Product failure: component failure or functional failure
Tuesday 4/13/10 time 2:29 PM - Andy
These failure types and definitions are used can be in Component FMEA and Functional FMEA. The category 'Functional failure' is very useful because a function can be produced with any technology, i.e. sofware, hardware, electronics, hydraulics etc.
When using the functional failure definition one must know the system's correct (intended) functioning. Without defining the correct functioning, it is impossible to say whether a functional failure exists. For example a valve can be erroneously open or erroneously closed in terns of functional failures. The correct valve position must be defined first!
This usually not a problem, since the design engineers participate in the FMEA sessions.
When analyzing component failures, generic failure modes are used, for example a resistor has at least the following failure modes: 'parameter change', 'open circuit' and even 'short circuit'.
The ultimate effect of these failure modes is of course different, depending on the design of the product.
The basic failure rate of a component can be allocated to these failure modes. Allocation percentages of component failure modes can be found in reliability literature or reliability data handbooks.