随机载荷作用下的零件动态可靠性模型

运用顺序统计量和概率微分方程建立随机载荷作用下的零件动态可靠性模型，并研究零件可靠度和失效率随时间的变化规律。首先，分析随机载荷多次作用时零件的失效过程，从载荷作用的统计学意义出发，运用顺序统计量建立随机载荷多次作用时等效载荷的累积分布函数和概率密度函数。进一步，根据应力—强度干涉理论建立载荷多次作用下的零件可靠性模型。运用泊松随机过程描述载荷的作用过程，分别建立强度不退化和强度退化时的零件动态可靠性模型。研究表明，强度不退化或退化不明显时，零件的可靠度随时间逐渐降低，失效率随时间逐渐减小；考虑强度退化或强度退化明显时，零件的可靠度随时间逐渐降低且较为明显，失效率具有“浴盆”曲线的全部特征。

TIME-DEPENDENT RELIABILITY MODEL OF COMPONENT UNDER RANDOM LOAD

The time-dependent reliability model of component is developed with the order statistic and the probability differential equation. The relationship between reliability and time and the relationship between failure rate and time are studied. First, the failure mechanism of component is analyzed when random load acts for multiple times, and from the statistic meaning of random load action, the cumulative distribution function and the probability density function of equivalent load are derived with the order statistic. Further, the reliability model of component under random repeated load is built with the stress-strength interference theory. The loading process is described with the Poisson stochastic process, and the time-dependent reliability model of component without strength degeneration and the model with strength degeneration are derived respectively. The result shows that reliablity decreases with time and the failure rate also decreases with time when strength degeneration is not considered and can be neglected. When strength degeneration is obvious and is considered, reliability decreases with time more obviously and the failure rate has the whole feature of bathtub curve.