Batch sequential designs for accelerated life tests and an application to polymer composite fatigue test

Accelerated life tests (ALTs) are widely used in industry and many optimal ALT test plans are developed in literature. To achieve an efficient optimal test plan, one needs to make sure that the planning values used in the test planning are not far away from the true parameters, which is challenging because lifetime data are not collected yet in the planning stage to estimate the true parameters. To overcome the weakness, sequential designs are developed and the parameter estimates are updated during the sequential testing process. Due to the sequential nature, one drawback of the sequential strategy is that it usually requires a long total testing time (TTT). Motivated by industrial needs, we propose batch sequential design (BSD) in ALT setting, in which multiple units are tested simultaneously while sequential parameter updates are also made. The proposed BSD for ALT can not only reduce the TTT but also preserves the advantage of sequential designs. After proposing two types of BSD strategies, we use a comprehensive simulation study to demonstrate the advantages of the proposed BSD in ALT setting. We also develop a method to find the optimal batch size which is essential for the deployment of the BSD in practice.