Practical lifetime estimation strategy based on partially step-stress-accelerated degradation tests

The number of samples available for testing of a newly developed item is quite small, and only limited reliability information is available in many real cases. Therefore, a multi-purpose test plan is essential for reliability estimation. To reflect real product development scenarios, this study presents a practical lifetime estimation strategy based on a partially step-stress-accelerated degradation test (PSSADT) with three stress levels. The PSSADT plan assumes that the degradation path follows a Wiener process and that the cumulative exposure model holds. The proposed test plan determines the stress level in the final loaded step that minimizes the asymptotic variance of the maximum likelihood estimator of the qth quantile of the lifetime distribution under the use condition. Finally, the test scenario, which includes the necessary validity check of the acceleration model, is illustrated with an example.