La méthode de Kikuchi appliquée aux équations de von Karman.
La trave in parete sottile a sezione aperta e variabile: formulazione teorica e risultati sperimentali
Theoretical and experimental results concerning the shear-center of a bent beam with variable section are carried out. The matrix methods of structural analysis for the static linear elastic problem is extended; the stiffness and load matrix are formulated starting from the sectorial areas theory in order to interpret the effect of non-uniform torsion. The formulation may be used through the general matrix displacement method of structural analysis.
Least square method for solving contact problems with friction obeying the Coulomb law
The paper deals with numerical realization of contact problems with friction obeying the Coulomb law. The original problem is formulated as the fixed-point problem for a certain operator generated by the variational inequality. This inequality is transformed to a system of variational nonlinear equations generating other operators, in a sense "close" to the above one. The fixed-point problem of these operators is solved by the least-square method in which equations and the corresponding quadratic...
Linear stability results in a magnetothermoconvection problem.
Locking effects in the finite element approximation of elasticity problems.
Locking free matching of different three dimensional models in structural mechanics
The present paper proposes and analyzes a general locking free mixed strategy for computing the deformation of incompressible three dimensional structures placed inside flexible membranes. The model involves as in Chapelle and Ferent [Math. Models Methods Appl. Sci.13 (2003) 573–595] a bending dominated shell envelope and a quasi incompressible elastic body. The present work extends an earlier work of Arnold and Brezzi [Math Comp.66 (1997) 1–14] treating the shell part and proposes a global...
Locking-Free Finite Elements for Unilateral Crack Problems in Elasticity
We consider mixed and hybrid variational formulations to the linearized elasticity system in domains with cracks. Inequality type conditions are prescribed at the crack faces which results in unilateral contact problems. The variational formulations are extended to the whole domain including the cracks which yields, for each problem, a smooth domain formulation. Mixed finite element methods such as PEERS or BDM methods are designed to avoid locking for nearly incompressible materials in plane elasticity....
Machine Computation Using the Exponentially Convergent Multiscale Spectral Generalized Finite Element Method
A multiscale spectral generalized finite element method (MS-GFEM) is presented for the solution of large two and three dimensional stress analysis problems inside heterogeneous media. It can be employed to solve problems too large to be solved directly with FE techniques and is designed for implementation on massively parallel machines. The method is multiscale in nature and uses an optimal family of spectrally defined local basis functions over a coarse grid. It is proved that the method has an...
Mathematical and numerical approaches for multiscale problems
Mathematical study of an evolution problem describing the thermomechanical process in shape memory alloys
In this paper we prove existence, uniqueness, and continuous dependence for a one-dimensional time-dependent problem related to a thermo-mechanical model of structural phase transitions in solids. This model assumes the free energy depending on temperature, macroscopic deformation and also on the proportions of the phases. Here we neglect regularizing terms in the momentum balance equation and in the constitutive laws for the phase proportions.
Membrane locking in the finite element computation of very thin elastic shells
Mesh r-adaptation for unilateral contact problems
We present a mesh adaptation method by node movement for two-dimensional linear elasticity problems with unilateral contact. The adaptation is based on a hierarchical estimator on finite element edges and the node displacement techniques use an analogy of the mesh topology with a spring network. We show, through numerical examples, the efficiency of the present adaptation method.
Méthode d'éléments finis pour le modèle des plaques en flexion de Naghdi-Reissner
Méthodes d'éléments finis quasilinéaires en déplacement pour l'étude de milieux incompressibles
Metodo della differenza ali'indietro e determinazione dei moduli tangenti per analisi evolutive elastoplastiche a passi finiti
Si discute l'applicazione di un procedimento per "differenza all'indietro" ("backward difference") all'integrazione numerica nel tempo di leggi costitutive elastoplastiche e se ne esaminano alcuni aspetti peculiari. Con riferimento a modelli costitutivi isotropi per i quali le funzioni di snervamento dipendono dall'invariante primo delle tensioni, dall'invariante secondo del deviatore delle tensioni e da opportune variabili interne, si ricavano le relazioni non lineari implicite in termini di incrementi...
Mixed finite element approximation of 3D contact problems with given friction : error analysis and numerical realization
This contribution deals with a mixed variational formulation of 3D contact problems with the simplest model involving friction. This formulation is based on a dualization of the set of admissible displacements and the regularization of the non-differentiable term. Displacements are approximated by piecewise linear elements while the respective dual variables by piecewise constant functions on a dual partition of the contact zone. The rate of convergence is established provided that the solution...
Mixed finite element approximation of 3D contact problems with given friction: Error analysis and numerical realization
This contribution deals with a mixed variational formulation of 3D contact problems with the simplest model involving friction. This formulation is based on a dualization of the set of admissible displacements and the regularization of the non-differentiable term. Displacements are approximated by piecewise linear elements while the respective dual variables by piecewise constant functions on a dual partition of the contact zone. The rate of convergence is established provided that the solution...
Mixed finite element discretization of some variational inequalities arising in elasticity problems in domains with cracks.
Mixed finite element methods for elastic rods of arbitrary geometry.
Mixed Finite Elements in IR3 .