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Pol Grasland-Mongrain edited Let_s_describe_the_phenomenon__.tex
over 8 years ago
Commit id: d1eb8c347581745972d671f3c2d08cddb64dfb40
deletions | additions
diff --git a/Let_s_describe_the_phenomenon__.tex b/Let_s_describe_the_phenomenon__.tex
index ed3da3b..783ec67 100644
--- a/Let_s_describe_the_phenomenon__.tex
+++ b/Let_s_describe_the_phenomenon__.tex
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\sigma_{zz} = (\lambda + 2 \mu) \frac{\partial u_z}{\partial z} - 3(\lambda + \frac{2}{3}\mu) \frac{\alpha E}{\rho C S \zeta}
\label{eq:stressThermo}
\end{equation}
where $\lambda + 2 \mu$ is the P-wave modulus and $\lambda + \frac{2}{3}\mu$ the bulk modulus with $\lambda$ and $\mu$ respectively the first and second Lamé's coefficient, $\alpha$ is the thermal dilatation coefficient and $\zeta$ the average depth of laser beam absorption. In the absence of external constraints normal to the surface, the stress across the surface must be zero, i.e. $\sigma_{zz} (z=0) = 0$, so that equation \ref{eq:stressThermo} can be integrated, giving a displacement from the surface
$u_z %$u_z = \frac{(3\lambda + 2\mu)}{(\lambda + 2\mu)} \frac{\alpha E \zeta}{\rho C S \zeta$. As in a biological soft tissues, $\mu \ll \lambda$, the displacement can be approximated as:
\begin{equation}
u_z = \frac{3 \alpha E}{\rho C S}
\label{eq:deplThermo}