Planning Optimal Degradation Tests in Consideration of Budget and Statistical Accuracy at Different Stress Levels

Degradation testing is a useful technique for demonstrating the process of failure over time. The challenge when planning a test is to determine how many test units should be examined and how long the test should run in order to get sufficient data and reach the predefined reliability targets within the provided and/or available test budget. In this paper, a novel strategic workflow for identifying the sample size and the number of measurements during each test run in consideration of the accuracy and budget will be proposed. The number of sample sizes and the testing time are constantly adapted until the predetermined requirements are met. The presented work results in a treatment of a mechanical failure mode, i.e., pitting of transmission gears. The tool covers the determination of resources in a novel procedure using existing methods. We apply this degradation model to degradation signals obtained through the relatively time-consuming and cost-intensive accelerated testing of gears on a test bench. The results contain the optimal sample size, the number of inspections for each sample and the asymptotic lifetime and its variance coefficients.