Characterization of superalloy tertiary creep by inverse modeling

Abstract

The design of new alloys for high-temperature engineering applications frequently requires the rapid characterization of material mechanical behavior, particularly creep resistance. Such information is ordinarily extracted by conducting a series of time-consuming and costly experiments under uniform load or stress. To expedite material prototyping we have developed a technique that allows estimation of the stress-dependence of material behavior from a single, short-duration, tensile test performed under non-uniform stress. The approach involves inverse modeling of experiments conducted using a novel tensile testpiece with a concave gauge-length profile. Temporal strain and post-deformation spatial strain distribution are simulated using a well-founded mechanistic creep damage model, and agreement between model results and experimental data is optimized by systematic perturbation of model parameters. This inverse strategy has been validated by examining high temperature tertiary creep in three generations of nickel superalloy single-crystal materials, but has wider application to materials characterization generally