Time-resolved dynamic compaction and tensile fracture of low-porosity aluminum under impact loading

Abstract

Unlike the solid dense medium, the low-porosity metals exhibit many unique dynamic behaviors. These properties have been investigated in this work for aluminum with a porosity of 3.3% under high velocity and planar plate impact. A push-pull-type velocity interferometer system for any reflector was used to measure the rear free surface velocity profiles of the samples. Time-resolved dynamic compaction and tensile fracture properties are presented. Results demonstrated that there are three distinct shock compressive waves in succession, including elastic wave, compaction wave, and stable shock wave. The dynamic tensile fracture occurs after the porosity being fully compacted and the stable shock wave being formed. With the increase of impact velocity, the dynamic tensile strength becomes higher and the spalled layer becomes thicker. Nevertheless, the dynamic tensile strength of the shock compacted aluminum is apparently lower than that of the solid dense aluminum, and is approaching that of the aluminum alloy 6061-T6. Physical explanations are illustrated and discussed.