Publications

2013

• Crack growth characterisation of A356-T7 aluminum alloy under thermo-mechanical fatigue loading
  
  • Merhy Elias
  • Rémy Luc
  • Maitournam Habibou
  • Augustins Louis
  Engineering Fracture Mechanics, Elsevier, 2013, 110, pp.99-112. This paper presents results and interpretations of several long crack thermo-mechanical fatigue tests on A356-T7 cast aluminum alloy used in automotive cylinder heads. These tests were conducted on CT16 and SEN specimens for different positive and negative load ratios, temperatures, frequencies and stress intensity factor values in order to establish the contribution of each parameter governing the fatigue crack propagation. It was shown that the decrease of the frequency causes significant increase of the crack growth rate especially at high temperatures and load ratios. The performing of negative load ratio tests had shown a primordial importance of the compressive load part of fatigue on the crack advance. In addition, SEM, optical microscopy and other metallographic techniques were used to examine fracture surfaces and to analyze particles cracking. For positive load ratios tests, it was shown that in stage II (Paris regime) and stage III (high crack growth rates) the number of cracked particles increases with Kmax and gradual changes in fracture surface appearance occur. These changes were associated with different crack growth mechanisms at the microstructural scale. The amplitude of the inelastic deformations and the extent of the plastic zone ahead of the crack tip were used to explain the observed changes in crack growth mechanisms. The crack growth under negative load ratio loads is especially analyzed, and a way of deriving this rate is given and shown to be relevant even for nonisothermal loading. (10.1016/j.engfracmech.2013.03.019)
  DOI : 10.1016/j.engfracmech.2013.03.019
• State observers of a vascular fluid-structure interaction model through measurements in the solid
  
  • Bertoglio Cristobal
  • Chapelle Dominique
  • Fernández Miguel Angel
  • Gerbeau Jean-Frédéric
  • Moireau Philippe
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2013, 256, pp.149-168. We analyze the performances of two types of Luenberger observers -- namely, the so-called Direct Velocity Feedback and Schur Displacement Feedback procedures, originally devised for elasto-dynamics -- to estimate the state of a fluid-structure interaction model for hemodynamics, when the measurements are assumed to be restricted to displacements or velocities in the solid. We first assess the observers using hemodynamics-inspired test problems with the complete model, including the Navier-Stokes equations in Arbitrary Lagrangian-Eulerian formulation, in particular. Then, in order to obtain more detailed insight we consider several well-chosen simplified models, each of which allowing a thorough analysis -- emphasizing spectral considerations -- while illustrating a major phenomenon of interest for the observer performance, namely, the added mass effect for the structure, the coupling with a lumped-parameter boundary condition model for the fluid flow, and the fluid dynamics effect per se. Whereas improvements can be sought when additional measurements are available in the fluid domain in order to more effectively deal with strong uncertainties in the fluid state, in the present framework this establishes Luenberger observer methods as very attractive strategies -- compared, e.g., to classical variational techniques -- to perform state estimation, and more generally for uncertainty estimation since other observer procedures can be conveniently combined to estimate uncertain parameters. (10.1016/j.cma.2012.12.010)
  DOI : 10.1016/j.cma.2012.12.010
• ESEM study of the humidity-induced swelling of clay film
  
  • Carrier Benoît
  • Wang Linlin
  • Vandamme Matthieu
  • Pellenq Roland
  • Bornert Michel
  • Tanguy Arnaud
  • van Damme Henri
  Langmuir, American Chemical Society, 2013, 29 (41), pp.12823-12833. We measured the humidity-induced swelling of thin self-standing films of montmorillonite clay by a combination of environmental scanning electron microscopy (ESEM) and digital image correlation (DIC). The films were about 40µm thick. They were prepared by depositing and evaporating a suspension of clay and peeling off the highly oriented deposits. The rationale for creating such original samples was to obtain mesoscopic samples that could be used to bridge experimentally the gap between the scale of the clay layer and the engineering scale of a macroscopic clay sample. Several montmorillonite samples were used: the reference clay Swy-2, the same clay homoionized with sodium or calcium ions, and a sodium-exchanged Cloisite. The edges of the clay films were observed by ESEM at various relative humidity values between 14% and 95%. The ESEM images were then analyzed by DIC to measure the swelling or the shrinkage of the films. We also measured the adsorption/desorption isotherms by weighing the film samples in a humidity-controlled environment. In order to analyze our results, we compared our swelling/shrinkage and adsorption/desorption data with previously published data on the interlayer spacing obtained by X-ray diffraction and with numerical estimates of the interlayer water obtained by molecular dynamics simulation. The swelling and the hysteresis of this swelling were found to be comparable for the overall macroscopic films and for the interlayer space. The same correspondence between film and interlayer space was observed for the amount of adsorbed water. This suggests that, in the range of relative humidities values explored, the films behave like freely swelling oriented stacks of clay layers, without any significant contribution from the mesoporosity. The relevance of this result for the behavior of clayey sedimentary rocks and the differences with the behavior of nonoriented samples (powders or compacted powders) are briefly discussed. (10.1021/la402781p)
  DOI : 10.1021/la402781p
• Predicting Ductile Fracture of Low Carbon Steel Sheets: Stress-based versus Mixed Stress/Strain-based Mohr-Coulomb Model
  
  • Ebnöther Fabien
  • Mohr Dirk
  International Journal of Solids and Structures, Elsevier, 2013, 50 (7-8), pp.1055-1066. Two distinct implementations of the Mohr-Coulomb failure model are used in conjunction with a non-associated quadratic plasticity model to describe the onset of fracture in low carbon steel sheets. The stress-based version corresponds to the original Mohr-Coulomb model in stress space. For the mixed stress/strain-based version, the Mohr-Coulomb failure criterion is first transformed into the space of stress triaxiality, Lode angle parameter and equivalent plastic strain and then used as stress-state dependent weighting function in a damage indicator model. Basic fracture experiments including tensile specimens of different notch radii and a punch test are performed to calibrate the material parameters of the respective models. Subsequently, the models are used to predict the crack initiation in a Hasek test and during the stamping of an anticlastic structure. Unlike for the calibration experiments, the loading history during stamping is highly non-linear. Both models can be calibrated with similar accuracy, but the strain-based model predicts the instant of onset of fracture with greater accuracy in the stamping experiment which is an advantage of the empirical damage accumulation rule (10.1016/j.ijsolstr.2012.11.026)
  DOI : 10.1016/j.ijsolstr.2012.11.026
• An implicit integration procedure for an elasto-viscoplastic model and its application to thermomechanical fatigue design of automotive parts
  
  • Szmytka Fabien
  • Maitournam Habibou
  • Rémy Luc
  Computers & Structures, Elsevier, 2013, 119, pp.155-165. Thermomechanical fatigue (TMF) design has nowadays become essential for many industrial parts and cyclic elasto-viscoplastic constitutive models and their numerical integration are the crucial point of the problem. The paper first presents an implicit time integration scheme for an advanced constitutive model. This scheme is based on the return-mapping algorithm and proposes a use of the viscoplastic multiplier which enables to avoid Jacobian matrixes inversion and high computational cost. This peculiar numerical model is then integrated in a comprehensive computational TMF lifetime approach. The couple is shown to give the best agreement in terms of TMF lifetime estimation when compared with more simple TMF design approaches and an other constitutive model. (10.1016/j.compstruc.2013.01.009)
  DOI : 10.1016/j.compstruc.2013.01.009
• Cohesive model approach to the nucleation and propagation of cracks due to a thermal shock
  
  • Cyron Christian
  • Marigo Jean-Jacques
  • Sicsic Paul
  International Journal of Fracture, Springer Verlag, 2013, In press, pp.1-23. This paper studies the initiation of cohesive cracks in the thermal shock problem through a variational analysis. A two-dimensional semi-infinite slab with an imposed temperature drop on its free surface is considered. Assuming that cracks are periodically distributed and orthogonal to the surface, at short times we show that the optimum is a distribution of infinitely close cohesive cracks. This leads us to introduce a homogenized effective behavior which reveals to be stable for small times, thanks to the irreversibility. At a given loading cracks with a non-cohesive part nucleate. We characterize the periodic array of these macro-cracks between which the micro-cracks remain. Finally, for longer times, the cohesive behavior converges towards that from Griffith's evolution law. Numerical investigations complete and quantify the analytical results.
• A Galerkin strategy with Proper Orthogonal Decomposition for parameter-dependent problems -- Analysis, assessments and applications to parameter estimation
  
  • Chapelle Dominique
  • Gariah Asven
  • Moireau Philippe
  • Sainte-Marie Jacques
  ESAIM: Mathematical Modelling and Numerical Analysis, Société de Mathématiques Appliquées et Industrielles (SMAI) / EDP, 2013, 47 (6), pp.1821-1843. We address the issue of parameter variations in POD approximations of time-dependent problems, without any specific restriction on the form of parameter dependence. Considering a parabolic model problem, we propose a POD construction strategy allowing us to obtain some a priori error estimates controlled by the POD remainder - in the construction procedure - and some parameter-wise interpolation errors for the model solutions. We provide a thorough numerical assessment of this strategy with the FitzHugh-Nagumo 1D model. Finally, we give detailed illustrations of the approach in two parameter estimation applications, the first in a variational estimation framework with the FitzHugh-Nagumo model, and the second with a beating heart mechanical model for which we employ a sequential estimation method to characterize model parameters using real image data in a clinical case. (10.1051/m2an/2013090)
  DOI : 10.1051/m2an/2013090
• Plane-strain discrete dislocation plasticity with climb-assisted glide motion of dislocations
  
  • Danas Kostas
  • Deshpande V.S.
  Modelling and Simulation in Materials Science and Engineering, IOP Publishing, 2013, 21, pp.045008.
• The nonlinear elastic response of suspensions of rigid inclusions in rubber: II - A simple explicit approximation for finite-concentration suspensions
  
  • Lopez-Pamies Oscar
  • Goudarzi T.
  • Danas Kostas
  Journal of the Mechanics and Physics of Solids, Elsevier, 2013, 61, pp.19 - 37.
• Confrontation between Molecular Dynamics and micromechanical approaches to investigate particle size effects on the mechanical behaviour of polymer nanocomposites
  
  • Marcadon Vincent
  • Brown David
  • Herve ́ Éveline
  • Mele Patrice
  • Albérola Nicole Dominique
  • Zaoui André
  Computational Materials Science, Elsevier, 2013, 79, pp.495-505. This paper aims at developing a method to account for a particle size effect on the mechanical behaviour of particulate nanocomposites. An introduction of specific information at the atomic scale, through Molecular Dynamics (MD) simulations, into homogenisation models of the overall mechanical behaviour of heterogeneous materials (micromechanical approaches) is proposed here. By studying virtual nanocomposites, which consist of silica inclusions embedded in a polymer matrix, MD simulations have shown the existence of an interphase of disturbed matrix surrounding the inclusions, whose thickness depends neither on the inclusion size nor on the volume fraction of inclusions. By considering this interphase of fixed thickness, a particle size effect is then deduced from a dilute micromechanical model which derives from the classical Eshelby's inhomogeneity problem. Effective elastic moduli of the composite strongly vary with the particle size for a fixed volume fraction of particles. Nevertheless, opposite trends are observed relative to the interphase behaviour. Whereas effective moduli increase with the particle size for an interphase softer than the matrix, they decrease in the reverse case. The confrontation between MD and micromechanical approaches and the characterisation of the interphase elastic moduli by an inverse method allow the stiffening effects observed by MD to be explained in the case of an interphase softer than the pure matrix. (10.1016/j.commatsci.2013.07.002)
  DOI : 10.1016/j.commatsci.2013.07.002
• Modeling of latent hardening produced by complex loading paths in FCC alloys
  
  • Gérard Céline
  • Cailletaud Georges
  • Bacroix Brigitte
  International Journal of Plasticity, Elsevier, 2013, 42, pp.194-212. The present work aims at exploring self and latent hardening for FCC polycrystals under complex loading paths at room temperature. A relative quantification of the effect of the different interaction types between the 12 slip systems on the hardening is notably proposed. Combinations of simple loading sequences, such as tension and simple shear, with different orientations with regard to rolling direction, are considered. The material used is a 0.5 mm sheet of hot rolled OFHC copper. Two single crystal laws are independently identified. The experimental data are respectively compared with a finite element analysis, and two mean field models: the β-rule and the Kröner's model. A new order of the hardening matrix coefficients is proposed for FCC materials. Both identifications are compared and give rise to the same trend. (10.1016/j.ijplas.2012.10.010)
  DOI : 10.1016/j.ijplas.2012.10.010
• An asymptotic strain gradient Reissner-Mindlin plate model
  
  • Serpilli Michèle
  • Krasucki Françoise
  • Geymonat Giuseppe
  Meccanica, Springer Verlag, 2013, pp.1-13. In this paper we derive a strain gradient plate model from the three-dimensional equations of strain gradient linearized elasticity. The deduction is based on the asymptotic analysis with respect of a small real parameter being the thickness of the elastic body we consider. The body is constituted by a second gradient isotropic linearly elastic material. The obtained model is recognized as a strain gradient Reissner-Mindlin plate model. We also provide a mathematical justification of the obtained plate model by means of a variational weak convergence result. (10.1007/s11012-013-9719-6)
  DOI : 10.1007/s11012-013-9719-6
• Stability of homogeneous states with gradient damage models: size effects and shape effects in the three-dimensional setting
  
  • Pham Kim
  • Marigo Jean-Jacques
  Journal of Elasticity, Springer Verlag, 2013, 110 (1), pp.pp. 63--93. Considering a family of gradient-enhanced damage models and taking advantage of its variational formulation, we study the stability of homogeneous states in a full three-dimensional context. We show that gradient terms have a stabilizing effect, but also how those terms induce structural effects. We emphasize the great importance of the type of boundary conditions, the size and the shape of the body on the stability properties of such states. (10.1007/s10659-012-9382-5)
  DOI : 10.1007/s10659-012-9382-5
• A surface-based electrophysiology model relying on asymptotic analysis and motivated by cardiac atria modeling
  
  • Chapelle Dominique
  • Collin Annabelle
  • Gerbeau Jean-Frédéric
  Mathematical Models and Methods in Applied Sciences, World Scientific Publishing, 2013, 23 (14), pp.2749-2776. Computational electrophysiology is a very active field with tremendous potential in medical applications, albeit leads to highly intensive simulations. We here propose a surface-based electrophysiology formulation, motivated by the modeling of thin structures such as cardiac atria, which greatly reduces the size of the computational models. Moreover, our model is specifically devised to retain the key features associated with the anisotropy in the diffusion effects induced by the fiber architecture, with rapid variations across the thickness which cannot be adequately represented by naive averaging strategies. Our proposed model relies on a detailed asymptotic analysis in which we identify a limit model and establish strong convergence results. We also provide detailed numerical assessments which confirm an excellent accuracy of the surface-based model -- compared with the reference 3D model -- including in the representation of a complex phenomenon, namely, spiral waves. (10.1142/S0218202513500450)
  DOI : 10.1142/S0218202513500450
• Experimental investigation of the free swelling of crushed argillite
  
  • Wang Linlin
  • Bornert Michel
  • Chanchole S.
  • Heripre Eva
  , 2013.
• Vibroacoustics of the piano soundboard: (Non)linearity and modal properties in the low- and mid-frequency ranges
  
  • Ege Kerem
  • Boutillon Xavier
  • Rébillat Marc
  Journal of Sound and Vibration, Elsevier, 2013, 332 (5), pp.1288-1305. The piano soundboard transforms the string vibration into sound and therefore, its vibrations are of primary importance for the sound characteristics of the instrument. An original vibro-acoustical method is presented to isolate the soundboard nonlinearity from that of the exciting device (here: a loudspeaker) and to measure it. The nonlinear part of the soundboard response to an external excitation is quantitatively estimated for the first time, at ≈ -40 dB below the linear part at the ff nuance. Given this essentially linear response, a modal identification is performed up to 3 kHz by means of a novel high resolution modal analysis technique (Ege et al., High-resolution modal analysis, JSV, 325(4-5), 2009). Modal dampings (which, so far, were unknown for the piano in this frequency range) are determined in the midfrequency domain where FFT-based methods fail to evaluate them with an acceptable precision. They turn out to be close to those imposed by wood. A finite-element modelling of the soundboard is also presented. The low-order modal shapes and the comparison between the corresponding experimental and numerical modal frequencies suggest that the boundary conditions can be considered as blocked, except at very low frequencies. The frequency-dependency of the modal density and the observation of modal shapes reveal two well-separated regimes. Below ≈ 1 kHz, the soundboard vibrates more or less like a homogeneous plate. Above that limit, the structural waves are confined by ribs, as already noticed by several authors, and localised in restricted areas (one or a few inter-rib spaces), presumably due to a slightly irregular spacing of the ribs across the soundboard. (10.1016/j.jsv.2012.10.012)
  DOI : 10.1016/j.jsv.2012.10.012
• Onset of Failure in a Fiber Reinforced Elastomer Under Constrained Bending
  
  • Lignon Eric
  • Le Tallec Patrick
  • Triantafyllidis Nicolas
  International Journal of Solids and Structures, Elsevier, 2013, 50, pp.279 - 287. (10.1016/j.ijsolstr.2012.07.022)
  DOI : 10.1016/j.ijsolstr.2012.07.022
• Etude numérique des paramètres affectant les profils d'usure en fretting
  
  • Basseville Stéphanie
  • Proudhon Henry
  • Héripré Eva
  • Cailletaud Georges
  Matériaux et Techniques, EDP Sciences [1970-....], 2013, 101, pp.13 p.. L'étude est dédiée à l'endommagement lors d'un test numérique de fretting entre un cylindre et un plan. Un modèle d'usure s'appuyant sur un critère local énergétique permet de déterminer le profil d'usure dans différents contextes. La première simulation consiste à comparer des profils d'usure obtenus pour un matériau homogène lors d'un test d'usure unilatérale et d'un test d'usure bilatérale, i.e. chacune des surfaces de contact est usée. Dans la seconde simulation, un revêtement est pris en compte et présente un nombre important de pores. En leur présence, l'usure par abrasion est détectée et conduit naturellement à s'intéresser à la notion de troisième corps dans la zone de contact. Ainsi, une modélisation explicite des débris et la mise en œuvre du transfert de matière sont développés. Bien que la plasticité joue un rôle important dans les mécanismes d'endommagement, les simulations supposent un comportement élastique des matériaux en contact pour les tests (i) à (ii). Un dernier test permet d'aborder l'étude de l'effet d'une loi de comportement élasto-plastique pour le matériau usé. (10.1051/mattech/2013069)
  DOI : 10.1051/mattech/2013069
• Ductile deformation mechanisms of synthetic halite : a full field measurement approach
  
  • Dimanov Alexandre
  • Bourcier Mathieu
  • Heripre Eva
  • Bornert Michel
  • Raphanel Jean
  , 2013.
• A non-periodic two scale asymptotic method to take account of rough topographies for 2D elastic wave propagation
  
  • Capdeville Yann
  • Marigo Jean-Jacques
  Geophysical Journal International, Oxford University Press (OUP), 2013, 192, pp.163--189. We propose a two scale asymptotic method to compute the effective effect of a free surface topography varying much faster than the minimum wavelength for 2-D P-SV elastic wave propagation. The topography variation is assumed to be non-periodic but with a deterministic description and, in this paper, the elastic body below the topography is assumed to be ho- mogeneous. Two asymptotic expansions are used, one in the boundary layer close to the free surface and one in the volume. Both expansions are matched appropriately up to the order 1 to provide an effective topography and an effective boundary condition. We show that the effective topography is not the averaged topography but it is a smooth free surface lying below the fast variations of the real topography. Moreover, the free boundary condition has to be modified to take account of the inertial effects of the fast variations of the topography above the effective topography. In other words, the wave is not propagating in the fast topography but below it and is slowed down by the weight of the fast topography. We present an iterative scheme allowing to find this effective topography for a given minimum wavelength. We do not attempt any mathematical proof of the proposed scheme, nevertheless, numerical tests show good results. (10.1093/gji/ggs001)
  DOI : 10.1093/gji/ggs001
• Identification of transient heat sources using the reciprocity gap
  
  • Auffray Nicolas
  • Bonnet Marc
  • Pagano Stéphane
  Inverse Problems in Science and Engineering, Taylor & Francis, 2013, 21, pp.721-738. The deformation of solid materials is nearly always accompanied with temperature variations, induced by intrinsic dissipation and thermomechanical coupling. Heat sources give precious information on the thermomechanical behavior of materials. They can be indirectly observed from thermal measurements on the specimen boundary, obtained e.g. via infrared thermography. To solve the inverse problem of identifying heat sources from such observations, a non-iterative algebraical method based on the Reciprocity Gap Method is proposed. This approach, used elsewhere mainly for time-independent identification, is applied here to transient measurements. Under appropriate modelling assumptions the number of heat sources, their spatial locations and energies are retrieved, as demonstrated on numerical experiments where the robustness of the method to measurement noise is also studied. (10.1080/17415977.2012.731597)
  DOI : 10.1080/17415977.2012.731597
• From gradient damage laws to Griffith's theory of crack propagation
  
  • Sicsic Paul
  • Marigo Jean-Jacques
  Journal of Elasticity, Springer Verlag, 2013, 113 (1), pp.55-74. This paper is devoted to the comparison of the evolution of damage governed by a gradient damage model with the evolution of a crack predicted by Griffith's law. The analysis is made in a two-dimensional setting, assuming that damage is concentrated inside thin bands whose width is proportional to the internal length of the material. Taking advantage of the variational formulation based on the three principles of irreversibility, stability and energy balance, one introduces a generalized Rice path integral which contains terms involving the gradient of damage. Assuming that the internal length of the material is small by comparison with the dimension of the body, a separation of scales is achieved. Owing to the energy balance and the stability condition, one first proves some properties of this path integral with respect to the path. Then, one shows that the evolution of the damage zone is governed by Griffith's law, the dissipated surface energy being given by the energy dissipated in the damage process zone.
• Noise-Corrected Estimation of Complex Modulus in Accord With Causality and Thermodynamics: Application to an Impact Test.
  
  • Collet Pierre
  • Gary Gérard
  • Lundberg Bengt
  Journal of Applied Mechanics, American Society of Mechanical Engineers, 2013, 80 (011018-1), pp.JANUARY 2013. Methods for estimation of the complex modulus generally produce data from which discrete results can be obtained for a set of frequencies. As these results are normally afflicted by noise, they are not necessarily consistent with the principle of causality and requirements of thermodynamics. A method is established for noise-corrected estimation of the complex modulus, subject to the constraints of causality, positivity of dissipation rate and reality of relaxation function, given a finite set of angular frequencies and corresponding complex moduli obtained experimentally. Noise reduction is achieved by requiring that two self-adjoint matrices formed from the experimental data should be positive semidefinite. The method provides a rheological model that corresponds to a specific configuration of springs and dashpots. The poles of the complex modulus on the positive imaginary frequency axis are determined by a subset of parameters obtained as the common positive zeros of certain rational functions, while the remaining parameters are obtained from a least squares fit. If the set of experimental data is sufficiently large, the level of refinement of the rheological model is in accordance with the material behavior and the quality of the experimental data. The method was applied to an impact test with a Nylon bar specimen. In this case, data at the 29 lowest resonance frequencies resulted in a rheological model with 14 parameters. The method has added improvements to the identification of rheological models as follows: (1) Noise reduction is fully integrated. (2) A rheological model is provided with a number of elements in accordance with the complexity of the material behavior and the quality of the experimental data. (3) Parameters determining poles of the complex modulus are obtained without use of a least squares fit. (10.1115/1.4007081)
  DOI : 10.1115/1.4007081
• Solid Drops: Large Capillary Deformations of Immersed Elastic Rods
  
  • Mora Serge
  • Maurini Corrado
  • Phou Ty
  • Fromental Jean-Marc
  • Audoly Basile
  • Pomeau Yves
  Physical Review Letters, American Physical Society, 2013, 111 (11). Under the effect of surface tension a blob of liquid adopts a spherical shape when immersed in another fluid. We demonstrate experimentally that soft, centimeter-size elastic solids can exhibit a similar behavior: when immersed into a liquid, a gel having a low elastic modulus undergoes large, reversible deformations. We analyze three fundamental types of deformations of a slender elastic solid driven by surface stress, depending on the shape of its cross-section: a circular elastic cylinder shortens in the longitudinal direction and stretches transversally; the sharp edges of a square based prism get rounded off as its cross-sections tend to become circular; a slender, triangular based prism bends. These experimental results are compared to analysis and non-linear simulations of neo-Hookean solids deformed by surface tension, and are found to be in good agreement with each other. (10.1103/PhysRevLett.111.114301)
  DOI : 10.1103/PhysRevLett.111.114301
• Micro-scale experimental investigation of the swelling anisotropy of the Callovo-Oxfordian argillaceous rock
  
  • Wang Linlin
  • Bornert Michel
  • Chanchole Serge
  • Yang Diansen
  • Héripré Eva
  • Tanguy Arnaud
  • Caldemaison Daniel
  Clay Minerals, Mineralogical Society, 2013, 48 (2), pp.391-402. An experimental study of the swelling anisotropy of the Callovo-Oxfordian argillaceous rock under hydration is presented. The investigation, which combines environmental scanning electron microscopy (ESEM) and digital image correlation techniques, has been carried out at the micrometric scale of the composite microstructure of the rock. Specimens were hydrated in the ESEM over a wide range of relative humidity and observations conducted on two planes: plane 1 parallel to the bedding plane, and plane 2 perpendicular to it. The observations reveal that the local swelling (which can be quantified at a local gauge length of about 5 µm) is strongly anisotropic in both planes. The global swelling, measured over areas of about 500 µm in width, is also clearly anisotropic in plane 2 (with major swelling direction normal to the bedding plane), but not in plane 1. The global isotropy in plane 1 arises from the uniform distribution of the orientation of anisotropic local strains, while the anisotropic swelling in plane 2 is due to a preferred local orientation. (10.1180/claymin.2013.048.2.17)
  DOI : 10.1180/claymin.2013.048.2.17