Reliability evaluation and application for systems with different phases

Many systems are multi-phase mission systems. During different phases, the system reliability configuration, reliability requirements and operation environment can be different. For example, some components may change from active status to standby or the system reliability configuration may change from serial to parallel. In addition to configuration changes, the system may be exposed to different stress conditions; therefore, the time to failure distribution of some components will change due to the change in stress. In general, systems that operate under different phases are considered as dynamic systems. A way to estimate the reliability and availability of such systems is needed. In this paper, a systematic procedure of applying accelerated life tests and simulation to analyze the reliability and availability of such dynamic systems is first proposed. Methods for solving both non-repairable and repairable systems are provided. For non-repairable systems, an analytical solution based on cumulative damage theory is discussed. Therefore, the exponential assumption, which is used in many existing methods, is not required in the proposed method. In addition to the analytical solution, a cumulative- damage-based simulation solution is also provided. For repairable systems, based on different scenarios in real applications, the repairable phased-mission system is classified into three categories. Because of the complexity of the problem, only simulation results are given for repairable systems. The proposed systematic procedure of applying accelerated life tests in phased-mission system analysis provides a general guideline for dealing with real-world applications. The cumulative-damage-based analytical and simulation method provide a practical and useful approach for solving phased-mission system problems. The classification of repairable phased-mission systems gives a clear overview of the phased-mission systems and makes the analysis of complex real applications easier.