Prediction of material thermomechanical response with a unified viscoplastic constitutive model

Abstract

Abstract Results of a research program conducted to develop and apply a unified constitutive model to the prediction of material stress-strain behavior at elevated temperature are presented. Specifically, a model that represents inelastic behavior as coupled plastic and creep response was developed for a nickel base alloy, Hastelloy X, subjected to thermomechanical cycles in which both the mechanical strain and temperature are simultaneously changing. The basis for the constitutive model is the unified approach first proposed by Bodner. Adaptation of the approach to Hastelloy X for variable temperature loading cycles required significant modification of the original model. Prediction of the response of a uniaxial test specimen subjected to a thermomechanical loading cycle, representative of the local conditions present in a gas turbine combustor liner, are presented and serve as the basis for an assessment of the modified model.