Crack Arrest Analysis of Components With Compressive Residual Stress

ABSTRACT A finite element analysis and fracture mechanics methodology for determining the autofrettage pressure required to cause crack arrest in components under varying pressure loading are presented. Superposition of the autofrettage residual stress distribution and working load stress distribution is combined with ANSYS Separating Morphing and Adaptive Remeshing Technology (SMART) to determine the effective stress intensity factor as the crack grows. The condition for crack arrest is identified by comparison with a crack arrest model defining the crack propagation threshold stress intensity factor range for microstructurally short, physically short, and long cracks. The crack propagation threshold models of El Haddad and Chapetti are implemented and applied to fatigue analysis of stainless steel and low carbon steel double notch tensile test specimens with preinduced compressive residual stress. Based on comparison with fatigue test results, the Chapetti model is selected for use in the analysis of a 3D aluminum alloy valve body. The calculated minimum autofrettage pressure required to give crack arrest under a given working load cycle is found to be in good agreement with experimental observations from the literature.