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### A Bermúdez–Moreno algorithm adapted to solve a viscoplastic problem in alloy solidification processes

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

The aim of this work is to present a computationally efficient algorithm to simulate the deformations suffered by a viscoplastic body in a solidification process. This type of problems involves a nonlinearity due to the considered thermo-elastic-viscoplastic law. In our previous papers, this difficulty has been solved by means of a duality method, known as Bermúdez–Moreno algorithm, involving a multiplier which was computed with a fixed point algorithm or a Newton method. In this paper, we will...

### A convergence result and numerical study for a nonlinear piezoelectric material in a frictional contact process with a conductive foundation

Applications of Mathematics

We consider two static problems which describe the contact between a piezoelectric body and an obstacle, the so-called foundation. The constitutive relation of the material is assumed to be electro-elastic and involves the nonlinear elastic constitutive Hencky's law. In the first problem, the contact is assumed to be frictionless, and the foundation is nonconductive, while in the second it is supposed to be frictional, and the foundation is electrically conductive. The contact is modeled with the...

### A finite element solution for plasticity with strain-hardening

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

### A fixed point method in dynamic processes for a class of elastic-viscoplastic materials

Annales Polonici Mathematici

Two problems are considered describing dynamic processes for a class of rate-type elastic-viscoplastic materials with or without internal state variable. The existence and uniqueness of the solution is proved using classical results of linear elasticity theory together with a fixed point method.

### A frictionless contact problem for elastic-viscoplastic materials with internal state variable

Applicationes Mathematicae

We study a mathematical model for frictionless contact between an elastic-viscoplastic body and a foundation. We model the material with a general elastic-viscoplastic constitutive law with internal state variable and the contact with a normal compliance condition. We derive a variational formulation of the model. We establish existence and uniqueness of a weak solution, using general results on first order nonlinear evolution equations with monotone operators and fixed point arguments. Finally,...

### A generalization to nonlinear hardening of the first shakedown theorem for discrete elastic-plastic structural models

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

In the plastic constitutive laws the yield functions are assumed to be linear in the stresses, but generally non-linear in the internal variables which are non-decreasing measures of the contribution to plastic strains by each face of the yield surface. The structural models referred to for simplicity are aggregates of constant-strain finite elements. Influence of geometry changes on equilibrium are allowed for in a linearized way (the equilibrium equation contains a bilinear term in the displacements...

### A maximum reduced dissipation principle for nonassociative plasticity

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

The concept of reduced plastic dissipation is introduced for a perfectly plastic rate-independent material not obeyng the associated normality rule and characterized by a strictly convex plastic potential function. A maximum principle is provided and shown to play the role of variational statement for the nonassociative constitutive equations. The Kuhn-Tucker conditions of this principle describe the actual material behaviour as that of a (fictitious) composite material with two plastic constituents,...

### A mixed variational formulation for the Signorini frictionless problem in viscoplasticity.

Analele Ştiinţifice ale Universităţii “Ovidius" Constanţa. Seria: Matematică

### A model of macroscale deformation and microvibration in skeletal muscle tissue

ESAIM: Mathematical Modelling and Numerical Analysis

This paper deals with modeling the passive behavior of skeletal muscle tissue including certain microvibrations at the cell level. Our approach combines a continuum mechanics model with large deformation and incompressibility at the macroscale with chains of coupled nonlinear oscillators. The model verifies that an externally applied vibration at the appropriate frequency is able to synchronize microvibrations in skeletal muscle cells. From the numerical analysis point of view, one faces...

### A nonlinear evolution inclusion in perfect plasticity with friction.

Acta Mathematica Universitatis Comenianae. New Series

### A remark on the local Lipschitz continuity of vector hysteresis operators

Applications of Mathematics

It is known that the vector stop operator with a convex closed characteristic $Z$ of class ${C}^{1}$ is locally Lipschitz continuous in the space of absolutely continuous functions if the unit outward normal mapping $n$ is Lipschitz continuous on the boundary $\partial Z$ of $Z$. We prove that in the regular case, this condition is also necessary.

### A variationally consistent generalized variable formulation of the elastoplastic rate problem

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

The elastoplastic rate problem is formulated as an unconstrained saddle point problem which, in turn, is obtained by the Lagrange multiplier method from a kinematic minimum principle. The finite element discretization and the enforcement of the min-max conditions for the Lagrangean function lead to a set of algebraic governing relations (equilibrium, compatibility and constitutive law). It is shown how important properties of the continuum problem (like, e.g., symmetry, convexity, normality) carry...

### Abstract quasi-variational inequalities of elliptic type and applications

Banach Center Publications

A class of quasi-variational inequalities (QVI) of elliptic type is studied in reflexive Banach spaces. The concept of QVI was earlier introduced by A. Bensoussan and J.-L. Lions [2] and its general theory has been developed by many mathematicians, for instance, see [6, 7, 9, 13] and a monograph [1]. In this paper we give a generalization of the existence theorem established in [14]. In our treatment we employ the compactness method along with a concept of convergence of nonlinear multivalued operators...

### An elasto-plastic contact problem

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

### An extension of small-strain models to the large-strain range based on an additive decomposition of a logarithmic strain

Programs and Algorithms of Numerical Mathematics

This paper describes model combining elasticity and plasticity coupled to isotropic damage. However, the conventional theory fails after the loss of ellipticity of the governing differential equation. From the numerical point of view, loss of ellipticity is manifested by the pathological dependence of the results on the size and orientation of the finite elements. To avoid this undesired behavior, the model is regularized by an implicit gradient formulation. Finally, the constitutive model is extended...

### Anisotropic and dissipative finite elasto-plastic composite.

Rendiconti del Seminario Matematico

### Asymptotic behavior of solutions on a thin plastic plate.

Electronic Journal of Differential Equations (EJDE) [electronic only]

### $\mathrm{BV}$ solutions of rate independent differential inclusions

Mathematica Bohemica

We consider a class of evolution differential inclusions defining the so-called stop operator arising in elastoplasticity, ferromagnetism, and phase transitions. These differential inclusions depend on a constraint which is represented by a convex set that is called the characteristic set. For $\mathrm{BV}$ (bounded variation) data we compare different notions of $\mathrm{BV}$ solutions and study how the continuity properties of the solution operators are related to the characteristic set. In the finite-dimensional case...

### Certain remarks on a class of evolution quasi-variational inequalities.

International Journal of Mathematics and Mathematical Sciences

### Characterization of the limit load in the case of an unbounded elastic convex

ESAIM: Mathematical Modelling and Numerical Analysis

In this work we consider a solid body $\Omega \subset {ℝ}^{3}$ constituted by a nonhomogeneous elastoplastic material, submitted to a density of body forces $\lambda f$ and a density of forces $\lambda g$ acting on the boundary where the real $\lambda$ is the loading parameter. The problem is to determine, in the case of an unbounded convex of elasticity, the Limit load denoted by $\overline{\lambda }$ beyond which there is a break of the structure. The case of a bounded convex of elasticity is done in [El-Fekih and Hadhri, RAIRO: Modél. Math. Anal. Numér. 29 (1995)...

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