Special topics for consideration in a design for reliability process

In this paper, we look at certain areas of the Design For Reliability (DFR) process where missteps or misapplications are common due to misunderstood “common practices” or due to attempts to either oversimplify the process or introduce unnecessary complexity. We show how these practices can hav e detrimental effects on the reliability of a product and identify what the areas of improvement are. We identify three major areas where missteps most commonly occur. The first of these is during the early stage of the DFR process, including the practices of setting requirements and specifications. We explore the importance of understanding usage and environmental conditions and discuss issues such as using Mean Time Between Failures as a sole metric, or mean estimates without associated confidence bounds. The second area prone to missteps is during the DFR stage where the reliability of a product is quantified; here, we discuss problems such as testing for failure modes that don't correlate with actual usage, using inappropriate life-stress relationship models or modeling the failure rate behavior incorrectly. The third time problems are likely is during the DFR stage that addresses the assurance and sustaining of reliability; here, we present missteps related to setting up demonstration tests without statistical significance, not colleting the appropriate data for warranty analysis and either ignoring suspensions or assuming that units have survived beyond the warranty period.

SUMMARY & CONCLUSIONS

In this paper, we look at certain areas of the Design For Reliability (DFR) process where missteps or misapplications are common due to misunderstood “common practices” or due to attempts to either oversimplify the process or introduce unnecessary complexity. We show how these practices can have detrimental effects on the reliability of a product and identify what the areas of improvement are.