On the Determination of a Safe Life for Classes of Distributions Classified by Failure Rate

摘要

Using a lower tolerance bound as the derated life provides a guaranteed service period with the confidence level as a measure of safety in situations where mass production is contemplated. However, when only a limited number of items are to be produced, the probability of no failures among the fleet of specified size provides a better measure of assurance. Assuming that the life distribution is one of a specified set of subclasses of those distributions which have increasing failure rates we find those derating functions which can be used to provide lower tolerance bounds of given confidence or a safe service life with specified fleet assurance. A method of finding such derating functions is exhibited and the calculation of a lower bound for the probability of no failure in the fleet is carried out when such derating functions are used. The confidence in the tolerance bound and the assurance of no fleet failure are compared when using bounds obtained from these derating functions. (Author)