Recent Results from the NIST Pulse-Heated Kolsky Bar

A Kolsky bar laboratory for measuring dynamic material properties, in support of improved finite-element modeling of high-speed machining processes, has been developed at the National Institute of Standards and Technology (NIST). The NIST split-Hopkinson pressure bar has the capability of electrically pulse heating a test sample to a temperature on the order of 1000 oC in less than a second, then holding the sample at a fixed high temperature for several seconds (if desired), followed by loading of the sample in a dynamic compression test. Recent advances in temperature measurement and control capabilities are discussed, together with recent results on the constitutive response of AISI 1045 steel. The goal of the work is to study the influence of the rate of heating and time at high temperature on the stress-strain response of the material, which depends upon the dynamic evolution of the material’s microstructure. Figure 1. Schematic diagram of NIST pulse-heated Kolsky bar apparatus. Disclaimer Commercial products are identified in the text in order to specify certain procedures or equipment used. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the identified products are necessarily the best available for the purpose. Strain Gage 1, Incident and Reflected Strain Strain Gage 2, Transmitted Strain High Speed Visible/Thermal Camera Heating Controller And Power Supply Pyrometer Feedback Trigger Input Air Gun Trigger Input Trigger Input To Data Acq. IR Lamps IR Sensors To Data Acq. Timing Circuit Heating Trigger