For materials testing at elevated temperatures, we describe the design and the development of a resistively heated Kolsky-bar apparatus. The temperature of the sample is determined by non-contact thermometry and the spatial temperature gradients in the sample are measured using a thermal camera. The incident and the transmitted bars are constructed of 1.5 m long, 15 mm diameter maraging steel, and a typical sample is a 4 mm-diameter, 2 mm-long cylinder of 1045 AISI steel or 303 stainless steel. The sample is placed between the bars and held by friction. The current is transmitted through the graphite-sleeve bushings of the two bars. The non-contact temperatures are measured using an InGaAs near-infrared micro-pyrometer (NIMPY) and an InSb focal-plane (320 by 256) array (thermal camera). The NIMPY and the thermal camera are both calibrated using variable-temperature blackbodies, and the thermodynamic temperature of the metal is determined using the emissivity determined from the measured infrared spectral reflectance of the metal. Thermal videos of the sample which has been electrically heated prior to the impact and the room of the metal. Thermal videos of the sample which has been electrically heated prior to the impact and the room temperature impacts will be shown with 3 kHz frame rates, and the changes in the stress-strain curves with the temperature of the samples will be discussed.
Conference Dates: April 21-24, 2003
Conference Location: Orlando, FL
Conference Title: Proceedings of SPIE, ThermoSense XXV
Pub Type: Conferences
Kolsky, materials testing, split-Hopkinson, strain, stress, thermal imaging, thermodynamic temperatures