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Availability models of series mechanical systems considering failure and maintenance dependencies

Availability models of series mechanical systems based on system working mechanisms are developed by integrating the statistical characteristics of stress, strength, and maintenance parameters. Failure, maintenance, and strength degradation path dependence are taken into consideration in the proposed models without empirical parameters. Moreover, the problem of inconsistency between the failure rate and the availability in time is pointed out, and a method to solve this problem is proposed. Monte Carlo simulations are carried out to verify the proposed models. In addition, numerical examples are given to illustrate the established method. The results show that failure, maintenance, and strength degradation path dependence and time scale inconsistence in the state transition probability matrix have significant influences on the availability of mechanical systems. The proposed models provide an analytical basis for quantitative availability estimation, optimization design, and maintenance strategy decision-making of mechanical systems.