Comparison Analysis of Efficiency for Step-Down and Step-Up Stress Accelerated Life Testing

We compare the practical efficiency of step-down and step-up stress accelerated life tests based on four different criteria through theoretical studies, and intensive Monte-Carlo simulations. We consider Weibull, and lognormal distributions for the lifetime of products at each stress level; and deal with type-I, and type-II censoring schemes. Through theoretical and simulation studies, we demonstrate that under a type-I censoring scheme, the step-down test plan results in a shorter mean failure time of testing units than that of the step-up stress accelerated life test. With type-II censoring, the step-down test is also preferred for products with long lifetimes, while the step-up procedure works better applied to units with early and occasional failures.