Laser-driven flyer plate impact: Computational studies guided by experiments

We present a computational approach using a multimaterial, arbitrary Lagrangian-Eulerian code termed ALE3D to model the nanosecond/micrometer dynamics of the launch of 0.5-4.5 km/s laser-driven metal flyer plates and the impact with stationary targets of Pyrex and fused silica glasses, and Lexan and Plexiglas polymers, producing pressures in the target in the range of 5-20 GPa. The simulations are compared to experimental results where the flyer velocity profile and the velocity profile imparted to the target material were measured with high-speed velocimetry. The experimental flyer launch by a high-intensity pulsed laser is modeled by depositing heat into a thin vaporizable layer under the flyer plate. This model produces a flyer plate that has not been exposed to the laser pulse, allowing us to compare the properties of the real flyer to a simulated ideal flyer. The simulations of target impact are generally in good agreement with the experiment except at the highest impact velocities where the shock release process in the experiment is slower than that in the simulation. The cause of this disagreement is attributed to an inadequate description of the shock viscosity during the nanosecond unloading process.