Eliminating the thermal softening of dynamically loaded specimens in the Kolsky bar system by multi-step loading

Abstract

We performed series of multi-step loading tests in our Kolsky bar system, and demonstrated that the thermal softening in strong aluminum alloys can be eliminated by multi-step loading. We showed that there is a significant difference in their stress-strain curves, compared with the result of a single shot test, due to adiabatic heating. The tests were carried out using our interferometry-based system, where the bar velocities are measured directly rather than the strains. The optical technique has several advantages over traditional strain gauge measurements; it is non-intervening, highly repeatable, and more accurate at low strains, thus allowing good estimation of the dynamic yield point in these experiments.