Optimal design for step-stress accelerated degradation testing with competing failure modes

With the development of engineering and science technology, many products are able to operate for a long period of time before failure. Accelerated life testing (ALT) has been proposed to evaluate reliability and life of these products, but ALT may involve the collection of only a few failures (time-to-failure data). To overcome this problem, accelerated degradation testing (ADT) is presented. Competing failure mechanisms happen in many electronic devices. However, as for designing an efficient ADT experiment, competing failure mechanisms were seldom discussed. In this study, we first use drift Brownian motion to model a typical step-stress ADT (SSADT) problem. Then, according to competing failure rule, we established reliability model of the product. Next, under the constraint that the total experimental cost does not exceed a predetermined budget, our objective is to minimize the asymptotic variance of the estimated hundred percentile of the competing reliability model of product. This optimal testing plan gives the optimal number of test units and inspection times at each stress level. Finally, we analyze the different optimal plans with different budgets, different levels of stress and different stress steps. Based on these analyses, we propose the guideline of stress loading principles of SSADT.