Effect of Grain Disorientation on Early Fatigue Crack Propagation in FCC Polycrystals: Dislocation Dynamics Simulations and Corresponding Experimental Validation

摘要

3-dimensional dislocation dynamics (DD) simulations are performed, in face-centred cubic bi-crystals, to study the microcrack interaction with first microstructural barrier under high cycle fatigue loading conditions. Based on experimental observations, we presumed that microcracks are blocked by grain boundaries and that subsequent propagation/transmission occurs by the growth of surface relief in a secondary grain adjoining the primary crack. This mechanism is herein called indirect transmission and is found to strongly depend on grain-to-grain disorientation. A semi-analytical model proposed earlier is discussed with the DD simulation results in the context of first-barrier compliance. The proposed model describes the documented experimental results related to the effect of grain size, grain misorientation and microcrack propagation kinetics in fatigued 316L steel polycrystals.