Abstract
This paper focuses on system reliability analysis with dependent competing failure process due to soft failure and hard failure. Some new probabilistic methods based on cumulative shock model and nonlinear Wiener process under different shifting thresholds situation are obtained. Considering that nonlinearity exists extensively in practice, the continuous soft failure process is governed by random effected nonlinear Wiener process. Firstly, reliability evaluation models for hard failure and soft failure are obtained under the cumulative shock, respectively. Furthermore, some system reliability models under different shifting thresholds situation are studied, in which failure threshold will decrease after a certain number of shocks. A real numerical example about fatigue crack growth dataset is carried out to demonstrate the proposed procedure. Numerical results indicate that both random shocks and shifting threshold have significant effect on system reliability. Finally, some sensitivity analysis are also been given.
Highlights
In actual operation environment, most of products are often exposed to different types of risk. ose risks may come from products themselves or external environments, and the same risk can result in different failure categories
We consider two failure processes: soft failure process and hard failure process, where the soft failure is caused by a gradual degradation and additional abrupt degradation damages due to a shock process, and hard failure is caused by an abrupt stress from the same shock process
Conclusion indicates that the shock can decrease the failure threshold, both the soft failure and hard failure threshold. us, when the shifting thresholds are considered, the reliability of system is significantly lower than the fixed thresholds. (c) For different cases, we can find that the reliability almost keeps 1 when t < 105 cycles because the effect of random shocks is not significant during that time, and the gradual degradation amount is not large enough to cause any failure
Summary
Most of products are often exposed to different types of risk. ose risks may come from products themselves or external environments, and the same risk can result in different failure categories. Lehman [2] studied the competing failure model due to degradation and random shock. The reliability analysis of system with multiple dependent competing failure processes (DCFP) has been analyzed by many researchers. Hao and Yang [18] proposed a reliability analysis for DCFP with changing degradation rate and hard failure threshold levels. Gao et al [21] considered reliability models subject to DCFP with degradation-shock dependences. It is worth pointing out that little research has been carried out to consider nonlinearity stochastic process and changing failure threshold for system experiencing DCFP and those have become a critical issue for many complex systems.
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