Accelerated Stress Rupture Testing for Creep Life Prediction—Its Value and Limitations

Abstract

Accelerated stress rupture testing has become a common method for determination of the remaining life of in-service components subject to creep damage at elevated temperatures. Stress and temperature increases have both been used to cause accelerated test failures, although the temperature accelerated tests have been preferred during the last decade. Remaining life estimation schemes have essentially involved extrapolation of results of the accelerated tests to the operating conditions. The accelerated test approach has found such widespread acceptance that most users today are unaware of its limitations and have started using the results in a definitive and quantitative way as a direct prediction of the remaining life of the component. EPRI (Electric Power Research Institute) investigators have examined the application and validity of a number of aspects of accelerated testing, as well as the underlying assumptions in the extrapolation procedures. This paper reviews the current practice, describes results from a number of research activities, and provides general guidelines for accelerated rupture testing.