A study of fatigue crack tip characteristics using discrete dislocation dynamics

摘要: The near-tip deformation of a transgrannular crack under cyclic loading conditions has been modelled using discrete dislocation dynamics (DDD) with both climb and dislocation-grain boundary (GB) penetration considered. A representative cell was built to model the constitutive behaviour material, from which DDD parameters were fitted against experimental data. simulated for transgranular in polycrystalline nickel-based superalloy. phenomenon creep or strain ratchetting reproduced, similar that obtained viscoplastic crystal-plastic models continuum mechanics. Ratchetting found be associated accumulation, dislocation-GB penetration, among seems dominant mechanism cases considered at elevated temperature. have distinctive characteristic more pronounced occurred within slip bands than elsewhere. Multiple systems activated grains surrounding tip, as opposed single active system away tip. present results show that, ahead tip physical phenomenon, may particular significance developing physical-based growth.