Abstract: The dynamic reliability model of k-out-of-n system is developed with the load-strength interference model, the order statistic theory and the probability differential equation. Without the assumption of failure independence, the reliability model of k-out-of-n system with dependent failure is built with the system-level load-strength interference model. Further, the cumulative distribution function and the probability density function of strength for k-out-of-n system are built. From the statistic meaning of random load action, the reliability model of k-out-of-n system under repeated random load is derived. The loading process described with Poisson stochastic process, the dynamic reliability model of k-out-of-n system when strength doesn’t degenerate and that when strength degenerates are developed respectively. Finally, the relationship between reliability and time and that between failure rate and time are studied. The result shows that the reliability of k-out-of-n system decreases with time, and the larger k is the lower the reliability of k-out-of-n system will be. When strength doesn’t degenerate, the failure rate of k-out-of-n system decreases gradually with time and the failure rate in the initial period is higher. When strength degenerates, the failure rate of k-out-of-n system has the feature of bathtub curve.

Key words: Dynamic reliability, Failure dependence, Failure rate, k-out-of-n system reliability, Load-strength interference