This paper focuses on a one-dimensional wave equation being subjected to a unilateralboundary condition. Under appropriate regularity assumptions on the initial data, a newproof of existence and uniqueness results is proposed. The mass redistribution method,which is based on a redistribution of the body mass such that there is no inertia at thecontact node, is introduced and its convergence is proved. Finally, some numericalexperiments are reported.

The purpose of this paper is to provide a priori error estimates on the approximation of contact conditions in the framework of the eXtended Finite-Element Method (XFEM) for two dimensional elastic bodies. This method allows to perform finite-element computations on cracked domains by using meshes of the non-cracked domain. We consider a stabilized Lagrange multiplier method whose particularity is that no discrete inf-sup condition is needed in the convergence analysis. The contact condition is prescribed on the crack with a discrete multiplier which is the trace on the crack of a finite-element method on the non-cracked domain, avoiding the definition of a specific mesh of the crack. Additionally, we present numerical experiments which confirm the efficiency of the proposed method.

Il est impératif pour l’ingénieur de s’assurer de la validité de ses outils de modélisation numérique et il lui revient de vérifier s’ils donnent la solution attendue pour un problème donné. Dans un logiciel d’éléments-finis, ceci peut être fait par l’utilisation de solutions analytiques lorsqu’elles existent, ou par la méthode des solutions manufacturées (MSM). Nous proposons dans ce travail d’étendre la MSM aux problèmes de contact unilatéral en grandes déformations pour lesquels, à notre connaissance, il n’existe pas de solutions analytiques non triviales. Nous montrerons comment l’utiliser comme un outil de vérification pour l’ingénieur. De plus, nous analyserons la précision et les taux de convergence de différents espaces d’approximation mixtes (déplacement-pression de contact), sur des éléments triangulaires et quadrangulaires.

We investigate unilateral contact problems with cohesive forces, leading tothe constrained minimization of a possibly nonconvex functional. Weanalyze the mathematical structure of the minimization problem. The problem is reformulated in terms of a three-field augmentedLagrangian, and sufficient conditions for the existence of a localsaddle-point are derived. Then, we derive and analyze mixed finiteelement approximations to the stationarity conditions of the three-fieldaugmented Lagrangian. The finite element spaces for the bulk displacement andthe Lagrange multiplier must satisfy a discrete inf-sup condition, whilediscontinuous finite element spaces spanned by nodal basis functions areconsidered for the unilateral contact variable so as to use collocationmethods. Two iterative algorithms are presented and analyzed, namely anUzawa-type method within a decomposition-coordination approach and anonsmooth Newton's method. Finally, numerical results illustrating thetheoretical analysis are presented.

The contact between two membranes can be described by a system of variationalinequalities, where the unknowns are the displacements of the membranes and theaction of a membrane on the other one. We first perform the analysis of thissystem. We then propose a discretization, where the displacements areapproximated by standard finite elements and the action by alocal postprocessing. Such a discretization admits an equivalent mixedreformulation. We prove the well-posedness of the discrete problem and establishoptimal a priori error estimates.

In this work we consider a stabilized Lagrange multiplier method in order toapproximate the Coulomb frictional contact model in linear elastostatics. Theparticularity of the method is that no discrete inf-sup condition is needed. Westudy the existence and the uniqueness of solution of the discrete problem.

From the fundamental laws of elasticity, we write a model for the contact between two membranes and we perform the analysis of the corresponding system of variational inequalities. We propose a finite element discretization of this problem and prove its well-posedness. We also establish a priori and a posteriori error estimates.

We consider a two dimensional elastic body submitted to unilateral contact conditions, local frictionand adhesion on a part of his boundary. After discretizing the variational formulation with respectto time we use a smoothing technique to approximate the friction term by an auxiliary problem. A shiftingtechnique enables us to obtain the existence of incremental solutions with bounds independent of the regularization parameter. We finally obtain the existence of a quasistatic solution by passing to thelimit with respect to time.