STATISTICAL ANALYSIS AND RELIABILITY PREDICTION OF CREEP RUPTURE PROPERTY FOR T91/P91 STEEL

Life prediction is an important issue for components serviced at high temperature from both economic and safety reasons. For the purpose to correlate creep rupture data, the time-temperature parameter (TTP) method is often used to condense all the rupture data obtained at various stresses and temperatures to a narrow band. Because of uncertainty factors in materials and experiment conditions, creep rupture data generally exhibit dispersity which can be described using a so-called Z-parameter method. The current paper performs a statistical analysis for creep rupture data of T91/P91 (9Cr-1Mo-V-Nb) steel, a kind of ferritic steels widely used in power plants recently by Z-parameter method. The results indicate that all the creep rupture data distribute in a narrow band in stress sigma-TTP plot. The distribution of Z-parameter which is used to represent the dispersion of the creep rupture data follows normal distribution. sigma-TTP-reliability R, sigma-rupture time t(r)-R and allowable stress [sigma]-temperature T-R curves are proposed based on Z-parameter method. The results exhibit a good agreement with the experimental data promulgated by NRIM and ECCC.