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

Creep is an important damage mode of components at elevated temperatures, and the temperature and time-dependent stress intensity limit S_t is an essential indicator in creep assessment of components. In general, the safety factors are directly applied to three criteria in stress intensity limit S_t 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 S_t is proposed by correlating each criterion with mean creep rupture life data. The failure probability of three criteria in stress intensity limit S_t 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 S_t is conducted. Results indicate that the stress intensity limit S_t presents a low failure probability or high conservativeness, and the minimum stress to creep rupture is the governing role in stress intensity limit S_t for cases involved. The failure probability of stress intensity limit S_t 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.