Systems Engineering (SE)

New DFR Method Captures All Critical Failure Modes into FMEA in Half the Time

by Howard C Cooper; Dmitry Tananko; J. Gordon Shutek


Situation: There are many advantages during development of a design that come from doing Design Failure Mode Effects Analysis (DFMEA). These advantages include more reliable, safer, self-diagnosing, designs with higher Availability. Strictly from a Design for Reliability (DFR) viewpoint, DFMEA is the key tool to; a. identify and prioritize most critical potential Failure Modes (FMs) of the design, before design development, b. Document critical FM effects and root causes, and c. facilitate corrective actions and DVP&R planning, and d. form a reliability model which can be used to track reliability over the life of the design. Problem: Since even small and simple designs often have a few hundred potential failure modes, preparing a good DFMEA is always a problem of Effectiveness vs., Efficiency. Traditionally it has been very hard to achieve Effectiveness when limited time, money and resources are available and the push for Efficiency, speed or deadlines, causes critical FMs to be missed all together. Likewise, Efficiency is hard to achieve due to the large number of potential FMs for each Subsystem. DFMEA preparation time can easily consumes 50 – 80 hours, or more, for both Reliability and for Design Engineers. Solution Method & Tool: This paper presents for the first time, the “Function-to-Hardware Decomposition Table”, a simple method for systematically capturing all potential failure modes into an FMEA. It establishes confidence that failure modes are not being missed or overlooked in the FMEA. One can also use of the Function-to-Hardware Decomposition Table (FH-Decomp) to prioritize all subsystem (hardware) functions, further improving confidence of a trustworthy FMEA methodology and places focus on critical failure mode root causes and mitigating actions, to improve reliability. Presented are two forms of the FH-Decomp Table and how to use them to achieve the above three benefits to DFR and to DFMEA preparation activities.