Finite element analysis of crack-tip opening displacement and plastic zones considering the cyclic material behaviour

摘要

Propagation and behavior of fatigue cracks are governed by strain fields in the vicinity of the crack tip. The numerical description of strains in the crack tip presents some challenges in the modelling by the multiscale involved in the fracture analysis. In this study, it is proposed a 2D finite element analysis conducted for fatigue crack propagation experiments (mode I) performed for a railway axle steel EA4T under plane stress conditions. The analysis considers a geometric approach to define a multiscale mesh on a center-crack tension (CCT) specimen for which a nonlinear material model with kinematic hardening was assumed. Crack tip opening displacement (CTOD) and plastic zones were determined for several load levels during loading and unloading states. The results show that the applied correction factors approximate better the crack propagation rate. Furthermore, the quadratic dependence of CTOD with the stress intensity factor was in good agreement with the numerical solutions.