Definitions typically used in Failure Mode Effects Analysis (FMEA)
1.Failure: The loss under stated conditions.
2.Failure mode: The specific manner or way by which a failure occurs in terms of failure of the item (being a part or (sub) system) function under investigation; it may generally describe the way the failure occurs. It shall at least clearly describe a (end) failure state of the item (or function in case of a Functional FMEA) under consideration. It is the result of the failure mechanism (cause of the failure mode). For example; a fully fractured axle, a deformed axle or a fully open or fully closed electrical contact are each a separate failure mode.
3.Failure cause and/or mechanism: Defects in requirements, design, process, quality control, handling or part application, which are the underlying cause or sequence of causes that initiate a process (mechanism) that leads to a failure mode over a certain time. A failure mode may have more causes. For example; "fatigue or corrosion of a structural beam" or "fretting corrosion in an electrical contact" is a failure mechanism and in itself (likely) not a failure mode. The related failure mode (end state) is a "full fracture of structural beam" or "an open electrical contact". The initial Cause might have been "Improper application of corrosion protection layer (paint)" and /or "(abnormal) vibration input from another (possible failed) system".
4.Failure effect: Immediate consequences of a failure on operation, function or functionality, or status of some item.
a.Indenture levels (bill of material or functional breakdown): An identifier for system level and thereby item complexity. Complexity increases as levels are closer to one.
b.Local effect: The failure effect as it applies to the item under analysis.
c.Next higher level effect: The failure effect as it applies at the next higher indenture level.
d.End effect: The failure effect at the highest indenture level or total system.
5.Detection: The means of detection of the failure mode by maintainer, operator or built in detection system, including estimated dormancy period (if applicable)
6.Probability: Likelihood that a failure may happen.
7.Risk Priority Number (RPN) = Probability (of occurrence) * Severity (how severe is the impact) * Detection (ability to detect the failure)
8.Severity: The consequences of a failure mode. Severity considers the worst potential consequence of a failure, determined by the degree of injury, property damage, system damage and/or time lost to repair the failure.
9.Remarks / mitigation / actions: Additional info, including the proposed mitigation or actions used to lower a risk or justify a risk level or scenario.
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