Publications

2004

• The challenge of defining upper bounds on earthquake ground motions
  
  • Bommer Julian J
  • Abrahamson Norman A
  • Strasser Fleur O
  • Pecker Alain
  • Bard Pierre-Yves
  • Bungum Hilmar
  • Cotton Fabrice
  • Fäh Donat
  • Sabetta Fabio
  • Scherbaum Frank
  • Studer Jost
  Seismological Research Letters, Seismological Society of America, 2004, 75, pp.82-95. Recent studies to assess very long-term seismic hazard in the United States and in Europe have brought the issue of upper limits on earthquake ground motions into the arena of problems requiring attention from the engineering seismological community. Few engineering projects are considered sufficiently critical to warrant the use of annual frequencies of exceedance so low that ground-motion estimates may become unphysical if limiting factors are not considered, but for nuclear waste repositories, for example, the issue is of great importance. The definition of upper bounds on earthquake ground motions also presents an exciting challenge for researchers in the area of seismic hazard assessment. This paper looks briefly at historical work on maximum values of ground-motion amplitudes before illustrating why this is an important issue for hazard assessments at very long return periods. The paper then discusses the factors that control the extreme values of motion, both in terms of generating higher amplitude bedrock motions and of limiting the values of motion at the ground surface. Possible channels of research that could be explored in the quest to define maximum possible ground motions are also discussed. (10.1785/gssrl.75.1.82)
  DOI : 10.1785/gssrl.75.1.82
• Second-order estimates for the macroscopic response and loss of ellipticity in porous rubbers at large deformations
  
  • Lopez-Pamies Oscar
  • Ponte Castañeda Pedro
  Journal of Elasticity, Springer Verlag, 2004, 76 (3), pp.247-287. This work presents the application of a recently proposed “second-order” homogenization method (Ponte Castañeda, 2002) to generate estimates for effective behavior and loss of ellipticity in hyperelastic porous materials with random microstructures that are subjected to finite deformations. The main concept behind the method is the introduction of an optimally selected “linear thermoelastic comparison composite”, which can then be used to convert available linear homogenization estimates into new estimates for the nonlinear hyperelastic composite. In this paper, explicit results are provided for the case where the matrix is taken to be isotropic and strongly elliptic. In spite of the strong ellipticity of the matrix phase, the homogenized “second-order” estimates for the overall behavior are found to lose ellipticity at sufficiently large compressive deformations corresponding to the possible development of shear band-type instabilities (Abeyaratne and Triantafyllidis, 1984). The reasons for this result have been linked to the evolution of the microstructure, which, under appropriate loading conditions, can induce geometric softening leading to overall loss of ellipticity. Furthermore, the “second-order” homogenization method has the merit that it recovers the exact evolution of the porosity under a finite-deformation history in the limit of incompressible behavior for the matrix. (10.1007/s10659-005-1405-z)
  DOI : 10.1007/s10659-005-1405-z
• Experimental study of the influence of the degree of saturation on physical and mechanical properties in Tournemire shale (France)
  
  • Valès Frédéric
  • Nguyen-Minh Duc
  • Gharbi Hakim
  • Rejeb Amel
  Applied Clay Science, Elsevier, 2004, 26 (1-4), pp.197-207. In addition to direct mechanical perturbations, an excavation influences rock conditions (mechanical, hydraulic and chemical properties). The internal fluids could be drastically modified and, in particular, the presence of water in the rock with regard to hydration and desiccation. The aim of the present study is to investigate the influence between the degree of saturation and the physical/mechanical properties for Tournemire shale rock. Anisotropy effects are also studied to identify hydromechanical behaviour. The different degrees of saturation are imposed by controlled suctions with continuous measurement of physical parameters such as weight and deformations. The volume variations (swelling or shrinkage behaviour) would result principally from the opening or closing of the inter-layers space. Uniaxial and triaxial compressive tests are carried out in order to attempt to establish a relationship between different mechanical parameters (elastic and failure data) and the sample saturation. The mechanical behaviour is sensitive to the saturation state of the shale with an important part of the stratification and its relative orientation to the mechanical stress. (10.1016/j.clay.2003.12.032)
  DOI : 10.1016/j.clay.2003.12.032
• Elastodynamic rendering of internal cavities by way of topological derivative
  
  • Bonnet Marc
  • Guzina Bojan B
  , 2004.
• Topological sensitivity for 3D elastic and acoustic inverse scattering
  
  • Bonnet Marc
  , 2004. (10.1016/j.cma.2005.10.026)
  DOI : 10.1016/j.cma.2005.10.026
• Tailoring bulk and surface grafting of poly(acrylic acid) in electron-irradiated PVDF
  
  • Clochard Marie-Claude
  • Bègue J
  • Lafon A
  • Caldemaison D
  • Bittencourt C
  • Pireaux J.-J
  • Betz N
  Polymer, Elsevier, 2004, 45, pp.8683. Endowing conventional hydrophobic poly(vinylidene fluoride) (PVDF) films with hydrophilic properties was conducted using electron beam irradiation. Grafting of acrylic acid (AA) in/onto pre-irradiated PVDF films was investigated. Reaction parameters, monomer concentration and inhibitor concentration were examined. Radiation grafted films (PVDF-g-PAA) were synthesized with various grafting yields ranging from 12 to 130 wt % in presence of Mohr's salt (25 wt %). Below 80 wt % of monomer concentration, the degree of swelling was found to increase with the grafting yield. The PAA was arranged randomly in all PVDF matrix (grafting through). Above 80 wt % of monomer concentration, the PAA was grafted only onto the surface of PVDF films leading to a highly dense layer of PAA. Grafting through or surface grafting processes were achieved by varying the water fraction in the initial monomer solution. Water molecule acts not only as a carrier for the monomer but also as a plasticizer expanding the film in the three dimensions. Evidences of grafting through and surface grafting were produced using FTIR in ATR mode, SEM coupled to X-ray detection and XPS. An accurate quantification of AA units was possible up to the micromole via a Cu 2C –EDTA complex analyzed by UV–vis spectroscopy. q (10.1016/j.polymer.2004.10.052)
  DOI : 10.1016/j.polymer.2004.10.052
• Identification de loi de comportement cristallines à partir du couplage EBSD/Microextensométrie/Eléments Finis. Application au zirconium grade 702
  
  • Dexet Marie
  • Crépin Jérôme
  • Gélébart Lionel
  • Zaoui André
  , 2004.
• Topological sensitivity for 3D elastic and acoustic inverse scattering
  
  • Bonnet Marc
  , 2004. (10.1016/j.cma.2005.10.026)
  DOI : 10.1016/j.cma.2005.10.026
• T.G.V. disk brake squeal: a dynamic instability?
  
  • Lorang Xavier
  • Nguyen Quoc Son
  • Foy-Margiocchi Florence
  • Gautier Etienne
  , 2004, pp.959-960.
• 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
• 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
• 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
• Evaluation of linearization procedure sustaining nonlinear homogenization theories
  
  • Rekik Amna
  • Bornert Michel
  • Zaoui André
  • Auslender François
  , 2004. A systematic methodology for the evaluation of various existing linearisation procedures sustaining mean field theories for nonlinear composite materials is proposed and applied to the ’modified secant’ and various ’affine’ formulations. It relies on the analysis of a composite for which an exact treatment of both the nonlinear homogenisation problem and the linear homogenisation of the ’linear comparison material’ with identical microstructure is possible; the effects of the sole linearization method can then be evaluated.
• Mesure tridimensionnelle de champs cinématiques par imagerie volumique pour l'analyse des matériaux et des structures
  
  • Bornert Michel
  • Chaix Jean-Marc
  • Doumalin Pascal
  • Dupré Jean-Christophe
  • Fournel Thierry
  • Jeulin Dominique
  • Maire Éric
  • Moreaud Maxime
  • Moulinec Hervé
  Instrumentation, Mesure, Métrologie, Lavoisier, 2004, 3-4 (3-4), pp.43-88. Let techniques de corrélation d'images surfaciques sont étendues à l'analyse de don­nées volumiques obtenues par microtomographie X de résolution micrométrique ou, pour les matériaux transparents, par reconstruction sériée avec un éclairage laser plan. Le contraste d'image local est fourni par des marqueurs beaucoup plus petits que let dimensions caracté­ristiques des gradients à analyser, dont on vérifie par simulation qu'ils ne perturbent pas nota­blement ces derniers. Pour la tomograqhie, on ajoute aléatoirement des particules plut denses alors que des diffuseurs optiques sont introduits dans les matériaux transparents. La résolution de mesure, évaluée sur des mouvements rigides, peut descendre à 0,01 voxel, mais se dégrade fortement sur des images bruitées. De nouveaux critères d'appariement, moins sensibles au bruit, sont discutés. Les applications présentées concernent des échantillons plastiques homogènes plats ou entaillés sous traction, ainsi que des composites à matrice métallique et renforts particulaires.
• Characterization of Local Strain Field in Cortical Bone
  
  • Henry L.
  • Meunier A.
  • Aubry Denis
  • Crépin Jérôme
  • Caldemaison D.
  • Hoc T.
  , 2004. No abstract provided
• Etude expérimentale et modélisation du comportement mécanique des alliages TiAl à l'échelle du grain
  
  • E. Héripré E.
  • Crépin Jérôme
  • Roos A.
  • Chaboche J. L.
  , 2004. No abstract provided
• 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
• 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
• 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
• 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
• 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
• Incompressibility constraints in finite elements
  
  • Le Tallec Patrick
  , 2004, pp.33-45.
• 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.
• 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
• 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