The description of cyclic plasticity and viscoplasticity of waspaloy using unified constitutive equations

Abstract Cyclic plasticity and viscoplasticity of a nickel-based superalloy, waspaloy, have been described using a unified non-linear kinematic hardening model. Numerical strategies were developed to determine the relevant material parameters, utilising the monotonic, cyclic, relaxation and creep test data of waspaloy at 650 °C. A parameter identification routine with optimisation capacity was also developed. Additional kinematic and isotropic hardening terms were introduced to improve the model responses to cyclic loading, although the prediction of creep curves using the parameters obtained from the relaxation data is less satisfactory. Nevertheless, the unified constitutive model represents plasticity and creep using a single inelastic strain variable within the same set of equations hence offer much promise in life prediction of critical components at elevated temperature, where fatigue–creep interaction often occurs.