Publications

2002

• Reliability of structures during random loadings
  
  • Zarka J.
  • Karaouni H.
  , 2002. No abstract provided
• An elastodynamic boundary element approach to underground cavity detection
  
  • Guzina B. B.
  • Nintcheu Fata S.
  • Bonnet Marc
  , 2002.
• Mécanique des milieux continus
  
  • Salençon J.
  , 2002.
• Calcul à la rupture / Yield design
  
  • Salençon J.
  , 2002.
• Fatigue design of structures under thermomechanical loadings
  
  • Charkaluk Éric
  • Bignonnet André
  • Constantinescu Andreï
  • Dang Van Ky
  Fatigue and Fracture of Engineering Materials and Structures, Wiley-Blackwell, 2002, 25 (12), pp.1199-1206. This paper presents a global approach to the design of structures that experience thermomechanical fatigue loading, which has been applied successfully in the case of cast‐iron exhaust manifolds. After a presentation of the design context in the automotive industry, the important hypotheses and choices of this approach, based on a thermal 3D computation, an elastoviscoplastic constitutive law and the dissipated energy per cycle as a damage indicator associated with a failure criterion, are first pointed out. Two particular aspects are described in more detail: the viscoplastic constitutive models, which permit a finite element analysis of complex structures and the fatigue criterion based on the dissipated energy per cycle. The FEM results associated with this damage indicator permit the construction of a design curve independent of temperature; an agreement is observed between the predicted durability and the results of isothermal as well as non isothermal tests on specimens and thermomechanical fatigue tests on real components on an engine bench. These results show that thermomechanical fatigue design of complex structures can be performed in an industrial context. (10.1046/j.1460-2695.2002.00612.x)
  DOI : 10.1046/j.1460-2695.2002.00612.x
• A “quasi-elastic” affine formulation for the homogenised behaviour of nonlinear viscoelastic polycrystals and composites
  
  • Brenner Renald
  • Masson Renaud
  • Castelnau Olivier
  • Zaoui André
  European Journal of Mechanics - A/Solids, Elsevier, 2002, 21 (6), pp.943-960. The derivation of the overall behaviour of nonlinear viscoelastic (or rate-dependent elastoplastic) heterogeneous materials requires a linearisation of the constitutive equations around uniform per phase stress (or strain) histories. The resulting Linear Comparison Material (LCM) has to be linear thermoviscoelastic to fully retain the viscoelastic nature of phase interactions. Instead of the exact treatment of this LCM (i.e., correspondence principle and inverse Laplace transforms) as proposed by the “classical” affine formulation, an approximate treatment is proposed here. First considering Maxwellian behaviour, comparisons for a single phase as well as for two-phase materials (with “parallel” and disordered morphologies) show that the “direct inversion method” of Laplace transforms, initially proposed by Schapery (1962), has to be adapted to fit correctly exact responses to creep loading while a more general method is proposed for other loading paths. When applied to nonlinear viscoelastic heterogeneous materials, this approximate inversion method gives rise to a new formulation which is consistent with the classical affine one for the steady-state regimes. In the transient regime, it leads to a significantly more efficient numerical resolution, the LCM associated to the step by step procedure being no more thermoviscoelastic but thermoelastic. Various comparisons for nonlinear viscoelastic polycrystals responses to creep as well as relaxation loadings show that this “quasi-elastic” formulation yields results very close to classical affine ones, even for high contrasts. (10.1016/S0997-7538(02)01247-0)
  DOI : 10.1016/S0997-7538(02)01247-0
• Mechanical model of the inspiratory pump
  
  • Basso Ricci Sergio
  • Cluzel Philippe
  • Constantinescu Andrei
  • Similowski Thomas
  Journal of Biomechanics, Elsevier, 2002, 35, pp.139-145. The inspiratory pump (inspiratory muscles and the rib cage) translates inspiratory commands in alveolar ventilation by applying expanding forces to the lungs. Its functioning is of paramount importance to the physiology of breathing and of many pathological situations. Major difficulties in studying its function in relationship with its structure arise from the extremely complex geometrical disposition of its active and passive elements. We herein describe a two-compartment model of the inspiratory pump, with model parameters identification derived from actual measurements obtained by magnetic resonance imaging in normal humans. The equations governing the model are presented. Numerical simulations validate the model by showing a behaviour similar to physiological observations. This opens the possibility of predicting the behaviour of the respiratory system during diseases involving changes in its mechanical or geometrical characteristics. (10.1016/S0021-9290(01)00164-6)
  DOI : 10.1016/S0021-9290(01)00164-6
• Détermination de la réponse asymptotique d'une structure anélastique sous chargement thermomécanique cyclique
  
  • Maitournam Habibou
  • Pommier Benjamin
  • Thomas Jean-Jacques
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2002, 330, pp.703-708. Cet article présente une solution alternative aux méthodes classiques (comme la méthode incrémentale) de résolution de problèmes thermomécaniques cycliques non-linéaires. Il s'agit d'une Méthode Cyclique Directe qui consiste à rechercher directement la solution asymptotique d'une structure anélastique soumise à un chargement thermomécanique périodique, sans suivre l'histoire du chargement. Elle est fondée sur le Grand Incrément de Temps et la périodicité de l'état limite et la transformation de Fourier. (10.1016/S1631-0721(02)01516-4)
  DOI : 10.1016/S1631-0721(02)01516-4
• Cracking behaviour of PVD tungsten coatings deposited on steel substrates: the influence of film thickness
  
  • Ganne Thomas
  • Crépin Jérôme
  • Serror Serge
  • Zaoui André
  Acta Biomaterialia, Elsevier, 2002, 50, pp.4149-4163. Tungsten coatings have been deposited on steel substrates by magnetron sputtering. For the same processing conditions, the increase of the coating thickness enhances the (111) component of the crystallographic texture whereas the residual stress level decreases. Tensile and four-point bending tests, associated with an acoustic emission analysis, have been performed inside a SEM chamber in order to study the cracking mechanisms. When the residual stresses are taken into account, an intrinsic critical cracking stress and the associated energy release rate can be determined; the obtained values suggest an intergranular cracking mechanism. No debonding has been observed at the interface despite the large plastic deformation of the substrate at the crack tips. The observed strain localisation modes in the substrate near the interface have been shown to have a major influence on the limit crack density. (10.1016/S1359-6454(02)00256-2)
  DOI : 10.1016/S1359-6454(02)00256-2
• Simulation numérique d'un disque de frein automobile par une méthode de calcul eulérien
  
  • Nguyen-Tajan Thi Mac-Lan
  • Thomas Jean-Jacques
  • Maitournam Habibou
  , 2002, pp.131-138.
• Micro-mécanismes d'endommagement des zircaloy hydrurés: Essais in-situ et modélisation
  
  • Noël Racine Antoine
  • Bornert Michel
  , 2002.
• Les matériaux vieillissent aussi
  
  • Zaoui André
  , 2002.
• Etude micromécanique de la fissuration par fatigue de l'alliage de titane Ti6246
  
  • Mignot F.
  • Doquet V.
  • Sarrazin-Baudoux C.
  • Petit J.
  , 2002. No abstract provided
• Caractérisation expérimentale de paramètres thermomécaniques liés au frottement
  
  • Stalin Nadine
  • Eytard Jean-Christophe
  Mechanics & Industry, EDP Sciences, 2002, 3, pp.267-270. Les progrès technologiques accomplis en matière de thermographie infrarouge offrent aujourd'hui des possibilités accrues d'étudier des phénomènes thermiques dans le domaine de la mécanique du contact notamment lorsqu'il y a du frottement. Le coefficient de frottement instantané, pouvant varier continûment, est souvent difficile à évaluer. La mise au point d'une méthode basée sur l'émission infrarouge, qui s'appuie sur l'observation conjointe et en continu du coefficient de frottement et des élévations de température au cours d'un essai d'usure en glissement total, permet de disposer d'une autre technique d'évaluation du frottement. Cette démarche expérimentale met en évidence une similitude de comportement, en temps réel, de ces deux facteurs. Les variations de température résultant de la production de chaleur générée par le frottement sont mesurées sur la face opposée à celle du contact. Cette démarche utilise les propriétés de transfert de chaleur par conduction à travers l'épaisseur de l'éprouvette. Cette approche ouvre des perspectives de recherche notamment dans des domaines de la mécanique où les phénomènes se produisent dans des zones de contact difficiles d'accès.
• On the determination of elastoviscoplastic constants of hard marls from in situ measurements performed on a motorway tunnel in the Alps
  
  • Lecampion Brice
  • Constantinescu Andrei
  • Nguyen Minh Duc
  • Allagnat D.
  , 2002, pp.251-258.
• Infrared thermography of 3D-woven fabrics subjected to service loading
  
  • Gorog Sylvie
  • Luong Minh-Phong
  • Eytard Jean-Christophe
  , 2002, pp.1383-1386. The paper introduces the use of an infrared thermographic technique to detect the manifestation of physical processes of damage in a three-dimensional woven polyester fabric subjected to the traffic of heavy vehicles. Thanks to the thermomechanical coupling occurring in the polyester fabric, this non-destructive, noncontact and in real time technique (NDT) highlights the heat generation caused by the energy dissipated by the material during the passage of a wheel. Experimental results show that the infrared thermographic technique provides a useful means to evaluate the mechanical performance of geosynthetic products under full-scaleservice loading.
• Identification de la relation de dispersion dans les barres
  
  • Othman Ramzi
  • Blanc Robert
  • Bussac Marie-Noëlle
  • Collet Pierre
  • Gary Gérard
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2002, 330 (12), pp.849-855. Une méthode de mesure de la dispersion et de l'amortissement des ondes longitudinales dans une barre élastique ou faiblement viscoélastique est présentée. Elle est fondée sur l'analyse des résonances présentes dans le spectre du signal de la déformation produite par un chargement indéterminé. Appliquée à une barre d'aluminium, elle permet la mesure de la dispersion pour des fréquences allant jusqu'à 60 kHz. On vérifie la grande qualité de la relation de dispersion ainsi obtenue en testant la précision du transport des ondes calculé avec cette relation. (10.1016/S1631-0721(02)01541-3)
  DOI : 10.1016/S1631-0721(02)01541-3
• Approche locale de la déformation d'alliages de structure hexagonale
  
  • Bornert Michel
  • Bretheau Thierry
  • Caldemaison Daniel
  • Crépin Jérôme
  • Doumalin Pascal
  Matériaux et Techniques, EDP Sciences [1970-....], 2002, 5-6 (5-6), pp.85-90. Cette étude s’intéresse à la compréhension des mécanismes de déformation d’alliages de zirconium en relation avec la microstructure et leurs conséquences vis à vis de l’endommagement du matériau. Grâce à une approche micromécanique, il a été possible d’identifier les mécanismes de déformation activés, de déterminer leur cission critique d’activation ainsi que de mettre en évidence l’existence d’une interaction à “méso-échelle”, observable à l’aide de cartes de déformation et de covariogrammes. (10.1051/mattech/200290050088)
  DOI : 10.1051/mattech/200290050088
• Dynamics of rigid bodies systems with unilateral or frictional constraints
  
  • Ballard Patrick
  , 2002, pp.3-87. The classical theory of rigid bodies systems dynamics is extended into two directions. First, systematic formulation of the dynamics of systems undergoing perfect unilateral constraints is derived. The general admissible form of the impact constitutive equation is obtained. Well-posedness of the evolution problem is proved under the assumption that the data are analytic. Second, systematic formulation of systems undergoing frictional bilateral constraints is discussed. Well-posedness of the associated evolution problem is also demonstrated. (10.1007/978-1-4757-4435-4_1)
  DOI : 10.1007/978-1-4757-4435-4_1
• Fissuration par fatigue en mode II d'un acier maraging. Effets de fréquence et d'environnement
  
  • Doquet Véronique
  Revue de Métallurgie, EDP Sciences, 2002, pp.441-448. Des essais de fissuration par fatigue en mode Il ont été menés sur un acier maraging, à différentes fréquences, sous air ou sous vide. En affectant les conditions tribologiques le long des flancs de fissure, ces variations des conditions expérimentales jouent sur la cinétique de propagation en mode Il et sa stabilité. La mesure des profils de déplacement le long des flancs permet d'estimer ΔKII effectif et d'unifier les données cinétiques obtenues dans des conditions de frottement plus ou moins intense.
• Parameter Identification for lined tunnels in a viscoplastic medium
  
  • Lecampion Brice
  • Constantinescu Andrei
  • Nguyen Minh Duc
  International Journal for Numerical and Analytical Methods in Geomechanics, Wiley, 2002, 26 (12), pp.1191-1211. This paper is dedicated to the identification of constitutive parameters of elasto‐viscoplastic constitutive law from measurements performed on deep underground cavities (typically tunnels). This inverse problem is solved by the minimization of a cost functional of least‐squares type. The exact gradient is computed by the direct differentiation method and the descent is done using the Levenberg–Marquardt algorithm. The method is presented for lined or unlined structures and is applied for an elastoviscoplastic constitutive law of the Perzyna class. Several identification problems are presented in one and two dimensions for different tunnel geometries. The used measurements have been obtained by a preliminary numerical simulation and perturbed with a white noise. The identified responses match the measurements. We also discuss the usage of the sensitivity analysis of the system, provided by the direct differentiation method, for the optimization of in situ monitoring. The sensitivity distribution in space and time assess the location of the measurements points as well as the time of observation needed for reliable identification. (10.1002/nag.241)
  DOI : 10.1002/nag.241
• Numerical identification of planar cracks in elastodynamics using the reciprocity gap
  
  • Bui Huy Duong
  • Constantinescu Andrei
  • Maigre Hubert
  , 2002, pp.55-60.
• Formulation and well-posedness of impact problems in solid mechanics
  
  • Ballard Patrick
  , 2002.
• A novel inverse problem in medical emission imaging
  
  • Nguyen Maï K.
  • Truong Tuong Trong
  • Bui Huy Duong
  , 2002, pp.397-404.
• Using Domain Knowledge in Evolutionary System Identification
  
  • Schoenauer Marc
  • Sebag Michèle
  , 2002. Two example of Evolutionary System Identification are presented to highlight the importance of incorportaing Domain Knowledge: the discovery of an analytical indentation law in Structural Mechanics using constrained Genetic Programming, and the identification of the repartition of underground velocities in Seimsi Prospection. Critical issues for sucessful ESI are discussed in the light of these results.