The measurement of specimen surface temperature in high-speed tension and torsion tests

Abstract

A radiometric technique has been developed capable of measuring specimen surface temperatures as low as 25°C with a time resolution of ∼1 μs. The application of this technique to SHPB tests at strain rates of the order of 1000/s in both tension and torsion is described. In the torsion test results are obtained both during uniform deformation, using a single element radiometer, and during localised deformation and the onset of fracture, using a 12-element radiometer. In the tension test the same 12-element radiometer was used to obtain the surface temperature distribution along each half of the broken specimen immediately after fracture. The proportion of work converted to heat, β, has been calculated using the temperature data from torsion tests and was found to vary with increasing plastic strain from approximately 0.2 to approaching 0.7.