SPALLATION OF METALS UNDER LASER IRRADIATION

Laser-driven shock-wave loading enables the study of ultrahigh strain rates (10(7) s-1). A damage model for the spallation process has been included in a two-dimensional finite-difference hydrodynamic elastoplastic code using Lagrangian coordinates in order to calculate the laser-induced spall phenomena. The damage was investigated using shock waves induced by a short-pulsed laser in copper and aluminum foils. Laser irradiation intensities were in the range of 10(10)-10(12) W/cm2. The foil thickness was in the 100-600-mu-m range. The ablation pressure attained on the front surface of targets was a few hundred kilobars. The travelling time of the shock wave through the target was of the order of a few tens of nanoseconds. The spall width was calculated for both Al and Cu materials with different thicknesses of foils and various laser-induced shock-wave intensities. The numerical simulations were compared with previously reported experiments. Good agreement was obtained between experimental and simulation results for the spall pressure and the spall widths. The strain rates of materials under laser-induced shock loading were obtained from the computer code.