Cazacu Oana - Dynamic Damage and Fragmentation

Series Editor

Flix Darve

Edited by

David Edward Lambert

Crystal L. Pasiliao

Benjamin Erzar

Benoit Revil-Baudard

Oana Cazacu

First published 2019 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd

27-37 St Georges Road

London SW19 4EU

UK

www.iste.co.uk

John Wiley & Sons, Inc.

111 River Street

Hoboken, NJ 07030

USA

www.wiley.com

ISTE Ltd 2019

The rights of David Edward Lambert, Crystal Pasiliao, Benjamin Erzar, Benoit Revil-Baudard and Oana Cazacu to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Control Number: 2018959945

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN 978-1-78630-408-7

The engineering applications of the Air Force Research Laboratory exercise a diverse spectrum of extreme and dynamic loading conditions that challenges the state-of-the art capability of engineering tools. Munitions applications include the extreme conditions of operational employment as well as the safety protocols designed for protection from accidents and adversarial threats. The operational scenario begins with delivery platforms that can make the systems subject to long-duration ~0 (hrs), high-temperature vibrations and the combination thereof. The engagement phase can induce high-pressure (10s of kbar) mid-duration ~0 (ms) with a combined shear component. The terminal phase of detonation and fragmentation accentuates all of these loadings with ~0 (ns) detonation shock loading reaching Mbar peak pressures all under triaxial stress conditions at strain rates of nearly 0 (106 cm/s/s). The detonation process occurs on the timescale of nanoseconds, with giga watts of power being released in sub-millimeter length scales for shock- and blast-driven work. This seemingly rudimentary, stochastic event has had more than 100 years of research by the broader community, yet significant gaps remain in our understanding.

Furthermore, these systems are built to survive a suite of six hazards mandated via the insensitive munitions (IM) requirements. The IM hazards represent accidents and intentional threats a munition might encounter throughout its life cycle. Each of these also drives the need for constitutive models, including advanced mathematical frameworks for damage, fracture and fragmentation as well as complementary numerical frameworks, and furthermore, necessary experiments and diagnostics of such.

This book presents recent advances that have been made in the understanding, experimental characterization, theoretical models and numerical simulations of the aforementioned thermo-mechanical processes. It is based on selected invited lectures and lively exchanges of ideas at the 10th US-French symposium Dynamic damage and fragmentation, Fort Walton Beach, Fl, 1719 May 2017 organized under the auspices of the International Center for Applied Computational Mechanics (ICACM) at the University of Florida/REEF.

The first part of this book presents an overview of the numerical approaches developed for modeling instabilities leading to plastic flow localization and failure in isotropic metallic materials. For moderate loadings, models for description of strain localization induced by local softening either due to local heating and plastic dissipation (see , which is devoted to the characterization and modeling of the plastic behavior of refractory metals, it is shown that only by considering the combined influence of anisotropy and strength differential effects on the mechanical response, the particularities of the mechanical response of these materials under extreme environments can be captured with accuracy.

Advancement in understanding and modeling the mechanical behavior can be achieved only through integration with experiments. Recent progress made in the development of methodologies to measure the local strain fields and their direct exploitation to calibrate model parameters using inverse methods are presented in . Specifically, it is shown that laser-driven shocks can be used to investigate the mechanical response over a range of very high strain rates (~107 s1), high loading pressures, small spatial scales and very short durations of pressure application (~ns). Moreover, their relatively low destructiveness facilitates easier sample recovery and easier instrumentation than the more conventional shock loading techniques based on explosives or plate impacts.

The second part of this book presents an overview of the experimental methods and numerical approaches developed for modeling the overall mechanical behavior and instabilities in brittle materials, including cementitious and ceramic materials and granular media. Such materials are very heterogeneous, and contain a large number of defects such as micro-voids or micro-cracks that strongly influence their quasi-static and dynamic behavior. is devoted to modeling of the influence of the crack density and orientation on three-dimensional wave propagation.

The need to numerically model the limit stage when matter no longer sustain the imparted strains and more or less progressively transits from continuum to a discrete state has led to the development of discrete element methods (DEM). is devoted to modeling instabilities in this framework.

New experimental capabilities developed in the past decade for studying the high-rate behavior of concrete and ceramics are presented in .

Finally, another facet of this book is that a variety of materials are presented. As an example, presents an alternative approach to modeling the high-rate regime of behavior using a hypo-elastic modeling approach.

It is a privilege of the Editors to thank all the contributors for their enthusiastic collaboration. Oana Cazacu and Benoit Revil-Baudard gratefully acknowledge the financial support provided by the Office of the Vice-President for Research at the University of Florida, the Doolittle Institute, Niceville, USA, and CEA Gramat, France, for the 10th US-French symposium that enabled the writing of this book.

David Edward LAMBERT, Crystal L. PASILIAO, Benjamin ERZAR,

Benoit REVIL-BAUDARD and Oana CAZACU

October 2018

Engineering design of structures to withstand accidental events involving high strain rates and/or impact loading requires predictive modeling capabilities for reproducing numerically potential premature failure following adiabatic shear banding (ASB). The purpose of the present chapter is to review ASB-oriented modeling approaches available in the literature (while not pretending to be exhaustive) that provide a better understanding of ASB and its consequences in structural metals and alloys.