The National Institute of Standards and Technology (NIST) has developed an electrical pulse-heated Kolsky Bar technique for measuring the constitutive response of metals at heating rates of up to 6000 K/s and strain rates up to 104 1/s. Under these conditions, which are approaching those found in high speed machining, thermally-activated microstructural processes such as grain growth, solid state phase transformation and dislocation annealing can be bypassed, leading to unique non-equilibrium superheated microstructural states. Flow stresses can thus differ significantly from equilibrium high temperature conditions. This paper describes the NIST pulse-heated Kolsky bar technique in detail, including a thorough assessment of uncertainties in temperature and flow stress measurement.
Citation: Experimental Mechanics
Pub Type: Journals
flow stress measurement, high strain rate, Kolsky Bar, pulse heating