Publications

2014

• Stabilité mécanique d'une cavité saline soumise à des variations rapides de pression : Application au stockage souterrain de gaz naturel, d’air comprimé et d’hydrogène
  
  • Djizanne Hippolyte
  , 2014. Les cavités salines servant au stockage souterrain de grandes quantités de gaz naturel sont très sollicitées en raison des besoins énergétiques croissants. Le stockage des énergies renouvelables est aussi envisagé dans ces cavités sous forme d’air comprimé et d’hydrogène. Ces cavités qui sont plus sollicitées qu’auparavant, sont aussi soumises à des opérations d’injection et de soutirage rapides. Ces nouveaux modes d’exploitation soulèvent des problèmes mécaniques, illustrés en particulier par l’écaillage et les chutes de blocs en paroi de cavité. En fait, aux sollicitations purement mécaniques liées aux variations de la pression du gaz, se superposent des variations de température répétées de plusieurs dizaines de degrés Celsius qui occasionnent, notamment à la détente, des contraintes additionnelles de traction susceptibles d’engendrer des fractures à la paroi des cavernes dont l’évolution peut être dangereuse. Les lois de comportement mécanique du sel gemme (élasto-viscoplastique, non linéaire et thermosensible) et les critères de rupture et d’endommagement existants permettent d’analyser le comportement des cavités salines et du sel gemme sous l’effet de chargements nouveaux. Cette étude s’inscrit dans le domaine de la thermomécanique des roches et contribue à l’analyse des effets de nouveaux modes d’exploitation sur la stabilité mécanique des cavités salines. Dans un premier temps, la démarche a consisté à concevoir et à valider sur des cas réels un modèle thermodynamique du comportement du gaz dans la cavité. Ce modèle a permis de d’analyser l’éruption dans des cavités salines de stockage de gaz. Ensuite, le couplage thermomécanique a permis d’analyser les effets d’une détente rapide, d’une injection rapide et de cycles journaliers sur la stabilité des cavernes. Sur le plan expérimental, on a recherché au laboratoire les conditions d’apparition et de développement de fissures sur une pastille et sur un bloc de sel. Le fluage d’éprouvettes de sel gemme en extension a aussi été analysé.
• Room-temperature creep and stress relaxation in commercial purity titanium– Influence of the oxygen and hydrogen contents onincubation phenomena and aging-induced rejuvenation of thecreep potential
  
  • Barkia Bassem
  • Doquet Véronique
  • Couzinie Jean-Philippe
  • Guillot Ivan
  Materials Science and Engineering: A, Elsevier, 2014, A 624, pp.78-89. Creep and stress relaxation tests were run at room-temperature along the rolling and transverse directions in three batches of titanium with different solute oxygen and hydrogen contents. Oxygen-induced dynamic strain aging was shown to hinder creep at low stress level and solute hydrogen to enhance it and to promote a dramatic aging-induced rejuvenation of the creep potential. Primary creep could be described by a single power law equation in which both the anisotropy and the influence of the oxygen content were taken into account. Secondary creep rates varied exponentially with the applied stress, in the same way along rolling and transverse directions, but with a stress dependency which increased with the oxygen content. Creep of commercial purity titanium was controlled mainly by screw dislocations with a <1-210> Burgers vector gliding on prismatic and pyramidal planes, while for a Ti batch with a lower oxygen content and larger grain size, mechanical twinning also contributed to the creep strain. 33 to 40% of the flow stress was relaxed within 20 hours, according to logarithmic kinetics, which did not depend on the loading direction or oxygen content. (10.1016/j.msea.2014.11.073)
  DOI : 10.1016/j.msea.2014.11.073
• Revisiting the identification of distributed elastic coefficients in anisotropic media
  
  • Constantinescu Andrei
  • Simionescu Olivian
  • Stanciu Alexandru
  Annals of the University of Bucharest. Mathematical series, București : Editura Universității din București, 2014. The inverse problem discussed here is the identification of the distributed elastic moduli from overspecified boundary conditions. We present an extension of the classical result of Ikehata from the case of an isotropic material, for a class of anisotropic materials with cubic and orthotropic symmetry.
• Fatigue of 316L stainless steel notched
  
  • Auricchio Ferdinando
  • Constantinescu Andrei
  • Scalet Giulia
  International Journal of Fatigue, Elsevier, 2014, 68, pp.231-247. The aim of the present paper is to provide an in-depth analysis of the fatigue-life assessment for μm-size 316L stainless steel components. Such components find typical applications in the biomedical field, e.g., in cardiovascular stents. To this purpose, the present work analyzes experimental data on 316L stainless steel from literature for smooth and notched μm-size components using a global computational approach. Several aspects are discussed: (i) the choice of an appropriate constitutive law for cyclic material behavior, (ii) fatigue criteria based on shakedown concepts for finite and infinite lifetime, in particular distinguishing between low, high and very high-cycle fatigue regimes (denoted as LCF, HCF and VHCF, respectively), and (iii) gradient effects in relation with hot-spot as well as average or mean volume approaches for the lifetime estimation. The results give a new insight into the lifetime design of μm-size components and could be directly applied for the fatigue-life assessment of small size structures as, for instance, cardiovascular 316L stainless steel stents. (10.1016/j.ijfatigue.2014.04.013)
  DOI : 10.1016/j.ijfatigue.2014.04.013
• Modelling the internal stress field in argillaceous rocks under humidification/desiccation
  
  • Wang Linlin
  • Pouya Amade
  • Bornert Michel
  • Halphen Bernard
  International Journal for Numerical and Analytical Methods in Geomechanics, Wiley, 2014, 38 (16), pp.1664-1682. This paper deals with analytical and numerical modelling of the internal stress generated in argillaceous rocks during humidification/desiccation processes, which is an essential issue for damage study. This local stress field arises from two mechanisms: (i) complex interactions between free swelling/shrinking clay matrix and non-strained inclusions of carbonate and quartz and (ii) a self-restraint effect induced by the moisture gradient during the transient moisture exchange process. The inclusion-matrix interaction is investigated in different cases. Firstly, the analytical solution of the stress around a cylindrical inclusion embedded in an infinite swelling matrix is derived: The inclusion would suffer tension (compression) under humidification (desiccation), and the resulting cracking patterns are discussed. Then, the problem of two inclusions with different distances in an infinite swelling matrix is considered, and it is shown that the local stress around an inclusion will be perturbed and amplified by neighbouring inclusions. Finally, an inclusion outcropping at the free surface of a swelling matrix is modelled as to investigate the effect of free surface: The inclusion-matrix interface undergoes shear stresses of which the maximum is found at the free surface. In addition to the inclusion-matrix interaction, the self-restraint effect is investigated: The induced stress is maximal at the beginning of humidification/desiccation processes and vanishes gradually with time. The quantity of the self-restraint stress is strongly controlled by the hydric loading rate. (10.1002/nag.2267)
  DOI : 10.1002/nag.2267
• Binary tomography reconstructions of bone microstructure from few projections with stochastic level-set methods
  
  • Wang L.
  • Sixou B.
  • Peyrin F.
  , 2014.
• Viscoplasticité à l'ambiante du titane en relation avec ses teneurs en oxygène et hydrogène
  
  • Barkia Bassem
  , 2014. L’objectif de la thèse est l’étude aux échelles macro, méso et microscopique des effets des interstitiels (oxygène et hydrogène) en solution sur le comportement viscoplastique à la température ambiante du titane. Les essais macroscopiques de traction, saut de vitesse, relaxation et fluage ont montré une anisotropie de comportement liée à la présence d’une texture cristallographique assez marquée et à la diversité des mécanismes de déformation plus ou moins activés selon le sens de sollicitation. On note un effet durcissant de l’oxygène et un effet plus discret de l’hydrogène qui se manifeste surtout à l’entrée de plasticité (durcissement ou adoucissement, selon le sens de sollicitation) et en fluage (accélération ou ralentissement du fluage selon le niveau de contrainte). En outre, l’oxygène semble être à l’origine de phénomènes de vieillissement statique et accentuer les effets de vieillissement dynamique. Les données expérimentales ont permis d’identifier une loi de comportement viscoplastique anisotrope avec le code ‘Zébulon’. Toutefois, le modèle macroscopique reste incapable de bien simuler certains aspects de l’anisotropie du comportement des matériaux raison pour laquelle il a été décidé de s’orienter vers un modèle de plasticité cristalline. Afin d’alimenter ce modèle et d’étudier les effets des interstitiels sur les seuils d’activation des divers systèmes de glissement et de maclage, des essais interrompus de traction ont étés menés sous MEB et sous microscope optique pour différentes teneurs en oxygène et différentes directions de sollicitation. Ces essais montrent que le glissement prismatique est le mode de déformation principal, mais qu’une sollicitation dans le sens travers et une baisse de la teneur en oxygène favorisent le glissement basal et le maclage. Les cissions critiques des différents systèmes de glissement augmentent avec la teneur en oxygène. Les essais sous MEB ont également permis de calculer les champs de déformations locales par corrélation d’images numériques et de caractériser l’hétérogénéité de la déformation. Les coefficients de Lankford ainsi obtenus sont plus grands dans le sens travers et dans le matériau plus riche en oxygène. Une tendance à la déformation par glissement aux joints de grain conduisant finalement à un endommagement intergranulaire a été mise en évidence. Un modèle de plasticité cristalline « en champ moyen » a été identifié pour les matériaux de base. Il rend assez bien compte de leur comportement viscoplastique anisotrope. Des observations en microscopie électronique à transmission post-mortem de lames minces issues des éprouvettes déformées en fluage montrent que l’oxygène rend les dislocations plus rectilignes, coplanaires et parallèles avec un caractère vis dominant, ce qui suggère que l’oxygène augmente la friction de réseau et rend le glissement dévié plus difficile. La direction de sollicitation influence les modes de la déformation : on note plus de glissement pyramidal et de dislocations de type <c+a> après traction dans le sens travers, ce qui est en accord avec les observations à échelle mésoscopique.
• Asymptotic analysis in cardiac electrophysiology : applications in modeling and in data assimilation
  
  • Collin Annabelle
  , 2014. This thesis aims at developing innovative mathematical tools to improve cardiac electrophysiological modeling. A detailed presentation of the bidomain model - a system of reaction-diffusion equations - with a fixed domain is given based on the literature and we mathematically justify the homogenization process using the 2-scale convergence. Then, a study of the impact of the mechanical deformations in the conservation laws is performed using the mixture theory.As the atria walls are very thin and generally appear as thick surfaces in medical imaging, a dimensional reduction of the bidomain model in a thin domain to a surface-based formulation is studied. The challenge is crucial in terms of computational efficiency. Following similar strategies used in shell mechanical modeling, an asymptotic analysis of the diffusion terms is done with assumptions of strong anisotropy through the thickness, as in the atria. Simulations in 2D and 3D illustrate these results. Then, a complete modeling of the heart - with the asymptotic model for the atria and the volume model for the ventricles - allow the simulation of full electrocardiogram cycles. Furthermore, the asymptotic methods are used to obtain strong convergence results for the 3D-shell models.Finally, a specific data assimilation method is proposed in order to «personalize» the electrophysiological models. The medical data assimilated in the model - using a Luenberger-like state filter specially designed - are the maps of electrical activation. The proposed methods can be used in other application fields where models (reaction-diffusion) and data (front position) are very similar, as for fire propagation or tumor growth.
• Experimental and numerical study of crack healing in a nuclear glass
  
  • Doquet Véronique
  • Ben Ali N.
  • Chabert E
  • Bouyer F
  Mechanics of Materials, Elsevier, 2014, 80, pp.145-162. a b s t r a c t An experimental study of thermally or water-induced crack healing in an inactive borosil-icate glass, chemically analogous to that used in France for the vitrification of nuclear waste was carried out. Partial welding of glass plates was observed after annealing in air at 425 °C (77 °C below T g) when at least 20 MPa compressive stress was applied, while annealing at 450 °C under 20 MPa led to a complete disappearance of the interface. Closure of indenta-tion-induced cracks was observed during annealing at 400 °C in an ESEM as a result of viscous relaxation of residual stresses but it did not constitute a sufficient proof of crack healing. DCDC specimens were thus pre-cracked in an ESEM and then either annealed at various temperatures (350–490 °C) in secondary vacuum or in air, or left in water at 70–90 °C, sometimes under a compressive stress normal to the crack face. The specimens were then reloaded in the ESEM and the crack opening displacements under a given load were compared to those measured during pre-cracking. The cracks were bridged by an alteration layer over a distance from the crack tip which decreased as loading increased. The restraining effect of these bridges on crack opening was assessed via finite element simulations, using interface elements. The tensile strength of the bridging layer was estimated as 27–39 MPa after vacuum annealing at 400 °C, 11–20 MPa after 15 days in water at 90 °C and 44–78 MPa after 11 days in water at 70 °C under 5 MPa normal compression. Partially healed cracks did not resume propagation from their former crack tip, but due to branch cracks re-initiated a few hundred microns behind it which grow avoiding the healed area. This behaviour was explained using finite element simulations. (10.1016/j.mechmat.2014.09.003)
  DOI : 10.1016/j.mechmat.2014.09.003
• Statistical inverse method for the multiscale identification of the apparent random elasticity field of heterogeneous microstructures
  
  • Soize Christian
  • Desceliers Christophe
  • Guilleminot Johann
  • Nguyen M.T.
  • Allain Jean-Marc
  • Gharbi H.
  , 2014, pp.Pages: 1-1. The presentation is devoted to a multiscale statistical inverse problem related to materials for which the elastic heterogeneous microstructure cannot be described in terms of constituents (for instance, a biological tissue such as the cortical bone). The objective is to identify the tensor-valued elasticity random field, (apparent elasticity field) at mesoscale, using multiscale experimental data. After introducing the difficulties induced by such a problem, the multiscale identification method is presented in two steps. The first one is devoted to the mathematical construction of an advanced prior stochastic model of the apparent elasticity random field at mesoscale, introducing a family of prior stochastic models for the non-Gaussian tensor-valued random field at mesoscale, and its generator. The second one deals with the multiscale identification of the prior stochastic model using a multiscale experimental digital image correlation, at macroscale and at mesoscale. The statistical inverse problem is then formulated as a multi-objective optimization problem. Finally, an application of the method is presented for multiscale experimental measurements of cortical bone in 2D plane stresses.
• Three-dimensional elasticity based on quaternion-valued potentials
  
  • Weisz-Patrault Daniel
  • Bock S.
  • Gürlebeck K.
  International Journal of Solids and Structures, Elsevier, 2014, 51 (19), pp.3422-3430. One of the most fruitful and elegant approach (known as Kolosov–Muskhelishvili formulas) for plane isotropic elastic problems is to use two complex-valued holomorphic potentials. In this paper, the algebra of real quaternions is used in order to propose in three dimensions, an extension of the classical Muskhelishvili formulas. The starting point is the classical harmonic potential representation due to Papkovich and Neuber. Alike the classical complex formulation, two monogenic functions very similar to holomorphic functions in 2D and conserving many of interesting properties, are used in this contribution. The completeness of the potential formulation is demonstrated rigorously. Moreover, body forces, residual stress and thermal strain are taken into account as a left side term. The obtained monogenic representation is compact and a straightforward calculation shows that classical complex representation for plane problems is embedded in the presented extended formulas. Finally the classical uniqueness problem of the Papkovich–Neuber solutions is overcome for polynomial solutions by fixing explicitly linear dependencies. (10.1016/j.ijsolstr.2014.06.002)
  DOI : 10.1016/j.ijsolstr.2014.06.002
• Full-Field Measurements on Low-Strained Geomaterials Using Environmental Scanning Electron Microscopy and Digital Image Correlation: Improved Imaging Conditions
  
  • Wang Linlin
  • Bornert Michel
  • Héripré Eva
  • Chanchole S.
  • Tanguy Alexandre
  Strain, Wiley-Blackwell, 2014, 50 (5), pp.370-380. Full-field strain measurement at microscale on geomaterials by means of hydromechanical in situ testing and imaging in an environmental scanning electron microscope and digital image correlation techniques is a challenging task because of both low magnitude of investigated strains (typically of the order of 10−3) and unfavourable imaging conditions. In view of improving strain measurement accuracy, three major sources of measurement errors are evaluated, and methods to minimise their effects are proposed. First, a fast and simple procedure to accurately quantify image noise is proposed and subsequently used to optimise various environmental scanning electron microscope setting parameters, such as dwell time, spot size, working distance and chamber pressure. Second, a specific procedure to limit magnification fluctuations to a sufficiently low level is described. Finally, digital image correlation systematic errors are quantified on real images, and several ways to reduce their amplitude are compared. The combination of these improvements finally allows us to reach an appropriate accuracy for overall strain measurements and characterisation of microscale heterogeneities. (10.1111/str.12076)
  DOI : 10.1111/str.12076
• Fatigue design of railway wheels: a probabilistic approach
  
  • Roux Clément
  • Lorang Xavier
  • Maitournam Habibou
  • Nguyen Tajan Mac Lan
  Fatigue and Fracture of Engineering Materials and Structures, Wiley-Blackwell, 2014, 37 (10), pp.1136-1145. This paper deals with a method to evaluate and optimize the design of railway wheels subjected to multiparameter variable fatigue loading. The fatigue loads are statistically evaluated from in-service measurements. Representative realistic loading paths are built from the knowledge of the influence of various factors (such as train speed and track curvature). Using these paths, the method combines finite element computations and the fatigue equivalence method for damage evaluation in the structure. An extension of the Dang Van fatigue criterion in the high-cycle fatigue finite life domain associated with a damage accumulation law is adopted. The probability of failure of the structure is directly obtained from the interference between a local fatigue equivalent stress and fatigue strength distributions (based on the stress-strength interference approach). The result is useful for the optimization during the design stage or the validation of the fatigue strength of structures. (10.1111/ffe.12194)
  DOI : 10.1111/ffe.12194
• Fourth order energy-preserving localy implicit discretization for linear wave equations
  
  • Chabassier Juliette
  • Imperiale Sébastien
  , 2014.
• Fourth order energy-preserving locally implicit discretization for linear wave equations
  
  • Chabassier Juliette
  • Imperiale Sébastien
  , 2014.
• Bone microstructure reconstructions from few projections with stochastic nonlinear diffusion
  
  • Sixou B.
  • Wang L.
  • Peyrin F.
  , 2014, pp.1826-1830.
• Improved numerical integration for locking treatment in isogeometric structural elements, Part I: Beams
  
  • Adam Cédric
  • Bouabdallah Salim
  • Zarroug Malek
  • Maitournam Habibou
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2014, 279, pp.1-28. A general mathematical framework is proposed, in this paper, to define new quadrature rules in the context of BB-spline/NURBS-based isogeometric analysis. High order continuity across the elements within a patch turned out to have higher accuracy than C0C0 finite elements, as well as a better time efficiency. Unfortunately, a maximum regularity accentuates the shear and membrane locking in thick structural elements. The improved selective reduced integration schemes are given for uni-dimensional beam problems, with basis functions of order two and three, and can be easily extended to higher orders. The resulting BB-spline/NURBS finite elements are free from membrane and transverse shear locking. Moreover, no zero energy modes are generated. The performance of the approach is evaluated on the classical test of a cantilever beam subjected to a distributed moment, and compared to Lagrange under-integrated finite elements. (10.1016/j.cma.2014.06.023)
  DOI : 10.1016/j.cma.2014.06.023
• Micromechanical experimental investigation of mudstones
  
  • Wang L.
  • Bornert Michel
  • Chanchole S.
  • Héripré E.
  • Yang D.
  Géotechnique Letters, ICE Publishing, 2014, 4 (October–December), pp.306-309. This paper reports on a micromechanical investigation of mudstones using a novel experimental method, based on a combination of environmental scanning electron microscopy (ESEM) and digital image correlation techniques. A specifically designed rig was developed, allowing in situ tests under combined hydric and mechanical loadings in the ESEM chamber. Observations were performed on the scale of the composite microstructure of the involved rocks (i.e. numerous grains of carbonate and quartz embedded in a clay matrix). Preliminary results from a uniaxial compression test on a sample with 5?4% water content are presented. Heterogeneous strain fields that correlate well with the microstructure of mudstones are illustrated, enabling different deformation modes (particularly shear bands and tensile microcracks) and their interactions to be identified. (10.1680/geolett.14.00056)
  DOI : 10.1680/geolett.14.00056
• Mécanique des Milieux Continus I
  
  • Marigo Jean-Jacques
  , 2014, pp.340. Ce cours est une introduction à la mécanique des milieux continus déformables. Les concepts fondamentaux sont présentés dans le cadre simplifié des structures élancées ce qui permet d'arriver rapidement à des applications et de traiter de nombreux phénomènes avec un formalisme mathématique allégé. Toutefois, la démarche suivie pour présenter les concepts est la même que celle sur laquelle s'appuiera la deuxième partie du cours de Mécanique des milieux continus (MEC431) pour décrire les structures tridimensionnelles : efforts intérieurs, efforts extérieurs, équations d'équilibre, conditions aux limites, déformations, lois de comportement et problèmes aux limites. Une fois tous les concepts introduits, on s'intéressera à la résolution des problèmes obtenus et à la mise en évidence des phénomènes qui en découlent tant en statique qu'en dynamique, en petits qu'en grands déplacements. On étudiera ainsi les problèmes de statique de fils, de tiges, de poutres ou d'arcs élastiques ce qui permettra de traiter les problèmes classiques de la résistance des matériaux, de mettre en évidence des phénomènes d'instabilité comme le flambement ou d'aborder les questions de couche limite. Dans l'étude du comportement dynamique de telles structures on s'intéressera plus particulièrement à la propagation des ondes, aux vibrations et aux chocs. De plus, on présentera l'approche variationnelle qui offre d'une part une autre vision des lois physiques qui gouvernent le comportement mécanique de telles structures, et qui fournit d'autre part des outils mathématiques et numériques pour traiter les équations. Ceci nous permettra en particulier d'obtenir des propriétés énergétiques fondamentales, de définir des concepts de stabilité et de faire une introduction à la méthode des éléments finis.
• Dimensional reductions of a cardiac model for effective validation and calibration
  
  • Caruel Matthieu
  • Chabiniok Radomir
  • Moireau Philippe
  • Lecarpentier Yves
  • Chapelle Dominique
  Biomechanics and Modeling in Mechanobiology, Springer Verlag, 2014, 13 (4), pp.897-914. Complex 3D beating heart models are now available, but their complexity makes calibration and validation very difficult tasks. We thus propose a systematic approach of deriving simplified reduced-dimen\-sional models, in ''0D'' --~typically, to represent a cardiac cavity, or several coupled cavities --~and in ''1D'' --~to model elongated structures such as muscle samples or myocytes. We apply this approach with an earlier-proposed 3D cardiac model designed to capture length-dependence effects in contraction, which we here complement by an additional modeling component devised to represent length-dependent relaxation. We then pre\-sent experimental data produced with rat papillary muscles samples when varying preload and afterload conditions, and we achieve some detailed validations of the 1D model with these data, including for the length-dependence effects that are accurately captured. Finally, when running simulations of the 0D model pre-calibrated with the 1D model parameters, we obtain pressure-volume indicators of the left ventricle in good agreement with some important features of cardiac physiology, including the so-called Frank-Starling mechanism, the End-Systolic Pres\-sure-Volume Relationship (ESPVR), as well as varying elastance properties. This integrated multi-dimensional modeling approach thus sheds new light on the relations between the phenomena observed at different scales and at the local vs. organ levels. (10.1007/s10237-013-0544-6)
  DOI : 10.1007/s10237-013-0544-6
• Irreversible deformation and damage in argillaceous rocks induced by wetting/drying
  
  • Wang Linlin
  • Bornert Michel
  • Héripré Eva
  • Yang Diansen
  • Chanchole S.
  Journal of Applied Geophysics, Elsevier, 2014, 107, pp.108–118. Some irreversible phenomena of argillaceous rocks during wetting and drying processes are experimentally investigated at the micrometric scale, by combining environmental scanning electron microscope (ESEM) imaging and digital image correlation (DIC) techniques. According to previous macroscopic experimental results, argillaceous rocks under a free wetting–drying cycle usually exhibit a reversible deformation; however, the microscopic observation of this work evidences several irreversible phenomena. Some irreversible deformations located in clay matrix are observed and their mechanisms are identified. Some local damage phenomena, in the form of a network of micro-cracks typically with ~ 1 μm openings, are also observed in both the wetting and drying cases: the former locates in the bulk of clay matrix and/or at inclusion-matrix interfaces, whereas the latter is mostly found in the bulk of clay matrix. The two types of micro-cracks are activated by different mechanisms, and their morphology and extension have been evidenced to be strongly dependent on the wetting or drying rate. All these irreversible phenomena are localized and sometimes counteracted each other, leading the macroscopic deformation to be apparently reversible. Nevertheless, they are of crucial importance for the reliability of long-term storage.
• TEMPERATURE INFLUENCE ON SMART STRUCTURES: A FIRST APPROACH
  
  • Bonaldi F
  • Geymonat G
  • Krasucki F
  • Serpilli M
  , 2014, pp.3357-3368. We study a linear coupled thermo-electromagnetoelastic problem and the nondi-mensionalization of the corresponding linear mixed parabolic-hyperbolic system. We deduce from the quasi-static equations a thin thermo-electromagnetoelastic plate model through the asymptotic expansions method.
• Multi-scale Modelling of the Mechanical Behaviour of Textile Reinforcements
  
  • Attia Houda
  • Durville Damien
  • Le Tallec Patrick
  , 2014. The role of textile reinforcements is particularly important in the development of composite materials with optimal performances in terms of mechanical behavior and weight, whose use is increasing in various fields such as tire, aeronautic and automotive industries. In our study we are interested in unidirectional textile reinforcements, made of bundles of fibers which are twisted together to form yarn. The global mechanical behavior of these yarns is very complex, and largely controlled by contact-friction interactions taking place between elementary fibers. This kind of structure is characterized by continuous features along its longitudinal direction, although it should be considered as a discrete assembly in its transversal directions. Since the trajectory of each filament within the yarn depends on the assembly process, the initial configuration of such structures can not be known a priori, and the assembly process needs therefore to be simulated. Besides mechanical properties at macroscopic scale, the determination of local stresses at the fibers scale is very important to predict the occurrence of damage. A finite element code, based on an implicit solver, has been developed in order to simulate the mechanical behavior of such fibrous materials [1, 2]. However, due to computational costs, the use of this approach is limited to structures made of few hundred fibers, whereas cords in the scope of our study are formed of few thousand fibers. The purpose of this work is to develop a multi-scale approach to characterize mechanical properties of such material with a large numbers of fibers, at different scales. This approach is based on the introduction of so-called macro-fibers, aimed at representing the behavior of bundles of filaments.
• Identification of the mesoscale model of a microstructure in using experimental measurements with an image field method and one specimen
  
  • Nguyen M.-T.
  • Desceliers Christophe
  • Soize Christian
  • Allain Jean-Marc
  • Gharbi H.
  , 2014, pp.1-2. Biomechanical materials, as cortical bones, are complex materials to be modeled with respect to the complexity level of their constitutive materials at the micro-scale. At micro-scale, this material is not only non homogenous and random but it also cannot be described in terms of mechanical constituents. It is the reason why a meso-scale is considered and for which the medium is modeled with apparent properties represented by an elasticity-tensor random field. A complete methodology is proposed for the experimental identification of the random field at meso-scale (1) using image field measurements at macro- and meso-scales, (2) introducing three numerical indicator quantifying distances between the experimental measurements and a probabilistic computational model for simulating the experimental measurements. An application will be presented for cortical bone with experimental measurements performed on only one specimen at macro and meso-scale simultaneously for a given specimen submitted to a given load.
• Elasto-plastic parameters identification trough Finite Element Model Updating
  
  • Baudoin Pierre
  • Witz Jean-Francois
  • Magnier Vincent
  • El Bartali Ahmed
  • Dufrenoy Philippe
  • Charkaluk Eric
  , 2014.