Using plastic instability to validate and test the strength law of a material under pressure

CEA, DAM, DIF, 91297 Arpajon, France

^a Corresponding author: cyril.bolis@cea.fr

Published online: 7 September 2015

Abstract

In dynamical experiments (pressures higher than 10 GPa, strain rate around 104–106 s⁻¹), metals are classically described using an equation of state and a strength law which is usually set using data from compression or traction tests at low pressure (few MPa) and low strain rates (less than 103 s⁻¹). In consequence, it needs to be extrapolated during dynamical experiments. Classical shock experiments do not allow a fine validation of the stress law due to the interaction with the equation of state. To achieve this aim, we propose to use a dedicated experiment. We started from the works of Barnes et al. (1974 and 1980) where plastic instabilities initiated by a sinusoidal perturbation at the surface of the metal develop with the pressure. We adapted this principle to a new shape of initial perturbation and realized several experiments. We will present the setup and its use on a simple material: gold. We will detail how the interpretation of the experiments, coupled with previous characterization experiments helps us to test the strength lax of this material at high pressure and high strain rate.