中文摘要：

本文考虑了一个其产品保修期内免费小修的退化生产系统的定期检修策略．系统的退化过程包括三个状态：可控制状态，不可控制状态，故障状态．过程呆在可控制状态和不可控制状态的时间假设都服从指数分布．生产系统在固定的时刻t或发生故障时进行检修，两者以先发生为准．本文讨论了使单位产品每周期期望成本最小的最优定期检修时间t‘，三种特殊情况显示了最优值t’的性质．此外，灵敏性分析和数字实例说明了模型中的参数对最优定期检修策略的影响．

英文摘要：

A periodic maintenance policy for a degenerate production system in which the products are sold with free minimal repair warranty is considered. The degenerate process of the system is characterized by three states： in-control state, out-of control state and failure state. The amount of time that the process stays in in-control state and out-of-control state are both assumed to be exponentially distributed. The production system is overhauled at fixed time t or at failure, whichever occurs first. The optimal periodic overhaul time t＊ minimizing the expected cost per item per cycle is analytically discussed, and three special cases show the property of the optimal value t. In addition, sensitivity analysis and numerical examples concerning model parameters are carried out to illuminate the effects of the model parameters on the optimal periodic overhaul policy.