Constitutive Modeling for Thermo-Mechanical Fatigue Responses of Haynes 230

High temperature thermal gradients, and start-up and shut-down operations of gas turbines may induce thermo-mechanical fatigue (TMF) failures in jet engine gas turbines. Dwell periods at high temperatures as high as 982°C (1800°F) accompanied by repeated loading cycles may lead to failure of jet engine components through creep-fatigue processes. Non-linear thermo-mechanical analysis is essential for design development against creep-fatigue induced failures. In an effort to understand the complex high temperature fatigue failure phenomena, a large set of isothermal and thermo-mechanical fatigue experiments have been carried out on the gas turbine combustor liner material Haynes 230. A unified viscoplastic constitutive model based on the Chaboche type nonlinear kinematic hardening rule was developed including the added features of strain range dependence, rate dependence, temperature rate dependence, static recovery, mean stress evolution, and maximum temperature influence. The constitutive model was validated against the stress-strain responses of Haynes 230. The robustness of the constitutive model in simulating a large set of fatigue response is demonstrated and model improvement needed to accurately predict various features of low-cycle fatigue responses are identified.