The preheating effect on the dynamic strength of aluminium containing helium bubbles

Abstract

The influence of helium bubbles or boron inclusions in an aluminum target is studied by plane impact experiments with a gas gun and VISAR diagnostic. The experiments were carried out on targets with initial temperatures of 25 °C and near melting at 600 °C. The Hugoniot elastic limit yHEL for all targets becomes substantially higher at 600 °C, related to the phonon drag mechanism at high strain rates and high temperatures. The spall strength for all targets becomes substantially lower at 600 °C. The spall strength of Al-¹⁰B with helium bubbles is significantly reduced in comparison to Al-¹⁰B without helium, while at 25 °C the spall strength is the same for both cases. This effect might be explained by a local strength reduction of the aluminium at pre-heating conditions, allowing the helium bubbles to be more dominant in the spallation process