Failure Rate Model of Materials under Uncertain Constant Amplitude Cyclic Load

Abstract

Failure rate is an important reliability index of mechanical components. Failure rate is usually used to characterize the degradation rule of material performance under the cyclic load, which is critical to fatigue life prediction as well as reliability assessment of Ti–6Al–2Sn–4Zr–6Mo (Ti-6246) alloy. In order to reveal the probability characteristics of failure rate of Ti-6246 alloy under uncertain cyclic load, the equation of P-S-N curve is studied in this paper. Firstly. The probability density function for fatigue life under uncertain cyclic loading is derived from the probability density function for external stresses. A probabilistic model for the failure rate is then presented based on the basic assumptions. It is assumed that the failure rate and fatigue life of the material depend on the same damage state. Finally, the validity of the proposed model is verified by the Ti-6246 alloy fatigue test. The results show that the fatigue life of Ti-6246 alloy is more affected by material parameters (internal factors) than stress (external factors) under uncertain constant amplitude cyclic loading.