From 2d02167a4c75021a54842ba9cf30ace0df9cb646 Mon Sep 17 00:00:00 2001 From: Robin Clark Date: Tue, 26 Oct 2010 23:00:40 +0100 Subject: [PATCH] . --- fmmd_concept/fmmd_concept.tex | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/fmmd_concept/fmmd_concept.tex b/fmmd_concept/fmmd_concept.tex index 0326c43..ed58dba 100644 --- a/fmmd_concept/fmmd_concept.tex +++ b/fmmd_concept/fmmd_concept.tex @@ -167,7 +167,7 @@ decide which interactions are important. Let N be the number of components in our system, and K be the average number of component failure modes (ways in which the component can fail). The total number of base component failure modes is $N \times K$. To even examine the affect that one failure mode has on all the other components -will be $$(N-1) \times N \times K$$, in effect a set cross product. +will be $(N-1) \times N \times K$, in effect a set cross product. Complicate this further with applied states or environmental conditions @@ -179,17 +179,17 @@ failure mode behaviour for say, differnet ambient pressures or temperatures. If $E$ is the number of applied states or environmental conditions to consider in a system, the job of the bottom-up analyst is complicated by a cross product factor again -$$(N-1) \times N \times K \times E$$. +$(N-1) \times N \times K \times E$. If we were to consider multiple simultaneous failure modes we have yet another complication cross product. For instance for looking at double simultaneous failure modes -the equation reads $$(N-2) \times (N-1) \times N \times K \times E$$. +the equation reads $(N-2) \times (N-1) \times N \times K \times E$. The bottom-up methodologies FMEA, FMECA and FMEDA take single failure modes and link them -to SYSTEM level failure modes. Because of the number of possible interactions that -must be missed, we can term this analysis a `leap of faith' from the +to SYSTEM level failure modes. Because of the astronomical number of possible interactions, +some valid ones are in danger of being missed, we can term this analysis a `leap of faith' from the component failure mode to the SYSTEM level.