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In this paper a new thermoplastic damage model for plain concrete subjected to combined thermal and cyclic loading is developed using the concept of plastic-work hardening and stiffness degradation in continuum damage mechanics. Two damage variables are used: one for mechanical action and the other one for thermal action. Further, thermomechanical interaction strains have been introduced to describe the influence of mechanical loading on the physical process of thermal expansion of concrete. The constitutive relations for elastoplastic responses are decoupled from the degradation damage responses by using the effective stress concept. This method provides advantages in the numerical implementation. Efficient computational algorithms for the proposed model are subsequently explored and performance of this model is demonstrated with numerical examples.Key words: damage theory, plasticity, thermal, unilateral phenomenon, thermomechanical interaction.Dans ce papier un nouveau modèle thermo-plastique endommageable pour le béton soumis à des chargements mécaniques cycliques et thermiques combinés est développé. Ce modèle est basé sur la théorie de l'endommagement, deux variables y sont introduites, une première variable pour modéliser les effets du chargement mécanique et la seconde pour modéliser les effets du chargement thermique. L'influence du chargement mécanique sur le processus de déformation thermique est introduit en utilisant le concept de déformation d'interaction thermo-mécanique. Un critère multi-surface de plasticité est utilisé. Les relations constitutives de la réponse thermo-elasto-plastique sont découplées de celles de la réponse endommagée en utilisant le concept de la contrainte effective. Cette méthode confère une souplesse dans l'implémentation numérique. Une variable scalaire de dégradation est introduite pour simuler les effets d'endommagements thermo-mécaniques sur la rigidité et l'effet unilatéral lors de la fermeture de fissures. Ce modèle est mis en œuvre dans l'analyse du comportement de spécimens en béton d'une part, et de structures en béton armé soumis à des sollicitations thermo-mécaniques cycliques à hautes températures. Le résultat des simulations est comparé avec l'expérience.Mots clés : théorie de l'endommagement, plasticité, thermique, phénomène unilatéral, interaction thermo-mécanique. [ABSTRACT FROM AUTHOR]

In the deformation analysis of geodetic networks, there are two conventional methods for estimating movement of an area of study: displacement vectors and strain tensors. However, the evaluation and representation of the deformation depend on the priori reference system and the configuration of chosen figures that constitute the entire network. These constraints make difficult the interpretation of the results. Through this present paper, a solution based on the finite element method (FEM) is proposed to refine the estimation and the representation of the deformation of geodetic networks. In this context, a study of the deformation is carried out to analyze the horizontal motion of the geodetic network Cheliff observed by classical triangulation in 1976 (by INCT) and 1981 (by CRAAG), based on a twodimensional elastic finite element model. The different results are illustrated in terms of displacement vectors, strain tensors and stress tensors. Deformation of the area thus determined is interpreted according to previous geophysical studies. In addition, different results revealed the following phenomena: A phenomenon of compressive of Cheliff area, in the NNW-SSE orientation, due to the rapprochement of the African and Eurasian tectonic plates that caused the fault opposite the famous earthquake of 10 October 1980. A phenomenon of block rotation in the SE and NW parts of the fault, in a retrograde direction. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical behaviour of a titanium alloys is modelised for the cold forming processes. The elasto-plastic constitutive law is decomposed in an anisotropic plastic criterion, an isotropic hardening and a kinematic hardening. Non quadratic criteria have been developed by Cazacu et al. (Orthotropic yield criterion for hexagonal closed packed metals, Tnt. J. Plasticity 22 (2006) 1171-1194), to model the plasticity of hexagonal closed packed materials. The implementation of this model in a finite element software switches between two bases, the equilibrium is calculated in a reference basis and the anisotropy axes define a local basis, updated by the deformation gradient. An identification procedure, based on tensile tests, allows to define all the parameters needed to model the elasto-plastic behaviour. Simulation of cold forming processes (bulging and deep drawing) have been done to validate this model. Numerical results are compared with experimental data, obtained from speckles analysis. [ABSTRACT FROM AUTHOR]

CAD and virtual reality tools are useful to simulate the manipulation of rigid parts, and particularly their collisions. Real time simulation need to take into account the deformation of flexible part; this suppose the computation of the deformation of parts in real time, with mechanical contact. The finite-element method can not allow a real-time response for a non-linear mechanical model (geometry, material, mechanical contact). A methodology divided into two phases is proposed. First, the learning phase consists on a calculation campaign of characteristic load cases, in respect of the requirements of the real time simulation. Then, the real time phase, used the results of the first phase by interpolation. Only the first one is exposed in this paper. The aim is to obtain quickly a reduced response. In order to attempt this goal, model reduction methods are used. We focus on three reduction levels : adaptive method, POD approach, and hyper reduction. A crush of a cylinder in rubber is used to expose the performance of the model reduction methods. [ABSTRACT FROM AUTHOR]

The various stages of transformation of the textile material involve non Newtonian fluids. The knowledge of their rheological properties is of great importance to control the efficiency of the process. Two examples in the field of finishing are considered in this paper: the blade coating and the printing of fabrics. The results contribute to a better understanding of process where complex formulated fluids are used. [ABSTRACT FROM AUTHOR]

Silicate glasses are known to be brittle at the macroscopic scale but they can also undergo plastic deformation at the microscopic scale. More specifically, plastic densification occurs under contact loadings. In this paper, a constitutive model, which allows to take into account this phenomenon, is presented. An identification of the material parameters using instrumented indentation results is proposed. This identification is based on the comparison of local residual indentation-induced densification field obtained using Raman spectroscopy and computational results. This constitutive model is then used to analyse the distribution of densification after three-dimensional Vickers indentation and Cube Corner indentation. Finally, a finite-element analysis of the scratch test is done to show the plastic densification of such materials under scratching conditions. These different results show that the size of the densified zone under indentation-scratch loading is strongly related to the contact size. [ABSTRACT FROM AUTHOR]

This paper presents an enriched bilinear quadrilateral thin shell element for spot welded structures modelling. This element is implemented as an Abaqus user element. The base element is a Simo-Rifaï quadrilateral. The present treatment of spot welds is inspired from the inclusion problem treatment in the extended finite element framework. Each spot weld is considered as a point detail in the steel sheet 2D continuous medium; the enrichment functions to the displacement approximation space are chosen to represent accurately the local deformation modes near the spot weld, and give an acceptable representation of the deformed assembled steel sheets without requiring an explicit meshing of spot welds. Numerical examples demonstrate the method capability to model spot welded structures from independently obtained steel sheets meshes. [ABSTRACT FROM AUTHOR]

Abstract: The bi-potential method has been successfully applied for the modeling of frictional contact problems in static cases. This paper presents the application of this method for dynamic analysis of impact problems with multiple deformable bodies. A first order algorithm is applied for numerical integration of the time-discretized equation of motion. The numerical results show clearly the physical energy dissipation introduced by frictional effects between the solids in contact. To cite this article: B. Magnain et al., C. R. Mecanique 333 (2005). [Copyright &y& Elsevier]