Evaluation of Fatigue Crack Propagation by ΔJ Approach

Abstract

An analysis of fatigue crack growth is required for large cast components to evaluate the possible defect evolution during the service life. These components are subjected to both mechanical loading and thermal loading. Due to their high thickness, temperature variations through the thickness can be significant. Thus, a conventional elastic analysis of fatigue crack propagation could be over conservative. In order to take into account the effect of plasticity, the ΔJ approach of fatigue crack propagation evaluation is implemented in FE software SYSTUS [9]. The quarter of cycle method [11] (or twice-yield method in ASME code) will be used in this work to calculate ΔJ values under both thermal transient and mechanical loadings. Two strategies will be proposed to create the virtual monotonically increasing loading in 3D elastic–plastic FE calculations. The result in terms of numerical scheme will be validated by comparing with FE software CAST3M [10] and the RSE-M [3] simplified ΔKcp method.