre`i in zavzemajo prostor
zreagiranega C-delca. Zaradi pozitivne razlike v
specifi~nem volumnu med nastalimi plini (CO, CO2) ter
grafitom, naj bi le-to posledi~no povzro~ilo tla~ne nape-
tosti na okoli{ko Cu-matico in s tem njeno deformacijo
(V(s)C = 5,298 cm3 < V(g)CO,CO2 = 24789,2 cm3)8. Z
metalografskimi preiskavami NO-mikrostruktur smo
opazili, da so po kratkih ~asih NO (do 15 min) v coni
notranje oksidacije nastale plinske pore, ki so nekoliko
R. RUDOLF ET AL.: [TUDIJ NOTRANJE OKSIDACIJE V NAOGLJI^ENIH HITROSTRJENIH TRAKOVIH Cu
56 Materiali in tehnologije / Materials and technology 41 (2007) 1, 53–58
Slika 9: Globina CNO h pri notranje oksidiranih Cu-C-trakovih po
razli~nih ~asih `arjenja
Figure 9: Depth of the internal oxidation zone by internally oxidized
Cu-C ribbons after different time of annealing
Slika 8:Mikroposnetek notranje oksidiranega Cu-C-traku s presevnim
elektr. mikroskopom – svetlo polje, ZF-filter; EELS-spekter O K: A) v
obmo~ju plinske pore, B) v obmo~ju Cu-matice
Figure 8: TEM micrograph of internally oxidized Cu-C ribbons-
bright field, ZL filter; EELS spectre O K: A) in the region of gas
bubble, B) in the region of Cu-matrix
Slika 7: Porazdelitev elementov (EFTEM) v zrnu v presevnem
podro~ju z lo~ljivostjo ≈ 1 nm
Figure 7: Elemental distribution maps inside of grain in thin films at a
spatial resolution of ≈ 1 nm
ve~je od grafitnih delcev v neoksidiranem delu vzorca in
dosegajo velikost med 50 nm in 500 nm. Povsem
druga~no mikrostrukturo pa smo opazili pri vzorcih, ki
so bili NO dalj{i ~as (tNO > 30 min). V tem primeru smo
identificirali le plinske pore, ki so bile tudi precej ve~je
(tudi do 500 nm), zato predvidevamo, da po dalj{ih ~asih
NO za~ne potekati proces sferoidizacije plinskih por.
Kinetiko NO smo dolo~ili z meritvijo pomika ~ela
CNO v notranjost pre~nega prereza vsakega vzorca
traku, kar je pomenilo dolo~itev globine podro~ja, kjer je
pri{lo do oksidacije grafitnih delcev. ^eprav je bila
dose`ena globina CNO na nekaterih mestih v pre~nem
prerezu vzorcev dokaj neenakomerna in slab{e lo~ljiva,
smo pri dolo~evanju CNO ugotovili, da je mo`no le-to
dolo~iti samo pri vzorcih, ki so bili oksidirani kratek ~as
(7, 15) min, saj je v drugih primerih CNO `e pre{la
celoten prerez traku (slika 9). Izhodna debelina
hitrostrjenih trakov Cu-C je bila za te preskusne ~ase NO
premajhna. Na podlagi opravljenih meritev lahko sklene-
mo, da je kinetika notranje oksidacije Cu-C-kompozita
kontrolirana z difuzijo kisika v Cu-matici.
Za dodatno potrditev prisotnosti plinskih por v
mikrostrukturi smo naredili prelome popolnoma notranje
oksidiranih hitrostrjenih trakov Cu-C. Prelome teh
trakov smo izvedli v teko~em N2, s ~imer smo posku{ali
ohraniti ~im bolj avtenti~no mikrostrukturo. Pri
SEM-opazovanju prelomnih povr{in smo ugotovili, da je
pri teh trakovih nastala prelomna povr{ina, ki je
karakteristi~na za t. i. porozne materiale9, kar je razvidno
tudi s slike 10. Na prelomni povr{ini teh trakov so
namre~ bile zna~ilne jamice, katerih velikost je ocenjena
na ≈ 0,5 µm.
Eksperimenti notranje oksidacije predhodno notranje
oglji~enih hitro strjenih trakov ~istega Cu so pokazali, da
je pri{lo:
V prvi stopnji do adsorpcije in raztapljanja kisika v
bakru, pri ~emer je bila dose`ena koncentracija kisika
enaka maksimalni topnosti. Ko je koncentracija kisika na
meji Cu-matica/grafitni delec dosegla kriti~no vrednost
(oksidativna atmosfera za ogljik), je pri tem potekla na
tej meji direktna oksidacija nano-metrskih grafitnih
delcev, ki jo lahko zapi{emo z reakcijama C + [O]Cu→
CO in C + 2[O]Cu→ CO2. Pri tem so nastale plinske
molekule, ki so zasedle volumenski prostor zreagiranega
grafita. Nastale plinske molekule se niso mogle raztopiti
v bakru, in ker je molski volumen plina V(g)CO,CO2
bistveno ve~ji kot volumen trdnih grafitnih delcev, se je
v tem prostoru ustvaril vi{ji tlak. To je povzro~ilo
nastanek plinskih por in velikih tla~nih napetosti na
okoli{ko kristalno mre`o, kar je imelo za posledico
plasti~no deformacijo matice in nastanek plinskih por.
Ko se je grafitni delec na stiku s Cu-matico oksidiral,
ni bilo ve~ neposrednega stika med grafitom in kisikom,
raztopljenim v bakru. Neoksidiran grafitni delec je postal
obdan s plinsko fazo, preko katere se je prena{al kisik za
nadaljnjo oksidacijo. Glede na teoreti~en izra~un
TD-pogojev10 predvidevamo, da je pri tem na meji plin-
ska faza/Cu-matica potekala reakcija [O]Cu + CO → CO2,
in nastali CO2 je nato prena{al kisik do neoksidiranega
grafita, kjer je v naslednji stopnji potekala na meji
plinska faza/grafit reakcija C + CO2 ⇔ 2CO.
Tak{no shemo poteka notranje oksidacije nano-
metrskih grafitnih delcev prikazuje slika 11.
R. RUDOLF ET AL.: [TUDIJ NOTRANJE OKSIDACIJE V NAOGLJI^ENIH HITROSTRJENIH TRAKOVIH Cu
Materiali in tehnologije / Materials and technology 41 (2007) 1, 53–58 57
Slika 11: Shematska predstavitev notranje oksidacije za hitro strjeni
trak Cu-C
Figure 11: Schematic presentation of the internal oxidation for the
Cu-C rapidly solidified ribbon
Slika 10: Prelomna povr{ina popolnoma notranje oksidiranega
Cu-C-traku
Figure 10: Fracture surface after complete internally oxidized Cu-C
ribbons
4 SKLEPI
Na osnovi dobljenih rezultatov in analiz lahko
povzamemo naslednje sklepe:
– Po delni notranji oksidaciji Cu-C trakov je dobljena
mikrostruktura sestavljena iz dveh razli~nih con: iz
(i) cone notranje oksidacije z enakomerno razpo-
rejenimi plinskimi porami v Cu-matici in iz (ii)
neoksidiranega dvofaznega podro~ja s C-delci v
Cu-matici.
– Razporeditev plinskih por v coni NO je podobna
razporeditvi C-delcev v {e neoksidiranem dvofaz-
nem podro~ju, pri ~emer so plinske pore ve~inoma
bolj okrogle in nekoliko ve~je kot C-delci, njihovo
{tevilo pa je po volumnu nekoliko manj{e.
– Posnet EELS-spekter O K za kisik, ki se nahaja v
plinski pori pod povr{jem, ima maksimalno vi{ino
vrha pri 540 eV; oblika in lega krivulja pa sta
zna~ilni za molekulski kisik. V primeru posnetega
EELS-spektra O K v obmo~ju matice ima le-ta
zna~ilnosti za kisik, ki je vezan v Cu(II)O oksid.
– V prvi stopnji NO poteka v Cu matici reakcija med
grafitom in raztopljenimi kisikovimi atomi kot
direktna notranja oksidacija, v drugi stopnji, pa
preide reakcija na indirektno preko plinske faze
CO2, ki prena{a kisik do grafita.
– Po dalj{ih ~asih NO za~ne potekati proces sfe-
roidizacije plinskih por.
– Pri prelomu popolnoma notranje oglji~enih Cu-C-
trakov je nastala prelomna povr{ina z jamicami, ki je
karakteristi~na za duktilne porozne materiale.
5 LITERATURA
1 B. Reppich: On the attractive particle-dislocation interaction in
dispersion-strengthened material; Acta mater., 46 (1998)1, 61–67
2 J. Rösler, E. Arzt: A new model-based creep equation for dispersion
strengthened materials; Acta metall., 38 (1990) 4, 671–683
3 R. Rudolf, I. An`el, A. Kri`man: Kvalitativna mikrostrukturna
analiza kompozita Cu-C, Mater. Tehnol. 34 (2000) 5, 243–248
4 R. Rudolf, I. An`el, A. Kri`man: Visokotemperaturna oksidacija
kompozita Cu-C; Mater. Tehnol. 35 (2001) 5, 219–226
5 I. An`el, A. Kri`man, T. Bon~ina, F. Zupani~, G. Lojen, L. Kosec, B.
[u{tar{i~: Mikrostruktura hitro strjenih trakov zlitine Cu-Zr. Kovine
zlit. tehnol., 29 (1995) 1-2, 57–61
6 Shterenberg, L. E., Bogdanova, S. V., Slesarev, V. N.: Inorganic
Materials, 13 (1977) 8, 1424
7 Shterenberg, L. E., Bogdanova, S. V.: Inorganic Materials, 15 (1979)
5, 632
8 E. A. Brandes, G. B. Brook, Smithell´s Metals Reference Handbook,
London, 1992
9 Randal M. German: Particle Packing Characteristics; New Jersey,
Materials Engineering Department, 1989
10 R. Rudolf: Notranja oksidacija diskontinuirnih kompozitov iz
sistema Cu-C, Ph. D. Thesis (in Slovene), 2002, 40 p.
11 B. [u{tar{i~, J. Rodi~: Amorfne kovine in tehnologija hitrega strje-
vanja na IMT Ljubljana; @elez. zb., 23 (1989), 159–164
R. RUDOLF ET AL.: [TUDIJ NOTRANJE OKSIDACIJE V NAOGLJI^ENIH HITROSTRJENIH TRAKOVIH Cu
58 Materiali in tehnologije / Materials and technology 41 (2007) 1, 53–58
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA – DOCTOR'S, MASTER'S AND DIPLOMA DEGREES
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA –
DOCTOR'S, MASTER'S AND DIPLOMA DEGREES
DOKTORSKA DELA – DOCTOR'S DEGREES
Na Fakulteti za strojni{tvo Univerze v Ljubljani je dne 8. decembra 2006 pred
komisijo v sestavi: prof. dr. Karl Kuzman kot predsednik in ~lani: prof. dr. Janez
Tu{ek, prof. dr. Alojz Kodre, akad. prof. dr. Igor Grabec in prof. dr. Edvard Govekar
Tadej Kokalj, univ. dipl. fiz. zagovarjal doktorsko delo z naslovom:
Modeliranje in optimizacija laserskega tvorjenja kapljic iz kovinske `ice
Modeling and Optimization of Laser Droplet Formation from Metal Wire
Mentor pri pripravi disertacije je bil prof. dr. Edvard Govekar, somentor pa akad. prof.
dr. Igor Grabec. Recenzenti predlo`ene disertacije so bili: prof. dr. Janez Tu{ek, prof.
dr. Alojz Kodre, prof. dr. Edvard Govekar, akad. prof. dr. Igor Grabec.
MODELIRANJE IN OPTIMIZACIJA LASERSKE-
GA TVORJENJA KAPLJICE IZ KOVINSKE @ICE
UDK: 621.791.724:536.21/.22:004.94(043.3)
POVZETEK
V delu je teoreti~no in eksperimentalno raziskana
mo`nost modeliranja in optimizacije procesa laserskega
tvorjenja kapljice (LTK) iz kovinske `ice. LTK je nov
tehnolo{ki proces, pri katerem z laserskim `arkom
segrevamo in pretalimo konec kovinske `ice. Po lo~itvi
od `ice kapljico odlo`imo na izbrano mesto, kjer jo
uporabimo za tvorjenje spojev ali kot polnilo. Glavni
problem procesa LTK je dolo~itev primernih parametrov
procesa, ki zagotavljajo tvorjenje kapljic z `elenimi
lastnostmi brez izbrizgavanja taline na podlago in
raztrosa kapljic. Vzrok za razvoj te tehnologije je
potreba po tvorjenju spojev brez prisotnosti svinca in
spojev z vi{jo temperaturno odpornostjo kot sedaj. Poleg
slednjega ka`ejo prve raziskave spojev z lasersko
tvorjenimi kapljicami tudi dobro korozijsko odpornost.
V delu sta predstavljena zgrajena fizikalna modela
procesa LTK za proces s tremi laserskimi `arki in za
proces z enim laserskim `arkom. Numeri~na obravnava
modela omogo~a izra~un ~asovnega razvoja tempe-
raturnega polja `ice v odvisnosti od parametrov procesa.
Izra~unano temperaturno polje je podlaga za optimiranje
procesa LTK, ki ga obravnavamo v dveh fazah: tvorjenje
vise~e kapljice in lo~itev kapljice od `ice. Pri opti-
miranju smo se omejili na dolo~itev ~asovnega poteka
laserskega bliska. Pri dolo~itvi poteka bliska za tvorjenje
vise~e kapljice z uporabo treh laserskih `arkov smo
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA – DOCTOR'S, MASTER'S AND DIPLOMA DEGREES
Materiali in tehnologije / Materials and technology 41 (2007) 1, 59–64 59
MODELING AND OPTIMIZATION OF LASER
DROPLET FORMATION FROM METAL WIRE
UDC: 621.791.724:536.21/.22:004.94(043.3)
ABSTRACT
Investigation of Laser Droplet Formation (LDF) from
the metal wire and the possibility of process optimization
on the basis of numerical model are presented in this
doctoral thesis. LDF is a novel technological process,
where laser beams are used to heat a metal wire and
produce molten metal droplets. After detachment of the
droplet from the wire the droplet can be deposited onto a
substrate to form a joint or to fill gaps in material.
Determination of proper process parameters which
assure a stable LDF without splashes of material and
radial scatter is essential for the successful application of
the process. The aim for development of LDF is the need
for high temperature resistant joints. Besides,
preliminary investigations on LDF joints show good
corrosion resistivity.
Physical model of LDF processes by the use of three
and one laser beams are presented in this work.
Numerical solutions of physical model enable the
calculation of time development of the temperature field
of the wire at different sets of process parameters.
Calculated temperature field is the basis for the LDF
process optimization. The LDF process was separated
into two phases: pendant droplet formation and droplet
detachment. Time course of laser pulse power was
optimized. A genetic algorithm optimization method
was used for the determination of laser pulse in the case
uporabili metodo optimiranja z genetskimi algoritmi. Pri
dolo~itvi poteka bliska za tvorjenje vise~e kapljice z
uporabo enega laserskega `arka smo uporabili metodo
simulacije krmiljenja v zaprti zanki. Uporabnost izra~u-
nanih bliskov smo preverili s preizkusi. Z numeri~no
dolo~enimi poteki laserskih bliskov nam je uspelo zago-
toviti uspe{no tvorjenje posameznih kapljic in zmanj{ati
variabilnost procesa. Raziskali smo tudi mo`nost zapo-
rednega tvorjenja niza kapljic, ki je posebej pomembno
za prenos in uporabo procesa laserskega tvorjenja
kapljice v industriji.
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA – DOCTOR'S, MASTER'S AND DIPLOMA DEGREES
60 Materiali in tehnologije / Materials and technology 41 (2007) 1, 59–64
of three laser beams and the simulation of closed loop
control was used for laser pulse determination in the
case of one laser beam. Theoretical results were verified
experimentally. With numerically determined laser
pulses a stable LDF was accomplished and the
variability of the process was decreased. Possibility of
sequential droplet formation generating several droplets
per second, which is especially important for industrial
purposes, was also investigated.
Na Naravoslovnotehni{ki fakulteti Univerze v Ljubljani je dne 28. februarja 2006
pred komisijo v sestavi: red. prof. dr. Radomir Turk kot predsednik in ~lani: red.
prof. dr. Savo Spai}, red. prof. dr. Ladislav Kosec, red. prof. dr. Alojz Kri`man
Iztok Nagli~, univ. dipl. in`. metal. zagovarjal doktorsko disertacijo z naslovom:
Karakterizacija aluminija in zlitine Al-Fe z dodatkom sredstev za zmanj{e-
vanje zrn AlTi5B1 in AlTi3C0,15
Characterization of aluminium and Al-Fe alloy with the addition of AlTi5B1
and AlTi3C0.15 grain refiners
Doktorska disertacija je bila izdelana pod pedago{kim mentorstvom izr. prof. dr.
Antona Smoleja ter mentorstvom dr. Mirka Dober{ka.
KARAKTERIZACIJA ALUMINIJA IN ZLITINE
Al-Fe Z DODATKOM SREDSTEV ZA
ZMANJ[EVANJE ZRN AlTi5B1 IN AlTi3C0,15
UDK: 669.715:620.18
POVZETEK
Delo obravnava karakterizacijo tehni~no ~istega
aluminija in industrijsko izdelane zlitine Al-Fe z
dodatkom udrobnilnih sredstev AlTi5B1 in AlTi3C0,15.
Aluminij in zlitino Al-Fe sem talil v indukcijski pe~i z
grafitnim loncem. Potek strjevanja sem preiskoval s
termi~no analizo, vzorce v litem stanju pa sem karak-
teriziral z metodami opti~ne mikroskopije, kvantitativne
metalografije, SEM z elektronsko mikroanalizo EDS in
WDS ter TEM.
Udrobnilno sredstvo AlTi5B1 je pri enaki koncen-
traciji titana u~inkovitej{e od sredstva AlTi3C0,15 tako v
aluminiju kot tudi v zlitini Al-Fe. Kristalizatorji za
kristalna zrna aAl so v aluminiju z dodatkom udrobnil-
nega sredstva AlTi5B1 TiB2 v aluminiju z dodatkom
udrobnilnega sredstva AlTi3C0,15 pa TiC. Kristalizatorji
v obliki aglomeratov delcev TiB2 oziroma TiC se
nahajajo v osrednjem delu kristalnih zrn αAl s pove~ano
koncentracijo titana v trdni raztopini, tako da se
koncentracija titana zmanj{uje z oddaljenostjo od
kristalizatorja.
V aluminiju z dodatkom udrobnilnega sredstva
AlTi3C0,15 je orientacijska zveza med TiC in αAl
potrjena z metodo EBSD. Rezultati raziskav aluminija z
dodatkom udrobnilnega sredstva AlTi3C0,15 v tem delu
pa z metodo TEM potrjujejo, da so delci TiC z matrico
αAl v orientacijski zvezi. Ugotovljeni sta bili dve krista-
lografski orientacijski zvezi med TiC in matrico αAl:
[111]aAl II [111]TiC in (220)aAl II (220)TiC ter
[114]αAl II [110]TiC in (220)αAl II (220)TiC.
Pri pretaljevanju aluminija z dodatkom udrobnilnega
sredstva AlTi5B1 se zaradi gravitacijskega izcejanja
delcev TiB2 koncentracija bora v ulitku zmanj{uje ob
tem pa se pove~uje velikost kristalnega zrna αAl.
U~inkovitost zmanj{evanja velikosti kristalnega zrna
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA – DOCTOR'S, MASTER'S AND DIPLOMA DEGREES
Materiali in tehnologije / Materials and technology 41 (2007) 1, 59–64 61
CHARACTERIZATION OF ALUMINIUM AND
AL-FE ALLOY WITH THE ADDITION OF
ALTI5B1 AND ALTI3C0.15 GRAIN REFINERS
UDC: 669.715:620.18
ABSTRACT
The objective of this work is to characterise
commercial-pure aluminium and industrial Al-Fe alloy
with the addition of AlTi5B1 and AlTi3C0.15 grain
refiners. Aluminium and Al-Fe alloy were melted in a
graphite crucible inside an induction furnace. Solidifi-
cation process was investigated by thermal analysis. The
characterisation of castings was carried out using optical
microscopy and quantitative metallography, SEM with
EDS and WDS, and TEM.
It has been established that the addition of AlTi5B1
grain refiner is more effective than the addition of
AlTi3C0.15 to aluminium or Al-Fe alloy, regarding the
same concentration of titanium. Nucleants in aluminium
with AlTi5B1 were TiB2 particles and in aluminium with
AlTi3C0.15 were TiC particles. Both types of nucleants
were found in the form of agglomerates in the central
regions of the aluminium grains, where the concentration
of titanium in solid solution was increased. The
concentration of titanium in these regions decreases with
increasing distance from these agglomerates.
Orientation relationship between TiC and αAl in
aluminium with addition of AlTi3C0.15 grain refiner has
been previously conformed with EBSD. TEM analysis in
this work has conformed that TiC in aluminium with
addition of AlTi3C0.15 grain refiner is in orientation
relationship with surrounding aluminium. Two orien-
tation relationships between TiC and αAl were found:
[111]αAl II [111]TiC, (220)αAl II (220)TiC and
[114]αAl II [110]TiC, (220)αAl II (220)TiC..
It has been found that the concentration of boron in
aluminium with the addition of AlTi5B1 grain refiner is
decreasing during remelting as a consequence of the
TiB2 particles settlement while grain size is increasing.
preostalih delcev TiB2 po {tirih pretaljevanjih je manj{a
od u~inkovitosti enake koli~ine delcev TiB2 dodanih v
obliki udrobnilnega sredstva AlTi5B1.
Pri enakem dodatku titana v obliki udrobnilnega
sredstva AlTi5B1 oziroma AlTi3C0,15 v aluminij je
velikost rekalescence pri strjevanju manj{a pri dodatku
sredstva AlTi5B1. Pri so~asnem dodatku udrobnilnih
sredstev AlTi5B1 in AlTi3C0,15 v zlitino Al-Fe je
velikost kristalnega zrna enaka kot samo pri dodatku
udrobnilnega sredstva AlTi5B1. Kristalizatorji za
kristalna zrna αAl pri so~asnem dodatku obeh udrobnilnih
sredstev v zlitino Al-Fe so delci TiB2, kar je mogo~e
pojasniti z manj{o velikostjo rekalescence pri strjevanju
aluminija z dodatkom udrobnilnega sredstva AlTi5B1 v
primerjavi s sredstvom AlTi3C0,15.
V zlitini Al-Fe prisotni delci TiB2 pri strjevanju brez
dodatka udrobnilnega sredstva predstavljajo kristali-
zatorje za kristalna zrna αAl. Pri dodatku udrobnilnega
sredstva AlTi3C0,15 v zlitino Al-Fe se velikost
kristalnega zrna zmanj{a, kristalizatorji za kristalna zrna
αAl pa so delci TiC. V zlitini Al-Fe prisotni delci TiB2 ne
prepre~ijo, da bi pri dodatku v zlitino Al-Fe udrobnilno
sredstvo AlTi3C0,15 imelo u~inek zmanj{evanja
velikosti kristalnega zrna, kar lahko pojasnimo s tem, da
`e prisotni delci TiB2 ka`ejo manj{i u~inek zmanj{evanja
velikosti kristalnih zrn in s tem ve~jo rekalescenco od
enake koli~ine delcev TiB2 dodanih z udrobnilnim
sredstvom AlTi5B1.
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA – DOCTOR'S, MASTER'S AND DIPLOMA DEGREES
62 Materiali in tehnologije / Materials and technology 41 (2007) 1, 59–64
The grain refinement effectiveness of still present TiB2
particles after four remelts is less than the grain
refinement effectiveness of the same quantity of TiB2
particles added in the form of AlTi5B1 grain refiner.
It has been found that recalescence magnitude at
solidification of aluminium with the addition of the same
quantity of titanium in the form of the grain refiner is
lower for AlTi5B1 grain refiner. The grain size in Al-Fe
alloy with the addition of both AlTi5B1 and AlTi3C0.15
grain refiners is the same as with the addition of only
AlTi5B1 grain refiner. The nucleation of αAl grains in
Al-Fe alloy with the addition of both AlTi5B1 and
AlTi3C0.15 grain refiners takes place on TiB2 particles.
This phenomenon can be explained with lower
recalescence magnitude found at solidification of
aluminium with the addition of AlTi5B1 grain refiner.
The nucleation of αAl grains on solidification in
Al-Fe alloy without addition of grain refiner takes place
on TiB2 particles already present in Al-Fe alloy. The
grain size in Al-Fe alloy is decreasing with the addition
of AlTi3C0.15 grain refiner and the nucleation of αAl
grains on solidification takes place on TiC particles. It
has been found that TiB2 particles already present in
Al-Fe alloy did not prevent AlTi3C0.15 grain refiner
effectiveness. This finding can be explained with less
effective grain refinement of already present TiB2
particles and consequently higher recalescence
magnitude on solidification in comparison to the same
quantity addition of TiB2 particles in the form of
AlTi5B1 grain refiner.
Na Faculté des Sciences Appliquées – Université Catholique de Louvain (Belgium) je
dne 20. decembra 2006 pred komisijo v sestavi: prof. dr. Francis Delannay kot
predsednik in ~lani: dr. Stéphane Godet, prof. dr. Bart Blanpain, prof. dr. Pascal
Jacques, dr. Jacques Charles, dr. Nathalie Gey
mag. Arnaud Pétein, univ. dipl. in`. zagovarjal doktorsko disertacijo z naslovom:
On the interactions between strain-induced phase transformations and mecha-
nical properties in Mn-Si-Al steels and Ni-Cr austenitic stainless steels
Doktorska disertacija je bila izdelana pod pedago{kim mentorstvom prof. dr. Pascal
Jacques, delovna mentorja prof. dr. Francis Delannay in prof. dr. Bart Blanpain.
ABSTRACT
The continuously increasing use of automobiles all
over the world, is making of gas effluents one of the
major concerns for all modern societies. From
economical and ecological points of view, everyone
agrees on the fact that the consumption of fossil fuels for
transport must decrease, particularly by vehicle weight
reduction. Development of high performance materials
at low cost is therefore needed.
In order to achieve this requirement, the present work
aimed at investigating the interactions between straining
and phase transformations in high performance steels
that could meet the weight saving requirements. Indeed,
a wide range of studies has shown that mechanically-
induced phase transformations (TRIP effect) of the
austenite may bring about improved mechanical proper-
ties in different steel grades.
Strain-induced phase transformations depend on two
parameters: the relative stability and the stacking fault
energy of the austenite, which are affected by different
factors. The interactions between the phase transfor-
mations and the mechanical properties of different
Fe-Cr-Ni and Fe-Mn-Al-Si grades were examined under
various conditions of grain size, temperature or stress
state. Particular relationships were clearly established
between the phenomena taking place at the scale of the
individual grains and at the macroscopic scale. The
crystallographic mechanisms of the successive strain-
induced phase transformations (austenite – e-martensite
– a'-martensite) has been clarified.
Finally, different techniques of grain refinement were
used to process stainless steels with various grain sizes,
assessing the efficiency of these techniques. Therefore,
the kinetics of retransformation, recrystallisation and
grain growth were studied. Grain refinement by cycles
of phase transformations was found more effective than
the classical deformation - recrystallisation method.
Complete dissertation (free access and download):
http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available
/BelnUcetd-01032007-144255/
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA – DOCTOR'S, MASTER'S AND DIPLOMA DEGREES
Materiali in tehnologije / Materials and technology 41 (2007) 1, 59–64 63
MAGISTRSKA DELA – MASTER'S DEGREES
Na Naravoslovnotehni{ki fakulteti, Oddelku za materiale in metalurgijo Univerze v
Ljubljani je dne 27. oktobra 2006 prek komisijo v sestavi: red. prof. dr. Savo Spai}
kot predsednik in red. prof. dr. Ladislav Kosec in izr. prof. dr. Anton Smolej kot
~lana.
Alenka Kosma~, univ. dipl. in`. metal., zagovarjala magistrsko delo z naslovom:
Razvoj mikrostrukture pri preoblikovanju in toplotni obdelavi nerjavnega
jekla z dupleksno mikrostrukturo
Microstructure development during hot deformation and heat treatment of
duplex stainless steel
Magistrsko delo je bilo opravljeno pod mentorstvom red. prof. dr. Ladislava Kosca.
Recenzenti predlo`enega magistrskega dela so bili red. prof. dr. Savo Spai}, red.
prof. dr. Ladislav Kosec in izr. prof. dr. Anton Smolej.
RAZVOJ MIKROSTRUKTURE PRI PREOBLI-
KOVANJU IN TOPLOTNI OBDELAVI
NERJAVNEGA JEKLA Z DUPLEKSNO
MIKROSTRUKTURO
POVZETEK
Preiskovali smo razvoj mikrostrukture in
precipitacijo sekundarnih faz v dupleksnem nerjavnem
jeklu z nominalno kemi~no sestavo 23 Cr, 5,3 Ni, 2,7
Mo in 0,14 N. Vro~e valjanje je bilo izvedeno na labo-
ratorijskem valjalnem stroju v temperaturnem obmo~ju
od 850 °C do 1250 °C. Pri vro~em valjanju smo
uporabili ve~stopenjsko in enostopenjsko deformacijo
(specifi~na deformacija od 0,03 do 0,67). Ohlajanje
vzorcev je bilo v vodi in na zraku. Predstavljena je
kriti~na razprava o razli~nih uporabljenih tehnikah
(opti~na mikroskopija, SEM, TEM, EDS, EBSD,
rentgenska strukturna analiza) za odkrivanje sekundarnih
faz v primerih, ko je njihov dele` majhen. Ugotovili
smo, da se sekundarni avstenit pojavlja v {irokem
temperaturnem obmo~ju. Z EDS smo izmerili kemijsko
sestavo vseh faz. Izmerili smo dele` ferita v mikro-
strukturi in vpliv na mehanske lastnosti z meritvami
trdote in `ilavosti.
Odkrivanje sekundarnih faz z metodo povratno
sipanih elektronov v SEM se je pokazalo kot zanesljivo
in enostavno, saj ni potrebna posebna priprava vzorcev.
Metoda, ki jo predpisuje standard ASTM A 923 in
obsega dolo~anje sekundarnih faz z opti~no mikro-
skopijo, je premalo natan~na.
Rezultate eksperimentalnega dela smo uspe{no
uporabili pri industrijski izdelavi {ar`e dupleksnega
nerjavnega jekla.
DOKTORSKA, MAGISTRSKA IN DIPLOMSKA DELA – DOCTOR'S, MASTER'S AND DIPLOMA DEGREES
64 Materiali in tehnologije / Materials and technology 41 (2007) 1, 59–64
MICROSTRUCTURE DEVELOPMENT DURING
HOT DEFORMATION AND HEAT TREATMENT
OF DUPLEX STAINLESS STEEL
ABSTRACT
A duplex stainless steel containing nominally 23 Cr,
5.3 Ni, 2.7 Mo and 0.14 N has been investigated for
microstructure development and secondary phases
precipitation. The specimens were hot rolled on the
laboratory rolling mill in the temperature range 850 °C
to 1250 °C. The multipass rolling was performed as well
as one step rolling with the specific deformations from
0.03 up to 0.67. A cooling with water and on the air was
applied. A critical discussion of different techniques
(optical microscopy, SEM, TEM, EDS, EBSD, X-ray
diffraction) for revealing secondary phases when the
quantity of secondary phases precipitated is low is
presented. The secondary austenite was distinguished in
wide temperature range. The chemical composition of
each phase was determined by means of EDS. The ferrite
phase content was measured and effects on mechanical
properties have been studied with hardness test and
impact test.
The SEM – BSE method seems to be the most
reliable and easy to use for secondary phases
identification while no extra specimen preparation is
needed. When optical microscopy is used according to
ASTM A 923 it seems to be insufficient.
The results were successfully used in industrial heat
production with respect to secondary phases precipi-
tation.