Fatigue life prediction based on an equivalent initial flaw size approach and a new normalized fatigue crack growth model

Abstract

Abstract A general procedure for fatigue life prediction of structural details based on Fracture Mechanics approach is presented in this paper, taking advantage of the new normalized fatigue crack growth model proposed by Castillo et al., here denoted as CCS model. An extension to the CCS model is proposed by adopting the cyclic J-integral range instead of the stress intensity factor range as reference parameter. This enables the generalized elastoplastic conditions resulting for the cracked geometry of the structural detail to be considered by means of the cyclic J-integral values obtained from a finite element analysis, for different loading levels and crack lengths. As a practical application, the proposed approach is applied to a notched plate made of P355NL1 steel, using the equivalent initial flaw size (EIFS) concept. Fatigue crack growth data for CT specimens from the literature is evaluated to estimate the modified CCS crack growth model parameters. The predicted fatigue propagation lifetime prediction is compared with the results and, finally, the goodness of the predictions is analysed and deviations discussed.