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

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Displacement amplitude maps along Y axis and Z axis 5, 6, 7, 8 and 9 ms after laser emission in the graphite-filled tissue mimicking phantom are illustrated in Fig. \ref{Figure2}. A typical shear wave pattern can be recognized (dissymetry recognized: dissymetry  for Y-displacement, symmetry for Z-displacement) Z-displacement  \cite{undefined}. Maximum displacement was equal to 1 $\mu$m. Displacement propagated at a velocity of 4 $\pm$ 1 m.s$^{-1}$, which is a typical value for shear wave, and far lower than compression wave velocity, about 1500 m.s$^{-1}$ in soft solids. Supposing the medium density $\rho$ of 1000 kg.m$^{-3}$, it corresponds to a shear modulus of 16 kPa, which is in the range of the expected value of the phantom. However, it is not known at this stage if the shear waves are due to thermal stress or ablation, especially as the used power is close to the transition between the two regimes in metals.