Article Contents
Article Contents

# Constructing free energies for materials with memory

• The free energy for most materials with memory is not unique. There is a convex set of free energy functionals with a minimum and a maximum element. Various functionals have been shown to have the properties of a free energy for materials with particular types of relaxation behaviour. Also, over the last decade or more, forms have been given for the minimum and related free energies. These are all quadratic functionals which yield linear memory terms in the constitutive equations for the stress.
A difficulty in constructing free energy functionals arises in making choices that ensure a non-negative quadratic form both for the free energy and for the rate of dissipation. We propose a technique which renders this task more straightforward. Instead of constructing the free energy and determining from this the rate of dissipation, which may not have the required non-negativity, the procedure is reversed, which guarantees a satisfactory free energy functional.
Certain results for quadratic functionals in the time and frequency domains are derived, providing a platform for this alternative approach, which produces new free energies, including a family of functionals that are generalizations of the minimum and related free energies.
Mathematics Subject Classification: 80A17, 74A15, 74D05.

 Citation:

•  [1] G. Amendola, M. Fabrizio and J. M. Golden, Free energies in a general non-local theory of a material with memory, Mathematical Models and Methods in Applied Sciences, 24 (2014), 1037-1090.doi: 10.1142/S0218202513500760. [2] G. Amendola, M. Fabrizio and M. Golden, Thermodynamics of Materials with Memory: Theory and Applications, Springer, New York, 2012.doi: 10.1007/978-1-4614-1692-0. [3] G. Amendola, M. Fabrizio and J. M. Golden, Algebraic and numerical exploration of free energies for materials with memory, submitted for publication. [4] V. Berti and G. Gentili, The minimum free energy for isothermal dielectrics with memory, J. Non-Equil. Thermodyn., 24 (1999), 154-176. [5] B. D. Coleman, Thermodynamics of materials with memory, Arch. Rational Mech. Anal., 17 (1964), 1-46.doi: 10.1007/BF00283864. [6] W. A. Day, The thermodynamics of materials with memory, in Materials with Memory, (ed. D. Graffi), Liguori, Naples, (1979). [7] G. Del Piero and L. Deseri, On the analytic expression of the free energy in linear viscoelasticity, J. Elasticity, 43 (1996), 247-278.doi: 10.1007/BF00042503. [8] G. Del Piero and L. Deseri, On the concepts of state and free energy in linear viscoelasticity, Arch. Rational Mech. Anal., 138 (1997), 1-35.doi: 10.1007/s002050050035. [9] L. Deseri, M. Di Paola, P. Pollaci and M. Zingales, The state of fractional hereditary materials (FHM), Discrete and Continuous Dynamical Systems - B to appear. [10] L. Deseri, G. Gentili and J. M. Golden, An explicit formula for the minimum free energy in linear viscoelasticity, J. Elasticity, 54 (1999), 141-185.doi: 10.1023/A:1007646017347. [11] L. Deseri, M. Fabrizio and J. M. Golden, On the concept of a minimal state in viscoelasticity: New free energies and applications to $PDE_S$, Arch. Rational Mech. Anal., 181 (2006), 43-96.doi: 10.1007/s00205-005-0406-1. [12] L. Deseri and J. M. Golden, The minimum free energy for continuous spectrum materials, SIAM J. Appl Math., 67 (2007), 869-892.doi: 10.1137/050639776. [13] M. Fabrizio and A. Morro, Mathematical Problems in Linear Viscoelasticity, SIAM, Philadelphia, 1992.doi: 10.1137/1.9781611970807. [14] M. Fabrizio and J. M. Golden, Maximum and minimum free energies for a linear viscoelastic material, Quart. Appl. Math., 60 (2002), 341-381. [15] M. Fabrizio, G. Gentili and J. M. Golden, Nonisothermal free energies for linear theories with memory, Mathematical and Computer Modeling, 39 (2004), 219-253.doi: 10.1016/S0895-7177(04)90009-X. [16] M. Fabrizio, C. Giorgi and V. Pata, A new approach to equations with memory, Arch. Rational Mech. Anal., 198 (2010), 189-232.doi: 10.1007/s00205-010-0300-3. [17] J. M. Golden, Free energies in the frequency domain: The scalar case, Quart. Appl. Math., 58 (2000), 127-150. [18] J. M. Golden, A proposal concerning the physical rate of dissipation in materials with memory, Quart. Appl. Math., 63 (2005), 117-155.doi: 10.1177/1081286506061450. [19] J. M. Golden, A proposal concerning the physical dissipation of materials with memory: the non-isothermal case, Mathematics and Mechanics of Solids, 12 (2007), 403-449.doi: 10.1177/1081286505061450. [20] I. S. Gradshteyn and I. M. Ryzhik, Tables of Integrals, Series, and Products, Academic Press, New York, 1965. [21] D. Graffi, Analytic expression of some thermodynamic quantities in materials with memory, Rend. Sem. Mat. Univ. Padova, 68 (1982), 17-29. [22] D. Graffi and M. Fabrizio, On the notion of state for viscoelastic materials of "rate'' type, Atti della Accademia Nazionale dei Lincei, 83 (1990), 201-208. [23] D. Graffi, More on the analytic expression of free energy in materials with memory, Atti Acc. Scienze Torino, 120 (1986), 111-124. [24] W. Noll, A new mathematical theory of simple materials, Arch. Rational Mech. Anal., 48 (1972), 1-50.doi: 10.1007/BF00253367.