Publications

2003

• Optimal dip based on dissipation of backthrusts and hinges in fold-and-thrust belts
  
  • Maillot Bertrand
  • Leroy Yves
  Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2003, 108 (B6), pp.2320. Back thrusts and hinges are two types of transition between rigid sections of hanging walls observed in fold‐and‐thrust belts. Back thrusts are typical of frictional and homogeneous solids and hinges of creeping and layered materials. Our objective is to study the orientation of these transitions for the special case of a lower flat‐ramp transition in a fault‐bend fold with the following general two‐step methodology. In the first step, the forces acting on the transition are determined using equilibrium of each rigid section. In the second step, the optimal dip of the transition is obtained by minimizing the total dissipation of the structure. The three sources of dissipation, of comparable magnitude, are at the transition, on the flat, and on the ramp. For frictional material flows, the back thrusts are velocity discontinuities with optimal dips always less than half the complementary ramp angle, leading to hanging wall thickening. The optimal dip agrees well with the results of physical analogue and numerical experiments. For creeping and layered materials, it is shown that a destabilizing deformation mechanism, selected to be flexural slip, is necessary for the strain to localize and the existence of hinges to be justified. Activation of flexural slip reduces dissipation at the transition and affects the optimal transition dip. The two‐step methodology proposed here could be seen as a first attempt in producing mechanically balanced cross sections accounting for material rheology. This approach should complement the now classical kinematic models of folding. (10.1029/2002JB002199)
  DOI : 10.1029/2002JB002199
• Modeling the dynamics of piano keys
  
  • Brenon Céline
  • Boutillon Xavier
  , 2003. The models of piano keys available in the literature are crude: two degrees of freedom and a very few dynamical or geometrical parameters. Experiments on different piano mechanisms (upright, grand, one type of numerical keyboard) exhibit strong differences in the two successive phases of the key motion which are controlled by the finger. Understanding the controllability of the escapement velocity (typically a few percents for professional pianists), the differences between upright and grand pianos, the rationale for the numerous independent adjustments by technicians, and the feel by the pianist require sophisticated modeling. In addition to the inertia of the six independently moving parts of a grand piano mechanism, a careful modeling of friction at pivots and between the jack and the roll, of damping and nonlinearities in felts, and of internal springs will be presented. Simulations will be confronted to the measurements of the motions of the different parts. Currently, the first phase of the motion and the transition to the second phase are well understood while some progress must still be made in order to describe correctly this short but important phase before the escapement of the hammer. [Work done in part at the Laboratory for Musical Acoustics, Paris.] (10.1121/1.4777652)
  DOI : 10.1121/1.4777652
• Numerical and experimental modal analysis of the reed and pipe of a clarinet
  
  • Facchinetti Matteo
  • Boutillon Xavier
  • Constantinescu Andrei
  Journal of the Acoustical Society of America, Acoustical Society of America, 2003, 113 (5), pp.2874-2883. A modal computation of a complete clarinet is presented by the association of finite-elementmodels of the reed and of part of the pipe with a lumped-element model of the rest of the pipe. In the first part, we compare modal computations of the reed and the air inside the mouthpiece and barrel with measurements performed by holographic interferometry. In the second part, the complete clarinet is modeled by adjoining a series of lumped elements for the remaining part of the pipe. The parameters of the lumped-resonator model are determined from acoustic impedance measurements. Computed eigenmodes of the whole system show that modal patterns of the reed differ significantly whether it is alone or coupled to air. Some modes exhibit mostly reed motion and a small contribution of the acoustic pressure inside the pipe. Resonance frequencies measured on a clarinet with the mouthpiece replaced by the cylinder of equal volume differ significantly from the computed eigenfrequencies of the clarinet taking the actual shape of the mouthpiece into account and from those including the (linear) dynamics of the reed. This suggests revisiting the customary quality index based on the alignment of the peaks of the input acoustical impedance curve. (10.1121/1.1560212)
  DOI : 10.1121/1.1560212
• Identification of rock mass properties in elasto-plasticity
  
  • Deng D.
  • Nguyen Minh D.
  Computers and Geotechnics, Elsevier, 2003, 30, pp.27-40. A simple and effective back analysis method has been proposed on the basis of a new criterion of identification, the minimization of error on the virtual work principle. This method works for both linear elastic and nonlinear elasto-plastic problems. The elasto-plastic rock mass properties for different criteria of plasticity can be well identified based on field measurements. (10.1016/S0266-352X(02)00033-2)
  DOI : 10.1016/S0266-352X(02)00033-2
• A procedure for identifying the plastic behaviour of single crystals from the local response of polycrystals
  
  • Hoc Thierry
  • Crépin Jérôme
  • Gélébart Lionel
  • Zaoui André
  Acta Materialia, Elsevier, 2003, 51, pp.5479-5490. The overall and local tensile responses of an α iron multicrystalline sample are investigated in order to derive the plastic constitutive equations for the constituent single crystals. The macroscopic stress–strain curve and some statistical characteristics of the strain field measured on the sample surface are compared with their simulated counterparts. The optimal values of the material parameters of four types of hardening laws are derived by a minimization procedure. The best results are obtained with a nonlinear anisotropic law which uses the dislocation densities on the slip systems. This procedure is then validated on a fine-grained polycrystalline sample of a similar material by using the measured displacement field on the edge of a selected area as boundary conditions for finite element method (FEM) computation. The resulting optimal material parameters for the single crystal are found to be consistent with the values available in the literature, and the whole simulated strain fields as well as the evolution of the crystallographic texture, is compared satisfactorily with the experimental data. (10.1016/S1359-6454(03)00413-0)
  DOI : 10.1016/S1359-6454(03)00413-0
• An `affine' micromechanical approach for the prediction of the elastoplastic behaviour of polycrystals at finite strain
  
  • Auslender F.
  • Bornert Michel
  • Hoc T.
  • Masson Renaud
  • Zaoui A.
  , 2003.
• Analyse des instabilités numériques liées au modèle de comportement élasto- viscoplastique dans les codes explicites
  
  • Mouro P.
  • Gary G.
  , 2003, pp.101-108 (tome 2). No abstract provided
• Calcul de l'usure sous chargement cyclique par une méthode de minimisation
  
  • Peigney Michaël
  , 2003, pp.405-412 (tome 1). No abstract provided
• Tenue en service des structures en caoutchouc
  
  • Raoult Ida
  • Bourgeois Myriam
  • Stolz Claude
  , 2003, pp.397-404 (tome 1).
• Prédiction de la géométrie d'une soudure à l'arc: un exemple de modélisation multiphysique
  
  • Roger F.
  • Dang Van K.
  , 2003, pp.353-360 (tome 2). No abstract provided
• Determination of the stabilized response of a structure undergoing cyclic thermal-mechanical loads by a direct cyclic method
  
  • Nguyen-Tajan Thi Mac-Lan
  • Pommier Benjamin
  • Maitournam Habibou
  • Mechkour Houari
  • Verger Loick
  • Du Z. Z.
  • Snyman M.
  , 2003.
• Non-uniqueness of solutions for elastic problems with Coulomb friction at the boundary
  
  • Ballard P.
  , 2003. No abstract provided
• Micromecanical investigation of the effect of defect clustering on the brittle-ductile transition of a nuclear vessel steel
  
  • Bilger N.
  • Auslender F.
  • Bornert Michel
  • Michel J. C.
  • Moulinec H.
  • Suquet P.
  • Zaoui A.
  , 2003. No abstract provided
• Materially Nonlinear Analysis
  
  • Bonnet Marc
  , 2003, pp.55-114. This chapter presents a review of domain-boundary element techniques for solving materially nonlinear solid mechanics problems. Quasi-static and dynamic formulations are addressed, with emphasis on the use of implicit constitutive integration techniques and the local and global consistent tangent operators. Symmetric Galerkin BEM formulations are also presented. A section is devoted to steady-state elastoplastic calculations for moving loads, and another to the simulation of abrasive wear, both types of nonlinear analyses being well-suited to D/BEM treatments. Another section deals with energy methods in fracture mechanics. Finally, a symmetric formulation for BEM-FEM coupling is presented as another way to use BEM, this time combined with FEM, for materially nonlinear analyses. (10.1007/978-3-7091-2790-2_2)
  DOI : 10.1007/978-3-7091-2790-2_2
• Micro-mechanical modelling of small and large strain behaviour of particulate nanocomposites
  
  • Chabert Emmanuelle
  • Bornert Michel
  • Cavaillé Jean-Yves
  • Dendievel Rémy
  • Gauthier Catherine
  • Zaoui André
  , 2003, pp.75-78. This work presents experimental results and micro-mechanical modelling of the small and large strain behaviour of particulate nanocomposites consisting of a soft polymeric matrix filled with rigid submicronic (either PS or silica) inclusions. The small strain properties appeared to be governed by filler-filler interactions as soon as a percolating filler network is developed (> 20%). To account for these observations, a discrete simulation which takes into account the nature of contact between reinforcing particles has been developed. However, the large strain properties can be correctly modelled by means of homogenisation techniques, suggesting that the filler network is broken very soon. INTRODUCTION Nanocomposite materials consist of a nanometer-scale phase in combination with another phase acting as a matrix. Work about polymer nanocomposites has exploded over the last few years. Their properties are reported to be different from that of their micro-scale counterparts 1,2. These unusual properties may be a consequence of (i) the extremely high interfacial specific area which can reach 100-1000 m 2 /g and (ii) the very short average distance between reinforcing fillers (about 10-8 m), down to a value comparable with the macromolecule coils. This can favor the short-distance filler-filler interactions leading, above a critical volume, to the formation of a network (percolation). Though significant progress has been made in developing nanocomposites with different polymer matrices, a general understanding has yet to emerge. A major challenge to further development of nanocomposites is the development of specific micro-mechanical models.
• Analysis of continental midcrustal strain localization induced by microfracturing and reaction-softening
  
  • Gueydan F.
  • Leroy Y. M.
  • Jolivet J.
  • Agard Philippe
  Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2003, 108 (B2), pp.2064. (10.1029/2001JB000611)
  DOI : 10.1029/2001JB000611
• La microextensométrie : un outil de la mécanique des matériaux
  
  • Bretheau T.
  • Crépin Jérôme
  • Doumalin P.
  • Bornert Michel
  Revue de Métallurgie, EDP Sciences, 2003, 5, pp.567-575. On présente ici une technique expérimentale, tant qualitative que quantitative, permettant de caractériser le champ de déformation dans un matériau hétérogène, sur un domaine représentatif de sa microstructure. Cette technique utilise la microscopie électronique à balayage, la microélectrolithographie, l’analyse d’image et des moyens d’essais mécaniques in situ. Si elle permet, en relation avec une analyse microstructurale, de mettre en évidence les différents mécanismes responsables de la plasticité et/ou de l’endommagement des matériaux, son utilisation quantitative en fait un outil essentiel de validation des modèles de prédiction de comportement, que ce soit à l’échelle locale ou à l’échelle macroscopique. Enfin, la connaissance du champ de déplacement expérimentalement mesuré permet d’améliorer sensiblement le résultat des simulations numériques par éléments finis par une meilleure prise en compte des conditions aux limites imposées sur le bord de la cellule modélisée. (10.1051/metal:2003110)
  DOI : 10.1051/metal:2003110
• Etude expérimentale des micro-mécanismes d'endommagement et de rupture des zircaloys hydrurés
  
  • Racine A.
  • Bornert Michel
  • Sainte-Catherine C.
  • Caldemaison D.
  Journal de Physique IV Proceedings, EDP Sciences, 2003, 106, pp.109-118. Afin de mieux comprendre les mécanismes d'endommagement et de rupture des Zircaloy, des essais de traction sur anneaux ont été réalisés in-situ sous MEB sur des éprouvettes de tube de gainage de combustible, contenant environ 150 ppm d'hydrogène et avec différentes orientations d'hydrures : de circonférentielle à radiale. Ces essais ont mis en évidence deux modes de rupture selon l'orientation des hydrures. Les éprouvettes avec hydrures radiaux (perpendiculaires à la sollicitation) rompent brutalement par propagation d'une fissure suivant un chemin d'hydrures radiaux alignés. Les niveaux de déformation au voisinage de la fissure, estimés par des techniques de micro-électrolithographie associées à celle d'analyse par corrélation d'images, sont très faibles, de l'ordre du %. En revanche, dans celles avec hydrures circonférentiels (suivant l'axe de sollicitation), les effets de structure prédominent : des bandes de cisaillement macroscopique apparaissent, dans lesquelles la déformation se localise. En dehors de ces zones de localisation intense, la déformation reste inférieure à 10% et très peu d'endommagement par germination de cavités ou fissuration d'hydrures a été observé. Les hétérogénéités du champ local de déformation, corrélées à la présence des hydrures, semblent établir l'influence de ceux-ci sur le mode de déformation local, mais ces observations nécessitent d'être confirmées. (10.1051/jp4:20030221)
  DOI : 10.1051/jp4:20030221
• Exploiting partial or complete geometrical symmetry in 3D symmetric Galerkin indirect BEM formulations
  
  • Bonnet Marc
  International Journal for Numerical Methods in Engineering, Wiley, 2003, 57, pp.1053-1083. Procedures based on group representation theory, allowing the exploitation of geometrical symmetry in symmetric Galerkin BEM formulations, are investigated. In particular, this investigation is based on the weaker assumption of partial geometrical symmetry, where the boundary has two disconnected components, one of which is symmetric; e.g. this can be very useful for defect identification problems. The main development is expounded in the context of 3D Neumann elastostatic problems, considered as model problems; and then extended to SGBIE formulations for Dirichlet and/or scalar problems. Both Abelian and non-Abelian finite symmetry groups are considered. The effectiveness of the present approach is demonstrated through numerical examples, where both partial and complete symmetry are considered, in connection with both Abelian and non-Abelian symmetry groups. (10.1002/nme.716)
  DOI : 10.1002/nme.716
• Etude expérimentale micromécanique de la déformation, de l'endommagement et de la rupture des alliages à base zirconium hydrurés
  
  • Racine A.
  • Bornert Michel
  • Sainte-Catherine C.
  • Caldemaison D.
  , 2003. No abstract provided
• Evaluation of nonlinear homogenisation schemes at the global and local scale by means of comparisons with exact solutions
  
  • Rekik E.
  • Bornert Michel
  , 2003. No abstract provided
• A global computational approach in engineering problems: identification
  
  • Constantinescu Andrei
  • Dang Van Ky
  , 2003.
• On shakedown theorems in hardening plasticity
  
  • Nguyen Q. S.
  , 2003.
• A unified analysis for low and high cycle fatigue based on shakedown concepts
  
  • Constantinescu Andrei
  • Dang Van Ky
  • Maitournam Habibou
  Fatigue and Fracture of Engineering Materials and Structures, Wiley-Blackwell, 2003, 26, pp.561-568. The purpose of this paper is to present a unified analysis to both high and low cycle fatigue based on shakedown theories and dissipated energy. The discussion starts with a presentation of the fatigue phenomena at different scales (microscopic, mesoscopic and macroscopic) and of the main shakedown theorems. A review of the Dang Van high cycle fatigue criterion shows that this criterion is essentially based on the hypothesis of elastic shakedown and can therefore be expressed as a bounded cumulated dissipated energy. In the low cycle fatigue regime, recent results by Skelton and Charkaluk et al. show that we can speak of a plastic shakedown at both mesoscopic and macroscopic scale and of a cumulated energy bounded by the failure energy. The ideas are also justified by infrared thermography tests permitting a direct determination of the fatigue limit. (10.1046/j.1460-2695.2003.00675.x)
  DOI : 10.1046/j.1460-2695.2003.00675.x
• Rolling contact in railways: modelling, simulation and damage prediction
  
  • Dang Van Ky
  • Maitournam Habibou
  Fatigue and Fracture of Engineering Materials and Structures, Wiley-Blackwell, 2003, 26, pp.939-948. Various kinds of defects are induced by rolling contact on the rail track: kidney‐shaped cracking, shelling and nowadays squat and head checking, which are studied under the sponsorship of the French national railways company SNCF. Modelling of such defects requires the development of specific computational tools in order to evaluate, in the vicinity of the wheel–rail contact zone, the mechanical state (stress, plastic strain cycle and residual stress pattern), which is at the origin of the damages. Moreover, since the loadings induce multiaxial stress and strain states, it is necessary to use a multiaxial criterion to predict the occurrence of fatigue cracks. This review paper is devoted to the presentation of the main results of this research. (10.1046/j.1460-2695.2003.00698.x)
  DOI : 10.1046/j.1460-2695.2003.00698.x