Publications

2003

• Growth and cellular differentiation: a physical-biochemical conundrum? The example of the hand
  
  • Schwartz Laurent H
  • Maitournam Habibou
  • Stolz C.
  • Steayert J. M.
  • Ho Ba Tho Marie-Christine
  • Halphen Bernard
  Medical Hypotheses, Elsevier, 2003, 61, pp.45-51. Currently, the predominant hypothesis explains cellular differentiation as an essentially genetic intracellular process. The goal of this paper is to suggest that cell growth and differentiation may be, simply, the result of physical and chemical constraints. Bone growth occurs at the level of cartilage conjunction (growth plate) in a zone of lesser constrain. It appears that this growth also induces muscle, tendon, nerve and skin elongation. This cartilage growth by itself seems to explain the elongation of the hand. Growth stops at puberty likely because of feed-back from an increasing muscle load. The ossification (that is differentiation of cartilage into bone) appears to result from the shear stress induced. The study of bone age, obtained by X-ray picture of the hand, shows that ossification of epiphyses is very precise both in time and space. Computer modelization suggests that this ossification occurs where shear stress is greatest. The cartilage which does not ossify (joint, nose, larynx, ear, bronchus, etc.) is not exposed to high shear. Shear stress induces the secretion of extracellular matrix and a change of the biochemical environment of the cell. Precipitation of calcium phosphate, as in ossification, seems related to the alkalosis induced by shear stress. To speak in more general terms, loss of cellular differentiation, as occurs with cancer, can result from a change in the physical–chemical environments. (10.1016/S0306-9877(03)00102-6)
  DOI : 10.1016/S0306-9877(03)00102-6
• A shakedown analysis in hardening plasticity
  
  • Nguyen Quoc Son
  Journal of the Mechanics and Physics of Solids, Elsevier, 2003, 51, pp.101-125. The extension of classical shakedown theorems for hardening plasticity is interesting from both theoretical and practical aspects of the theory of plasticity. This problem has been much discussed in the literature. In particular, the model of generalized standard materials gives a convenient framework to derive appropriate results for common models of plasticity with strain-hardening. This paper gives a comprehensive presentation of the subject, in particular on general results which can be obtained in this framework. The extension of the static shakedown theorem to hardening plasticity is presented at first. It leads by min-max duality to the definition of dual static and kinematic safety coefficients in hardening plasticity. Dual static and kinematic approaches are discussed for common models of isotropic hardening, of limited or unlimited kinematic hardening. The kinematic approach also suggests for these models the introduction of a relaxed kinematic coefficient following a method due to Koiter. Some models for soils such as the Cam-clay model are discussed in the same spirit for applications in geomechanics. In particular, new appropriate results concerning the variational expressions of the dual kinematic coefficients are obtained. (10.1016/S0022-5096(02)00058-3)
  DOI : 10.1016/S0022-5096(02)00058-3
• Mechanical constraints on the chronology of fracture activation in folded Devonian sandstone of the western Moroccan Anti-Atlas
  
  • Guiton M. L. E.
  • Sassi W.
  • Leroy Y. M.
  • Gauthier B. D. M.
  Journal of Structural Geology, Elsevier, 2003, 25, pp.1317-1330. The three-dimensional meter-scale fracture networks, observed on exposed folds between the towns of Tata and Akka, western Moroccan Anti-Atlas, consist mostly of planar discontinuities, which are sub-perpendicular to the bedding and partitioned in three main sets. The chronology of their activation is proposed in five stages since the Hercynian orogeny. Stage 1 predates folding and involves the horizontal compression of the Emsian sandstone. It involves fracture set I, composed of systematic joints parallel to the direction of compression. Stages 2–4 correspond to the folding and are marked in the outer-arc by the activation of fracture set II, composed mainly of joints parallel to the fold axial plane. Stage 5 is a regional shear event during which sets I and III, separated by an angle close to 60°, are activated in a conjugate manner. To throw light on the recurrent difficulty in discriminating between activation of inherited and new fractures, an elasto-plastic model is used to construct a stress path in the pervasively fractured medium idealized as a continuum. Each fracture set obeys the Mohr–Coulomb criterion truncated in tension to describe both sliding and opening activations. Finite-element simulations of a simple buckling event accounting for the field fracture sets are presented. It is shown that set I cannot be generated by folding and thus does belong to stage 1. Set II is activated at a later stage of folding than expected from the field interpretation. Set III cannot be activated during stage 2, confirming its role in stage 5. The advantages and limitations of the proposed modeling are finally discussed. (10.1016/S0191-8141(02)00155-4)
  DOI : 10.1016/S0191-8141(02)00155-4
• Bearing capacity of strip footings with horizontal confinement
  
  • Salençon Jean
  Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2003, 331, pp.319-324. For a strip footing under axial loading, the bearing capacity is influenced by the presence of rigid walls confining the foundation soil. This problem is investigated within the framework of the theory of yield design, considering both a perfectly rough and a frictionless contact condition at the interfaces with the walls in the case of a purely cohesive soil. Upper bounds for the correction factor to be applied to the classical value of the bearing capacity are determined, as functions of the non-dimensional geometric parameter of the problem, through the kinematic approach, implementing virtual velocity fields inspired from the solution to the problem of inverted extrusion. In the perfectly rough case, it appears that the new upper bound is a significant improvement of those already available. A very simple relationship is established, which derives the upper bound for the frictionless walls from the upper bound for the rough walls. A general conclusion of the analysis is that, for the values of the geometric parameter that are likely to be encountered in practice, the increase in the bearing capacity due to the presence of the rigid walls remains very small. (10.1016/S1631-0721(03)00071-8)
  DOI : 10.1016/S1631-0721(03)00071-8
• Génie parasismique : aspects dynamiques et vibratoires en génie civil
  
  • Luong Minh-Phong
  , 2003, pp.3 tomes. Actes du colloque AFPS 2003. Plus de 160 communications ont été présentées, réparties selon les thèmes suivants : - Géosciences (vol. 1) : sismologie générale et aléa déterministe ; mouvements sismiques pour l'ingénieur ; effets de site classiques ; interaction sol-structure et effet de site "urbains" ; géotechnique parasismique (sols, fondations et ouvrages). - Dynamique des structures et conception (vol. 2) : méthodes d'analyse et de modélisation (analyse simplifiée et indicateurs de nocivité, méthodes spécifiques) ; expérimentation ; constructions métalliques ; équipements industriels et structures particulières ; ponts. - Gestion de l'existant et du risque (vol. 3) : diagnostic et renforcement de l'existant ; existant nucléaire ; méthode d'estimation de la vulnérabilité à grande échelle ; scénarios et vulnérabilité urbaine ; aspects socio-économiques ; vers un nouveau zonage sismique de la France. - Benchmark Camus (vol. 3).
• Identification de failles sismiques par une fonctionnelle de réciprocité généralisée
  
  • Bui Huy Duong
  • Constantinescu Andrei
  • Maigre Hubert
  , 2003, 1, pp.13-20.
• Microstructure influence on the damage initiation in unirradiated zirconium alloys
  
  • Elbachiri K.
  • Crépin Jérôme
  • Rebeyrolle V.
  • Bretheau T.
  , 2003. No abstract provided
• Identification de lois de comportement cristallines à partir du couplage EBSD/microextensometrie/Eléments Finis. Application au zirconium grade 702
  
  • Dexet M.
  • Crépin Jérôme
  • Gélébart L.
  , 2003. No abstract provided
• Contribution du fluage à froid et de l'hydrogène à la fissuration anormale du Ti 6246 sous chargement cyclique à fort Kmax
  
  • Doquet V.
  • Mignot F.
  • Sarrazin-Baudoux C.
  , 2003. No abstract provided
• Couplage EBSD - micro-extensométrie et identification de lois cristallines
  
  • Roos A.
  • Hoc T.
  • Gélébart L.
  • Crépin Jérôme
  • Bornert Michel
  • Bretheau T.
  , 2003. No abstract provided
• Caractérisation de la répartition de la déformation dans les matériaux hétérogènes
  
  • Doumalin Pascal
  • Bornert Michel
  • Crépin Jérôme
  Mechanics & Industry, EDP Sciences, 2003, 4, pp.607-617. On présente une méthode originale de caractérisation de la répartition de la déformation dans les matériaux hétérogènes, basée sur l'adaptation des techniques statistiques de caractérisation morphologique par covariance à 2 points aux champs locaux de déformation mesurés par microextensométrie MEB. Elle permet de montrer que le comportement mécanique n'est pas uniquement la conséquence d'interactions très locales entre grains ou domaines de phases voisins, mais résulte aussi de phénomènes à plus grande portée. (10.1016/j.mecind.2003.09.002)
  DOI : 10.1016/j.mecind.2003.09.002
• Thermomechanical properties of polycarbonate under dynamic loading
  
  • Lerch V.
  • Gary G.
  • Hervé P.
  Journal de Physique IV Proceedings, EDP Sciences, 2003, 110, pp.159-164. In the present study, dynamic compression tests have been performed on polycarbonate (PC) specimen for strain rates in the range of 500 to 2000s -1 and on aluminum for a strain rate around 1300s -1 using a Split Hopkinson Pressure Bar (SHPB). Temperature measurement has been carried out using a fast response infrared optical pyrometer which is able to measure the surface temperature rise of a specimen during the tests. The temperature data shows that the mechanical work is not completely converted into heat. It implies the existence of a stored energy within the material and possibly a subsequent delay for the conversion of mechanical work into heat. (10.1051/jp4:20020687)
  DOI : 10.1051/jp4:20020687
• Linear stability analysis in fluid-structure interaction with transpiration. Part II: Numerical analysis and applications
  
  • Fernández Miguel Angel
  • Le Tallec Patrick
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2003, 192 (43), pp.4837-4873. This paper constitutes the numerical counterpart of the mathematical framework introduced in Part I. We address the problem of flutter analysis of a coupled fluid-structure system involving an incompressible Newtonian fluid and a reduced structure. We use the Linearization Principle approach developed in Part I, particularly suited for fluid-structure problems involving moving boundaries. Thus, the stability analysis is reduced to the computation of the leftmost eigenvalues of a coupled eigenproblem of minimal complexity. This eigenproblem involves the linearized incompressible Navier-Stokes equations and those of a reduced linear structure. The coupling is realized through specific transpiration interface conditions. The eigenproblem is discretized using a finite element approximation and its smallest real part eigenvalues are computed by combining a generalized Cayley transform and an implicit restarted Arnoldi method. Finally, we report three numerical experiments : a structure immersed in a fluid at rest, a cantilever pipe conveying a fluid flow and a rectangular bridge deck profile under wind effects. The numerical results are compared to former approaches and experimental data. The quality of these numerical results is very satisfactory and promising. (10.1016/j.cma.2003.08.001)
  DOI : 10.1016/j.cma.2003.08.001
• Statistical and Numerical analysis of the nonlinear behaviour of a porous materials with a heterogeneous distribution of pores
  
  • Bilger Nicolas
  • Bornert Michel
  • Auslender François
  • Michel Jean-Claude
  • Moulinec Hervé
  • Suquet Pierre
  • Zaoui André
  , 2003. The yield stress of a ductile 2D porous material with a heterogeneous distribution of pores is investigated by means of a numerical tool based on the Fast Fourier Transform. Random distributions of circular voids, with a uniform or variable pore size and with overlapping or clearly separated pores, are compared, for a same overall porosity, to microstructures obtained as the intersection of the previous ones with a boolean scheme with a larger characteristic size. For pure shear and even more under purely hydrostatic load, the numerical simulations show that the pore distribution has a strong effect on the yield stress, with the so-called “Hashin Composite Cylinders Assemblage” being the hardest microstructure and the connected clusters the softest, while disconnected clusters lead to intermediate responses. An image analysis tool for the statistical characterization of the pore distribution is then proposed. It is based on the distribution function of the distance function, the width of which increases with the presence of clusters. An additional analysis allows one to distinguish microstructures with connected clusters from those with disconnected ones.
• Testing with SHPB from quasi-static to dynamic strain rates
  
  • Ohtman R.
  • Bussac M. N.
  • Collet P.
  • Gary G.
  Journal de Physique IV Proceedings, EDP Sciences, 2003, 110, pp.397-404. We have developed a new method for separating dispersive waves in elastic and viscoelastic rods from three-point strain and one-point velocity measurements. Stress, strain, displacement and velocity, which were supposed to be homogenous in a rod section, were therefore determined at any point ofthe bar. This method is based on the assumption of a one dimensional and single mode dispersive wave propagation. This method was used in the frequency domain and took into account wave dispersion. It was shown to be stable with respect to noise. The measuring time is increased considerably. Subsequently, the maximum strain which can be measured in a material tested with a classical SHPB (Split Hopkinson Pressure Bar) set-up is also increased and is no more limited by the length of the bars. The method was used to evaluate the rate sensitivity ofaluminum honeycomb over a wide range ofstrain-rates (from 10 -2 to 1000 s -1). (10.1051/jp4:20020726)
  DOI : 10.1051/jp4:20020726
• Ondes adhérence-glissement-décollement sous contact unilatéral frottant
  
  • Oueslati Abdelbacet
  • Nguyen Quoc Son
  • Baillet Laurent
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2003, 331 (2), pp.133-140. Il s'agit d'une étude numérique sur la réponse dynamique d'un système de deux cylindres coaxiaux, en rotation relative avec contact unilatéral frottant suivant la loi de Coulomb. On complète les résultats semi-analytiques antérieurs obtenus dans Moirot, Nguyen, C. R. Acad. Sci. Paris Sér. IIb 328 (2000) 663–669, sur les ondes adhérence–glissement en simulant par le calcul numérique la transition dynamique du système à partir d'un état initial quelconque vers la propagation d'une onde de surface. Le cas des ondes adhérence–glissement–décollement est examiné. (10.1016/S1631-0721(02)00009-8)
  DOI : 10.1016/S1631-0721(02)00009-8
• Creep of polycrystalline anorthite and diopside
  
  • Dimanov Alexandre
  • Lavie Marie-Pierre
  • Ingrin Jannick
  • Dresen Georg
  • Jaoul Olivier
  Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2003, 108 (B1), pp.doi:10.10292002JB001815. (10.1029/2002JB001815)
  DOI : 10.1029/2002JB001815
• Modélisation de la fatigue des matériaux à mémoire de forme
  
  • Moumni Ziad
  • Maitournam Habibou
  • Dang Van Ky
  , 2003, 1, pp.413-419.
• 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
• Fissuration par fatigue d'un acier pour application ferroviaire: effet synérgétique des modes d'ouverture et de cisaillement sous chargement séquentiel
  
  • Doquet V.
  • Pommier S.
  , 2003. No abstract provided
• Analytical methods for dynamic response of underground structures
  
  • Kurose A.
  • Bérest P.
  • Brouard B.
  , 2003, pp.263-276 (tome 1). No abstract provided
• Identification numérique des fissures planes en élastodynamique
  
  • Bui Huy Duong
  • Constantinescu Andrei
  • Maigre Hubert
  , 2003, 1, pp.201-208.
• On the stress-wave imaging of cavities in a semi-infinite solid
  
  • Guzina B. B.
  • Nintcheu Fata S.
  • Bonnet Marc
  International Journal of Solids and Structures, Elsevier, 2003, 40, pp.1505-1523. The problem of mapping underground cavities from surface seismic measurements is investigated within the framework of a regularized boundary integral equation (BIE) method. With the ground modeled as a uniform elastic half-space, the inverse analysis of elastic waves scattered by a three-dimensional void is formulated as a task of minimizing the misfit between experimental observations and theoretical predictions for an assumed void geometry. For an accurate treatment of the gradient search technique employed to solve the inverse problem, sensitivities of the predictive BIE model with respect to cavity parameters are evaluated semi-analytically using an adjoint problem approach and a continuum kinematics description. Several key features of the formulation, including the rigorous treatment of the radiation condition for semi-infinite solids, modeling of an illuminating seismic wave field, and treatment of the prior information, are highlighted. A set of numerical examples with spherical and ellipsoidal cavity geometries is included to illustrate the performance of the method. It is shown that the featured adjoint problem approach reduces the computational requirements by an order of magnitude relative to conventional finite-difference estimates, thus rendering the three-dimensional elastic-wave imaging of solids tractable for engineering applications. (10.1016/S0020-7683(02)00650-9)
  DOI : 10.1016/S0020-7683(02)00650-9
• 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