Numerical simulation of meso-mechanical response for superalloy ZSGH4169

Based on crystal plasticity constitutive theory, polycrystalline representative volume element (RVE) was used to investigate the cyclic stress/strain response of superalloy ZSGH4169 in meso scale under multiaxial stress state at 650℃. The simulations reveal that ratcheting is significant under biaxial load control, which is consistent with uniaxial stress state commonly conducted in low cycle fatigue tests. The comparison of the two stress states indicate that the residual strain of initial cycle under uniaxial stress state is three times of that under biaxial condition at 1150MPa. Meanwhile, the residual strain, which is about 1.2%, is stable under the biaxial stress, but the uniaxial condition is unstable. Analysis of inhomogeneity for the plastic strain accumulation and stress further shows that the inhomogeneity of the stress and strain will increase with the cycles under both conditions. However,the average stress increases with cycles under uniaxial conditions while it will remain almost constant under biaxial conditions.