Life-time reliability based assessment of structures submitted to thermal fatigue

A probabilistic approach of the current thermal fatigue design of nuclear components is set up. It aims at incorporating all kinds of uncertainties that affect the thermal fatigue behaviour. This approach is based on the theory of structural reliability. Two dual approaches of reliability analysis for the thermal fatigue are defined, respectively, in the time domain and in the frequency domain. Beside the probability of failure calculation, the sensitivity of the reliability index to each random variable is estimated. The proposed method is applied to a pipe submitted to thermal loading due to water flow. Both high cycles fatigue (HCF) and low cycles fatigue (LCF) regimes are investigated. The results show that it is possible to perform a complete reliability analysis to compute the failure probability. It is observed that the scatter of fatigue data and the heat transfer coefficient are the most important variables in thermal fatigue reliability.