Articles
Publication Date: 2025
Reliability Engineering and System Safety (18790836)257
An essential goal of reliability engineering is maintaining technical systems optimally, ensuring continuous operation. Random inspections of working systems are crucial in some industries to meet safety and quality standards. This paper proposes an opportunistic optimal age-based preventive maintenance (PM) strategy for n-component (n>1) coherent systems compromising redundant components. The system begins operating at t=0, with a PM time scheduled at TPM. To reduce the risk of unexpected and catastrophic failures, the system is inspected at a random time X before TPM. Based on the information about the number of failed components, m, the operator decides whether to perform the PM action early at X or to allow the system to continue operating on (X,TPM). By incorporating a cost function that considers cost parameters related to failures, we determine the optimal values for the decision variables TPM and m. The paper's results rely on the notion of the system signature as a powerful tool to represent the reliability of n-component systems. To evaluate the effectiveness of the proposed model, we conduct a comprehensive analysis of coherent systems using graphical and numerical examples. In particular, we consider a well-investigated parallel system related to the generator parts in a wind turbine. Using a data set related to the failure times of generators, the applicability of the proposed PM policy is illustrated. © 2025 Elsevier Ltd
In this paper, we consider a (k,ℓ)-out-of-n system with three states: up, partial performance, and down. The system has n binary components and is in up state if at least (n-k+1) out of its components work. The state of partial performance is defined when the number of working components is at least (n-ℓ+1) and less than (n-k+1); k<ℓ. It is assumed that the system is subject to Marshall–Olkin type of shocks where there are n shocks, each of them affects one component and destroys it, and there is one shock that affects all components and destroys simultaneously all of them. Under this scenario, the joint reliability function of state lifetimes and the corresponding singular and absolutely continuous parts are obtained. For the system with the age of t, the mean residual lifetimes of the system states are explored. Some other aging, stochastic, and dependence properties of the system states are investigated, too. We also extend the model for the case where the system is subject to Marshall–Olkin type of shocks in which the arrived shocks may affect one, two,.., or all components and destroy them. Some illustrative examples are also provided to show the applications of the proposed model. © The Author(s) under exclusive licence to Sociedad de Estadística e Investigación Operativa 2025.
