A finite element solution for plasticity with strain-hardening
A generalization to nonlinear hardening of the first shakedown theorem for discrete elastic-plastic structural models
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
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 nonlinear evolution inclusion in perfect plasticity with friction.
A variationally consistent generalized variable formulation of the elastoplastic rate problem
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...
An elasto-plastic contact problem
Asymptotic behavior of solutions on a thin plastic plate.
Characterization of the limit load in the case of an unbounded elastic convex
In this work we consider a solid body constituted by a nonhomogeneous elastoplastic material, submitted to a density of body forces and a density of forces acting on the boundary where the real is the loading parameter. The problem is to determine, in the case of an unbounded convex of elasticity, the Limit load denoted by 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)...
Characterization of the limit load in the case of an unbounded elastic convex
In this work we consider a solid body constituted by a nonhomogeneous elastoplastic material, submitted to a density of body forces and a density of forces acting on the boundary where the real is the loading parameter. The problem is to determine, in the case of an unbounded convex of elasticity, the Limit load denoted by 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)...
Determination of creep, fatigue and activation energy from constant strain-rate experiments
Si interpretano i risultati degli esperimenti fatti su mezzi anelastici mediante applicazione di deformazioni crescenti linearmente nel tempo. Si trova che dai risultati di questi esperimenti, si può risalire alla funzione di creep che viene determinata con tre diversi modelli di approssimazione. Si trova inoltre che per decidere sul comportamento a lungo termine dei materiali sono necessari esperimenti a più lungo termine di quelli fatti. Si dimostra poi che le relazioni classiche che rappresentano...
Efficient inexact Newton-like methods with application to problems of the deformation theory of plasticity
Newton-like methods are considered with inexact correction computed by some inner iterative method. Composite iterative methods of this type are applied to the solution of nonlinear systems arising from the solution of nonlinear elliptic boundary value problems. Two main quastions are studied in this paper: the convergence of the inexact Newton-like methods and the efficient control of accuracy in computation of the inexact correction. Numerical experiments show the efficiency of the suggested composite...
Elastic buckling behaviour of a four-lobed cross section cylindrical shell with variable thickness under non-uniform axial loads.
Elastic-plastic torsion problem over multiply connected domains
Elementary preamble to a theory of granular gases
Estensione a leggi costitutive a variabili interne dei teoremi di inadattamento in dinamica strutturale elastoplastica
Si considera il problema del mancato adattamento in campo dinamico per strutture elasto-plastiche incrudenti. Si dimostrano una condizione necessaria ed una sufficiente per il verificarsi di fenomeni di inadattamento (plasticità alternata o collasso incrementale) estendendo risultati precedenti ad un'ampia classe di modelli costitutivi a variabili interne in grado di rappresentare comportamenti incrudenti non lineari.
Estensione di un teorema sull'adattamento in dinamica elasto-plastica
Nell'articolo si tratta il problema dell'adattamento in dinamica elasto-plastica. La trattazione è fondata sulle seguenti basi: si adotta un legame costitutivo elasto-plastico di notevole generalità, basato su di una formulazione a variabili interne in grado di descrivere un comportamento incrudente genericamente non lineare; si fa riferimento ad un modello strutturale discreto, descritto mediante variabili generalizzate. I contributi presentati si possono così riassumere: si estendono risultati...
Étude dans d’un modèle de plaques élastoplastiques comportant une non-linéarité géométrique
Evolutionary variational inequalities and applications in plasticity
An abstract theory of evolutionary variational inequalities and its applications to the traction boundary value problems of elastoplasticity are studied, using the penalty method to prove the existence of a solution.
Existence of regular solutions for a one-dimensional simplified perfect-plastic problem with a unilateral gradient constraint.
Existence of regular solutions for a one-dimensional simplified perfect-plastic problem