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
• Identification du chargement thermique transitoire par contrôle optimal
  
  • Constantinescu Andrei
  • Ivaldi Damien
  • Stolz Claude
  , 2003, 1, pp.185-192.
• État thermodynamique d'un solide après passage d'une onde de choc
  
  • Stolz Claude
  • Dequiedt Jean-Lin
  , 2003.
• In situ field measurements
  
  • Bornert Michel
  , 2003.
• Dissipation and Fatigue Damage
  
  • Charkaluk Eric
  • Constantinescu Andrei
  , 2003, 46 (10), pp.524-530. The discussion of fatigue damage is generally separated in two domains: Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF). The transition zone concerns the case of limited endurance, while the unlimited endurance is generally assimilated with HCF. Fatigue failure is the result of complex microscopic phenomena which occur under cyclic loading. However, the principal mechanism responsible for the crack initiation, common to all domains, is the spatial extension of inelastic strains (plastic or viscous) in the grains due to the motion of dislocations. The major difference between HCF and LCF regimes is that inelastic strains develop at the material's mesoscopic and macroscopic scales, respectively. As the underlying mechanics are the same, there should be no reason to have distinct criteria in HCF and LCF. The objective of this paper is to give some further considerations based on dissipation towards a unified method to treat fatigue damage. (10.3139/120.100615)
  DOI : 10.3139/120.100615
• Direct evaluation of double singular integrals and new free terms in 2D (symmetric) Galerkin BEM
  
  • Bonnet Marc
  • Guiggiani Massimo
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2003, 192, pp.2565-2596. 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
• Underground cavity detection based on an elastodynamic boundary element approach and the topological derivative
  
  • Bonnet Marc
  • Guzina B.
  • Nintcheu Fata S.
  , 2003, pp.582-587. No abstract provided
• IABEM 2002
  
  • Kinnas S.
  • Bonnet Marc
  , 2003.
• An optimal approach to the analysis of inelastic structures under cyclic loading
  
  • Peigney Michaël
  • Stolz Claude
  Journal of the Mechanics and Physics of Solids, Elsevier, 2003, 51, pp.575-605. Optimal control theory is used to study the asmptotic behaviour of elasto-viscoplastic structures under cyclic loading. With this approach, the asymptotic state is found as the solution of a minimization problem. General properties of this method are established. A simple thermomechanical problem is studied to illustrate and validate this approach. An interest of the proposed metho lies in its capacity to handle other nonlinearities than plasticity. To illustrate this point, the approach is extended to the couples viscoplasticity/frictionless contact problem. Some numerical results are given for an elasto-viscoplastic half-plane under cyclic frictionless indentation. (10.1016/s0022-5096(02)00104-7)
  DOI : 10.1016/s0022-5096(02)00104-7
• 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