Estimation of system reliability using a "non-constant failure rate" model

One of the most controversial techniques in the field of reliability is reliability-prediction methods based on component constant-failure-rate data for the estimation of system failure rates. This paper investigates a new reliability-estimation method that does not depend upon constant failure rates. Many boards were selected from the Loughborough University field-reliability database, and their reliability was estimated using failure-intensity based methods and then compared with the actual failure intensity observed in the field. The predicted failure-intensity closely agrees with the observed value for the majority of a system operating lifetimes. The general failure intensity method lends itself very easily to system-reliability prediction. It appears to give an estimate of the system-reliability throughout the operating lifetime of the equipment and does not make assumptions, such as constant failure rate, which can be detrimental to the validity of the estimate. The predictions seem, on present evidence, to track the observed behavior well, given the uncertainties that are evident in the field. The failure intensity method should be investigated further to see if it is feasible to estimate the system reliability throughout its lifetime and hence provide a more realistic picture of the way in which electronic systems behave in the field