Unified Viscoplasticity Modeling Features Needed for Simulation of Grade 91 Creep and Fatigue Responses

Chaboche unified viscoplasticity model and uncoupled plasticity and creep models (nonunified) are evaluated for their capability in simulating low-cycle fatigue, creep and creep-fatigue responses of Grade 91 steel. The primary objective of this study is to develop a constitutive model incorporating various advanced modeling features for design-by-analysis of elevated temperature power plant components. For validation of the model a broad set of experimental responses of Grade 91 in the temperature range 20–600°C are collected from literature. Performance of the models is demonstrated against simulating these experimental responses. It is demonstrated that the unified Chaboche model simulation capability can be improved through implementing strain range dependence, cyclic hardening through kinematic hardening rule and static recovery modeling features.