Cost Optimization of Step-Down-Stress Accelerated Life Testing

Abstract

Many products have a high failure rate in their early operating lives. step-down-stress accelerated life testing has been widely accepted as a method of screening out defects before a product is shipped to the customer. In the literature it is often assumed that the failure pattern follows a specific distribution and the step-down-stress accelerated life testing is operated under approximately the same environment as that of the early operating life of the product. In this paper we require the product life distribution to have some specified properties. The step-down-stress accelerated life testing is operated under severe (stress) conditions involving high temperature, voltage, etc. and the product’s residual life depends on the step-down-stress level and the length of step-down-stress accelerated life testing period. Accelerated step-down-stress before shipment will reject poor-quality products and improve product reliability within a warranty period. Accelerated step-down-stress saves time but may cost more. Our goal is to find the appropriate testing parameters to minimize the total of testing, manufacturing, quality and reliability costs. The upper and lower bounds for the optimal step-down-stress accelerated life testing time are derived.