engleski

Application of the ΔK, ΔJ and ΔCTOD Parameters in Fatigue Crack Growth Modelling

This paper presents the developed fatigue crack growth models based on parameters ΔK, ΔJ-integral and ΔCTOD determined by using linear elastic and elastic plastic FE analysis. The fatigue crack growth threshold values of the considered crack growth driving force parameters, below which crack propagation does not occur, were taken into account. Fatigue crack growth tests with constant load amplitude were carried out on a centrally cracked plate specimen until collapse occurred. The tests were performed on mild steel specimens at room temperature in laboratory air, at a loading frequency of 5 Hz. For the analyzed specimen, the calculated ΔJ-integral range values obtained by linear elastic analysis, ΔJle, and the elastic-plastic values, ΔJep, were close at lower crack growth rates. As the crack length increases the ΔJep values became higher as compared with the linear elastic values, ΔJle, This indicates that small scale yielding conditions prevailed only for smaller crack lengths. The models based on the EPFM parameters ΔJep and ΔCTOD provide better agreement with experimental results for higher crack growth rates, compared with the models based on the LEFM parameters ΔK and ΔJle.

CTOD; EPFM; fatigue crack growth; LEFM; J-integral

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