Browsing by Author "Henriques, Elsa"
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- Multi-variable prioritization model for risk evaluation scenarios in mechanical designPublication . Anes, Vitor; Henriques, Elsa; Freitas, Sofia de; Reis, LuísRisk prioritization is an important procedure in FMEA methodology where failure modes are prioritized using the so-called risk priority number (RPN), which prioritizes failure modes based in only three risk variables usually, severity, occurrence, and detectability. However, in some risk scenarios, more than three risk variables can improve risk prioritization, but an ease risk prioritization model like RPN for more than three risk variables cannot be found in literature. We developed a risk prioritization model to prioritize failure modes evaluated with more than three risk variables. The model has the same ease of use found in the traditional risk prioritization number model, but it overcomes its drawbacks. Results show that the risk prioritization made with the proposed model agrees with the expectations made for the risk scenario. Moreover, it was shown that the proposed model is injective, surjective and can prioritize failure modes based on a given order of importance defined by the user. These features show that the major shortcoming found in the conventional risk prioritization were overcome on the proposed model. Our model opens the possibility of traditional FMEA users to use more than three risk variables without the need of prior knowledge, fact that has been the main reason of traditional risk priority number popularity, despite its strong shortcomings.
- A new risk prioritization model for failure mode and effects analysisPublication . Anes, Vitor; Henriques, Elsa; de Freitas, M.; Reis, LuisFailure modes and effects analysis is a framework that has been widely used to improve reliability by prioritizing failures modes using the so‐called risk priority number. However, the risk priority number has some problems frequently pointed out in literature, namely its non‐injectivity, non‐surjectivity, and the impossibility to give weights to risk variables. Despite these disadvantages, the risk priority number continues to be widely used due to its higher simplicity when compared with other alternatives found in literature. In this paper, we propose a novel risk prioritization model to overcome the major drawbacks of the risk priority number. The model contains 2 functions, the risk isosurface function that prioritizes 3 risk variables considering their order of importance in a given risk scenario, and the risk prioritization index function which prioritizes 3 risk variables considering their weights. The novelty of the proposed model is its injectivity, surjectivity, and ease of use in failure modes prioritization. The performance of the proposed model was analyzed using some examples typically used to discuss the conventional risk priority number shortcomings. The model was applied to a case study and its performance correlated with other risk prioritization models. Results show that the failure modes prioritization reached with the proposed model agrees with the expectations made for the risk scenario.