Development of practical Methods for Design and Reliablility Testing Based on Structura Reliability Engineering

本研究以结构可靠性调查为基础，旨在发展具有理论基础和实用价值的设计和可靠性试验方法。方法在不使用分布表的情况下，开发了使用分布表的方法，并编制了计算机程序。不使用分布形式的方法的发展(1)仅基于均值和方差使用失效概率上界Pfgu的方法：在没有施加严重条件的情况下，得到了计算Pfgu的公式。这个公式可以使PFU比现有公式给出的值低约50%。利用该公式，建立了陶瓷的设计方法和可靠性检验方法，并对二阶矩方法中使用的可靠性指标进行了检验。(2)陶瓷验证试验方法：考虑卸载过程中的断裂发生，提出了一种保证最小所需强度的试验方法。(3)基于模糊集理论的方法：将主观模糊性考虑到设计和可靠性试验中，提出了一种将两个或多个主观评价相结合的方法。(1)基于可靠性的变幅疲劳设计方法：考虑临界累积循环比对断裂的离散性和实际累积循环比的离散性，提出了一种实用的设计方法。(2)基于可靠性的低周疲劳设计方法，对现有的基于ASME锅炉压力容器规范的方法进行了分析，提出了一种更合理地考虑疲劳寿命离散性的方法。计算机程序的开发用PROLOG语言开发了故障树自动生成的计算程序。

Based on structural reliability enquineering, this research project aims to develop methods for design and reliability testing which have theoretical basis and practical applicability. Methods without use of distribution forms, methods with use of distribution forms, and a computer program were developed.1. Development of methods without use of distribution forms(1) The method which uses the upper bound of the probability of failure, Pfgu, based on the mean and variance alone: A formula for Pfu was obtained for the case where no serious condition was imposed. This formula could give Pfu about 50% lowe than the value given by the existing formula. Using this new formula, the methods for design and reliability testing were developed and examined< The reliability index used in the second moment method was alos examined.(2) Method of proof testing of ceramics: Taking account of fracture occurrence during unloading, a testing method of assuring the minimum required strength was developed.(3) Method based on fuzzy set theory: Taking account of subjective fuzzyness into design and reliability tesing, a method of combining two or more subjective evaluation was developed.2. Development of methods with use of distribution forms(1) Reliability-based design method for variable amplitude fatigue: Considering scatter of the critical cumulative cycle ratio to fracture and that of the applied cumulative cycle ratio, a practical design method was developed.(2) Reliability-based design method for low cycle fatigue; The existing method based on ASME Boiler and pressure Vessel Code was examined, and a more rational method to take account of the scatter of fatigue life was devaloped.3. Development of computer programThe compute program for automatic construction of fault tree used in FTA was developed using PROLOG.