Multi-Stress Equivalent Optimum Design for Ramp-Stress Accelerated Life Test Plans Based on D-Efficiency

Due to time and cost limitations, multi-stress accelerated life tests (ALTs) have been gradually applied in the fields of experimental design and reliability estimation for highly reliable and long-life products. To develop more efficient and concise test plans, it is necessary to study an equivalent experimental design method to create an equivalent conversion approach for different ALT plans. This paper presents the equivalent optimum design method combined with D-efficiency and asymptotic variance. In this method, the Fisher information matrix determinant is proposed as the equivalent feature variable. D-efficiency is a new equivalent criterion applied in the ALT design method and is measured using the ratio of Fisher information matrix determinants. The objective is to minimize the test time at a given efficiency and under asymptotic variance constraints without loss of test estimation accuracy. Based on the proposed equivalent method, a constant-stress ALT plan was successfully converted into its equivalent step-stress or ramp-stress ALT plan. Finally, an example is presented to demonstrate the equivalent ALT design of an electrical product with two stresses. The constant-stress ALT is equivalently designed for the ramp-stress ALT plan, and the sensitivity of the D-efficiency is analyzed. The results show that the proposed equivalent test scheme can shorten test time while achieving the same estimation accuracy.