Uniqueness Theorems in Linear Elasticity - Knops, Robin J.

Résumé :
The classical result for uniqueness in elasticity theory is due to Kirchhoff. It states that the standard mixed boundary value problem for a homogeneous isotropic linear elastic material in equilibrium and occupying a bounded three-dimensional region of space possesses at most one solution in the classical sense, provided the Lame and shear moduli, A and J1 respectively, obey the inequalities (3 A + 2 J1) > 0 and J1>O. In linear elastodynamics the analogous result, due to Neumann, is that the initial-mixed boundary value problem possesses at most one solution provided the elastic moduli satisfy the same set of inequalities as in Kirchhoffs theorem. Most standard textbooks on the linear theory of elasticity mention only these two classical criteria for uniqueness and neglect altogether the abundant literature which has appeared since the original publications of Kirchhoff. To remedy this deficiency it seems appropriate to attempt a coherent description ofthe various contributions made to the study of uniqueness in elasticity theory in the hope that such an exposition will provide a convenient access to the literature while at the same time indicating what progress has been made and what problems still await solution. Naturally, the continuing announcement of new results thwarts any attempt to provide a complete assessment. Apart from linear elasticity theory itself, there are several other areas where elastic uniqueness is significant.

Sommaire:
1 Introduction.- 2 Basic Equations.- 2.1 Formulation of Initial-Boundary Value Problems.- 2.2 The Classical and Weak Solutions.- 2.3 The Homogeneous Isotropic Body. Plane Elasticity.- 2.4 Definiteness Properties of the Elasticities.- 3 Early Work.- 4 Modern Uniqueness Theorems in Three-Dimensional Elastostatics.- 4.1 The Displacement Boundary Value Problem for Bounded Regions.- 4.2 Exterior Domains.- 4.3 The Traction Boundary Value Problem.- 4.4 Mixed Boundary Value Problems.- 5 Uniqueness Theorems in Homogeneous Isotropic Two-Dimensional Elastostatics.- 5.1 Kirchhoff's Theorem in Two-Dimensions. The Displacement and Traction Boundary Value Problems.- 5.2 Uniqueness in Plane Problems with Special Geometries.- Appendix: Uniqueness of Three-Dimensional Axisymmetric Solutions.- 6 Problems in the Whole- and Half-Space.- 6.1 Specification of the Various Boundary Value Problems. Continuity onto the Boundary and in the Neighbourhood of Infinity.- 6.2 Uniqueness of Problems (a)-(d). Corollaries for the Space EN.- 6.3 Uniqueness for the Mixed-Mixed Problem of Type (e).- 7 Miscellaneous Boundary Value Problems.- 7.1 Problems for a Sphere.- 7.2 The Cauchy Problem for Isotropic Elastostatics.- 7.3 The Signorini Problem. Other Problems with Ambiguous Conditions.- 8 Uniqueness Theorems in Elastodynamics. Relations with Existence, Stability, and Boundedness of Solutions.- 8.1 The Initial Displacement and Mixed-Boundary Value Problems. Energy Arguments.- 8.2 The Initial-Displacement Boundary Value Problem. Analyticity Arguments.- 8.3 The Initial-Mixed Boundary Value Problem for Bounded Regions. Further Arguments.- 8.4 Summary of Existing Results in the Uniqueness of Elastodynamic Solutions.- 8.5 Non-Standard Problems, including those with Ambiguous Conditions.- 8.6 Stability,Boundedness, Existence and Uniqueness.- References.