Failure modes describe the ways in which an objectcan fail. Associated with each failure mode is a value representing that failure mode's percentageof the object's total failures. Failure modes are considered to be mutually exclusive, in accordance with Military Standards and Best Practices. If the percentages assigned to an object's failure modes add up to 100%, then it is assumed that all of the ways in which that object can fail have been accounted for.
NOTE: Object Failure modes normally use functional failure modes as apposed to "physics of failure modes". [Physics of failure (open, short, cracked, etc.)]. The exception to this is capacitors and resistors (Open capacitors are not detectable and shorted resistors may not be detectable.)
When to Use Failure Modes
Failure Modes help provide more detailed visibility of component behavior. Failure modes are typically added at the lowest levels of a design and do not roll up (that is a job reserved for Failure Effects). Instead, failure modes represent the reason for an object failure. As such, failure modes are often used in lieu of providing an additional level of modeling. One excellent example of when failure modes can be used to handle a particularly troublesome situation is when modeling COTS components. There are dangers in creating both too many or too few failure modes. Creating too many failure modes can lead to a dramatic increase in the number of hours spent modeling and can significantly reduce the speed in which changes can be made. Creating too few failure modes can result in an incomplete model, increasing the challenge of trying to get tests and diagnostics to the desired resoluton.
