INVESTIGATION OF LASER SHOCK INDUCED DUCTILE DAMAGE AT ULTRA-HIGH STRAIN RATE BY USING LARGE SCALE MD SIMULATIONS

Laser driven shocks allow an investigation of materials behavior at very high strain rate (10(7)s(-1)) and present a great interest for research applications. Microscopic simulations of ultra-short laser driven shock on micrometric Tantalum single-crystals have been performed by using the CEA-DAM Classical Molecular Dynamics code. This method, complementary to continuum models, provides an analysis the microscopic processes related to damage (ductile pore nucleation and growth) which occurs during spallation. These results are compared to spallation experimental data (VISAR signals, micro-tomography) obtained with the LULI100TW femtosecond laser in order to validate the MD behavior. Moreover, in the framework of a multi-scale approach, we show the possibility to use MD simulation to fit macroscopic damage models. This method is illustrated with an application to the parameters determination of Kanel damage model parameters. This also shows the high strain rates involved during damage process, around 10(9)s(-1), can approach the inter-atomic theoretical cohesion stress threshold.