Pol Grasland-Mongrain edited Absorption_of_the_laser_beam__.tex  almost 8 years ago

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To calculate the propagation of the displacements as shear waves, we must first consider the transverse dilatation, which leads to stronger displacements than those occurring along the Z axis. We thus modeled the thermoelastic regime in 2D as two opposite forces directed along the Y axis with a depth of 40 $\mu$m and with an amplitude decreasing linearly respectively from 2.5 to 0 mm and from -2.5 to 0 mm \cite{Davies_1993}. The magnitude of the force along space and time is stored in a matrix, $H_y^{thermo}(y,z,t)$. Displacements along the Z axis are then equal to the convolution between $H_y^{thermo} (y,z,t)$ and $G_{yz}$ \cite{aki1980quantitative}:  \begin{equation}  G_{yz}(r,\theta,t) = \frac{\cos \theta \sin \theta}{4\pi \rho c_p^2 r} \delta(t-\frac{r}{c_p}) - \frac{\sin \theta \cos \theta}{4\pi \rho c_s^2 r} \delta(t-\frac{r}{c_s})\label{eq:Gyz}  \end{equation}  \begin{equation}  +\frac{3\cos \theta \sin \theta}{4\pi \rho r^3} \int\limits_{r/c_p}^{r/c_s}{\tau \delta(t-\tau) d\tau} \label{eq:Gyz2}  \end{equation}  where (r,$\theta$) are the coordinates of the considered point with regards to the force location and direction, $c_p$ and $c_s$ are the compression and shear wave speed respectively, $\tau$ is the time, and $\delta$ is a Dirac distribution. The three terms of the equation correspond respectively to the far-field compression wave, the far-field shear wave, and the near-field component.