Reliability modeling of phased degradation under external shocks

The failure of many electromechanical components is the interactive results of progressive degradation and sudden shocks. Specifically, catastrophic failure occurs once the magnitude of any external shock is beyond the strength limit, or degradation failure occurs when the total degradation performance exceeds a certain threshold. Due to intrinsic characteristics of component and effects of external energy shocks, the degradation trajectory and strength limit of components can be phased and discontinuous. In addition, the interaction between degradation failure and external energy shocks are twofold: 1) nonfatal shocks add random increases to the natural degradation process, and 2) the resistance limit of component to external impacts decreases as the cumulative number of sustained shock and degradation state grow by degrees. In this study, a reliability model focused on the interactive failure mode of components is derived and elaborated from the perspective of energy, taking the phased characteristics of gradual degradation, energy-based interaction between natural degradation and external shocks and uncertainty factors into account. Finally, a numerical example is provided to illustrate the implementation and effectiveness of proposed model.