Progressive-Stress Accelerated Degradation Test for Highly-Reliable Products

For highly reliable products with very few test units, a progressive-stress accelerated degradation test (PSADT) has been proposed in the literature to obtain timely information of the product´s lifetime distribution. The results, however, are restricted to the case where the product´s degradation path follows a Wiener process (Brownian motion) with a linear drift rate. But in practical applications, the product´s mean degradation path may be non-linear. Hence, how to address the lifetime distribution in this situation is a worthy topic for reliability analysts. In this paper, a PSADT with a non-linear degradation path is constructed using the cumulative exposure model. Then the product´s lifetime distribution can be analytically obtained by the first passage time of its degradation path. Furthermore, we derive an exact relationship between the lifetime distributions of the PSADT, and the conventional constant-stress degradation test (CSDT), which allows us to extrapolate the product´s lifetime distribution under typical stress. Finally, the usage of the proposed model, and the efficiency of PSADT to reduce the product´s life testing time are demonstrated in the example.