Spallation and dynamic elongation of metals as an effect of laser induced shock waves

Spall and dynamic elongation at ultra high strain rate was investigated using short pulsed laser induced shock waves in metallic foils. The controlled stepwise increase in laser energies in a one-dimensional shock wave geometry was used to find the stages of damage evolution from incipient to complete perforation of the target. A phenomenological model was developed for laser produced spall in the 100 kilobars regime. By substituting experimental values in the model it was found for pure aluminum a spall pressure of 26±6 kbar and for pure copper 28±6 kbar at a strain rate of about 3×10⁷ sec^-1. The experimental results and results calculated with the model were compared to simulations and good agreement was found. A novel method was developed to measure the total elongation at fracture at ultra high strain rate.