Date of Award

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Engineering Management

Abstract

This study investigated the possibility of including the cost consequence of a failure in the a priori risk assessment methodology known as Failure Modes and Effects Analysis (FMEA). This entailed developing a model of the standard costs that are incurred when an electronic control module in an automotive application fails in service. These costs were related to the DFMEA ranking of the level of severity of the failure mode and the probability of its occurrence. A series of Monte Carlo simulations were conducted to establish the average costs expected for each level of severity at each level of occurrence. The results were aggregated using fuzzy utility sets into a 9 point ordinal scale of cost consequence. The criterion validity of this scale was assessed with warranty cost data derived from a case study. It was found that the model slightly underestimated the warranty costs that accrued, but the fit could be improved with adjustments dictated by actual usage conditions. The problems with the risk prioritization system of FMEA, referred to as RPN, were discussed and citations of literature on possible corrections to this system were presented. An attempt was made to compare the tendency of RPN to produce Pareto Optimality violations with a parallel system of risk prioritization involving cost. It was found that the Cost Priority Number” had a lower likelihood of producing optimality violations than did RPN. However, this is not heralded as a major advantage as CPN” is not put forth as a method of prioritizing financial risks inherent in a design or process.

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