A Review of Recent Research and Current Issues in Accelerated Testing

Abstract

Summary Accelerated tests are used to obtain timely information on the life distribution or performance over time of products. Test units are used more frequently than usual or are subjected to higher than usual levels of stress or stresses like temperature and voltage. Then the results are used to make predictions about product life or performance over time at the more moderate use or design conditions. Changes in technology, the calls for rapid product development, and the need to continuously improve product reliability have put new demands on the applications for these tests. In this paper we briefly review the basic statistical and other ideas behind accelerated testing and give an overview of some current and planned statistical research to improve accelerated test planning and methods. Today's manufacturers are facing strong pressure to develop newer, higher technology products in record time, while improving productivity, product field reliability, and overall quality. This has motivated the development of methods like concurrent engineering and encouraged wider use of designed experiments for product and process improvement efforts. The requirements for higher reliability have increased the need for more up-front testing of materials, components and systems. This is in line with the generally accepted modern quality philosophy for producing high reliability products: achieve high reliability by improving the design and manufacturing processes; move away from reliance on inspection to achieve high reliability. Estimating the time-to-failure distribution or long-term performance of components of high reliability products is particularly difficult. Most modern products are designed to operate without failure for years, tens of years, or more. Thus few units will fail or degrade importantly in a test of practical length at normal use conditions. For this reason, Accelerated Tests (ATS) are used widely in manufacturing industries, particularly to obtain timely information on the reliability of product components and materials. Generally, information from tests at high levels of stress (e.g., use rate, temperature, voltage, or pressure) is extrapolated, through a physically reasonable statistical model, to obtain estimates of life or long-term performance at lower, normal levels of stress. In some cases stress is increased or otherwise changed during the course of a test (step-stress and progressive-stress ATS). AT results are used in the reliability-design process to assess or demonstrate component and subsystem reliability, certify components, detect failure