Dynamic Indentation of Copper and an Aluminium Alloy with a Conical Projectile at Elevated Temperatures

Abstract

The dynamic indentation of copper (B.S. 1433) and an aluminium alloy (B.S. 1476 HE 10) has been investigated, using cylindro-conical projectiles fired from an air-actuated gun. The experiments were performed with impact velocities varying between 1000 and 2500 in/s and at elevated temperatures up to 600°C for the copper and 550°C for the aluminium alloy. The magnitude of the corresponding range of mean strain rate was then 10^3-10⁴/s, depending upon the material; impact velocity and temperature (see Appendix I).

For the range of impact velocities investigated no consequential transition temperature ^† was encountered. The dynamic temperature coefficient† thus remained constant throughout the test temperature range for each material. This dynamic temperature coefficient was found to be equal to the static temperature coefficient corresponding to the sub-transitional temperature range for the respective materials.

The mean effective dynamic indentation pressure is shown to decrease with temperature but the ratio of this dynamic pressure to the static indentation pressure increases with temperature.

Strain rate effects for both materials were negligible for sub-transitional temperatures but become important at super-transitional temperatures. It was observed that the parameters on which the strain rate effect depends are in some way related to the absolute melting point of a pure metal.