Continuum Mechanics and Thermodynamics
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Continuum Mechanics and Thermodynamics Continuum mechanics and thermodynamics are foundational theories of many fields of science and engineering. This book presents a fresh perspective on these important subjects, exploring their fundamentals and connecting them with micro- and nanoscopic theories. Providing clear, in-depth coverage, the book gives a self-contained treatment of topics di- rectly related to nonlinear materials modeling with an emphasis on the thermo-mechanical behavior of solid-state systems. It starts with vectors and tensors, finite deformation kine- matics, the fundamental balance and conservation laws, and classical thermodynamics. It then discusses the principles of constitutive theory and examples of constitutive models, presents a foundational treatment of energy principles and stability theory, and concludes with example closed-form solutions and the essentials of finite elements. Together with its companion book, Modeling Materials (Cambridge University Press, 2011), this work presents the fundamentals of multiscale materials modeling for graduate students and researchers in physics, materials science, chemistry, and engineering. A solutions manual is available at www.cambridge.org/9781107008267, along with a link to the authors’ website which provides a variety of supplementary material for both this book and Modeling Materials. Ellad B. Tadmor is Professor of Aerospace Engineering and Mechanics, University of Minnesota. His research focuses on multiscale method development and the microscopic foundations of continuum mechanics. Ronald E. Miller is Professor of Mechanical and Aerospace Engineering, Carleton University. He has worked in the area of multiscale materials modeling for over 15 years. Ryan S. Elliott is Associate Professor of Aerospace Engineering and Mechanics, University of Minnesota. An expert in stability of continuum and atomistic systems, he has received many awards for his work. Continuum Mechanics and Thermodynamics From Fundamental Concepts to Governing Equations ELLAD B. TADMOR University of Minnesota, USA RONALD E. MILLER Carleton University, Canada RYAN S. ELLIOTT University of Minnesota, USA CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao˜ Paulo, Delhi, Tokyo, Mexico City Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9781107008267 C E. Tadmor, R. Miller and R. Elliott 2012 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2012 Printed in the United Kingdom at the University Press, Cambridge A catalog record for this publication is available from the British Library Library of Congress Cataloguing in Publication data Tadmor, Ellad B., 1965– Continuum mechanics and thermodynamics : from fundamental concepts to governing equations / Ellad B. Tadmor, Ronald E. Miller, Ryan S. Elliott. p. cm. Includes bibliographical references and index. ISBN 978-1-107-00826-7 1. Continuum mechanics. 2. Thermodynamics – Mathematics. I. Miller, Ronald E. (Ronald Earle) II. Elliott, Ryan S. III. Title. QA808.2.T33 2012 531 – dc23 2011040410 ISBN 978-1-107-00826-7 Hardback Additional resources for this publication at www.cambridge.org/9781107008267 Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. Contents Preface page xi Acknowledgments xiii Notation xvii 1Introduction 1 Part I Theory 7 2 Scalars, vectors and tensors 9 2.1 Frames of reference and Newton’s laws 9 2.2 Tensor notation 15 2.2.1 Direct versus indicial notation 16 2.2.2 Summation and dummy indices 17 2.2.3 Free indices 18 2.2.4 Matrix notation 19 2.2.5 Kronecker delta 19 2.2.6 Permutation symbol 20 2.3 What is a tensor? 22 2.3.1 Vector spaces and the inner product and norm 22 2.3.2 Coordinate systems and their bases 26 2.3.3 Cross product 29 2.3.4 Change of basis 31 2.3.5 Vector component transformation 33 2.3.6 Generalization to higher-order tensors 34 2.3.7 Tensor component transformation 36 2.4 Tensor operations 38 2.4.1 Addition 38 2.4.2 Magnification 38 2.4.3 Transpose 39 2.4.4 Tensor products 39 2.4.5 Contraction 40 2.4.6 Tensor basis 44 2.5 Properties of tensors 46 2.5.1 Orthogonal tensors 46 2.5.2 Symmetric and antisymmetric tensors 48 2.5.3 Principal values and directions 48 2.5.4 Cayley–Hamilton theorem 51 v t vi Contents 2.5.5 The quadratic form of symmetric second-order tensors 52 2.5.6 Isotropic tensors 54 2.6 Tensor fields 55 2.6.1 Partial differentiation of a tensor field 56 2.6.2 Differential operators in Cartesian coordinates 56 2.6.3 Differential operators in curvilinear coordinates 60 2.6.4 Divergence theorem 64 Exercises 66 3 Kinematics of deformation 71 3.1 The continuum particle 71 3.2 The deformation mapping 72 3.3 Material and spatial field descriptions 74 3.3.1 Material and spatial tensor fields 75 3.3.2 Differentiation with respect to position 76 3.4 Description of local deformation 77 3.4.1 Deformation gradient 77 3.4.2 Volume changes 79 3.4.3 Area changes 80 3.4.4 Pull-back and push-forward operations 82 3.4.5 Polar decomposition theorem 83 3.4.6 Deformation measures and their physical significance 87 3.4.7 Spatial strain tensor 90 3.5 Linearized kinematics 91 3.6 Kinematic rates 93 3.6.1 Material time derivative 93 3.6.2 Rate of change of local deformation measures 96 3.6.3 Reynolds transport theorem 100 Exercises 101 4 Mechanical conservation and balance laws 106 4.1 Conservation of mass 106 4.1.1 Reynolds transport theorem for extensive properties 109 4.2 Balance of linear momentum 110 4.2.1 Newton’s second law for a system of particles 110 4.2.2 Balance of linear momentum for a continuum system 111 4.2.3 Cauchy’s stress principle 113 4.2.4 Cauchy stress tensor 115 4.2.5 An alternative (“tensorial”) derivation of the stress tensor 117 4.2.6 Stress decomposition 119 4.2.7 Local form of the balance of linear momentum 119 4.3 Balance of angular momentum 120 4.4 Material form of the momentum balance equations 122 4.4.1 Material form of the balance of linear momentum 122 4.4.2 Material form of the balance of angular momentum 124 4.4.3 Second Piola–Kirchhoff stress 125 Exercises 127 t vii Contents 5 Thermodynamics 129 5.1 Macroscopic observables, thermodynamic equilibrium and state variables 130 5.1.1 Macroscopically observable quantities 131 5.1.2 Thermodynamic equilibrium 133 5.1.3 State variables 133 5.1.4 Independent state variables and equations of state 136 5.2 Thermal equilibrium and the zeroth law of thermodynamics 137 5.2.1 Thermal equilibrium 137 5.2.2 Empirical temperature scales 138 5.3 Energy and the first law of thermodynamics 139 5.3.1 First law of thermodynamics 139 5.3.2 Internal energy of an ideal gas 143 5.4 Thermodynamic processes 147 5.4.1 General thermodynamic processes 147 5.4.2 Quasistatic processes 147 5.5 The second law of thermodynamics and the direction of time 148 5.5.1 Entropy 149 5.5.2 The second law of thermodynamics 150 5.5.3 Stability conditions associated with the second law 152 5.5.4 Thermal equilibrium from an entropy perspective 153 5.5.5 Internal energy and entropy as fundamental thermodynamic relations 156 5.5.6 Entropy form of the first law 159 5.5.7 Reversible and irreversible processes 161 5.6 Continuum thermodynamics 168 5.6.1 Local form of the first law (energy equation) 170 5.6.2 Local form of the second law (Clausius–Duhem inequality) 175 Exercises 177 6 Constitutive relations 180 6.1 Constraints on constitutive relations 181 6.2 Local action and the second law of thermodynamics 184 6.2.1 Specific internal energy constitutive relation 184 6.2.2 Coleman–Noll procedure 186 6.2.3 Onsager reciprocal relations 190 6.2.4 Constitutive relations for alternative stress variables 191 6.2.5 Thermodynamic potentials and connection with experiments 192 6.3 Material frame-indifference 195 6.3.1 Transformation between frames of reference 196 6.3.2 Objective tensors 200 6.3.3 Principle of material frame-indifference 202 6.3.4 Constraints on constitutive relations due to material frame-indifference 203 6.3.5 Reduced constitutive relations 207 6.3.6 Continuum field equations and material frame-indifference 213 6.3.7 Controversy regarding the principle of material frame-indifference 213 6.4 Material symmetry 215 6.4.1 Simple fluids 218 6.4.2 Isotropic solids 221 t viii Contents 6.5 Linearized constitutive relations for anisotropic hyperelastic solids 225 6.5.1 Generalized Hooke’s law and the elastic constants 229 6.6 Limitations of continuum constitutive relations 236 Exercises 237 7 Boundary-value problems, energy principles and stability 242 7.1 Initial boundary-value problems 242 7.1.1 Problems in the spatial description 243 7.1.2 Problems in the material description 245 7.2 Equilibrium and the principle of stationary potential energy (PSPE) 247 7.3 Stability of equilibrium configurations 249 7.3.1 Definition of a stable equilibrium configuration 250 7.3.2 Lyapunov’s indirect method and the linearized equations of motion 251 7.3.3 Lyapunov’s direct method and the principle of minimum potential energy (PMPE) 255 Exercises 259 Part II Solutions 263 8 Universal equilibrium