The development of science and technology makes the system become more and more complex, systems with protective auxiliary component are common in engineering industry. When the auxiliary components fail, it will not only weaken the ability to protect the main parts, but also affect the state of the remaining operational auxiliary components. However, the structure and dependence between the auxiliary components are often overlooked, which is very important in real operation. In this paper, we studied a system consisting of a main component and a protective auxiliary subsystem, the latter is a load-sharing k-out-of-n system. Since the dependence between main and auxiliary components, as well as between auxiliary components, so it is important to find the failure state of the auxiliary components in time and take the corresponding maintenance strategy. The opportunistic inspection and periodic inspection are proposed in this model. A semi-regenerative process is used to calculate the long-run average cost, based on which the optimal inspection period of the auxiliary subsystem is derived by an enumeration method. © 2022 IEEE.

For multi-component systems, components can be classified according to the impact of component failures: failures of the main component cause the system failures, while failures of the auxiliary component cannot be directly detectable and may put the system at some risk. In this paper, we study a system equipped with main and auxiliary components, and what differs this paper from previous studies on maintenance strategies for such systems is that, we consider not only the failure dependence between components due to the protective effect of the auxiliary component, but also the complex scenario where the system operates in dynamically evolving environments. Environmental evolution results in variations of failure rates of the auxiliary component and some dynamic negative impacts on degradation of the main component. Since hidden auxiliary component failures can only be found by inspection, we consider periodic inspection and opportunistic inspection of the auxiliary component in developing the maintenance strategy. Then we model the system operation by using a semi-regenerative process to obtain the long-run average cost, and minimize the long-run average cost using the inspection period τ as an optimizable decision variable. © 2022 IEEE.

Systems with protective auxiliary component are common in engineering industry. The auxiliary components in these systems play an essential role to protect the main components from severe environment impact, however, dependence between the main and auxiliary components are usually ignored in most existing literatures. Besides, failures of auxiliary components are hidden in most systems since they do not halt the system. Therefore, inspections are necessary. In most existing studies, inspections are assumed to be perfect, which is not consistent with the reality. In this paper, a new reliability model is developed for systems with dependent main and auxiliary components under imperfect inspections. Some important indexes, such as system reliability and availability, are derived by the recursive and matrix methods, respectively. Thereafter, a numerical example is presented to illustrate the results and verify the correctness of the proposed method, in which influences of imperfect inspections are also studied by conducting sensitivity analysis on the inspection accuracy parameter. © 2022 IEEE.