CONSTITUTIVE MODEL DEVELOPMENT FOR THERMO-MECHANICAL FATIGUE RESPONSE SIMULATION OF HAYNES 230

Turbine engine combustor components are subject to thermo-mechanical fatigue (TMF) during service. The combustor liner temperatures can sometimes reach as high as 1800 F. An accurate estimate of the strains at critical locations in the combustor liner is required for reliable lifing predictions. This demands the need for a detailed analysis of the TMF responses and a robust constitutive model capable of predicting the same. A large set of experiments have been carried out on the liner material, a nickel based alloy, HA 230, in an effort to understand its thermo-mechanical fatigue constitutive response. The out-of-phase strain-controlled TMF experiments with a negative mean strain show a positive mean stress response, while the in-phase TMF experiments with a positive mean strain show a negative mean stress response. A Chaboche based viscoplastic constitutive model is under development. It will have several essential features such as nonlinear kinematic hardening, isotropic hardening, strain range dependence, rate dependence, temperature dependence and static recovery. The constitutive model being developed for accurately calculating the stress-strain response is being carried out with the final objective of predicting the strains in an actual combustor liner in service through finite element simulation for fatigue lifing.