A system approach to reliability verification test design

In automotive and other industries, reliability validation involves a series of individual reliability tests, each targeting a subset of product overall failure modes. The design of each individual test is based on the predefined reliability target and confidence level, generally set as standards rather than customized per component and test. This method has been very useful. However, there are two major questions frequently asked about the validity of this approach. First, it is not clear how the reliability requirements of these individual tests are determined and how they relate to the product's overall reliability performance. Consequently, evaluating product overall reliability based on all individual test results is not straightforward. Second, it is not clear how the individual tests directly impact the warranty cost and the overall customer experience at the product level. If customer experience needs be improved or if the warranty cost needs to be reduced, it is difficult to determine what the new reliability requirement for these individual tests ought to be to achieve the necessary improvement at the product level. In this paper, a system approach to reliability testing is presented. The product reliability goal must first be determined by establishing a product field reliability performance requirement. Then the individual tests are linked to field performance through distributional usage and stress. Lastly, three methods are proposed to allocate the overall reliability goal to the reliability targets of each individual test. Each method utilizes different information to provide a possible quantitative way for such an allocation. This methodology bridges the gap between the individual tests and the product-level reliability performance, allowing for an easier risk assessment and statistically sound decision making.