Estimating threshold stresses using parametric equations for creep: application to low-alloy steels

Abstract

The power law model produces both temperature varying and unreliable estimates for its parameters. Threshold stresses have been suggested as a solution. The power law and Wilshire models are modified to include this stress and estimation and error decomposition methods applied to assess its importance in representing failure times. A statistically significant and temperature-dependent threshold stress was identified in two low-alloy steels. This threshold stress was closer to the operating stress in the Wilshire model. The inclusion of this stress reduced interpolation errors, but this improvement was greater in the Wilshire model. The Wilshire model increased the random component of these errors at all temperatures in one material, but only at some temperatures for the other.