Reliability modeling for dependent competing failure processes between component degradation and system performance deterioration

Mechanical systems are usually subjected to multiple dependent competing failure processes. The processes were categorized two type of failures: soft failure caused by continuous component degradation together with additional abrupt degradation due to a shock process, and hard failure caused by the instantaneous stress from the same shock process. The models in open literature have simulated the aforementioned processes. However in practice, some mechanical systems have phenomena that all the components still in the good states, but the system functions cannot meet the requirements of performance. This paper studies reliability for multi-components system subject to dependent competing risks of components degradation, components random stress shocks and system performances deterioration. These failure processes are dependent in three respects: 1) the component stress shocks over certain critical threshold affects the component degradation process, 2) the component degradation impacts the component catastrophic failure threshold level, and 3) the component degradation influences the system performances. Based on component degradation, component random shocks and system performance modeling, a reliability model for systems considering three dependent failure patterns is derived. Then an application example using an electro-mechanical system illustrates the effectiveness of the proposed approach with sensitivity analysis. The results whether considering system performance deterioration or not are compared and discussed.