Assessment of crack face contact using a weight function with application to fatigue crack growth in residual stress bearing bodies

This work develops a method to predict crack face contact under linear elastic conditions with application to fatigue crack growth in a residual stress bearing body. Residual stress changes the shape of the crack faces in a cracked body and can cause crack face contact that affects fatigue crack growth. Earlier work shows that the weight function can predict crack face shapes for applied or residual stress fields. The present work applies the weight function to compute a system of linear equations that can determine crack face contact pressure via quadratic programming. We validate the new method against the finite element method (FEM) in the context of fatigue crack growth in a single edge cracked beam having residual stress from prior elastic-plastic bending. The new method agrees with FEM over a range of crack sizes. Crack opening profiles agree when crack face contact is ignored (where the crack exhibits unrealistic over-closure) and when crack face contact is included. Stress intensity factors are also in agreement, comprising those due to applied loads, residual stress, and contact pressure. Being more efficient than FEM, the new crack face contract assessment method is useful for predicting residual stress effects in fatigue crack growth.