Common cause failure (CCF) is analyzed as a manifestation of the probabilistic characteristics of component failure rate:probability stemming from stochastic environment load. CCF revolved concepts, such as 'root cause' and 'coupling mechanism' are interpreted mathematically from the viewpoint of random environment load bringing about failure dependency. Opinions about 'inherent CCF' and 'additional CCF', 'absolute CCF' and 'relative CCF' are presented and discussed. An easy-to-use CCF model is developed through multi-dimension environment load-component strength interference analysis and knowledge based parameter discretization. Owing to its strict statistical foundation, such a model has the ability of estimating component failure rate:probability and common cause failure rates: probabilities consistently, dealing with low redundancy system CCF and high redundancy system CCF uniformly, and predicting high multiplicity failure rate:probability based on low multiplicity failure data satisfactorily.

文章分析了生产线制造过程的数字化制造环境，提出了基于扩展事件过程链的生产线制造过程建模仿真方法。在此基础上，采用面向对象软件方法，详细设计和实现了生产线制造过程建模仿真系统的各个组成模块。该软件系统应 用于实际生产线的规划设计，对生产线进行仿真分析和性能优化，与’149 其它子系统集成运行，提高了生产线制造过程的整体性能和经济效益。

The present paper is mainly concerned with pipe system failure probability estimation. For this purpose, a multiple component dependent failure (MCDF) model is introduced to deal with dependency among pipe segment failures. The MCDF model is directly derived from load-strength interference analysis with the underlying notion that stochastic environment load brings about failure dependency. The influence of pipe segment failure dependency on pipe system failure probability is addressed and a modified system failure probability model is presented. It is also shown that, with regard to a pipe system, the multiple failures of pipe segment leaks might lead to a pipe system disabling leak or even to a break. The probability of pipe system disabling leak or break induced by the imultaneous failures of multiple segment leaks is estimated by means of the MCDF model. The estimation results indicate that pipe system failure probability depends not only on the mean values of the respective segment failure probability random variables, but also on other distribution parameters (e.g., the standard deviations) of them. Pipe system failure probability estimated by means of the modified model is sometimes several times lower than that estimated by the conventional system failure probability model.

In order to demonstrate the role of multi-crack growth:coalescence in the leak-before-break concept, Monte Carlo method is applied to simulate multiple crack growth:coalescence behavior which are quite common to component vulnerable zone such as weld. For the multi-crack behavior simulation, typical component vulnerable zone is postulated to have randomly distributed initial cracks. The parameters such as crack number, crack location and crack length are all treated as random variables. The crack distribution parameters are assumed according to generic knowledge available. For single crack situation, the crack size with detectable leak and the critical crack size with unstable propagation are cited from literature. For the multi-crack situation, an equivalent crack-opening area is used to identify the detectable leak. The simulation results show that, for LBB concept related components, the existence of multiple cracks might lead to much shorter leak-free time and much shorter allowable response time compared with those in single crack situation.

对TC2钛合金焊接接头进行硬度测试以及拉伸、疲劳对比试验，并观察全部疲劳断口，分析焊接接头光滑试样的疲劳性能与影响因素。结果表明，焊缝区的硬度最高，约高于母材50HV，塑性较差，焊缝中的微观焊接缺陷是不可避免的，是影响焊接接头疲劳寿命的主要因素；热影响区的硬度较低，塑性较好，其拉伸强度是焊接接头部位的最薄弱区，但却有较好的疲劳性能。在99%可靠度的前提下，焊接接头的疲劳寿命约为母材寿命的46%。