Practical design of partially accelerated degradation test with two stress variables under step-stress loading scheme

Abstract

The number of samples and test duration during the development stage are usually insufficient, since it is time consuming and costly to collect reliability information for highly reliable products. Therefore, a more efficient test design is required to collect as much information as possible. In addition, considering two or more stress variables simultaneously can catalyze the degradation mechanism. Thus, a planning strategy for partially step-stress accelerated degradation tests with two stress variables is developed under the assumption that the degradation characteristic follows a Wiener process. Based on the compromise concept, the mid stress levels of each stress variable is determined, such that asymptotic variance of the maximum likelihood estimator of the qth quantile of the distribution under use conditions is minimized. A scenario analysis for a numerical example considering the experimental situation is provided to demonstrate the practicality of the proposed strategy.