Calculation and assessment of measures of the residual operating life of non-restorable items

Abstract

The widespread use of cutting-edge components in the composition of non-restorable items has made it difficult to assess their reliability at the stages of designing and production. Therefore, items with underestimated values of the assigned (warranted) operating life are put into operation. By now, the service life of such items has reached the assigned limits, the items still maintaining a fairly high dependability rate. Thus, there has been a problem of extending the service life beyond the originally assigned rates. As originally assigned rates are determined by such measures as the mean operating life and gamma-percentile operating life, the non-restorable item’s life margin is determined as related to these rates by means of measures of the residual operating life, namely the mean residual operating life and gamma-percentile residual operating life. The mean residual operating life and gamma-percentile residual operating life are determined in this paper, to calculate the extendable service life. For these measures, we have derived calculation formulas and assessments which make it possible to determine the extended service life. In addition, for these measures, calculation formulas and assessments are obtained for non-restorable items whose margin allocation is distributed exponentially and uniformly. The paper examines the issues of attainability of the obtained assessments and the conditions of their attainability; also, the influence of failure rate monotonic change on the assessments is analyzed.