Measurement of local strain and heat propagation during high-temperature testing in a split-Hopkinson tension bar system

¹ Structural Impact Laboratory (SIMLab), Centre of Research-based Innovation (CRI), Department of Structural Engineering, Norwegian University and Science and Technology, 7491 Trondheim, Norway
² Hydro Aluminium Extrusion Eurasia, Hydro Aluminium, Extrusion Competence Centre, 0240 Oslo, Norway

Abstract

Aluminium alloys are commonly used by the industry due to their good mechanical properties and their relatively low density. An accurate prediction of the behaviour of aluminium alloys under a wide range of temperatures and strain rates is important in numerical simulations of forming processes or applications involving adiabatic heating like penetration and crash situations. Several tests are needed at low, medium and high strain rates to study this behaviour. This paper will focus on the high strain rate test rig, which is a split- Hopkinson tension bar system (SHTB), the acquisition system for strain measurements, and a thermal analysis of the bars due to heating of the sample. A new way of doing local measurements with a high-speed camera will be presented. The thermal boundary conditions of the tests have been measured and simulated, and the results indicate that the stress wave propagation in the bars is not significantly affected by a local heating of the part of the bars which is closest to the sample.