Reliability demonstration based on accelerated degradation testing for unknown model parameters

Conventional reliability demonstration tests are becoming increasingly difficult to apply for high-reliability and long-lifetime products owing to the excessive test duration, which conflicts with the marketplace demands for decreased development time. Accelerated degradation testing has been strongly recommended to reduce test time, but few studies employ this method for reliability demonstrations. In this article, a test methodology based on accelerated degradation testing is developed to demonstrate the reliability target for the case in which the model parameters for the test plan design are unknown. In the proposed procedure, step-stress accelerated degradation testing is employed as a preliminary test to estimate the model parameters. The data from step-stress accelerated degradation testing are converted based on equivalent degradation criterion and then used to make decisions by the method of two steps accelerated reliability demonstration test. If there are not enough converted data to make a decision, an accelerated degradation testing as a complementary test is conducted to complete the demonstration according to the estimates of the model parameters from the preliminary test; the two steps accelerated reliability demonstration test method is applied. The proposed methodology incorporates step-stress accelerated degradation testing with two steps accelerated reliability demonstration test to permit the test duration to be reduced as much as possible. It is useful to demonstrate a high-reliability target at long mission times within a feasible test duration when the design parameters are unknown.