Reliability Assessment Method for Motors under Extreme Environments Based on Competing Failure Modeling

Under certain special environmental conditions, the failure mechanisms of motor systems often exhibit the coexistence of degradation-induced failures and sudden shock-induced failures, making traditional reliability analysis methods based on a single failure mode inadequate for accurately characterizing such complex failure behaviors. To address this issue, this paper proposes a motor reliability assessment method based on competing failure modeling. First, by analyzing lifetime data of motors operating under special environments such as low temperature and icing/freezing rain, marginal distribution models for degradation failures and shock failures are established, respectively. Subsequently, a Copula function is introduced to describe the statistical dependence between the two failure modes, and a degradation-shock competing failure model is constructed to capture the joint failure behavior of the motor system. Finally, combined with simulation data, the variations in reliability under different environmental stress levels are evaluated. The results demonstrate that, compared with single-failure-mode approaches, the proposed method yields reliability predictions that are closer to actual conditions, effectively reflecting the coupled effects of multiple failure mechanisms in special environments and significantly improving the accuracy and applicability of reliability assessment. The proposed approach provides a new modeling framework and theoretical reference for reliability design and lifetime prediction of motor systems under complex service conditions.

Keywords: Motor reliability, Competing failure model, Degradation failure, Shock-induced failure, Copula function, Special environments.