Numerical solution of Variational Inequalities by Adaptive Finite Elements

Franz-Theo Suttmeier describes a general approach to a posteriori error estimation and adaptive mesh design for finite element models where the solution is subjected to inequality constraints. This is an extension to variational inequalities of the so-cal

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VIEWEG+TEUBNER RESEARCH Advances in Numerical Mathematics Herausgeber | Editors: Prof. Dr. Dr. h. c. Hans Georg Bock Prof. Dr. Dr. h. c. Wolfgang Hackbusch Prof. Mitchell Luskin Prof. Dr. Rolf Rannacher

Franz-Theo Suttmeier

Numerical solution of Variational Inequalities by Adaptive Finite Elements

VIEWEG+TEUBNER RESEARCH

Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available in the Internet at http://dnb.d-nb.de.

1st Edition 2008 All rights reserved © Vieweg+Teubner | GWV Fachverlage GmbH, Wiesbaden 2008 Readers: Christel A. Roß Vieweg+Teubner is part of the specialist publishing group Springer Science+Business Media www.viewegteubner.de No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the copyright holder. Registered and/or industrial names, trade names, trade descriptions etc. cited in this publication are part of the law for trade-mark protection and may not be used free in any form or by any means even if this is not specifically marked. Cover design: KünkelLopka Medienentwicklung, Heidelberg Printing company: Strauss Offsetdruck, Mörlenbach Printed on acid-free paper Printed in Germany ISBN 978-3-8348-0664-2

Summary This work describes a general approach to a posteriori error estimation and adaptive mesh design for finite element models where the solution is subjected to inequality constraints. This is an extension to variational inequalities of the so-called Dual-Weighted-Residual method (DWR method) which is based on a variational formulation of the problem and uses global duality arguments for deriving weighted a posteriori error estimates with respect to arbitrary functionals of the error. In these estimates local residuals of the computed solution are multiplied by sensitivity factors which are obtained from a numerically computed dual solution. The resulting local error indicators are used in a feed-back process for generating economical meshes which are tailored according to the particular goal of the computation. This method is developed here for several model problems. Based on these examples, a general concept is proposed, which provides a systematic way of adaptive error control for problems stated in form of variational inequalities.

F¨ ur Alexandra, Katharina und Merle

Contents

1 Introduction

1

2 Models in elasto-plasticity

13

2.1

Governing equations . . . . . . . . . . . . . . . . . . . . . . . .

14

2.2

Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20

3 The dual-weighted-residual method

23

3.1

A model situation in plasticity . . . . . . . . . . . . . . . . . .

24

3.2

A posteriori error estimate . . . . . . . . . . . . . . . . . . . . .

25

3.3

Evaluation of a posteriori error bounds . . . . . . . . . . . . . .

26

3.4

St