Publications

2000

• Spatial localization of the error of constitutive law for the identification of defects in elastic bodies
  
  • Bui Huy Duong
  • Constantinescu Andreï
  Archives of Mechanics, Polish Scientific Publishers Pwn, 2000, 52, pp.511-522. The error on constitutive law (ECL) is a cost functional currently used in inverse problems for identifying interior distribution of coefficients of partial differential equations from overspecified boundary conditions. In previous works, different authors have shown that the ECL permits a good spatial localization of the perturbations of the coefficients. The purpose of this paper is to justify this spatial localization property. The result is obtained for the elliptic equations of elasticity using boundary integral representations of the solutions and comparing the linear and the perturbed solution of the problem.
• Usure induite par vibrations sous écoulement: le cas des grappes de commande des réacteurs a eau pressurisée. Des études théoriques aux applications industrielles
  
  • Zbinden M.
  • Dragon-Louiset M.
  Mechanics & Industry, EDP Sciences, 2000, 1, pp.581-592. Différents composants internes des réacteurs à eau pressurisée (REP), et en particulier les grappes de commande, subissent un endommagement par usure sous l'action des vibrations induites par les écoulements. Pour faire face à ce problème, un important programme de R&D a été lancé par EDF et ses partenaires. Afin de permettre des calculs prédictifs, un modèle industriel d'usure a été développé, fondé à la fois sur des résultats expérimentaux et sur la cinétique d'usure réelle observée en réacteur. La modélisation de l'usure proprement dite est le maillon final d'une suite de calculs qui commence par la détermination des excitations hydrauliques, se poursuit par le calcul de la réponse dynamique de la structure et des chargements dans les zones de contact, pour s'achever par l'estimation des volumes et des profondeurs d'usure. Des travaux plus théoriques, visant à comprendre et à modéliser les phénomènes mis en jeu ont également été entrepris. Une démarche pour la simulation des phénomènes d'usure douce est proposée, en annexe, associant une étude thermodynamique globale à un modèle de l'interface des deux corps en contact. Elle permet de tenir compte de l'influence de ce milieu complexe sur le chargement et l'usure des solides. L'originalité de ce travail réside dans la prise en compte de la perte de matière et de la physique de l'interface dans un modèle macroscopique.
• Evaluation non destructive des structures mécaniques par thermographie infrarouge
  
  • Luong Minh-Phong
  Rev. Franç. Mécanique, 2000, 2000, pp.19-25.
• Dynamic tensile testing of sheet metal
  
  • Gary Gérard
  • Mouro Pierre
  • Zhao Han
  , 2000. (10.1051/jp4:2000925)
  DOI : 10.1051/jp4:2000925
• Modèles micromécaniques : effets de l'anisotropie et de l'hétérogénéité de la répartition des renforts dans un composite à particules
  
  • Bornert Michel
  • Lebail H.
  • Franciosi P.
  • Jeulin Dominique
  , 2000. No abstract provided
• Etude pétro-structurale du détachement du Tende (Corse). Rôle des micas blancs dans la localisation de la déformation ductile
  
  • Gueydan F.
  • Jolivet L.
  • Agard Philippe
  , 2000. No abstract provided
• On viscous fluid flow near the moving crack tip
  
  • Bui Huy Duong
  • Guyon Corinne
  • Thomas Bernadette
  , 2000, 76, pp.63-74. We consider a crack partially filled with a fluid. We show that the presence of a lag avoids the appearance of pressure and velocity singularities. For the static equilibrium, we recall the previous result on the Capillary Stress Intensity Factor which provides a purely mechanical explanation of the Rehbinder effect, according to which the toughness of the material can be lowered by humidity. For the steady state propagation of a crack due to viscous fluid flow, we set the coupled system of non-linear equations. (10.1007/0-306-46946-4_4)
  DOI : 10.1007/0-306-46946-4_4
• On discontinuous stresses at the interface of a bimaterial thermo-elasto-plastic body
  
  • Bui Huy Duong
  • Taheri Said
  • Dang Van Ky
  Advances in Natural Sciences, 2000, 1, pp.79-84.
• The dynamics of discrete mechanical systems with perfect unilateral constraints
  
  • Ballard Patrick
  Archive for Rational Mechanics and Analysis, Springer Verlag, 2000, 154 (3), pp.199-274. The dynamics of discrete mechanical systems with perfect unilateral constraints is formulated in a very general setting. The well-posedness of the resulting evolution problem is studied. It is proved that existence and uniqueness of a maximal solution is ensured provided strong assumptions are made on the regularity of the data: they are supposed to be analytic. Simple examples show that this regularity assumption may not be relaxed. Sufficient conditions to ensure that the maximal solution is defined for all time are supplied. The continuous dependence of the solution on initial conditions is also studied and the numerical computation of the solution is discussed. (10.1007/s002050000105)
  DOI : 10.1007/s002050000105
• An energetic approach in thermomechanical fatigue for silicium molybden cast iron
  
  • Charkaluk E.
  • Constantinescu Andreï
  Materials at High Temperatures, Taylor and Francis, 2000, 17 (3), pp.373-380. The purpose of this paper is to define a low cycle fatigue criterion in order to predict the failure of engineering structures. The major problem in defining a predictive fatigue criterion is that it should be applicable for structures submitted to complex multiaxial thermo-mechanical loadings but should be identifiable from simple experiments on specimens. After a short critical review of the principal criteria used in low cycle fatigue it will be shown that the dissipated energy per cycle permits a correlation of isothermal and anisothermal results obtained on silicon molybdenum cast iron in the case of specimens and also on structures. (10.1179/mht.2000.17.3.001)
  DOI : 10.1179/mht.2000.17.3.001
• Plan/plan sliding contact modelling by the boundary element method
  
  • Serre Ingrid
  • Bonnet Marc
  • Pradeilles-Duval Rachel Marie
  , 2000.
• Hétérogénéité des contraintes au sein d'un matériau lamellaire. Application à un alliage intermétallique TiAl
  
  • Gélébart Lionel
  • Crépin Jérôme
  • Bretheau Thierry
  • Bornert Michel
  , 2000.
• A plasticity model for discontinua
  
  • Leroy Yves
  • Sassi William
  , 2000, pp.77-107. This article is concerned with the development and application of a simple continuum theory for rocks that may contain both randomly as well as preferentially oriented plane discontinuity surfaces. The theory stipulates that displacement discontinuities are independently activated on these surfaces as soon as an appropriate yield criterion is fulfilled; these displacement jumps account for the irreversible, ‘plastic’ part of the bulk deformation. In stress space, the critical conditions for the activation of discontinuous slip or opening displacements define an overall yield envelope that could be initially anisotropic, reflecting for example a weakness of certain orientations due to pre-existing joint sets. For the yield conditions studied in this paper, essentially a Coulomb-type friction law and a simple fracture opening condition, the inferred stress-strain response under typical triaxial loading conditions reveals the sensitivity of the two discontinuous deformation modes to the confining pressure. The incipient growth of a geological fold in such a material is modelled as a problem of plate bending. The slip- and opening-modes of deformation are found to be activated typically in the fold intrados and extrados, respectively. Under certain conditions, both modes will be activated simultaneously at the same locality and contribute to the total deformation. Field observations on a well exposed sandstone anticline are reported here, which support this conclusion. The present plasticity model for discontinua can clearly be explored in more detail for realistic distributions of faults and joints taken from field observations. It could also be improved in various ways in its description of the underlying deformation mechanisms. Apart from its interest as a mechanical constitutive model, it can also serve as a point of departure for studies of stress-sensitive, anisotropic permeability distributions in fractured formations. (10.1007/978-3-642-59617-9_5)
  DOI : 10.1007/978-3-642-59617-9_5
• An affine formulation for the prediction of the effective properties of nonlinear composites and polycrystals
  
  • Masson Renaud
  • Bornert Michel
  • Suquet Pierre
  • Zaoui André
  , 2000. Variational approaches for nonlinear elasticity show that Hill's incremental formulation for the prediction of the overall behaviour of heterogeneous materials yields estimates which are too stiff and may even violate rigorous bounds. This paper aims at proposing an alternative `affine' formulation, based on a linear thermoelastic comparison medium, which could yield softer estimates. It is first described for nonlinear elasticity and specified by making use of Hashin±Shtrikman estimates for the linear comparison composite; the associated affine self-consistent predictions are satisfactorily compared with incremental and tangent ones for power-law creeping polycrystals. Comparison is then made with the second-order procedure and some limitations of the affine method are pointed out; explicit comparisons between different procedures are performed for isotropic, two-phase materials. Finally, the affine formulation is extended to history-dependent behaviours; application to the self-consistent modelling of the elastoplastic behaviour of polycrystals shows that it others an improved alternative to Hill's incremental formulation. (10.1016/S0022-5096(99)00071-X)
  DOI : 10.1016/S0022-5096(99)00071-X
• Dynamic testing at high rates of strain
  
  • Gary G.
  , 2000.
• La programmation logique inductive à la lumière de la transition de phase
  
  • Giordana Attilio
  • Saitta Lorenza
  • Sebag Michèle
  • Botta Marco
  , 2000, pp.157-172. En logique du premier ordre, le test de couverture correspond à un problème de satisfaction de contraintes. Or, dans le domaine de la satisfaction de contraintes, les problèmes les plus difficiles à résoudre en moyenne se concentrent dans une étroite région, appelée transition de phase, qui marque la transition entre les problèmes presque surement satisfiables, et les problèmes presque surement insatisfiables. Pour étudier la complexité et la faisabilité de la Programmation Logique Inductive (PLI), nous avons généré quelques centaines de problèmes d’apprentissage, situés dans et hors de la transition de phase; ces problèmes ont été soumis à FOIL, SMART+ et G-Net. Ces expérimentations systématiques établissent deux résultats. Tout d’abord, la transition de phase constitue un attracteur pour l’apprentissage, dans le sens où toutes les hypothèses produites appartiennent à cette région. En second lieu, une "zone aveugle de l’apprentissage" apparaît: pour tout problème situé dans cette zone, les systèmes de PLI considérés échouent tous à apprendre quelque hypothèse pertinente que ce soit. Ces résultats sont interprétés, et la discussion conduit à remettre en cause les biais usuels de la PLI.
• Self-consistent estimates for nonlinear viscoelastic polycrystals: a simplified resolution of the affine formulation adapted to monotonic loading paths
  
  • Brenner Rénald
  • Castelnau Olivier
  • Masson Renaud
  • Bacroix Brigitte
  • Zaoui André
  , 2000, 177-180, pp.153-158. A simplified resolution of the self-consistent model for non-linear viscoelastic polycrystals is presented. The formulation is based on an affine linearization of the constitutive relations as recently proposed by Masson and Zaoui [4], which adapts Hill's conception of self-consistent modelling to nonlinear viscoelastic behaviours. The approximation of the inverse Laplace-Carson transform introduced here, which is believed to be well adapted to monotonic loading paths, makes the resolution of the whole self-consistent problem possible in the direct time space. This results in a largely simplified numerical algorithm. Comparisons with the predictions of a model treating accurately the inverse Laplace-Carson transform are presented, and very good results are obtained for creep of FCC and HCP polycrystals. (10.4028/www.scientific.net/KEM.177-180.153)
  DOI : 10.4028/www.scientific.net/KEM.177-180.153
• Approche multi-échelle en fatigue polycyclique anisotherme
  
  • Maitournam Habibou
  • Nguyen-Tajan Thi Mac-Lan
  Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2000, 328 (5), pp.373-379. Une extension de l'approche macro-méso développée par Dang Van en fatigue isotherme à grand nombre de cycles est proposée dans le cas de structures subissant des chargements cycliques anisothermes et dont les limites de fatigue dépendent de la température. Elle est essentiellement fondée sur l'hypothèse d'adaptation aux échelles macroscopique et mésoscopique. L'utilisation d'une condition locale d'adaptation écrite dans le cas anisotherme conduit à une nouvelle formulation des critères de fatigue. (10.1016/S1620-7742(00)00049-0)
  DOI : 10.1016/S1620-7742(00)00049-0
• Intelligent numerical simulations in engineering problems
  
  • Zarka J.
  , 2000.
• An elasto-plastic modelling for lamellar crystalline materials
  
  • Gélébart L.
  • Bretheau T.
  • Crépin Jérôme
  • Bornert Michel
  , 2000. No abstract provided
• Thermodynamical description of moving discontinuities : applications to fracture and wear
  
  • Stolz C.
  , 2000. No abstract provided
• Simulation of hard particle impact on a TI-6Al-4V substrate coated by a tungsten film
  
  • Graff G.
  • Stolz C.
  • Pradeilles Duval R. M.
  • Sainte Catherine M.-C.
  , 2000. No abstract provided
• Influence of thickness on crystallographic and mechanical properties of PVD tungsten coatings
  
  • Ganne T.
  • Crépin Jérôme
  • Zaoui A.
  • Pradeilles-Duval R. M.
  , 2000, pp.413-418. No abstract provided
• Standard dissipative systems and stability analysis
  
  • Nguyen Quoc Son
  , 2000, pp.343-354. Stability and bifurcation analyses are discussed here for time-independent standard dissipative systems of materials and structures. This discussion is illustrated by some simple applications in plasticity and fracture mechanics. (10.1007/0-306-46946-4_26)
  DOI : 10.1007/0-306-46946-4_26
• Mathematical Aspects of Boundary Element Methods
  
  • Bonnet Marc
  , 2000. (10.1201/9780429332449)
  DOI : 10.1201/9780429332449