Propagation of laser-generated shock waves in metals: 3D axisymmetric simulations compared to experiments
Résumé
This work aims at demonstrating the ability of an acoustic linear code to model the propagation of a shockwave created by a laser impact over a metallic surface. In this process, a high pressure surface level is reached using a ns laser pulse that heats the surface of the material and generates a dense plasma expansion. The pressure reaches few GPa so shockwaves are generated and propagate into the bulk of the material. Currently, shockwave propagation is modeled using continuity equations and an ad hoc equation of state for the illuminated material, very limiting because it is numerically intensive. Here, we propose to model the shockwave bulk propagation using a linear acoustic code. A nonlinear surface pressure term, resulting from the laser-matter interaction, is used as boundary condition. The applied numerical scheme is based on the Virieux scheme, including a fourth order finite difference discretization of the linearized elasto-mechanical equations. Role of longitudinal and transverse waves and it origin is highlighted. Importance of considering 3D geometries is pointed out. Simulations are finally confronted with experimental results obtained with the Hephaistos Laserlab facility (Energy up to 14 J at 532 nm wavelength laser. Pulse duration : 7 ns). Illuminations up to the optical breakdown in water are easily achieved with laser focal spots of 5 mm width. Excellent agreement between experiments and simulations is observed for several sets of experimental parameters for titanium, a material of high elastic limit, while limitations are founded for aluminum. Code available in MetaData.
Domaines
Physique [physics]Origine | Fichiers produits par l'(les) auteur(s) |
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