System Reliability Assessment Under Multiple Degradation Models With Shock‐Dependent Competing Failure Mechanisms

ABSTRACT Many engineering systems experience not only gradual performance degradation but also random shock effects from external environments, where shocks may significantly influence degradation processes and accelerate system failures. This paper establishes a unified competing failure reliability analysis framework to systematically investigate two fundamentally different shock influence mechanisms: degradation level increment (Case A) and degradation rate increment (Case B). Case A assumes each effective shock causes immediate jumps in degradation level, reflecting instantaneous damage effects, while Case B assumes shocks cause permanent increases in degradation rate that continuously accumulate over time. Under this framework, we derive analytical or semi‐analytical expressions for system reliability across three representative degradation models—general path models, Wiener process models, and Gamma process models. For Case A, explicit reliability expressions are obtained utilizing additivity properties of normal or Gamma distributions. For Case B, reliability is expressed in conditional expectation form with effective numerical computation schemes proposed. Through systematic numerical analysis and Monte Carlo simulation validation, we quantitatively reveal that the degradation rate increment mechanism, due to temporal accumulation effects, has significantly stronger adverse impacts on system reliability compared to the level increment mechanism, with differences amplifying over time. Parameter sensitivity analysis further demonstrates differentiated influence patterns of failure thresholds, shock intensity, and degradation parameters under different mechanisms. This research provides theoretical foundations and quantitative tools for accurate reliability assessment and maintenance optimization of degradation‐shock dependent systems, with particular relevance for critical engineering applications such as aircraft engine turbine blades.