title: A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests.
abstract: Owing to their significant hardness and compressive strengths, ceramic materials are widely employed for use with protective systems subjected to high-velocity impact loadings. Therefore, their mechanical behaviour along with damage mechanisms need to be significantly investigated as a function of loading rates. However, the classical plate-impact testing procedures produce shock loadings in the brittle sample material which cause unrealistic levels of loading rates. Additionally, high-pulsed power techniques and/or functionally graded materials used as flyer plates to smooth the loading pulse remain costly, and are generally difficult to implement. In this study, a shockless plate-impact technique based on the use of either a wavy-machined flyer plate or buffer plate that can be produced by chip-forming is proposed. A series of numerical simulations using an explicit transient dynamic finite-element code have been performed to design and validate the experimental testing configuration. The calculations, conducted in two-dimensional (2D) plane-strain or in 2D axisymmetric modes, prove that the 'wavy' contact surface will produce a pulse-shaping effect, whereas the buffer plate will produce a homogenizing effect of the stress field along the transverse direction of the sample. In addition, 'wavy-shape' geometries of different sizes provide an easy way to change the level of loading rate and rise time in an experimentally tested ceramic specimen. Finally, when a shockless compression loading method is applied to the sample, a Lagrangian analysis of data is made possible by considering an assemblage of ceramic plates of different thicknesses in the target, so the axial stress-strain response of the brittle sample material can be provided.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.
authors.affiliation: Laboratoire Sols, Solides, Structures-Risques (3SR), Université Grenoble Alpes, BP 53, 38041 Grenoble Cedex 9, France pascal.forquin@3sr-grenoble.fr.
authors.forename: Pascal
authors.identifier: http://orcid.org/0000-0003-0730-5483
authors.initials: P
authors.lastname: Forquin
authors.affiliation: CEA, DAM, Gramat, 46500 Gramat, France.
authors.forename: Jean-Luc
authors.identifier: http://orcid.org/0000-0002-4347-3903
authors.initials: JL
authors.lastname: Zinszner
keywords: ceramics; isentropic compression experiments; numerical simulation; plate impact; pulse-shaper; shockless