Temperatures at critical locations in propulsion turbine engine combustor components can be as high as 982°C (1800°F). High temperature thermal gradients, and start-up and shut-down operations of gas turbines, induce thermo-mechanical fatigue (TMF) failure. Dwell periods at high temperatures accompanied by repeated loading cycles, eventually lead to failure of the components through creep-fatigue processes. In an effort to decipher the complex high temperature phenomena, a large set of isothermal and thermo-mechanical fatigue experiments have been carried out on the gas turbine combustor liner material, Haynes 230. The out-of-phase strain-controlled TMF experiments with compressive peak hold result in mean stress evolution in the tensile direction, whereas the in-phase TMF experiments with tensile peak hold result in mean stress evolution in the compressive direction. Experimental results indicate that the maximum temperature in the loading cycle influences the material property evolution with cycle. 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 new constitutive model was validated against stress-strain responses of Haynes 230 under TMF loading.
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