Reliability Inference for Failure Mode of Sequential Hard and Soft Failure with Application on Crack data

Degradation process has been successfully applied in modeling the deterioration failure modes like wearout and corrosion for reliability assessment. However, deterioration failure modes are different from each other due to different physical mechanisms with different products operated under different environments, and specific attentions should be paid for non-standard circumstances. As it is well known, the failure with fatigue crack is composed of two sequential stages: the crack initiation and the crack propagation. The lifetime distribution models have been applied for the crack initiation, and the degradation process is well modeled by degradation process. Intuitively, a lifetime delayed degradation process (LDDP) would provide a general framework for such typical mixture failure mode composed of hard and soft ones sequentially. In this study, a general reliability inference approach has been proposed for the LDDP based on the maximum likelihood method, with numerical simulations and practical application with real testing data. Furthermore, the inspection planning issue is also studied for LDDP, with the first inspection time addressed which can increase the efficiency of inspection.