Simultaneous full-field strain and temperature measurements in tensile Hopkinson bar experiments at extreme temperatures

Simultaneous full-field strain and temperature measurements were used to monitor tension Split Hopkinson Pressure Bar (SHPB) tests at elevated temperatures. A direct heating system was used to increase the specimen temperature up to 1350 °C. Digital Image Correlation (DIC) and Infrared Thermography (IRT) were used was used to simultaneously monitor the evolution of the full-field strain and temperature of the specimen. Data acquisition was synchronized using a function generator, a camera pinhole model was used to represent both strain and temperature on the same coordinate system, and the displacement vector field from DIC was used to represent both datasets on the same reference frame. The use of full-field techniques was essential at elevated temperatures, as necking occurred soon after yielding and the usability of the data obtained from the SHPB after the onset of necking is debatable. The method was able to follow the full-field strain and the temperature evolution under extreme conditions. Some challenges were found in the development of the method and recommendations as well as future applications are also described in this paper. This experimental approach is versatile and can be applied to different materials at similar testing conditions but also different loading modes and testing setups.