Optimal design of accelerated degradation test plan under modified ramp-stress loading

Abstract

This paper deals with the design of optimal modified ramp-stress Accelerated Degradation Test (ADT) using the assumption that the product's degradation path follows Wiener process. In an ADT, failure occurs when the performance characteristic crosses the critical value the first time. The model parameters are estimated using method of maximum likelihood. The optimum plan consists of finding the optimum number of specimens, optimum stress change point(s), and optimum stress rates by minimising asymptotic variance of estimate of q-th quantile life at use condition, subject to the constraint that total testing or experimental cost does not exceed a pre-specified budget. A numerical example is given to demonstrate the proposed model. Sensitivity analysis is carried out to examine the robustness of the proposed plan. A comparative study is performed to highlight the merit of the proposed plan.