AN AGE-BASED MAINTENANCE STRATEGY FOR A DEGRADATION-THRESHOLD-SHOCK-MODEL FOR A SYSTEM SUBJECTED TO MULTIPLE DEFECTS

A system subject to internal defects and external shocks is analyzed in this paper. Internal defects initiate following a nonhomogeneous Poisson process (NHPP) and they grow according to deterioration processes modeled as gamma processes. A corrective replacement is performed when the deterioration of a defect exceeds a failure threshold. The system is subject to external shocks. After an external shock, the system is replaced with probability 1 - p and is minimally repaired with probability p. The system is preventively replaced at the age of T. Costs are associated with the maintenance actions. The value of T that minimizes the expected cost rate is obtained analytically. Numerical examples are showed to illustrate the theoretical results.