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.