Publications

2000

• A regularized BIE formulation for thermo-hydro-mechanical analysis of fractured rocks
  
  • Vahida B.
  • Bonnet Marc
  • Pouya A.
  , 2000. No abstract provided
• On global behaviour of heterogeneous media with mechanical transformation along moving surfaces
  
  • Pradeilles-Duval R. M.
  • Stolz C.
  , 2000. No abstract provided
• Intelligent optimal design of naval structures: is it possible?
  
  • Zarka Joseph
  , 2000.
• Tribological and corrosion behaviours of graphite and titanium alloys couple during ring-on-disk tests
  
  • Serre I.
  • Celati N.
  • Pradeilles Duval R. M.
  , 2000, pp.591-596. No abstract provided
• On the determination of elastic coefficients from indentation experiments
  
  • Tardieu Nicolas
  • Constantinescu Andrei
  Inverse Problems, IOP Publishing, 2000, 16, pp.577-588. The main result of this paper is the extension of the adjoint state method to variational inequalities. This is done for the Signorini contact problem (Kikuchi N and Oden J T 1988 Contact Problems in Elasticity: a Study of Variational Inequalities and Finite Element Methods (Philadelphia: SIAM)) and used for the identification of elastic coefficients from an indentation test. The result is obtained by two independent approaches based on the penalized and respectively, mixed formulations of the direct problem, a Signorini contact problem. An important and astonishing result is that the obtained adjoint problem is a linear problem with Dirichlet boundary conditions. This is expected for problems described with variational equalities (Bui H D 1993 Introduction Aux Problèmes Inverses en Mécanique des Matériaux (Paris: Eyrolles) (Engl. Transl. (Boca Raton, FL: CRC Press)), Lions J L 1968 Contrôle Optimal des Systèmes Gouvernés par des Équations aux Dérivées Partielles (Dunod)), but is a new result for problems described with variational inequalities. As an application, the elastic coefficients of an isotropic body have been identified from the knowledge of a displacement-force curve measured during an indentation test. The efficiency of the method is illustrated on numerical examples for the identification of a bimaterial and a functional gradient material. (10.1088/0266-5611/16/3/303)
  DOI : 10.1088/0266-5611/16/3/303
• Crack propagation from a pre-existing flaw at a notch root. II: Detailed form of the stress intensity factors at the initial crack tip and conclusion
  
  • Leblond Jean-Baptiste
  • Mouro Pierre
  International Journal of Fracture, Springer Verlag, 2000, 104, pp.225-239. This paper pursues the study of crack kinking from a pre-existing crack emanating from some notch root. It was shown in Part I that the stress intensity factors at the tip of the small initial crack are given by universal (that is, applicable in all situations, whatever the geometry of the body and the loading) formulae; they depend only on the `stress intensity factor of the notch' (the multiplicative coefficient of the singular stress field near the apex of the notch in the absence of the crack), the length of the crack, the aperture angle of the notch and the angle between its bisecting line and the direction of the crack. Here we identify the universal functions of the two angles just mentioned which appear in these formulae, by considering the model problem of an infinite body endowed with a notch with straight boundaries and a straight crack of unit length. The treatment uses Muskhelishvili's complex potentials formalism combined with some conformal mapping. The solution is expressed in the form of an infinite series involving an integral operator, which is evaluated numerically. Application of Goldstein and Salganik's principle of local symmetry then leads to prediction of the kink angle of the crack extension. It is found that although the direction of the crack is closer to that of the bisecting line of the notch after kinking than before it, the kink angle is not large enough for the crack tip to get closer to this line after kinking, except perhaps in some special situations. (10.1023/A:1007637416241)
  DOI : 10.1023/A:1007637416241
• Folding and localized faulting in a frictional, cohesive overburden resting over a viscous substratum
  
  • Leroy Y.M.
  • Triantafyllidis N.
  , 2000, pp.109-140.
• Évaluation de la biodisponibilité des dermocorticoïdes par thermographie infrarouge différentielle
  
  • Luong Minh Son
  • Luong Minh-Phong
  • Lok Catherine
  • Carmi Esther
  • Chaby Guillaume
  • Viseux Valérie
  Annales de Dermatologie et de Vénéréologie, Elsevier Masson, 2000, 127 (8-9), pp.701-705. Introduction</br> La technique thermographique infrarouge différentielle utilise le rayonnement infrarouge émis par la peau pour détecter, de façon non invasive et sans contact, les températures et leurs variations. Elle permet ainsi d'analyser les propriétés pharmacodynamiques (vasoconstriction) des dermocorticoïdes.</br></br> Matériels et méthodes</br> La carte thermique (thermogramme) cutanée a été enregistrée en temps réel à l'aide d'un système de détection de rayonnement infrarouge. Un test d'application unique sur un temps court, sans occlusion, et un test classique de blanchiment cutané après occlusion ont été réalisés. Un traitement par soustraction d'images a facilité l'analyse thermographique de l'effet des dermocorticoïdes des quatre classes d'activité sur peau saine.</br></br> Résultats</br> Nos résultats montrent, après une application unique sur un temps court, sans occlusion, des différences de température dans les 3 premières heures selon les corticoïdes. Le dermocorticoïde de classe II étudié en crème a provoqué un refroidissement plus intense que les autres dermocorticoïdes. L'effet de blanchiment cutané a été plus marqué pour les dermocorticoïdes de classe I et II et n'a pas été détecté pour celui de la classe IV.</br></br> Discussion</br> La possibilité de soustraire les thermogrammes les uns des autres permet d'exploiter le concept de différentielle d'images. Des différences évolutives de température après application unique, sans occlusion, de dermocorticoïdes sont mises en évidence dès les 3 premières heures. Ceci pourrait correspondre à des différences de puissance alors que le test classique de vasoconstriction n'étudie la blancheur cutanée induite qu'à partir de la 6 e heure. Pour le test de blanchiment cutané, les résultats de cette première étude sont insuffisants pour apporter une interprétation précise qualitative et quantitative. L'intérêt de la technique thermographique infrarouge différentielle est d'être une méthode quantitative, ne nécessitant pas de contact avec la peau, permettant un enregistrement continu en temps réel. Elle est plus sensible que la thermographie infrarouge classique. Elle a permis de réaliser une étude évolutive objective de l'action des dermocorticoïdes.
• Elasticity: Thermodynamic Treatment
  
  • Zaoui André
  • Stolz Claude
  , 2000, pp.2445-2449. The elastic behavior of materials is usually described by direct stress±strain relationships which use the fact that there is a one-to-one connection between the strain and stress tensors $\varepsilon$ and $\sigma$; some mechanical elastic potentials can then be defined so as to express the stress tensor as the derivative of the strain potential with respect to the strain tensor, or conversely the latter as the derivative of the complementary (stress) potential with respect to the former. Nevertheless, these potentials are restricted to specific thermodynamic conditions. This purely mechanical treatment may be generalized and improved by integrating its temperature dependence and by connecting the elastic potentials with the classical thermodynamic functions within a consistent thermodynamic framework. This leads to a more general definition of thermoelasticity (Sect. 1), which can be used for a better understanding of the properties of the elastic moduli (Sect. 2), for a natural definition of rubber elasticity (Sect. 3), and for the prediction of the effective thermal expansion coefficients of heterogeneous materials (Sect. 4). (10.1016/B0-08-043152-6/00436-8)
  DOI : 10.1016/B0-08-043152-6/00436-8
• Cavités de stockage dans le sel : évaluation de l'étanchéité
  
  • Bérest P.
  , 2000, pp.115-134. No abstract provided
• Finite element simulation of the deformation of b.c.c. aggregates using a crystal plasticity model - local orientation effects
  
  • Arizmendi D.
  • Raphanel J. L.
  , 2000, pp.27-32. No abstract provided
• Full or partial geometrical symmetry in symmetric Galerkin BEM
  
  • Bonnet Marc
  , 2000, pp.57-62. No abstract provided
• Etude expérimentale du comportement à la fissuration des dépôts de tungstène PVD en fonction de leurs épaisseurs
  
  • Ganne T.
  • Crépin Jérôme
  • Zaoui A.
  • Pradeilles-Duval R. M.
  , 2000. No abstract provided
• Caractérisation morphologique 3D des matériaux de structure hétérogènes par microtomographie X et traitement d'image pour la prévision du comportement mécanique
  
  • Bornert Michel
  • Jeulin Dominique
  • Maire E.
  • Moulinec H.
  • Chaix J.-M.
  , 2000. No abstract provided
• Experimental investigation and micromechanical modeling of the hot deformation of duplex stainless steels
  
  • Pinna C.
  • Bornert Michel
  • Beynon J. H.
  • Sellars C. M.
  , 2000. No abstract provided
• Principles for the `intelligent' optimal design of materials and structures
  
  • Zarka Joseph
  , 2000.
• Identification strategies for recovering material parameters from indentation experiments
  
  • Constantinescu Andrei
  • Tardieu Nicolas
  , 2000, pp.181-190. This chapter describes the progress obtained by the authors on the development of a numerical method for the identification of material parameters from indentation experiments. An indentation experiment is performed by pressing a punch on a material sample and measuring the applied force and the indentation depth. The proposed technique minimizes a least squares cost functional using gradient descent methods. In addition, the adjoint state method is extended to variational inequalities and this permits to compute the gradient of the cost functional with low numerical cost. Using this technique, a series of identifications from indentation experiments have been done and their results are discussed in this chapter. Inverse problem is of practical interest as the indentation test does not demand the creation of complicated specimens and is simple to perform. However, the applications are restricted by the difficult mechanical interpretation of the test. (10.1016/B978-008043693-7/50091-X)
  DOI : 10.1016/B978-008043693-7/50091-X
• On the stability of rate-dependent solids with application to the uniaxial plane strain test
  
  • Nestorović Miroslav
  • Leroy Yves
  • Triantafyllidis Nicolas
  Journal of the Mechanics and Physics of Solids, Elsevier, 2000, 48, pp.1467-1491. The linear stability criterion, proposed for structural models in an earlier paper, is now extended for a general class of elastic–viscoplastic continua. The time-dependent trajectories, whose stability is under investigation, are functions of two characteristic times: the relaxation time of the viscous solid and the rate of the applied loading, with their ratio denoted by T. It is assumed that the loading conditions of the trajectory are not modified by the perturbation. The criterion predicts that a solid is initially unstable if there exists a unit norm perturbation in the velocity field whose time derivative is positive. This condition is equivalent to finding a positive eigenvalue in the self-adjoint part of the operator relating the initial first and second rate of the displacement perturbations. If the dominant eigenvalue is obtained from the non self-adjoint operator, the change in sign of its real part is a sufficient condition for instability. For solids with an associated flow rule, it is shown that the exclusion of instability in a trajectory, in the limit of vanishing T, coincides with stability of the corresponding rate-independent solid in the sense of Hill. The theory is applied to the analysis of a finitely strained rectangular block under uniaxial tension and compression, for different elastic–viscoplastic solids of the von Mises and Drucker–Prager type. (10.1016/S0022-5096(99)00094-0)
  DOI : 10.1016/S0022-5096(99)00094-0
• Plastic heterogeneities of a copper multicrystal deformed in uniaxial tension: experimental study and finite element simulations
  
  • Delaire F.
  • Raphanel Jean L
  • Rey Colette
  Acta Materialia, Elsevier, 2000, 48, pp.1075-1087. A copper sample made of a single layer of grains is plastically deformed by uniaxial tension at room temperature and low strain rate. The deformation field is measured by means of grids deposited on the polished surface of the undeformed specimen and local orientations are recorded using electron back scattering diagrams in a scanning electron microscope. These measures are compared with simulations made by a finite element code using a physically based model for the deformation and hardening of face centered cubic crystals. A good agreement is found between measured and computed values. The simulations give access to much more detail about the history of glide in each grain and help establish which systems are active at a local level. They also provide the evolution of internal variables such as dislocation densities. A new insight into intergranular accommodation as well as intragranular heterogeneities is provided. (10.1016/S1359-6454(99)00408-5)
  DOI : 10.1016/S1359-6454(99)00408-5
• An inverse approach to determine the non-linear properties of induction heat-treated steels
  
  • Niclas André
  • Bourgeois Lament
  European Journal of Mechanics - A/Solids, Elsevier, 2000, 19, pp.69-88. The identification of the through-the-thickness variation of the non-linear properties of a steel structure due to a heat treatment by induction is considered. An inverse approach to that problem is proposed, which is based on a 4-point bending test of a heat-treated parallelepipedic bar. It includes a layer-removal method for measuring residual stresses. Precisely, two different inverse methods are described. For a medium carbon steel, an application based on experimental data is performed, which shows the efficiency of our approach and a good agreement between the two methods. (10.1016/S0997-7538(00)00152-2)
  DOI : 10.1016/S0997-7538(00)00152-2
• A Concept for Earthquake-Resistant Design of Underground Structures: Stress Response Spectrum
  
  • Kurose Ayumi
  • Bérest Pierre
  , 2000, pp.1043-1049. This paper introduces a method to evaluate the mechanical effects induced in the cross-section of an underground structure, constructed in a medium of great thickness, under earthquake ground motion. Damage observations after large earthquakes (e.g., Kobe, 1995) have shown the cross-sectional vulnerability of underground structures at shallow or great depth. Present earthquake-resistant design standards only suggest calculation methods for structures constructed in a soil laying over a rigid basement and cannot be applied to a structure constructed in a medium of great thickness, such as a tunnel, an underground hydrocarbon storage facility or a nuclear-waste disposal site. Thus, development of a systematic method to evaluate the seismic effects induced in the cross-section of a structure in an unbounded medium is of interest. The approach proposed here is conceptually similar to that used for earthquake response analysis of buildings: using a simple but realistic model of an underground linear structure (a 2D cavity with circular cross-section in an infinite, elastic, linear, homogeneous and isotropic medium) and real earthquake records, we propose a response spectrum more suitable, than the usual velocity or acceleration response spectrum, for analyzing the structural stability of underground construction during earthquakes: the Stress Response Spectrum (SRS), which is defined as the maximum value of the maximum shear stress at the cavity wall during the duration of ground motion. The SRS values are computed by using 21 earthquake motions (provided by the Japan Meteorological Agency) of magnitude higher than 4, which were recorded by the Japan Nuclear Cycle Research Institute (JNC) in a 315-meter deep gallery excavated in an a granodioritic rock mass at the Kamaishi Mine in Iwate, Japan. In light of the numerical analysis, the SRS appears to be a potential tool for the earthquake-response analysis of underground structures. The Stress Response Spectrum will provide engineers with the order of magnitude of mechanical effects in an underground structure for a given earthquake motion; conversely, for a given target SRS, may assist in producing a design earthquake more suitable for analysis of deep underground structures than those currently available.
• Effet de la fréquence de sollicitation et de l'environnement sur la propagation des fissures de fatigue en mode II dans l'acier maraging M250
  
  • Doquet V.
  , 2000. No abstract provided
• Influence of the film thickness on texture, residual stresses and cracking behaviour of PVD tungsten coatings deposited on a ductile substrate
  
  • Ganne T.
  • Farges G.
  • Crépin Jérôme
  • Pradeilles-Duval R. M.
  • Zaoui A.
  , 2000. No abstract provided
• Effets d'un préécrouissage ou d'un surécrouissage cyclique sur la durée de vie en fatigue de divers aciers, à contrainte ou déformation imposée.
  
  • Doquet Véronique
  • Taheri Said
  Revue Française de Mécanique, 2000, 1, pp.27-33.
• Solid-fluid phase transformation within grain boundaries
  
  • Leroy Yves M
  • Ghoussoub Joumana
  , 2000. The overall compaction of porous rocks due to intergranular pressure solution (IPS) results from the dissolution of minerals within contact regions and the diffusive transport through the grain boundary of the dissolved species towards the fluid-filled pore space. The grain boundary structure can be imagined to be composed of dry contact zones, thin fluid films and fluid-filled cavities. The connectiveness and tortuosity of this structure determine the effective diffusivity of grain contacts and thus the potential of porous rock to compact by the action of IPS. The evolution in time of the grain-boundary structure, and thus of the effective diffusivity, is discussed here with the help of two 2D initial- and boundary-value problems which are solved by analytical and numerical means. The evolution of the solid–fluid interfaces within the grain boundary is governed by a phase transformation between the non-hydrostatically stressed elastic solid and the trapped fluid assumed in mechanical equilibrium. The characteristic time is provided by a linear kinetic law. The evolution of the structure away from a state of thermodynamic equilibrium during a loading normal to the grain boundary is found to occur in two steps. The first one consists of a diffuse morphology evolution in time and results in an enhancement of any initial stress concentration. The second step is characterized by a rapid and localized dissolution in the region of stress concentration. The latency period prior to localization is governed by the magnitude of the non-hydrostatic remote stress as well as the microstructural geometric factor responsible for the initial stress concentration at the solid–fluid interface. The localized dissolution is shown to provide a mechanism for the fluid to penetrate a previously dry contact region by marginal dissolution and thus to create a fluid film. However, the newly formed thin fluid layer is found to be unstable pointing to a possible repeated reorganization or dynamic evolution of the grain boundary internal structure during the action of IPS. (10.1016/S0022-5096(01)00012-6)
  DOI : 10.1016/S0022-5096(01)00012-6