DD Simulations of Dislocation-Crack Interaction During Fatigue

The effect of different shaped cracks on fatigue behavior in metals is investigated with the help of the discrete dislocation dynamics (DD) technique. The cracks are represented as distributions of infinitesimal dislocation loops. The distribution is determined by an integral equation satisfying stress-free boundary conditions and containing a singular kernel of the third type. The stress field in the cracked domain is calculated using a superposition principle. The derived stress field describes the interaction between the crack and the dislocations into the framework of dislocation dynamics. The simulation results provide an insight on the three-dimensional character of the dislocation structure around the crack tip and its relation to the crack shape and number of cycles. The effect of the crack on the macroscopic yield stress is also computed for various crack sizes and shapes.