多个模式联合失效的设计点及概率的计算

提出了多个模式联合失效设计点的概念，并以此设计点作为计算联合失效概率的重要抽样函数的密度中心，算例表明本文方法可大大提高求多阶失效概率重要抽样法的投点效率和收敛速度，从而提高系统失效概率的计算精度。

Joint design point and failure probability calculations of multi mode

The failure probabilities of series and parallel system may be calculated by single failure probability and joint failure probability of multi mode. Importance sampling function centered at design point of single failure mode is generally adopted to compute the SFP. In reference , the JFP is simutaniously obtained as the importance sampling function of the single failure mode is adopted. However, when the joint failure domain is far away from the design points of the single failure modes, the sampling point efficiency is usually lower. Accoding to this case, a design point concept of the joint failure domain is presented, and the importance sampling function is centered at this point for estimating of the JFP. The sampling point efficiency and convergence for JFP are greatly increased based on the presented method, therefore the precision of system failure probability is also increased, which is proved by several illustrative examples.