Publications

2003

• Constitutive modelling in plasticity
  
  • Stolz Claude
  , 2003.
• Evaluation non destructive de la performance mécanique du cuir
  
  • Luong Minh-Phong
  , 2003. Cette communication propose l'utilisation de la thermographie infrarouge pour évaluer la performance mécanique du cuir, appelée limite d'endommagement acceptable LEA du matériau cuir, facilement obtenue à partir des essais mécaniques couplés avec une scrutation infrarouge non contact, non destructive et en temps réel.
• Principes variationnels et exploitation de mesures de champs en élasticité
  
  • Bonnet Marc
  • Bui Huy Duong
  • Constantinescu Andrei
  Mechanics & Industry, EDP Sciences, 2003, 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
• Structure and morphology of [icosahedral Al62Cu25.5Fe12.5]100−x[decagonal Al70Co15Ni15]x alloys, for (0∼3 and 5∼10)
  
  • Lei Yi
  • Calvo-Dahlborg M.
  • Dubois J.M
  • Hei Z
  • Weisbecker P.
  • Dong C.
  Journal of Non-Crystalline Solids, Elsevier, 2003, 330 (1-3), pp.39-49. (10.1016/j.jnoncrysol.2003.08.059)
  DOI : 10.1016/j.jnoncrysol.2003.08.059
• Étude micro-mécanique de l'effet de la présence d'amas d'inclusions sur la transition fragile-ductile d'aciers nucléaires.
  
  • Bilger Nicolas
  , 2003. Résumé non disponible
• Cavity identification using 3-D elastodynamic BEM, shape sensitivity and topological derivative
  
  • Bonnet Marc
  • Guzina Bojan B
  • Nintcheu Fata Sylvain
  , 2003, pp.205-212. The problem of mapping underground cavities from surface, i.e. using non-intrusive seismic measurements, is investigated via a regularized boundary integral equation method. With the ground modeled as a three-dimensional uniform, isotropic elastic half-space, the inverse analysis of seismic waves scattered by a three-dimensional void is formulated as a task of minimizing a cost function involving the misfit between experimental observations and theoretical (i.e forward) predictions. This conventional choice of setting is dictated by the very high computational cost of solving the forward elastodynamic scattering problem, which makes e.g. global search strategies infeasible. For an accurate treatment of the gradient search technique employed to solve the inverse problem, derivatives of the predictive boundary element model with respect to the cavity parameters are evaluated using an adjoint problem approach. Here as in most situations where conventional descent methods (here the quasi-Newton algorithm with BFGS formula) are used, results depend on the choice of initial guess and occasional lack of convergence occurs. This has prompted the authors to investigate the use of topological derivative as a tool for preliminary probing. The topological derivative field is computed via a relatively inexpensive procedure, and appears to yield useful indications as to the topology and approximate location of the cavity system. Numerical examples are included to illustrate the effectiveness of the various steps developed so far. (10.1142/9789812702593_0022)
  DOI : 10.1142/9789812702593_0022
• Détermination de la réponse asymptotique d'une structure anélastique soumise à un chargement thermomécanique cyclique.
  
  • Pommier Benjamin
  , 2003. Dans le cadre du dimensionnement à la fatigue thermomécanique des culasses automobiles, nous proposons une méthode de simulation des structures soumises à des chargements cycliques. Cette méthode, alternative aux méthodes classiques (comme la méthode incrémentale) permet de résoudre des 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 les techniques de grand incrément de temps [Ladevèze et al.], en prenant en compte la périodicité de l'état limite [Nguyen et al.] et la transformation de Fourier. Cette méthode permet des gains de temps importants pour les structures comprenant un grand nombre de degrés de liberté. Un développement de cette méthode dans une version commerciale d'Abaqus, a permis de montrer la faisabilité de cette approche dans le cas de la simulation d'une culasse.
• A discussion of sensitivity analysis for the identification of poroelastic material parameters
  
  • Constantinescu Andrei
  • Lecampion Brice
  , 2003.
• Modelling attemps to predict fretting fatigue life in turbine components
  
  • Arrieta Hernan
  • Wackers Patrick
  • Van Ky Dang
  • Maitournam Habibou
  • Constantinescu Andrei
  , 2004. Wherever two or more turbine components are in tight contact, Fretting-Fatigue becomes a relevant failure mechanism. Despite of on-going research on Fretting Fatigue, life prediction under fretting conditions continues being a challenge. To analytically predict fretting-fatigue life, key driving factors need to be identified and quantified in mechanical terms (stress and strain). Due to the intrinsic characteristics of contact, stress and strain fields around contact areas evolve with the loading history. They, together with material non-linearity and contact conditions need to be taken into account in order to perform a reliable life prediction. The present paper focuses on identifying the driving factors for fretting damage on blade-disk attachment under real engine conditions. Two-dimensional finite element contact calculations were carried out to quantify the influence of the key factors on mechanical quantities (stress and strain). Special attention was paid to material models and surface interaction (friction coefficient and contact conditions) in order to balance computational effort with result’s accuracy. Finally, the multi-axial fatigue criteria developed by Dang Van and co-workers is used to predict failure. For validation purposes life prediction is compared with experimental results.
• Modèles standards généralisés à convexe fixe en endommagement
  
  • Cimetière Alain
  • Halm Damien
  • Marigo Jean-Jacques
  • Molines Estelle
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2003, 331 (4), pp.291-294. Un cadre thermodynamique d'écriture de modèles d'endommagement est introduit. Obtenu par l'adjonction de variables internes complémentaires, il s'inscrit dans celui des matériaux standards généralisés pour lesquels le domaine convexe des forces thermodynamiques admissibles est indépendant des variables internes. Il en présente ainsi les avantages. Le modèle de Marigo est replacé dans ce cadre et un autre exemple est donné combinant à la fois écrouissage isotrope et cinématique. (10.1016/S1631-0721(03)00057-3)
  DOI : 10.1016/S1631-0721(03)00057-3
• Peierls-Nabarro landscape for martensitic phase transitions
  
  • Truskinowsky Lev
  • Vainchtein Anna
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2003, 67 (17). We consider a prototypical model of a martensitic phase transition, which takes discreteness and nonlocality into account and allows one to reconstruct explicitly the Peierls-Nabarro energy landscape for the phase boundaries. We solve the discrete problem exactly and obtain a simple expression for the critical Peierls force that is necessary to release a lattice-trapped phase boundary. The model suggests specific relations between the microscopic parameters of the lattice and the size of the hysteresis in martensitic materials, which we verify for the cubic-$β'_1$-monoclinic phase transition in Cu-Al-Ni alloy. (10.1103/physrevb.67.172103)
  DOI : 10.1103/physrevb.67.172103
• The treatment of 'pinching locking' in 3D-shell elements
  
  • Chapelle Dominique
  • Ferent Anca
  • Le Tallec Patrick
  ESAIM: Mathematical Modelling and Numerical Analysis, Société de Mathématiques Appliquées et Industrielles (SMAI) / EDP, 2003, 37 (1), pp.143-158. We consider a family of shell finite elements with quadratic displacements across the thickness. These elements are very attractive, but compared to standard general shell elements they face another source of numerical locking in addition to shear and membrane locking. This additional locking phenomenon - that we call ''pinching locking'' - is the subject of this paper and we analyse a numerical strategy designed to overcome this difficulty. Using a model problem in which only this specific source of locking is present, we are able to obtain error estimates independent of the thickness parameter, which shows that pinching locking is effectively treated. This is also confirmed by some numerical experiments of which we give an account. (10.1051/m2an:2003015)
  DOI : 10.1051/m2an:2003015
• Etude micromécanique de la disparition du seuil de fissuration par fatigue dans un alliage de titane biphasé à fort K_max
  
  • Mignot Frédéric
  • Doquet Véronique
  • Sarrazin-Baudoux Christine
  • Petit Jean
  Journal de Physique IV Proceedings, EDP Sciences, 2003, 106, pp.33-42. L'alliage Ti6246 présente, lors d'essais de fissuration par fatigue à K_max constant et ΔK décroissant un comportement atypique : lorsque K_max> 0.7K_IC, on observe, sous air comme sous vide, au lieu du seuil attendu, un régime de propagation à vitesse constante, dix fois plus élevée à l'ambiante qu'à 500°C. Le fluage, qui se manifeste dès l'ambiante dans cet alliage semble jouer un rôle dans ce phénomène. Toutefois, des analyses par spectrométrie de masse d'ions secondaires font apparaître une sur-concentration en hydrogène au voisinage d'une fissure développée dans le régime anormal. Des essais de fissuration, traction et fluage sont donc entrepris sur le matériau brut, appauvri ou enrichi en hydrogène, pour partie dans la chambre d'un microscope électronique à balayage, dans le but d'explorer ce phénomène. On constate qu'un enrichissement en hydrogène augmente la ductilité du matériau et sa tendance au fluage à l'ambiante et un enrichissement plus prononcé la diminue. (10.1051/jp4:20030213)
  DOI : 10.1051/jp4:20030213
• Crystallographic fatigue crack growth in a polycrystal: simulations based on FEM and discrete dislocation dynamics
  
  • Bertolino Graciela
  • Doquet Véronique
  • Sauzay Maxime
  , 2003. An attempt to model the variability of short cracks development in high-cycle fatigue is made by coupling finite element calculations of the stresses ahead of a microcrack in a polycrystal with simulations of crack growth along slip planes based on discrete dislocations dynamics. The model predicts a large scatter in growth rates related to the roughness of the crack path. It also describes the influence of the mean grain size and the fact that overloads may suppress the endurance limit by allowing arrested cracks to cross the grain boundaries.
• A “Numerical Mesoscope” for the Investigation of Local Fields in Rate-Dependent Elastoplastic Materials at Finite Strain
  
  • Haddadi Halim
  • Teodosiu Cristian
  • Héraud S.
  • Allais L.
  • Zaoui André
  , 2001, 108, pp.311-320. We propose a “numerical mesoscope” which could be used for the analysis of the local mechanical fields over small critical areas of microheterogeneous materials, in order to predict the local initiation of specific deformation or damage mechanisms. The subdomain under investigation is embedded in a very large homogeneous matrix obeying the overall behavior of the studied material, as determined experimentally. This matrix is subjected to homogeneous stress or strain boundary conditions and the homogeneous elements of the subdomain and their interfaces are given their known or assumed constitutive behavior. A finite element analysis is then performed on the whole body by making use of different constitutive equations within the subdomain and in the surrounding matrix. The general methodology of this approach is reported and applied to a metallic rate-dependent elastoplastic polycrystal and to microheterogeneous subdomains consisting of given multicrystalline patterns whose grains obey crystalline elastoplastic constitutive equations of Schmid type at finite strain. Application to the intergranular creep damage of a stainless steel shows a good agreement between the largest computed normal stresses on the grain boundaries and the observed debonded boundaries of the actual material. (10.1007/978-94-017-0297-3_28)
  DOI : 10.1007/978-94-017-0297-3_28
• Testing with SHPB from quasi-static to dynamic strain rates
  
  • Othman Ramzi
  • Bussac Marie-Noëlle
  • Collet Pierre
  • Gary Gérard
  , 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
• Remarques sur les contraintes résiduelles
  
  • Bérest Pierre
  • Vouille Gérard
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2003, 331 (6), pp.455-460. Les contraintes résiduelles observées dans les solides peuvent résulter de déformations initiales non compatibles. Elles sont alors déterminées, en général, par le tenseur d'incompatibilité du tenseur des déformations initiales. Toutefois, réciproquement, la nullité du tenseur d'incompatibilité ne suffit pas pour conclure à l'absence de contraintes résiduelles, dans le cas où le solide est non simplement connexe, ou présente des surfaces de discontinuité. Plusieurs exemples sont présentés. (10.1016/S1631-0721(03)00090-1)
  DOI : 10.1016/S1631-0721(03)00090-1
• Prise en compte de la rugosité dans le prévision de la tenue en fatigue des roulements
  
  • Thoquenne Guillaume
  • Lubrecht Ton
  • Dang Van Ky
  • Maitournam Habibou
  • Peyrac Catherine
  • Lieurade Henri-Paul
  , 2003.
• Linear stability analysis in fluid-structure interaction with transpiration. Part I: Formulation and mathematical analysis
  
  • Fernández Miguel Angel
  • Le Tallec Patrick
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2003, 192 (43), pp.4805-4835,. The aim of this work is to provide a new Linearization Principle approach particularly suited for problems in fluid-structure stability. The complexity here, and the main difference with respect to the classical approach, comes from the fact that the full non-linear fluid equations are written in a moving (i.e. time dependent) domain. The underlying idea of our approach uses transpiration techniques [J. Fluid Mech. 4 (1958) 383 ; G. Mortchéléwicz, Application of linearized Euler equations to flutter, in : 85th AGARD SMP Meeting, Aalborg, Denmark, 1997 ; P. Raj, B. Harris, Using surface transpiration with an Euler method for cost-effective aerodynamic analysis, in : AIAA 24th Applied Aerodynamics Conference, number 93-3506, Monterey, Canada, 1993 ; AIAA 27(6) (1989) 777], with the formalization and linearization recently developed in [Rév. Européenne Élém. Finis, 9(6-7) (2000) 681, A. Dervieux (Ed.), Fluid-Structure Interaction, Kogan Page Science, London, 2003 (Chapter 3)]. This allows us to obtain a new grid independent coupled spectral problem involving the linearized Navier-Stokes equations and those of a reduced linear structure. The coupling is realized through specific transpiration conditions acting on a fixed interface, while keeping a fixed fluid domain. We provide a rigorous mathematical treatment of this eigenproblem. We prove that the corresponding eigenmodes, characterizing the free evolution of the system, can be obtained from the characteristic values of a compact operator acting on a Hilbert space. Moreover, we localize the eigenfrequencies of the system in a parabolic region of the complex plan centered along the positive real axis. (10.1016/j.cma.2003.07.001)
  DOI : 10.1016/j.cma.2003.07.001
• A computational basis for elastodynamic cavity identification in a semi-infinite solid
  
  • Nintcheu Fata Sylvain
  • Guzina Bojan B
  • Bonnet Marc
  Computational Mechanics, Springer Verlag, 2003, 32, pp.370-380. The focus of this paper is a computational platform for the non-intrusive, active seismic imaging of subterranean openings by means of an elastodynamic boundary integral equation (BIE) method. On simulating the ground response to steady-state seismic excitation as that of a uniform, semi-infinite elastic solid, solution to the 3D inverse scattering problem is contrived as a task of minimizing the misfit between experimental observations and BIE predictions of the surface ground motion. The forward elastodynamic solution revolves around the use of the half-space Greenrsquos functions, which analytically incorporate the traction-free boundary condition at the ground surface and thus allow the discretization and imaging effort to be focused on the surface of a hidden cavity. For a rigorous approach to the gradient-based minimization employed to resolve the cavity, sensitivities of the trial boundary element model with respect to (geometric) void parameters are evaluated using an adjoint field approach. Details of the computational treatment, including the regularized (i.e. Cauchy principal value-free) boundary integral equations for the primary and adjoint problem, the necessary evaluation of surface displacement gradients and their implementation into a parallel code, are highlighted. Through a suite of numerical examples involving the identification of an ellipsoidal cavity, a parametric study is presented which illustrates the importance of several key parameters on the imaging procedure including the prior information, ldquomeasurementrdquo noise, and the amount of experimental input. (10.1007/s00466-003-0494-4)
  DOI : 10.1007/s00466-003-0494-4
• Stability and bifurcation with moving discontinuities
  
  • Stolz Claude
  • Pradeilles-Duval Rachel-Marie
  , 2003, pp.261-268. The propagation of moving surface inside a body is analysed in the framework of thermodynamics, when the moving surface is associated with an irreversible change of mechanical properties. The thermodynamical force associated to the propagation has the form of an energy release rate. Quasistatic rate boundary value problem is given when the propagation of the interface is governed by a normality rule. Extension to generalised media to study delamination is also investigated. (10.1007/0-387-26261-X_26)
  DOI : 10.1007/0-387-26261-X_26
• Modélisation du comportement dynamique d'une courroie de distribution
  
  • Bourgeois M.
  • Thomas J.-J.
  • Stolz Claude
  , 2003, pp.189-196 (tome 2). No abstract provided
• Méthode numérique pour l'identification de cavités enterrées à l'aide de données élastodynamiques
  
  • Bonnet Marc
  • Guzina Bojan B
  • Nintcheu Fata Sylvain
  , 2003, 1, pp.209-216.
• Investigation of hydrogen and creep contributions to the abnormal fatigue cracking of Ti6246 at high Kmax
  
  • Mignot Frédéric
  • Doquet Véronique
  • Sarrazin-Baudoux Christine
  • Petit Jean
  • Raimbault Louis
  , 2003.
• Activation of diffuse discontinuities and folding of sedimentary layers
  
  • Guiton Martin
  • Leroy Yves
  • Sassi William
  Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2003, 108 (B4), pp.1-20. Folding of sedimentary layers is often accommodated by the opening or sliding of inherited and new discontinuities which are assumed here to be diffuse so that a continuum description applies at the fold scale. The rock rheology is then described with an elastoplasticity model for which the permanent deformation is of simple shear (sliding) or dilation (opening) with respect to specific orientations of the new or inherited diffuse discontinuities. To illustrate the relation between folding and activation of diffuse discontinuities, a three-dimensional layer under compression in the two horizontal directions and sustaining the overburden lithostatic pressure is studied. Cylindrical buckling occurs either before (elastic) or after the diffuse discontinuities have been activated. If buckling is elastic, inherited vertical discontinuities, striking obliquely to the fold geometrical axes, are activated in a sliding mode in the outer arc, leading to a rotation of the principal stress directions. Opening is then detected across new vertical planes striking obliquely to the fold axis. The activation of inherited or new vertical discontinuities can be suppressed if sliding takes place along weak bedding interfaces. Alternatively, early and homogeneous layer-parallel shortening, marked by a reverse fault mode, drastically reduces the critical buckling load compared to the Euler load and modifies the final geometry of buckling which is then more of a circular dome shape. The switching in buckling mode results in the fold limbs in a change from the early reverse fault to a strike-slip fault sliding and to opening across diffuse planes oriented consistently with the final circular structure. (10.1029/2002JB001770)
  DOI : 10.1029/2002JB001770