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

Abstract

New spallation threshold data for 6061-T6 aluminum were obtained under stress-wave loading conditions m 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 spail location. The exploding-foil impact conditions were reduced to stress-pulse loading parameters by using a onedimensional 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 onentecl, 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 apphcable, supplemental information in the literature concerning dynamic fracture of 6061-T6 ahlminum was utilized

Dynamic Failure of Materials. Volume 1 - Experiments and Analyses

“…These criteria range in complexity from the relatively simple empirical formulations to the more complex physically based microstatistical formulations. Empirical criteria (e.g., Butcher et al, 1964;Cohen and Berkowitz, 1971;Ivanov, 1975) are based on macroscopic observations and measurements; they tend to be easy to use, but they do not provide any insight about the micromechanisms that underlie the development of fracture damage. Typically, these criteria depend on both the magnitude and duration of the applied load, with fitting parameters determined from experimental data.…”