Improving `MIL-HDBK-217 type´ models for mechanical reliability prediction

A combination of the MIL HDBK 217-type reliability-prediction model and Weibull distribution techniques which will account for the fact that the failure rate varies with time is suggested. Techniques to determine the main population Weibull parameters from a hazard plot are also discussed. When a prediction is to be performed, the MIL HDBK 217-type model is used to predict the failure rate. The characteristic life is then calculated by dividing the expected Weibull slope by the predicted failure rate. A point is then plotted on Weibull probability paper at a time equal to the predicted characteristic life and at a failure percentage of 63.2. A line is then drawn through this point at the expected Weibull slope. This graph can be used to determine the percent failure at any time of interest. The reliability, in percent, can be calculated at any point by subtracting the failure percent from 100