Reliability analysis of multiple-component series systems subject to hard and soft failures with dependent shock effects

New reliability models have been developed for systems subject to competing hard and soft failure processes with shocks that have dependent effects. In the new model, hard failure occurs when transmitted system shocks are large enough to cause any component in a series system to fail immediately, soft failure occurs when any component deteriorates to a certain failure threshold, and system shocks affect both failure processes for all components. Our new research extends previous reliability models that had dependent failure processes, where the dependency was only because of the shared number of shock exposures and not the shock effects associated with individual system shocks. Dependency of transmitted shock sizes and shock damages to the specific failure processes for all components has not been sufficiently considered, and yet for some actual examples, this can be important. In practice, the effects of shock damages to the multiple failure processes among components are often dependent. In this article, we combine both probabilistic and physical degradation modeling concepts to develop the new system reliability model. Four different dependent patterns/scenarios of shock effects on multiple failure processes for all components are considered for series systems. This represents a significant extension from previous research because it is more realistic yet also more difficult for reliability modeling. The model is demonstrated by severalexamples.