Publications

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
• On some recent trends in modelling of contact fatigue and wear in rail
  
  • Dang Van Ky
  • Maitournam Habibou
  Wear, Elsevier, 2002, 253, pp.219-227. Specific numerical methods for the computational analysis of damage induced in rail by repeated rolling are presented. The calculations of mechanical stabilized states (shakedown, ratchetting) of rail-like structures subjected to moving contact loads are performed using the “stationary methods”. An association of 2-D finite element method, Fourier expansion in the longitudinal direction of the rail and steady-state assumption reduces the computational cost of such procedures. These methods constitute the key for the quantitative prediction of fatigue. Three types of damage (low-, high-cycle fatigue and damage) are encountered. Special attention to high-cycle fatigue is paid, through the use of Dang Van multi-axial fatigue criterion. The 3-D simulations of rolling contact and investigation of rail high-cycle fatigue illustrate the applicability of the methodology. (10.1016/S0043-1648(02)00104-7)
  DOI : 10.1016/S0043-1648(02)00104-7
• Formulation and Well-Posedness of Unilateral Multibody Dynamics
  
  • Ballard Patrick
  , 2002, 103, pp.25-32. The classical theory of rigid bodies systems undergoing perfect bilateral constraints has received firm mathematical foundations for a long time. We extend it to the case where there are perfect unilateral constraints also. The formulation follows the line initiated by Schatzman (1978) and Moreau (1983). We give a parametrization-free formulation and try to identify the most general form of impact constitutive equation which is compatible with well-posedness. Then, well-posedness is proved under the assumption of analyticity of the data, since it is known, thanks to Bressan (1960) and Schatzman (1978), that uniqueness does not hold in the C∞ setting. (10.1007/978-94-017-1154-8_3)
  DOI : 10.1007/978-94-017-1154-8_3
• An integral formulation for steady-state elastoplastic contact over a coated half-plane.
  
  • Dong C.
  • Bonnet Marc
  Computational Mechanics, Springer Verlag, 2002, 28, pp.105-121. A boundary-domain integral equation for a coated half-space (elastically isotropic homogeneous substratum, possibly anisotropic coating layer) is developed. The half-space fundamental solution is used, so that the discretization is limited to the potential contact zone (boundary elements), the potentially plastic part of the substratum and the coating layer (domain integration cells). Steady-state elastoplastic analysis is implemented within this framework, for plane-strain conditions, for solving rolling and/or sliding contact problems, where at the moment the contact load comes from either a purely elastic contact analysis or is of Hertz type. The constitutive integration is of implicit type. In order to improve accuracy and computational efficiency, infinite elements are used. Comparison of numerical results with other sources, when available, is satisfactory. The present formulation is also used to compute the contact pressure for an isotropic (or anisotropic) coating on an isotropic homogeneous half-space indented by an elastic punch. (10.1007/s00466-001-0274-y)
  DOI : 10.1007/s00466-001-0274-y
• New bounds and estimates for porous media with rigid perfectly plastic matrix
  
  • Bilger Nicolas
  • Auslender François
  • Bornert Michel
  • Masson Renaud
  Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2002, 330, pp.127-132. We derive new rigorous bounds and self-consistent estimates for the effective yield surface of porous media with a rigid perfectly plastic matrix and a microstructure similar to Hashin's composite spheres assemblage. These results arise from a homogenisation technique that combines a pattern-based modelling for linear composite materials and a variational formulation for nonlinear media. (10.1016/S1631-0721(02)01438-9)
  DOI : 10.1016/S1631-0721(02)01438-9
• Application du contrôle optimal à l'identification d'un chargement thermique
  
  • Delattre Benoît
  • Ivaldi Damien
  • Stolz Claude
  Revue Européenne des Éléments Finis, HERMÈS / LAVOISIER, 2002, 11, pp.393-404. La détermination du champ de température sur certaines pièces d'un moteur est obtenue par la résolution d'un problème inverse. Une alternative aux méthodes expérimentales coûteuses utilisées aujourd'hui est la méthode du contrôle optimal qui permet d'estimer le champ de température à partir de quantités mesurées sur pièce. Différents tests préfigurent des possibilités de prédiction et de fiabilité de la méthode. (10.3166/reef.11.393-404)
  DOI : 10.3166/reef.11.393-404
• Infrared observation of thermomechanical couplings in solids
  
  • Luong M. P.
  , 2002, pp.492-506. No abstract provided
• Effet de la répartition hétérogène en amas des particules de MnS sur la rupture fragile et ductile des aciers de cuve
  
  • Bilger N.
  • Bornert Michel
  • Auslender F.
  • Masson Renaud
  • Michel J. C.
  • Moulinec H.
  • Suquet P.
  • Zaoui Z.
  , 2002. No abstract provided
• Direct evaluation of double hypersingular integrals and new free terms in 2D symmetric Galerkin BEM
  
  • Bonnet Marc
  • Guiggiani Massimo
  , 2002. In this paper a new general algorithm is developed for the direct evaluation of all singular double integrals arising in the 2D Galerkin BEM, including those with hypersingular kernels. A distinguishing feature of the proposed method is that double singular integrals are treated as a whole, that is, not as inner integrals followed by outer ones. Therefore, when applied to the symmetric Galerkin BEM, the proposed technique is strictly symmetry preserving. Moreover, a careful analysis of the limiting process is performed which shows that some new free terms may arise. (10.1016/S0045-7825(03)00286-X)
  DOI : 10.1016/S0045-7825(03)00286-X
• BEM and shape sensitivity techniques in defect identification problems
  
  • Bonnet Marc
  , 2002.
• Pattern-based modelling of composite materials; principles, applications and limitations
  
  • Bornert Michel
  , 2002. No abstract provided
• Behaviour characterization of polymeric foams over a large range of strain rates
  
  • Zhao Han
  • Gary Gérard
  International Journal of Vehicle Design, Inderscience, 2002, 30, pp.135-145. The testing and modelling of the mechanical behaviour of some polymeric foams involved in the automotive industry are presented. A variety of current experimental arrangements over a large range of strain rates have been reviewed. Recent improvements of a particularly useful technique for impact loading–the split Hopkinson bar–are presented. A phenomenological model is developed to describe experimental data. Difficulties for 3-dimensional testing and modelling are also discussed. (10.1504/IJVD.2002.002028)
  DOI : 10.1504/IJVD.2002.002028
• An optimisation method for separating and rebuilding one-dimensional dispersive waves from multi-point measurements
  
  • Bussac Marie-Noël
  • Collet Pierre
  • Gary Gérard
  • Othman Ramzi
  Journal of the Mechanics and Physics of Solids, Elsevier, 2002, 50 (2), pp.321-349. When using a classical SHPB (split Hopkinson pressure bar) set-up, the useful measuring time is limited by the length of the bars, so that the maximum strain which can be measured in material testing applications is also limited. In this paper, a new method with no time limits is presented for measuring the force and displacement at any station on a bar from strain or velocity measurements performed at various places on the bar. The method takes the wave dispersion into account, as must inevitably be done when making long time measurements. It can be applied to one-dimensional and single-mode waves of all kinds propagating through a medium (flexural waves in beams, acoustic waves in wave guides, etc.). With bars of usual sizes, the measuring time can be up to 50 times longer than the time available with classical methods. An analysis of the sensitivity of the results to the accuracy of the experimental data and to the quality of the wave propagation modelling was also carried out. Experimental results are given which show the efficiency of the method. (10.1016/S0022-5096(01)00057-6)
  DOI : 10.1016/S0022-5096(01)00057-6
• Principes variationnels et exploitation de mesures de champs en élasticité
  
  • Bonnet Marc
  • Bui Hui Duong
  • Constantinescu Andrei
  , 2002, 4 (6), pp.687-697. Il est parfois nécessaire d'identifier certaines grandeurs ou certains paramètres caractérisant des structures ou des matériaux. Cela passe dans tous les cas par l'exploitation de données expérimentales, et les mesures de champs, par la richesse des informations fournies, sont particulièrement bien adaptées à ces objectifs. Cet article a pour objet de présenter certaines techniques d'inversion particulièrement adaptées à l'exploitation de mesures de champs. L'identification de champs de modules élastiques est choisie comme un problème modèle commode pour l'exposition, mais d'autres problèmes d'identification peuvent être abordés dans le même esprit. On s'efforce en particulier de montrer que l'identification par exploitation de mesures de champs ne doit pas nécessairement se faire par la minimisation de critères de type moindres carrés sur les observations, car le fait de disposer de champs mesurés permet de définir d'autres critères, d'une part adaptés à ce type de données et d'autre part obtenus comme conséquences directes des principes variationnels de l'élasticité. Les critères considérés ici sont principalement l'erreur en relation de comportement et l'écart à la réciprocité. Divers exemples d'illustration, de nature purement numérique pour la plupart, sont présentés. (10.1016/j.mecind.2003.09.011)
  DOI : 10.1016/j.mecind.2003.09.011
• Micromechanical study of abnormal fatigue cracking of Ti6246 at high Kmax
  
  • Mignot F.
  • Doquet V.
  • Baudoux C.
  • Petit J.
  , 2002, pp.1773-1780. During cyclic tests performed with a constant Kmax and increasing Kmjn on a α/β titanium alloy, if Kmax is higher than 60-70% of Klc the crack growth rate does not drop, as normally expected, but reaches an asymptotic value. Solute hydrogen is shown to segregate at the crack tip when the cyclic plastic zone vanishes and to enhance room temperature creep, strain localisation and decohesion along α/β interfaces. (10.1515/JMBM.2005.16.3.195)
  DOI : 10.1515/JMBM.2005.16.3.195
• Transition vers une onde glissement-adhérence-décollement sous contact frottant de Coulomb
  
  • Oueslati A.
  • Baillet L.
  • Nguyen Q. S.
  , 2002, pp.155-162. No abstract provided
• Analysis of the numerical instabilities in the hydrocodes when using an elasto­viscoplastic behaviour
  
  • Mouro P.
  • Gary G.
  , 2002. No abstract provided
• Optimal reliability of metallic structures during variable amplitude loadings
  
  • Zarka Joseph
  • Karaouni Habib
  , 2002.
• The use of inverse methodologies in geotechnical problems
  
  • Tavares de Castro António
  • Lenao N. S.
  • Ribeiro E Sousa Luís
  • Desheng Defeng
  • Nguyen-Minh D.
  ISRM News journal, 2002, 7, pp.24-32. Back analysis problems, also known as inverse problems or characterization problems, can be formulated as parameter estimation problems, by which means two basic types of problems can be solved: i) Determination of external loads from the structural properties and from observed response, sometimes called inverse problems of the first kind; ii) Determination of structural properties parameters as a function of the external loads and observed responses, sometimes called inverse problems of the second kind. The structural properties are defined by the geometry of the structure and by the properties and zoning of the different constituent materials. The observed effects (displacements, unit strains, stresses, etc.) represent the structural response. The former type of problems corresponds to the determination of the actions on basis of structural properties and of observed effects, whereas the latter refer to the deter­ mination of the characteristics parameters of the structural properties on basis of actions and corresponding observed effects. Back analysis problems can be solved in two ways, which Cividini calls direct approach and inverse approach (Cividini et al., 1981). The direct approach uses the same numerical solutions as the direct analysis, determining the val­ ues of the parameters in accordance to some identi­fication criteria, corresponding, for instance, to the least square, Markov or maximum likelihood meth­ ods (Eykhoff, 1974). The inverse approach requires a reformulation of the problem equations in such a form that the observed effects correspond to known quantities whereas the parameters to be identified appear as unknown. Direct approach methodologies allow the identi­fication of model parameters related with actions or with structural properties (in particular, with mater­ ial properties), which includes the combined use of a numerical model and of an adequate minimiza­tion method. This approach is less sensitive to the quality of the observed values and to the degree of approximation of the numerical model. An impor­tant feature of these methodologies is the separate use of the numerical model and of the minimiza­tion method, which allow the use of complex mod­ els developed in commercial programs (without access to its code). Inverse approach methodologies allow, in princi­ple, faster convergence taxes than direct approach methodologies. Nevertheless, these methodologies are more sensitive to the quality and to the quanti­y of the observed effects and require numerical models that can reproduce approximately the observed response. Usually, the resolution of specif­ ie problems requires the development of specific codes since it is difficult or even impossible to adapt commercial programs to this purpose. In the next paragraphs three different back analysis approaches will be presented.
• Utilisation de symétries géométriques totales ou partielles dans la méthode variationnelle des éléments de frontière
  
  • Bonnet Marc
  , 2002.
• Thermal and thermoelastic behaviour of multiply coated inclusion-reinforced composites
  
  • Hervé E.
  International Journal of Solids and Structures, Elsevier, 2002, 39, pp.1041-1058. This work is devoted first to the derivation of the temperature field in an infinite medium constituted of an n-layered isotropic spherical inclusion, embedded in a matrix subjected to a uniform temperature gradient at infinity, under assumptions of no coupling between mechanical and thermal effects and of steady state conditions. These results lead to an estimate of the effective thermal conductivity coefficient of an n-layered inclusion-reinforced material. The second objective of this work is the derivation of the thermoelastic stress and strain fields in the same basic configuration but now, a coupling between stress and thermal properties is considered and the infinite matrix is stress free and subjected to a uniform change of temperature. These results and the solution of the same problem with a hydrostatic loading are used to estimate the effective thermal expansion coefficient and the specific heats for heterogeneous inclusion-reinforced materials. (10.1016/S0020-7683(01)00257-8)
  DOI : 10.1016/S0020-7683(01)00257-8
• Matériaux pour le bâtiment et le génie civil
  
  • Boch Philippe
  • Halphen Bernard
  L'Actualité Chimique, Société chimique de France (SCF), 2002, pp.29-31. Les matériaux pour le bâtiment et le génie civil constituent l’exemple extrême des « matériaux de grande diffusion » : tonnages énormes (exprimés en milliards de tonnes, à l’échelle mondiale) et prix moyens très bas (la tonne de ciment vaut moins que quelques grammes de semiconducteur !) mais, et ce n’est pas le moindre paradoxe, performances remarquables et sans cesse améliorées... Un matériau est un « solide utile », qui revendique cette utilité, et dont la conception, la réalisation, et la mise en oeuvre, ne peuvent s’imaginer autrement que par référence à l’application escomptée. Or, l’application entrelace les exigences sur le matériau et celles sur le design (terme pris au sens le plus large), avec de permanents aller-retour : tantôt c’est l’amélioration du matériau qui permet une avancée sur le design, et tantôt c’est l’idée d’un nouveau design qui exige la mise au point d’un nouveau matériau. Parmi les ouvrages d’art, les ponts constituent sans doute l’illustration la plus spectaculaire de cette fructueuse coopération entre concepteurs et autres mécaniciens d’une part, technologues et autres physico-chimistes des matériaux d’autre part.
• A new spectral problem in fluid-structure interaction with transpiration
  
  • Fernández Miguel Angel
  • Le Tallec Patrick
  Comptes Rendus. Mathématique, Académie des sciences (Paris), 2002, 334 (2), pp.167-172. The aim of this Note is to provide a rigorous mathematical treatment of a new spectral problem, coming from a linear stability analysis in fluid-structure interaction. This eigenproblem involves the linearized incompressible Navier-Stokes equations coupled with those of a reduced structure, by means of specific transpiration boundary conditions. We prove that the eigensolutions of this spectral problem can be obtained from the characteristic values of a compact operator acting on a Hilbert space. (10.1016/S1631-073X(02)02236-7)
  DOI : 10.1016/S1631-073X(02)02236-7