Publications

2004

• Characterization of Local Strain Field in Cortical Bone
  
  • Henry L.
  • Meunier A.
  • Aubry Denis
  • Crépin Jérôme
  • Caldemaison D.
  • Hoc T.
  , 2004. No abstract provided
• Fluage du sel gemme sous très faibles charges
  
  • Bérest Pierre
  • Blum Pierre-Antoine
  • Charpentier Jean-Pierre
  • Gharbi Hakim
  • Valès Frédéric
  Comptes Rendus. Géoscience, Académie des sciences (Paris), 2004, 336, pp.1337-1344. On décrit des essais de fluage de longue durée sur des éprouvettes de sel gemme soumises à des chargements mécaniques très faibles ($\sigma=0,02$ à $0,1$ MPa). Le chargement était fourni par des charges mortes ; le déplacement était mesuré par des capteurs de résolution $\Delta ɛ=10^{-8}$. On a placé le dispositif d'essai dans une galerie souterraine profonde, où les fluctuations naturelles de température sont de l'ordre du centième de degré Celsius. On a pu ainsi mesurer des vitesses de déformation inférieures à $10^{-12}$/s. Les essais montrent qu'on ne peut extrapoler à ces faibles charges les relations de comportement obtenues sous charge plus élevée. (10.1016/j.crte.2004.09.005)
  DOI : 10.1016/j.crte.2004.09.005
• Elements of poro-micromechanics applied to concrete
  
  • Dormieux L.
  • Lemarchand E.
  • Kondo D.
  • Fairbairn E.
  Materials and structures, Springer Verlag, 2004, 37 (1), pp.31-42. (10.1007/BF02481625)
  DOI : 10.1007/BF02481625
• Lattice friction for crystalline defects: from dislocations to cracks
  
  • Kresse Olga
  • Truskinovsky Lev
  Journal of the Mechanics and Physics of Solids, Elsevier, 2004, 52, pp.2521-2543. We propose a discrete model providing a unified description of lattice induced drag for a class of defects which includes martensitic phase boundaries, dislocations and cracks. Although the model is Hamiltonian, it generates a non-trivial macroscopic friction law which we present as a closed form functional relation between the velocity of the defect and the conjugate configurational force. The possibility to obtain an exact analytic solution of the dynamic problem allows us to expose both the similarities and the differences in the kinetics of various types of defects. In particular, we trace the origin of the symmetry related resonances, specific for dislocations, and show how the flattening of one of the energy wells, indicating transition to fracture, generates a morphological instability of the displacement profile at a critical velocity. (10.1016/j.jmps.2004.04.011)
  DOI : 10.1016/j.jmps.2004.04.011
• Exact solutions of the interface crack between elastic and rigid bodies under contact with friction
  
  • Bui Huy Duong
  • Oueslati Abdelbacet
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2004, 332, pp.709-716. One considers an interface crack between an elastic half-plane and a rigid half-plane, in the presence of Coulomb's friction. There exists two singular solutions at the semi-infinite crack tip, which correspond physically to the push-in and the pull-out of a rigid fiber in an elastic matrix. The exact solutions show that only the mode II is present and there is no oscillatory behavior of the stress and the displacement near the crack tip, but an oscillatory behavior is observed at the transition point with the stress free zone. There exists four types of singular solutions for finite crack in bounded medium, but only one in an infinite medium. (10.1016/j.crme.2004.04.008)
  DOI : 10.1016/j.crme.2004.04.008
• On the Ekberg, Kabo and Andersson calculation of the Dang Van high cycle fatigue limit for rolling contact fatigue
  
  • Ciavarella M.
  • Maitournam Habibou
  Fatigue and Fracture of Engineering Materials and Structures, Wiley-Blackwell, 2004, 27, pp.523-526. Recently, various methods have been proposed to assess the risk of rolling contact fatigue failure by Ekberg, Kabo and Andersson, and in particular, the Dang Van multiaxial fatigue criterion has been suggested in a simple approximate formulation. In this note, it is found that the approximation implied can be very significant; the calculation is improved and corrected, and focused on the study of plane problems but for a complete range of possible friction coefficients. It is found that predicted fatigue limit could be much higher than that under standard uniaxial tension/compression for ‘hard materials’ than for ‘ductile materials.’ This is in qualitative agreement, for example, with gears' design standards, but in quantitative terms, particularly for frictionless condition, the predicted limit seems possibly too high, indicating the need for careful comparison with experimental results. Some comments are devoted to the interplay of shakedown and fatigue. (10.1111/j.1460-2695.2004.00772.x)
  DOI : 10.1111/j.1460-2695.2004.00772.x
• Incompressibility constraints in finite elements
  
  • Le Tallec Patrick
  , 2004, pp.33-45.
• An estimate of maximum ground surface motion for non zero surface velocity
  
  • Pecker Alain
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2004, 332, pp.725-730. The increasing need for probability seismic hazard assessment (PSHA) of critical facilities sometimes leads to unrealistic earthquake scenarios with very high induced ground motions. From a physical standpoint these high motions cannot exist because of the limiting resistance capacity of the soil strata through which the seismic waves travel. A simple analytical model is proposed to bound the maximum ground surface acceleration that any soil deposit can transfer. This model is an extension to non zero ground surface velocity of a previously presented model. (10.1016/j.crme.2004.04.005)
  DOI : 10.1016/j.crme.2004.04.005
• Identification of crystalline behavior on macroscopic response and local strain field analysis: application to alpha zirconium alloys
  
  • Gélébart Lionel
  • Crépin Jérôme
  • Dexet Marie
  • Sauzay Maxime
  • Roos Arjen
  Journal of ASTM International (JAI), ASTM, 2004, 1. The purpose of this paper is to present an identification method of the crystalline behavior of a material from a mechanical test performed on a polycrystalline sample. Because of the lack of knowledge about its crystalline behavior, this method is applied to a Zirconium alloy. This identification is based on a finite element modeling of the microstructure, and the results are compared to both the macroscopic and the microscopic experimental results. On the microscopic scale, the plastic strains are obtained using a micro-extensometry technique and the crystalline orientation using an EBSD technique. In order to validate the method, an identification is performed with only two free parameters: the evolutions of the macroscopic and microscopic errors appear to be regular and exhibit a well-defined minimum so that the parameters can be clearly identified. (10.1520/JAI12333)
  DOI : 10.1520/JAI12333
• Stick-slip-separation waves under frictional and unilateral contact
  
  • Oueslati Abdelbacet
  • Son Nguyen Quoc
  Revue Européenne des Éléments Finis, HERMÈS / LAVOISIER, 2004, 13, pp.617-626. The dynamical problem of a brake-like mechanical system composed of an elastic cylindrical tube with Coulomb's friction in contact with a rigid and rotating cylinder is considered. This model problem enables us to give an example of non-trivial periodic solutions in the form of stick-slip or stick-slip-separation waves propagating on the contact surface. It is shown in particular that the stick-slip-separation solutions would occur for small normal pressures or high rotational speeds. The existence and the characteristics of stick-slip and stick-slip-separation waves are discussed numerically.
• A novel inverse problem in γ-rays emission imaging
  
  • Nguyen Mai K.
  • Truong Tuong T.
  • Bui Huy Duong
  • Delarbre Jean-Luc
  Inverse Problems in Science and Engineering, Taylor & Francis, 2004, 12 (2), pp.225-246. This article presents a recent result on the feasibility of reconstruction of the radioactivity distribution of an object from a sequence of Compton-scattered radiation data in emission imaging. This may be regarded as a novel inverse principle as opposed to the traditional one in which the object is reconstructed only from the non-scattered rays collected at different incident directions. The new inversion procedure is described by an invertible linear integral transform which may be viewed as a generalized Radon transform and has several advantages over the old one. It improves significantly the contrast of the reconstructed image. The required data for reconstruction is easily acquired from an energy and position sensitive gamma camera under the form of scattered distribution images classified by their Compton-scattering angle. The motion of the camera in standard tomographic procedure is here no longer necessary for data taking. (10.1080/10682760310001598661)
  DOI : 10.1080/10682760310001598661
• Prediction of the weld shape in arc welding
  
  • Roger Frédéric
  • Dang Van Ky
  Revue Européenne des Éléments Finis, HERMÈS / LAVOISIER, 2004, 13 (5-7), pp.713-724. A numerical model of the arc welding process is presented. It deals with all arc welding process with and without filler metal (Gas Metal Arc Welding and Gas Tungsten Arc Welding). We consider the three dimensional modelling of the stationary weld pool with a free deformable surface. All coupled equations are solved by the finite volume method. We consider heat transfer ands fluid flow in the weld pool and the geometry of the free surface subjected to arc pressure and drop impact in GMAW. The location of the energy supplied by drops in the weld pool is assumed to be a function of the Weber number. Comparison with macrography shows a really good agreement of the model. (10.3166/reef.13.713-724)
  DOI : 10.3166/reef.13.713-724
• Contribution to the definition of a partial overlapping plastic strain rates domain for moderate loadings - application to tensile testing on metallic materials
  
  • Haugou Grégory
  • Markiewicz Eric
  • Fabis Jacky
  • Gary Gérard
  International Journal of Crashworthiness, Taylor & Francis, 2004, 9 (2), pp.187-194. Generally, tensile testing on Hopkinson bars requires some particular considerations. Most of the specific devices, designed to hold tensile sheet specimens on the bars, involve the degradation of the pulses in particular case of no-direct tensile loadings. A tensile testing configuration for sheet specimens is proposed on the basis of classical split Hopkinson pressure bars (SHPB). Specimens holding is obtained with an epoxy adhesive and provides good measurements on sheet specimens. A comparison is made for the same two metallic materials results extracted from literature and dynamic tensile tests performed with a high speed hydraulic machine and another split Hopkinson bars (SHPB) facility using hat-specimens. A partial overlapping domain in terms of plastic strain is shown at moderate strain rates from 200 to 400 s−1. (10.1533/ijcr.2004.0278)
  DOI : 10.1533/ijcr.2004.0278
• On a new computational method for the simulation of periodic structures subjected to moving loads: application to vented brake disks
  
  • Nguyen-Tajan Mac Lan
  • Maitournam Habibou
  • Maestro Luis
  Revue Européenne des Éléments Finis, HERMÈS / LAVOISIER, 2004, 13 (5-7), pp.627-636. The purpose of the paper is to present a new numerical method suitable for the computation of periodic structures subjected to repeated moving loads. It directly derives from the stationary methods proposed for cylindrical and axisymmetrical structures. Its mains features are the use of a calculation reference related to the moving loads and the periodic property of the thermomechanical response. These methods are developped by PSA and the Ecole Polytechnique, in order to design vented brake discs. In this paper, a brief description of the algorithm is first given and examples of numerical simulations of a vented brake disc are treated. (10.3166/reef.13.627-636)
  DOI : 10.3166/reef.13.627-636
• Critère de fatigue polycyclique pour des métaux anisotropes: application au monocristaux
  
  • Cano Florian
  • Constantinescu Andrei
  • Maitournam Habibou
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2004, 332 (2), pp.115-121. Les critères de fatigue polycycliques fondés sur un passage macro–méso, initiés par Dang Van, ont essentiellement été utilisés pour des matériaux polycristallins. Dans les critères existants l'isotropie aux échelles macroscopique et mésoscopique joue un rôle crucial. L'objectif de ce travail est de revoir l'approche macro–méso en fatigue en tenant compte de l'anisotropie du matériau et en s'appuyant sur des résultats obtenus par Bui. Les applications possibles sont les aciers inclusionnaires ou encore des structures monocristallines comme les aubes de turbine en titane. (10.1016/j.crme.2003.11.005)
  DOI : 10.1016/j.crme.2003.11.005
• The origin of nucleation peak in transformational plasticity
  
  • Truskinovsky Lev
  • Vainchteyn Anna
  Journal of the Mechanics and Physics of Solids, Elsevier, 2004, 52, pp.1421-1446. A typical stress-strain relation for martensitic materials exhibits a mismatch between the nucleation and propagation thresholds leading to the formation of the nucleation peak. We develop an analytical model of this phenomenon and obtain specific relations between the macroscopic parameters of the peak and the microscopic characteristics of the material. Although the nucleation peak appears in the model as an interplay between discreteness and nonlocality, it does not disappear in the continuum limit. We verify the quantitative predictions of the model by comparison with experimental data for cubic to monoclinic phase transformation in NiTi. (10.1016/j.jmps.2003.09.034)
  DOI : 10.1016/j.jmps.2003.09.034
• Multiscale modelling of titanium aluminides
  
  • Roos Arjen
  • Chaboche Jean-Louis
  • Gélébart Lionel
  • Crépin Jérôme
  International Journal of Plasticity, Elsevier, 2004, 20, pp.811-830. In this work a three-scale model of the mechanical behaviour of titanium aluminides is presented. The first scale transition between the macroscopic length scale and the scale of an individual $α_2$, $γ$ or lamellar $α_2 + γ$ grain is made using elastically self-consistent transformation field analysis (TFA) with anisotropic elasticity. The constitutive equations of the $α_2$ and $γ$-phases are obtained through the framework of crystal plasticity. The effective behaviour of the lamellar $α_2–γ$ phase, however, necessitates a second scale transition. This transition, derived from a system of linear equations for a multilayer, is obtained and shown to be equivalent to the formalism of transformation field analysis. Some simple simulations are presented to show the viability of the method. (10.1016/j.ijplas.2003.08.005)
  DOI : 10.1016/j.ijplas.2003.08.005
• Stabilité de la forme de la goutte d'eau formée entre deux grains solides: méthode de résolution
  
  • Bérest Pierre
  • N'Dri Erik
  • Malinsky Laurent
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2004, 332, pp.665-672. On discute le signe de la seconde variation d'une Action lagrangienne en présence d'une contrainte intégrale, lorsque les conditions d'extrémité ne sont pas fixées, dans le cas où le lagrangien ne dépend pas explicitement de la variable d'intégration. Les résultats sont illustrés par le problème d'une goutte de liquide s'appuyant sur deux grains symétriques. (10.1016/j.crme.2004.01.015)
  DOI : 10.1016/j.crme.2004.01.015
• Identification en géotechnique par une méthode basée sur le théorème des travaux virtuels
  
  • Deng D.
  • Nguyen-Minh D.
  Revue française de Géotechnique, edp sciences, 2004, 108, pp.57-69. Une nouvelle méthode de rétro-analyse basée sur le théorème des travaux virtuels a été proposée, avec l’établissement d’un nouveau critère d’identification, la minimisation d’une fonction erreur basée sur le théorème des travaux virtuels. La méthode est simple et facile à programmer, tout en étant efficace et robuste. Elle permet d’identifier les paramètres mécaniques du matériau et les paramètres du chargement, et s’applique aux problèmes non linéaires élastoplastiques. L’application de la méthode au cas réel illustre sa faisabilité pratique en géotechnique. (10.1051/geotech/2004108057)
  DOI : 10.1051/geotech/2004108057
• Lamellar grains distribution and plastic strain heterogeneities in TiAl cast samples. Experiments and modelling
  
  • Gélébart Lionel
  • Bornert Michel
  • Bretheau Thierry
  • Caldemaison Daniel
  • Crépin Jérôme
  • Zaoui André
  Matériaux et Techniques, EDP Sciences [1970-....], 2004 (1-2), pp.69-75. During the cooling of TiAl cast alloys, the distribution of the dual-phase lamellar grains [ Ti$_3$Al ($\alpha_2$) $+$ TiAl ($\gamma$)] generates a so-called 'macrostructure'. Because of the highly anisotropic plastic behaviour of the lamellar grains, the distribution of the plastic strain is strongly influenced by such a macrostructure. This heterogeneity is clearly observed by means of a strainfield measurement technique applied to a compression test performed on a cast sample having a 'radial' macrostructure. As a result, a sample having such a macrostructure is not representative of the material and can not be used directly to evaluate 'material parameters'. Moreover the mechanical simulations of cast components should take into account such heterogeneities at the scale of the component. This strong influence is experimentally demonstrated and a way to take it into account in a mechanical simulation is proposed. (10.1051/mattech:2004008)
  DOI : 10.1051/mattech:2004008
• Propagation of a shock discontinuity in an elasto-plastic material: constitutive relations
  
  • Dequiedt Jean-Lin
  • Stolz Claude
  Archives of Mechanics, 2004, 56,5, pp.391-410. The shock discontinuity problem is analyzed in the case of elastoplastic materials ; the jump relations for internal state variables cannot be exhibited directly. For this purpose, we solve the internal shock structure problem, assuming that the shock front is a continuous transition in a thin layer, taking account of dissipative effects. The shock generating function is introduced. The canonical equations of the shock structure are determined in the general case when the evolution of plasticity is derived from a pseudo potential of dissipation. The plane wave is analyzed for an isotropic material obeying a von Mises criterion, assuming that inside the shock the material is under pure axial compression: the existence and uniqueness results are established.
• Full 3D investigation of the local strain field in particulate metal matrix composites
  
  • Bornert Michel
  • Doumalin Pascal
  • Maire Éric
  • Moulinec Hervé
  , 2004, pp.445-446.
• Energetical approach in non-linear mechanics Lecture Notes 11
  
  • Stolz Claude
  , 2004, pp.108.
• Topological derivative applied to cavity identification from elastodynamic data
  
  • Bonnet Marc
  • Guzina Bojan B
  , 2004, pp.355-362. This article is concerned with the use of topological derivative as a tool for preliminary elastic-wave probing of bounded or unbounded solids for buried objects. A formulation for computing the topological derivative field, based on an adjoint solution, is presented. A set of numerical results is included to illustrate the utility of topological derivative for outlining the cavity location and size prior to doing an actual inversion of measurements. The results presented here were obtained from a BIE solution, but the proposed methodology is applicable to other computational platforms such as the finite element method. (10.3166/reef.13.425-436)
  DOI : 10.3166/reef.13.425-436
• On Friction-Induced Instabilities and Vibrations
  
  • Nguyen Quoc Son
  Vietnam Journal of Mathematics, Springer, 2004, 32, pp.105-119. Some problems of friction-induced instabilities, vibrations and noise emissions are considered in this paper. The presentation is focussed on the possibility of flutter instability of the steady sliding equilibrium of an elastic solid in unilateral contact with a moving obstacle. The system of governing equations is given to obtain the steady sliding equilibrium and to discuss its stability. It is shown that the steady sliding equilibrium is generically unstable by flutter. This instability leads to a dynamic response which can be periodic or chaotic. Principal results of the literature are reported here. In the spirit of Hopf bifurcation, the existence problem of periodic solutions has been discussed in my research team for an academic problem of coaxial cylinders. It has been shown by a semi-analytical approach that an interesting family of these periodic solutions are stick-slip-separation waves propagating on the contact surface in a similar way as Schallamach waves in statics. The transition from a given position near equilibrium to the propagation of waves has been illustrated by a numerical approach using finite element simulations. Some phenomena of nonlinear vibration and noise emission in the daily life, such as brake squeal for example, can be discussed in this spirit.