Plastic dissipation in fatigue crack growth under mixed-mode loading

A new theory of fatigue crack growth in ductile solids has recently been proposed based on the total plastic energy dissipation per cycle ahead of the crack. This and previous energy-based approaches in the literature suggest that the total plastic dissipation per cycle can be closely correlated with fatigue crack growth rates under mode I loading. The goal of the current study is to extend the dissipated energy approach to steady-state crack growth under mixed-mode I/II loading conditions, with ultimate application to cyclic delamination of ductile interfaces in layered materials. The total plastic dissipation per cycle is obtained herein by 2-D elastic–plastic finite element analysis of a stationary crack in a general mixed-mode specimen geometry under constant amplitude loading. Both elastic–perfectly plastic and bilinear kinematic hardening constitutive behaviors are considered, and numerical results for a dimensionless plastic dissipation per cycle are presented over the full range of relevant mechanical properties and mixed-mode loading conditions. Results provide substantial insight into the effects of crack-tip constraint, material hardening behavior and applied mode–mix ratio on the dissipated energy during fatigue crack growth.