For the injector faceplate to stay fastened to the manifold, the bolts must satisfy a factor of safety for both tensile and shear stress. A net upward pressure acting on the faceplate applied to the area of the injector requires all bolts on the injector manifold -both axial and radial- to withstand this force to maintain structural integrity.
Tensile Stress on Each Bolt:
| Mathdisplay |
|---|
\begin{align*}
& F_{up} = P_{injector}*A_{injector} \\
& F_{up} + N*F_{bolt}=0 \\
& \\
&|F_{bolt}| = \frac{P_{injector}*A_{injector}}{N} \\
& \\
& Stress_{Tensile}: σ = \frac{|F_{bolt}|}{A_{bolt}} = \frac{P_{injector}*A_{injector}}{N*A_{bolt}} \\
\end{align*}
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The area of the bolt can be determined by using its pitch diameter, which is calculated using its major diameter and the spacing between each thread.
| Mathdisplay |
|---|
\begin{aligngather*}
& D_{pitch} = D_{major} - (0.6495*t) \\
\end{aligngather*} |