New results concerning the process of dynamic fracture of
materials (spallation) by laser-induced shock waves are presented.
The Nd-glass laser installations SIRIUS and KAMERTON were used
for generation of shock waves with pressure up to 1 Mbar in
plane Al alloy targets. The wavelengths of laser radiation were
1.06 and 0.53 μm, the target thickness was changed from
180 to 460 μm, and the laser radiation was focused in a
spot with a 1-mm diameter on the surface of AMg6M aluminum alloy
targets. Experimental results were compared to predictions of
a numerical code which employed a real semiempirical wide-range
equation of state. Strain rates in experiments were changed
from 106 to 5 × 107 s−1.
Two regimes of spallation were evidenced: the already known
dynamic regime and a new quasi-stationary regime. An ultimate
dynamic strength of 80 kbar was measured. Finally, experiments
on targets with artificial spall layers were performed showing
material hardening due to shock-wave compression.