Optimal Designs of Multiple Step-Stress Accelerated Life Tests for One-Shot Devices With Weibull Lifetime Distributions

Step-stress accelerated life tests have gained increased attention in industry and academia as a method to induce rapid product failures and gather more failure data for reliability analysis. This article presents the optimal step-stress accelerated life testing design with multiple stress levels for one-shot devices, which are designed for single-use and subsequent disposal. The proposed approach determines the optimal inspection times and allocation of test items at different stress levels to minimize the asymptotic variance of the maximum likelihood estimator of the reliability at a specific mission time under normal operating conditions, assuming Weibull lifetime distributions. One of the key contributions of this article is that the constrained optimization problem is reformulated as unconstrained, enabling the use of standard optimization techniques. A real case study of grease-based magnetorheological fluids is used to demonstrate the practicality of the proposed optimal design approach. The results indicate that a step-stress accelerated life test with three stress levels and gradually decreasing temperature levels is recommended for the reliability assessment. This article challenges the conventional assumption that step-stress accelerated life testing designs with increasing stress levels are always the most efficient approach. The proposed framework provides a useful tool for designing efficient step-stress accelerated life tests to evaluate the reliability of one-shot devices.