Crystal plasticity theory coupled with meso-damage to predict the ratchetting behavior of nickel-based single crystal superalloy

Stress-controlled low cycle fatigue tests with different mean stress of a second-generation nickel-based single crystal superalloy DD6 with [0 0 1] orientation is investigated in the current study. The observation of fracture surface and microstructure show that although the phase structure does not change for different conditions, the damage failure mode changes for different mean stress. It is found that ratcheting strain exhibits a significant dependency on mean stress and microstructure damage. Ratcheting strain cannot be simulated only considering the evolution of back stress. To simulate the whole process evolution of ratcheting strain, crystal plasticity constitutive model coupled with a new anisotropic damage is developed. The simulated results showed that the anisotropic damage model could accurately predict the ratcheting strain for different mean stress. Different damage evolution modes are well identified by a damage index in the proposed model.