A Stochastic Model for Evolution of Creep Damage in Engineering Material

The scatter observed in creep deformation and failure data is of considerable technological importance because it greatly complicates the task of making accurate deformation and lifetime estimates for high temperature components. In this work a stochastic model for the creep damage evolution and associated scatter has been developed in terms of a discontinuous Markov process. The magnitude of damage has been described in the form of a probability distribution function whose evolution in time characterizes the nondeterministic nature of the damage accumulation process. The model is able to describe the state of damage along with the associated scatter at a given time at any stress level. The validity of the model has been established by comparing the predicted creep curves generated for a specific loading condition with those experimentally obtained for an austenitic stainless steel (Type 316, 18Cr 8 Ni 2Mo).