EXISTENCE THEOREMS OF EXTREMAL SOLUTIONS FOR A CLASS OF NONLINEAR INTEGRO－DIFFERENTIAL EQUATIONS

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Existence theorems for two-dimensional linear shell theories

We consider linearly elastic shells whose middle surfaces have the most general geometries, and we provide complete proofs of the ellipticity of the strain energies found in two commonly used two-dimensional models: Koiter's model and Naghdi's model.This work is part of the Project Junctions in Elastic Multi-Structures of the Program S.C.I.E.N.C.E. of the Commission of the European Communities (ContractnSC1 * 0473-C(EDB)).     

Decay theorems for the Broadwell equations

Communicated by R. Muncaster     

Stochastic differential equations for the kinetic and hydrodynamic equations

A finite system of stochastic interacting particles is considered. The system approximates the solutions of the kinetic equations (the Boltzmann equation, the Boltzmann-Enskog equation) as well as the solutions describing the macroscopic evolution of fluids: the Euler and the Navier-Stokes hydrodynamic equations.     

EXISTENCE THEOREMS OF SOLUTIONS FOR TWO－POINT BOUNDARY VALUE PROBLEM OF SECOND ORDER ORDINARY DIFFERENTIAL EQUATIONS IN BANACH SPACES

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Energy theorems for solving equations of deflections

In this paper the unit-dummy-load method is generalized on the basis of Castigliano’s Theorem. On these grounds the general eguations of deflection surfaces of the structures, such as a kind of beams,plates and shells, are directly derived by the force method.We derived the eguations of the deflection surfaces of the rectangular thin plates and thick plates considering the effect of transverse shearing deformations with the inhomogeneous displacement boundary conditions. At the same time we give the equations of deflection axes of the corresponding straight beams.The applications of the reciprocal theorem are also generalized.Three simple calculated examples are given.     

Existence theorems for nonlinear elastic plates with periodic boundary conditions

The implicit function theorem is applied to the general three-dimensional equations for the equilibrium of a rectangular nonlinearly elastic plate subjected to suitable applied forces. The plate is assumed to have periodic boundary conditions or else to be with sliding edges. Regularity results in Sobolev spaces are used to define the equations in a suitable Banach space. Then, it is shown that the problem has a solution if the applied forces are small enough in a certain Sobolev norm.

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Résumé On applique le théorème des fonctions implicites au problème non linéaire de l'équilibre d'une plaque rectangulaire élastique soumise à des forces convenables. Cette plaque est supposée à bords glissants ou bien soumise à des conditions aux limites de type périodique. On utilise des résultats de régularité dans les espaces de Sobolev pour poser les équations dans un cadre fonctionnel adéquat. On montre alors que ce problème admet une solution si les forces appliquées sont assez petites dans une certaine norme de Sobolev.

     

Existence theorems in the theory of mixtures

This paper is concerned with boundary-value problems of the linear theory for binary mixtures of elastic bodies. First, a counterpart of the Boussinesq-Somigliana-Galerkin solution in classical elastostatics is established and the fundamental solutions in the equilibrium theory of homogeneous and isotropic mixtures are derived. Then, representations of Somigliana type for the displacement fields are presented. The potentials of single layer and double layer are used to reduce the boundary-value problems to singular integral equations. Existence and uniqueness results are established.     

Existence and uniqueness theorems for boundaryvalue problems involving incrementally non linear models

Sufficient conditions for existence and uniqueness of rate boundary value probleminvolving an incrementally non-linear constitutive equation useful for geomaterials are proved.The models considered are incrementally non-linear models not descending from a rate potentialand thus are not included into the Hill theory framework. Results are given in the framework ofsmall strain assumption. The main assumption is the positiveness of the second-order work. Theexistence theorem is a generalisation of the Lax-Milgram theorem, whereas uniqueness theoremis based on the well-known Hill exclusion functional.     

Existence and attractivity results for nonlinear first-order random differential equations

istence and attractivity results are proved for nonlinear first-order ordinary random differential equations. An example is given to demonstrate a realization of the abstract theory developed in the present paper.     

Immersed boundary method for unsteady kinetic model equations

Predicting unsteady flows and aerodynamic forces for large displacement motion of microstructures requires transient solution of Boltzmann equation with moving boundaries. For the inclusion of moving complex boundaries for these problems, three immersed boundary method flux formulations (interpolation, relaxation, and interrelaxation) are presented. These formulations are implemented in a 2‐D finite volume method solver for ellipsoidal‐statistical (ES)‐Bhatnagar‐Gross‐Krook (BGK) equations using unstructured meshes. For the verification, a transient analytical solution for free molecular 1‐D flow is derived, and results are compared with the immersed boundary (IB)‐ES‐BGK methods. In 2‐D, methods are verified with the conformal, non‐moving finite volume method, and it is shown that the interrelaxation flux formulation gives an error less than the interpolation and relaxation methods for a given mesh size. Furthermore, formulations applied to a thermally induced flow for a heated beam near a cold substrate show that interrelaxation formulation gives more accurate solution in terms of heat flux. As a 2‐D unsteady application, IB/ES‐BGK methods are used to determine flow properties and damping forces for impulsive motion of microbeam due to high inertial forces. IB/ES‐BGK methods are compared with Navier–Stokes solution at low Knudsen numbers, and it is shown that velocity slip in the transitional rarefied regime reduces the unsteady damping force. Copyright © 2015 John Wiley & Sons, Ltd.