Temperature and stress–regime dependent primary–secondary–tertiary creep constitutive model

Abstract

High temperature deformation analysis of components such as steam turbine rotors requires a knowledge of the material deformation response for a wide range of stresses and temperatures. Deformation analysis of steam turbine rotors deals with stresses ranging above the material proof strength (shortly after plant start-up) down to those responsible for very long rupture durations (for the steady running phase of operation) at various temperatures. This study describes the construction of a temperature and stress–regime dependent (primary–secondary–tertiary) creep constitutive model to provide a more reliable representation for the material deformation response over wide ranges of stresses and temperatures. The adopted equation set is a refinement of the ‘Characteristic Strain’ model and depends in its formulation mainly upon creep rupture data. Successful application of the model for a 1CrMoV steel for a wide range of stresses over the temperature range of 450–675°C is demonstrated.