Failure Mode and Effects Analysis - Basic Terms

Basic Terms

Failure

The loss of an intended function of a device under stated conditions.

Failure mode

The manner or way by which a failure is observed in terms of failure of the part 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/function under consideration as result of the failure mechanism (cause of the failure mode). For example; a fractured axle or an open electrical contact can be a failure mode.

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 beam or contact is a failure mechanism and not a failure mode. The related failure mode (state) under analysis could be a "full fracture of structural beam" or for example "a open electrical contact". The initial Cause might have been "Improper application of corrosion protection layer (paint)" and /or "(abnormal) vibration input from another failed system".

Failure effect

Immediate consequences of a failure on operation, function or functionality, or status of some item

Indenture levels

An identifier for item complexity. Complexity increases as levels are closer to one.

Local effect

The failure effect as it applies to the item under analysis.

Next higher level effect

The failure effect as it applies at the next higher indenture level.

End effect

The failure effect at the highest indenture level or total system.

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.