A practical reliability allocation method considering modified criticality factors

Reliability allocation is a very critical step of product development process for setting achievable reliability goals. The majority of existing methods allocate system level failure rate target to subsystems or components instead of allocating failure rate reduction (improvement) targets. This approach of reliability allocation often allocates reliability goals lower than existing reliability levels. Further, the existing methods failed to effectively capture potential for improvement and impact of improvement efforts on failure effects while calculating reliability allocation weights. This paper investigates the limitations of existing approaches and proposes a modified criticality measure for allocating system level reliability improvement goal to subsystems. The modified criticality measure is developed considering non-linear phenomena for both severity rating and failure rate to capture potential for improvement. The failure rate reduction targets are assigned in proportion of improvement potential. A case example is presented to demonstrate the effectiveness of the proposed approach.