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@ -825,7 +825,7 @@ mode (i.e. one or more failure modes that caused it).
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%
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\subsection{FMMD Hierarchy}
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\;
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By applying stages of analysis to higher and higher abstraction
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levels, we can converge to a complete failure mode model of the system under analysis.
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Because the symptom abstraction process is defined as surjective (from component failure modes to symptoms)
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@ -970,9 +970,18 @@ its range as the number of checks to perform to satisfy a rigorous FMEA inspecti
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This can be simplified if we can determine the total number of failure modes in the system $fT$, (i.e. $ fT = \sum_{n=1}^{|fg|} {|fm(c_n)|}$);
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equation~\ref{eqn:rd} becomes $$ RD(fg) = fT.(|fg|-1).$$
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Equation~\ref{eqn:rd} can also be expressed as
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\begin{equation}
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\label{eqn:rd2}
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%$$
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RD(fg) = {|fg|}.{|fm(c_n)|}.{(|fg|-1)} .
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%$$
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\end{equation}
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\pagebreak[4]
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\subsection{Reasoning Distance Examples}(c-1)
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\subsection{Reasoning Distance Examples}
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The potential divider discussed in section~\ref{potdivfmmd} has a four failure modes and two components and therefore has an $RD$ of 4.
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$$RD(potdiv) = \sum_{n=1}^{2} |2|.(|1|) = 4 $$
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@ -1032,17 +1041,17 @@ Starting at the top, we have a {\fg} with three derived components, each of whic
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three failure modes.
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Thus the number of checks to make in the top level is $3^0.3.2.3=18$.
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On the level below that, we have three {\fgs} each with a
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an identical number of checks, $3^1.3.2.3=56$.{\fg}
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an identical number of checks, $3^1.3.2.3=56$.%{\fg}
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On the level below that we have nine {\fgs}, $3^2.3.2.3=168$.
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Adding these together gives $242$ checks to make to perform RFMEA \textbf{within}
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{\fgs}.
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Adding these together gives $242$ checks to make to perform FMMD (i.e. RFMEA \textbf{within the}
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{\fgs}).
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If we were to take the system represented in figure~\ref{fig:three_tree}, and
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apply RFMEA on it as a whole system, we can use equation~\ref{eqn:rd},
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$ RD(fg) = \sum_{n=1}^{|fg|} |fm(c_n)|.(|fg|-1)$, where $|fg|$ is 27, $fm(c_n)$ is 3
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and $(|fg|-1)$ is 26.
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This gives:
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$ RD(fg) = \sum_{n=1}^{27} |3|.(|27|-1) = 2106$
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$RD(fg) = \sum_{n=1}^{27} |3|.(|27|-1) = 2106$.
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In order to get general equations with which to compare RFMEA with FMMD
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we can re-write equation~\ref{eqn:rd} in terms of the number of levels
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@ -1069,6 +1078,26 @@ We can now use equation~\ref{eqn:anscen} and \ref{eqn:fmea_state_exp22} to comp
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the two approaches, for the work required to perform rigorous checking.
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For instance, having four levels
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of FMMD analysis, with these fixed numbers,
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%(in addition to the top zeroth level)
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will require 81 base level components.
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$$
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%\begin{equation}
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\label{eqn:fmea_state_exp22}
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3^4.(3^4-1).3 = 81.(81-1).3 = 19440 % \\
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%(N^2 - N).f
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%\end{equation}
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$$
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$$
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%\begin{equation}
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% \label{eqn:anscen}
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\sum_{n=0}^{3} {3}^{n}.3.3.(2) = 720
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%\end{equation}
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$$
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\subsection{Exponential squared to Exponential}
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can I say that ?
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