Vol.3, No 13, 2003 pp. 635-646
UDC 620.172.24:621.82.031.4.001.24:535.5.012=861
CLOSED FORM EXPRESSION FOR FATIGUE LIFE
PREDICTION AT COMBINED HCF/LCF LOADING
D. Jelaska1, S. Glodez2,
S. Podrug1
1University of Split, Croatia, Faculty
of Electrical Engineering, Mechanical Engineering and Naval Architecture,
R. Boskovica b.b., Split, Croatia
e-mail: djelaska@marjan.fesb.hr
2University of Maribor, Slovenia, Faculty
of Mechanical Engin.
For the combined HCF/LCF loading, which stress history is simplified
in the way that it consists of one LCF stress block with number of
cycles equal to the number of start-up in-service operations and one HCF
stress block with summed-up all HCF cycles, the closed form expressions
are derived for estimating both the crack initiation life and the crack
propagation life at combined HCF/LCF loading. As an example of the use,
Smith and Haigh diagrams are obtained for the components made of
titanium alloy Ti-6Al-4V, which enable the fatigue strength estimation
for designed fatigue life, known load ratio and certain number of HCF cycles
per one combined stress block.
IZRAZ U ZATVORENOJ FORMI
ZA PREDVIDJANJE TRAJANJA PRI ZAMORU
KOD KOMBINOVANOG HCF/LCF OPTEREĆENJA
Za kombinovano HCF/LCF opterećenje, čija je istorija napona pojednostavljena
na takav način da se sastoji od jednog LCF naponskog bloka sa brojem ciklusa
koji je jednak broju početnih radnji unutrašnjeg servisa, i jednog HCF
naponskog bloka u kome su sumirani svi HCF ciklusi, izrazi u zatvorenoj
formi izvode se za procenu kako trajanja začetka prsline, tako i trajanja
prostiranja prsline kod kombinovanog HCF/LCF opterećenja. Kao primer upotrebe
dobijeni su Smit i Hej dijagrami za komponente nacinjene od titanijumske
legure Ti-6Al-4V, koje omogućavaju procenu snage pri zamoru za konstruisano
trajanje pri zamoru, pozanatom odnosu opterećenja i odredjenom broju HCF
ciklusa po jednom kombinovanom naponskom bloku.
