Methods of reliability determination and designing of reliability tests of mechanical structures

Abstract

Brief tests of methods of reliability assessment and designing of tests of mechanical structures, applying static, impact, heat, and vibration loads, including those based on a small volume of tests, are given. The methods are provided with PC software.At the Federal Nuclear Center much attention is being focused on reliability of mechanical structures at all stages of the life cycle, especially under vibration, heat, static, impact, blast, and other loads.A very important parameter of reliability of mechanical structures is probability of trouble-free performance over a fixed operation time. In general, mechanical structures can be regarded as a mixed combination of simple components, the probability of whose failure under loads is a typical problem.Several unique procedures for reliability assessment and designing of reliability tests in the process of laboratory design and development of articles and components thereof as well as methods for monitoring of reliability of articles and their parameters in the process of series production have been developed at VNIIÉF. Theoretical foundation has been laid and precision of the methods has been studied.Let us analyze the characteristics of each procedure. Procedure for Determining Reliability of Mechanical Structures Based on SingleTests. The foundation of this procedure is comprised of methods of determination of reliability parameters of single-use structures based on samples of a small number of tests:• by determining ultimate and actual (operating) loads;• at several levels based on Yes-No scheme; • by impact load at one or several levels; and • represented by repeatedly censored sampling. The procedure is based on fiducial distribution method using statistical modeling. Proximate values are obtained by modified linearization method. For determining reliability parameters, test and a priori data are used; the actual load may be both constant and random.Reliability parameters are determined as point values (mean value and standard deviation of probability of troublefree use or operation of the article), integral values of safe life, and so on.Combination of various types of data on operating (actual) F and ultimate Q loads may be presented in the form of a table (Table 1), where m Q , m F , Q, and F are mathematical expectations and values (mean values) of the random quantities