A macrostructural model for simulating the combined effects of roughness and plasticity induced fatigue crack closure

We adapt a weight function based modified strip-yield model to geometrically include the mode I effects of roughness induced crack closure. A rough crack geometry is simulated as a sine wave fitted to a sawtooth defined by an asperity angle and period. Additional crack closure due to the sliding of crack faces is incorporated into the strip-yield model by lengthening and shortening the crack face elements, creating a sawtooth-like crack wake. We study combined roughness and plasticity induced crack closure by varying the crack face asperity angle and period. The addition of rough crack face geometry effects causes the amount of crack closure to oscillate above and below an average value influenced primarily by the asperity angle. The periodicity of the rough crack has little or no effect on closure.