Abstract
Failure mode and effect analysis (FMEA) is a structured technique for identifying risks that may occur during a given stage of a system’s life cycle. However, the use of the risk priority number (RPN) in traditional FMEA results in difficulties with regard to quantification of the degree of risk in the hierarchical failure structure. This study proposes the use of a hierarchical time-dependent FMEA approach to overcome the limitations encountered during the implementation of traditional FMEA approaches. In place of the RPN, a probabilistic loss model is developed under a hierarchical structure considering the elapsed time from the failure-cause (FC) to the system failure. By assuming exponential and case functions for each occurrence and detection time instant, the expected loss corresponding to each FC can be evaluated. As a result of the practical application of the time-dependent probabilistic model through the numerical example, we could reasonably evaluate the risk from the cause of failure in the hierarchical structure in terms of economic loss.
Highlights
For assuring the safety and reliability of a system, engineers identify all possible failures and their corresponding failure-causes (FCs) and take actions to reduce the occurrence of FCs or mitigate the loss due to their consequences
In place of the risk priority number (RPN), a probabilistic loss model is developed under a hierarchical structure considering the elapsed time from the failure-cause (FC) to the system failure
Failure mode and effect analysis (FMEA) is a structured method used for defining, identifying, and mitigating known and/or potential causes of failures, problems, errors, etc. in systems, designs, processes, and services prior to them being made accessible to customers [1]
Summary
For assuring the safety and reliability of a system, engineers identify all possible failures and their corresponding failure-causes (FCs) and take actions to reduce the occurrence of FCs or mitigate the loss due to their consequences. FMECA was approached as a multi-criteria decision-making technique that integrates four different factors, as follows: The chance of failure, the chance of non-detection, the severity, and the expected cost. Assumed an exponential probability distribution for the evaluation of occurrence and detection times for failures and their corresponding causes, and the expected severity was derived for each FC. In another study by Jang et al [23], both time and a two-level hierarchical structure were employed to evaluate risks of the failure mode and its corresponding cause. Jang et al [37] tried to systematically identify the root causes of failure modes based on a their proposed FMEA sheet and scientifically evaluated the relevant risk priorities for hierarchical FCs. Peeters et al [32] presented the failures hierarchically through FTA and conducted risk assessment through FMEA.
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