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

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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.