A Probabilistic Evaluation Method on Temperature and Time-Dependent Stress Intensity Limit St in Creep Assessment of Components at Elevated Temperatures

Abstract

Creep is an important damage mode of components at elevated temperatures, and the temperature and time-dependent stress intensity limit St is an essential indicator in creep assessment of components. In general, the safety factors are directly applied to three criteria in stress intensity limit St in ASME code, but a quantitative evaluation on the failure probability covered in this indicator is rarely reported. Based on this, a probabilistic evaluation method on stress intensity limit St is proposed by correlating each criterion with mean creep rupture life data. The failure probability of three criteria in stress intensity limit St of 316 and 304 stainless steels is calculated, and the effect of safety factors on failure probability results is discussed. A probabilistic evaluation on stress intensity limit St is conducted. Results indicate that the stress intensity limit St presents a low failure probability or high conservativeness, and the minimum stress to creep rupture is the governing role in stress intensity limit St for cases involved. The failure probability of stress intensity limit St of 316 stainless steel is much lower than that of 304 stainless steel, attributed to the differences of creep deformation features and data scatter of the two stainless steels.