Abstract
A model for crack initiation, growth and coalescence of low cycle fatigue for steels was proposed based on experimental observations. In the present model, crack initiation resistance, R, was given for grain boundary by weibull random number. Grain boundary accumulated strain, ε, in each cycle and cracks initiated from the grain boundary when R < Σε. Parameters of weibull random number and ε was determined so that the number of cracks and sum of crack length agreed with the experimental results. Crack growth was calculated by elasto-plastic fracture mechanics. Crack coalescence was considered based on FEM simulations, while the effect of low aspect ratio caused by crack coalescence was considered. Fatigue simulations were performed for three steels, whose fatigue lives and crack growth behaviors of simulations exhibited fairly good agreement with those of experimental result including many coalescences.
