A Sensitivity Analysis on Component Reliability from Fatigue Life Computations

This paper identifies some uncertainties in determining high component reliability at a specified lifetime from a case study involving the fatigue life of a helicopter component. Reliabilities are computed from results of a simulation process involving an assumed variability (standard deviation) of the load and strength in determining fatigue life. The uncertainties in the high reliability computation are then examined by introducing small changes in the variability for the given load and strength values in the study. Results showed that for a given component lifetime a small increase in variability of load or strength produced large differences in the component reliability estimates. Among the factors involved in computing fatigue lifetimes, the component reliability estimates were found to be most sensitive to variability in loading. Component fatigue life probability density functions were obtained from the simulation process for various levels of variability. The range of life estimates were very large for relatively small variability in load and strength.