不确定性载荷作用下的零件时变可靠性模型

Time-variant Reliability Model of Components Under Uncertain Loads

分析现有时变可靠性建模方法的特点,建立不确定性载荷作用下的零件时变可靠性模型,给出基于载荷和强度分布的零件可靠度和失效率计算表达式。研究载荷作用的特点,建立不确定性载荷作用过程的二维描述法。在此基础上,分别得到强度不退化和退化时的零件时变可靠性表达式。研究表明,即使强度不退化,零件的可靠度和失效率也会随时间逐渐降低;强度退化时,可靠度随时间降低较为明显,失效率具有"浴盆"曲线的特征。在载荷和强度分布已知的情况下,可直接运用本文模型计算零件在任意时刻的可靠度和失效率。当给定许用失效率时,运用本文模型可以更客观地划分零件的早期失效期、偶然失效期和耗损失效期,进而确定零件筛选试验时间、可靠寿命等指标,对零件进行全寿命周期管理。

A new model of time-variant reliability under uncertain loads is developed after discussing the existing methods for modeling time-variant reliability. The uncertain loading process is studied and characterized by a two-dimension description. The expressions are derived of the reliability and failure rate of components based on the probability distribution of load and strength, with and without strength degeneration. The result shows that even without strength degeneration, the reliability and failure rate of components decrease with time. When strength degenerates, reliability decreases with time more obviously, and the failure rate has the feature of a bathtub curve. On condition that the probability characteristics of load and strength are known, the relia- bility and failure rate of components at any time can be calculated by the model proposed. When the allowable failure rate is specified, the three periods （namely, early failure period, random failure period, and wear-out failure period） can be reasonably divided according to the proposed model. Furthermore, the time for stress screening test and reliable operation life can be determined. Therefore, the model developed in this article is helpful for the life cycle management of components.