Pol Grasland-Mongrain edited The_two_regimes_have.tex  over 8 years ago

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This ablative regime can be simulated by calculating the displacement created by a force positive then negative over a disk of 5 mm in diameter and 100 $\mu$m in depth, as shown on Figure \ref{Figure3} which represents displacement maps along Y and Z axis 0.8, 1.6, 2.4, 3.2 and 4.0 ms after force application. It was calculated in a three-dimensional simulation with spatial steps of 10 $\mu$m and temporal steps of 50 $\mu$s using Green operator \cite{aki1980quantitative} with a medium density $\rho$ of 1000 kg.m$^{-3}$, a compression wave speed of 1500 m.s$^{-1}$ and a shear wave speed of 4 m.s$^{-1}$. The displacement maps present many similarities with the experimental results of the Figure \ref{Figure2}, which support the conclusion of an ablative regime.  This conclusion is confirmed by the observation of a disk of paler color of the same size as the beam diameter at the impact location of the laser on the phantom, which could correspond to a melting vaporization  of a fraction of the material.% From equation \ref{eq:eqTemperature}, with the laser characteristics and an initial temperature $T_0$ of 25 $^o$C, $T$ is higher than 50 $^o$C, approximate phantom melting temperature, over \textcolor{red}{XXX} $\mu$.