Measurement of the tensile strength of aluminium at a strain rate of 2×107 s-1

Laser-driven shock waves were used to measure the spall strength of pure aluminum at a strain rate of approximately 2*107 s-1. The measurement was made possible due to a novel method which uses the phenomenon of spallation as a measure of the constant pressure situation of laser-induced shock waves of nanosecond width. The authors have found a spall strength of sigma =3.0+or-0.2 GPa for pure aluminum at a strain rate of epsilon =(1.8+or-0.9)*107 s-1. Comparison of this result with those of Ek and Asay indicates a power law dependence of the spall strength on the strain rate: sigma =(1.5+or-0.2)( epsilon /106 s-1)0.22+or-0.04 GPa for epsilon >or=105 s-1. A short discussion on the variation of the spall thickness as a function of target thickness is also presented.