Time-dependent fracture criteria for 6061-T6 aluminum under stress-wave loading in uniaxial strain

New spallation threshold data for 6061-T6 aluminum were obtained under stress-wave loading conditions in uniaxial strain, covering the range of tensile pulse durations of 60 to 200 nsec. This range of pulse duration was achieved by using exploding-foil techniques to accelerate thin Mylar plates against thin aluninum specimens. A comparison was made between exploding-foil spallation tests on 6061-T6 aluminum in air and vacuum. The data indicate that the spallation threshold of 6061-T6 aluminum is sensitive to the tensile pulse duration, amplitude, and impulse at the spall location. The exploding-foil impact conditions were reduced to stress-pulse loading parameters by using a one-dimensional elastic-plastic hydrodynamic computer code. The time-dependent aspects of the spallation threshold of 6061-T6 aluminum were found to obey failure theories which were rate process oriented, and which combine the effects of tensile-pulse duration, peak tensile stress, tensile impulse, and tensile-pulse shape. The present data have been used to quantitatively establish failure relationships for 6061:T6 aluminum. Where applicable, supplemental information in the literature concerning dynamic fracture of 6061-T6 aluminum was utilized.