Progressive-Stress Accelerated Degradation Test for Highly-Reliable Products

Abstract

For highly reliable products with very few test units, a progressive-stress accelerated degradation test (PSADT) has been proposed in literature to assess the product’s lifetime distribution. The results, however, are restricted to the case that the product’s degradation path follows a Brownian motion with linear drift rate. In practical applications, the product’s mean degradation path may be nonlinear. Hence, how to address the lifetime distribution under such situation is an interesting topic for reliability analysts. In this paper, a PSADT example with a non-linear degradation path is constructed by a cumulative exposure model. Then the product’s lifetime distribution is analytically obtained by applying the first passage time of its degradation path. Furthermore, we derive a relationship between the lifetime distribution of the PSADT and that of the conventional constant-stress degradation test. The results illustrate a new finding to extrapolate the product’s lifetime distribution under a normal stress. Last but not least, the usage of the proposed model and the efficiency of PSADT to reduce the product’s life testing time are demonstrated in the example.