Title: Stable deformation at very high strain rates in UHCS

Authors: R.D. Caligiuri, L.E. Eiselstein, C.G. Schmidt, J.H. Giovanola

Addresses: Exponent, Menlo Park, CA, USA. ' Exponent, Menlo Park, CA, USA. ' Hewlett-Packard (HP), Corvallis, OR, USA. ' Laboratoire de Conception de Systemes Mecaniques, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland

Abstract: An experimental programme was conducted to investigate the conditions of microstructure and temperature necessary for the stable deformation of Ultrahigh Carbon Steel (UHCS) at very high strain rates (up to 106 s−1). Constitutive data were obtained from rod impact tests and Hopkinson bar tests over a range of strain rates and temperatures. Fracture modes were analysed, and the nature and degree of nonuniform deformation assessed. The strain-hardening behaviour was found to be strongly history-dependent as a result of solute-enhanced strain hardening in UHCS at elevated temperatures. The ductility of UHCS at high strain rates reduced at 600°C because of sharp increases in the temperature sensitivity of its strength, resulting in an increased propensity for shear banding. It is clear that changes in microstructure change the constitutive behaviour of UHCS at high strain rates.

Keywords: ultrahigh carbon steel; UHCS; high strain rates; deformation; rod impact; microstructure; fracture; ductility; Hopkinson bar; shaped charge; self-forging fragments; strain hardening; shear banding.

DOI: 10.1504/IJMMP.2008.022038

International Journal of Microstructure and Materials Properties, 2008 Vol.3 No.4/5, pp.591 - 606

Published online: 17 Dec 2008 *

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