The effect of threshold stress on the high-temperature fracture parameter

Abstract

ABSTRACTThe high-temperature fracture parameter Ct is an important parameter that is used to predict the service life and assess the safety of high-temperature structures in the entire creep stage. Therefore, it is necessary to investigate the effect of threshold stress on this parameter. In this paper, the effect of the threshold stress on Ct has been investigated using the Finite Element Method (FEM) for 9–12 wt-% Cr steels. For all the cases that were simulated the power-law creep exponent n was fixed at 5; this was because n is usually equal to 5 for the Chromium steels. The results of the FEM simulations showed that Ct was significantly affected by threshold stress. Based on the results of the FEM, a parameter was then introduced into the equation for estimating Ct in order to calculate the effect of the threshold stress. The results showed that was constant when there was no threshold stress, but that its value increased as the threshold stress and the power-law creep coefficient A increased. The effect A had on was negligible when A was smaller than 1E-19 MPa−n/h. In addition, decreased as both the value of A and the threshold stress increased. It was also found that and decreased slightly as the level of C*increased.