Design of accelerated reliability tests based on simple-step-stress model

The accelerated life tests can obtain information on lifetime characteristics of products quickly. Then, the products can be submitted to higher levels of stress in various ways such as constant, step, and progress stress. In a constant-stress model, products are run under a constant level of stress until all products fail or a time limit is reached. A step-stress model allows the stress setting to be changed at a prescribed time or upon the occurrence of a fixed number of failures. In a progress-stress model, the stress is continuously increased over time. Until now, under the assumption of the functional relationship between the parameters of lifetime distribution and applied stress, there are many studies about parameter estimation using data obtained from an accelerated life test. In this study, instead of the parameter estimate problem, the authors consider a new design procedure of accelerated life tests based on the simple-step-stress model for assuring the mean time to failure (MTTF) at usual stress with specified producer and consumer risks under the condition that the parameters of the lifetime distribution at two stress levels are provided. The practical usage of the proposed design procedure is illustrated through some numerical examples.