Reliability evaluation for an electronic system subject to competing risks of dependent soft and hard failures

Reliability evaluation plays an essential role in prognostics and health management for electronic systems. This paper proposes a new method for reliability evaluation of a degrading electronic system subject to competing risks of dependent soft and hard failures. The soft failure is described by a nonstationary Gamma process exceeding the predefined critical level. In the previous works the failure modes were considered to be independent, while in this paper the dependent relationship is facilitated using the Cox's proportional hazard model that incorporates the degradation process as a time-varying covariate. To make the evaluation feasible, an approximation technique is applied in both degradation path and time axis, thereby all the reliability quantities can be derived and calculated with basic manipulations of the transition probability matrix. Finally, the performance and effectiveness of the proposed method are illustrated and analyzed in a numerical study.