Computational model for a low-temperature laser-plasma driver for shock-processing of metals and comparison to experimental data

Abstract

Few-joule table-top lasers can generate pressures up to the 100 kbar range in solid materials by propagating a low-intensity beam through a transparent dielectric, which confines the ablation pressure, onto an ablation layer in contact with the material of interest. This technique has application in studies of material dynamic behavior and material processing. Development and application of physically based models of this process have lagged experiment. In this article the particulars of a detailed computational model incorporated into a two-dimensional radiationhydrodynamics code are presented. The model accounts for the initial absorption onto a metal surface, low-intensity photoionization absorption in neutral vapor, collisional ionization, recombination, dielectric breakdown, band gap collapse, electron conductivity, thermal transport, and constitutive properties of the materials. The model shows that most of the laser energy is absorbed in the dielectric tamper, not the ablator. Good agreement is found between simulated and measured pressure histories for materials irradiated with several tens of joules using a single-beam neodymium-glass laser at the Lawrence Livermore National Laboratory.

Shocked materials at the intersection of experiment and simulation

“…Current high-energy laser facilities have been shown to be excellent venues to generate both high pressure loading [6,12,55] and implement x-ray-based diagnostics [45]. Shock pressures between 10 and 1000 GPa are easily accessible through direct ablative drive.…”

Laser Shock Processing: an emerging technique for the enhancement of surface properties and fatigue life of high-strength metal alloys

“…The referred three-level description includes: i) Analysis of the plasma electronic population dynamics, including consideration of breakdown phenomenology in dielectric media ii) Simulation of the hydrodynamic phenomenology arising from plasma expansion between the confinement layer and the base material iii) Analysis of the propagation and induction of permanent structural changes by shock wave evolution in bulk material A calculational model dealing with these three main aspects of the process modelling in a coupled way has been developed by the authors. The developed calculational model (SHOCKLAS) is integrated by three principal modules, respectively called LSPSIM, HELIOS and HARDSHOCK, and has been conceived for the analysis of the problem of laser shock waves generation and propagation under three different but intercomplementary approaches (see references [10][11][12][13][14][15][16]). Fig.…”

Shock pressure induced by glass-confined laser shock peening: Experiments, modeling and simulation

“…7,[14][15][16][19][20][21][22]35,36 According to the laser irradiation time, the confined plasma will endure three typical stages including laser heating, adiabatic cooling, and impulse moment translation. 7 In the last stage, the pressure is too low to cause a plastic deformation of the material.…”

“…Some analytical models of shock pressure for LSP were developed. 7,8,[14][15][16][17][18][19][20][21][22] However, in the previous models, the dynamic effect of the material system was simplified as constant reduced shock impedance. As a result, the dynamic response of the material was not fully considered and a more realistic pressure model is demanded.…”