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Proper orthogonal decomposition preprocessing of infrared images to rapidly assess stressinduced heat source fields
Auteur(s): Benaarbia A., Chrysochoos A.
(Article) Publié:
Quantitative Infrared Thermography Journal, vol. 14 p.132152 (2017)
Ref HAL: hal01505316_v1
DOI: 10.1080/17686733.2017.1281553
Exporter : BibTex  endNote
Résumé: An image processing technique using the proper orthogonal decomposition (POD) of infrared thermal data was developed to improve the speed of assessment of 2D heat source fields accompanying mechanical transformation. This method involved the generation of a reduced orthonormal basis to approximate thermal fields prior to heat source estimation. The robustness of the method was first assessed using a penalising benchmark test. This test involved artificially setting several tricky situations that arise in practice (high diffusivity, low signaltonoise ratio, complex heat source distribution, etc.). Application of the method to several experimental temperature fields obtained by an infrared focal plane array camera is then presented. The error between the POD approximated solution in terms of heat sources and a reference solution, computed via a local least squares fitting method, was found to be negligible, thus confirming the efficiency and advantages of the POD preprocessing technique – the method enabled us to obtain a reliable estimate of heat sources while drastically reducing the computation cost in terms of CPU time.




Computing the elastic properties of sandstone submitted to progressive dissolution
Auteur(s): Wojtacki K., Daridon L., Monerie Y.
(Article) Publié:
International Journal Of Rock Mechanics And Mining Sciences, vol. 95 p.16  25 (2017)
Ref HAL: hal01502421_v1
DOI: 10.1016/j.ijrmms.2016.12.015
Exporter : BibTex  endNote
Résumé: We present a numerical method for estimating the stiffnesstoporosity relationships for evolving microstructures of Fontainebleau sandstone. The proposed study is linked to geological storage of CO 2 and focuses on longterm and far field conditions, when the progressive degradation of the porous matrix can be assumed to be homogeneous at the sample scale. The method is based on microstructure sampling with respect to morphological descriptors extracted from microtomography. First, an efficient method of generation of accurate numerical media is proposed. The method is based on grain deposit, compaction and diagenesis and allows to reproduce userdefined morphological parameters. Second, two simple numerical models that mimic chemical degradation of porous aquifers are presented. Effective elastic properties are estimated within the framework of periodic homogenization and finite element approach. A fixedpoint method on a selfconsisted outer layer allows to consider nonperiodic representative volume elements. Accurate predictions of elastic properties over a wide range of porosity are obtained. The overall evolutions of elastic behaviour due to the increase of porosity are in excellent agreement both, with experimental data and the results obtained by Arns et al. [1].




Chemical degradation of a numerical material  Application to a Fontainbleau sandstone
Auteur(s): Wojtacki K., Daridon L., Monerie Y.
(Affiches/Poster)
InterPore  8th International Conference on Porous Media & Annual Meeting (Cincinnati, US), 20160509
Ref HAL: hal01511167_v1
Exporter : BibTex  endNote
Résumé: The carbon capture and storage consists in injecting large quantities of CO2 in supercritical formdirectly into deeply located geological formations. During the geological storage, chemical reactionsmay induce some important and irreversible changes of the rock properties [1].The morphology of the pore network and solid skeleton defines important macroscopic properties ofthe rock (permeability, stiffness). The proposed micromechanical approach is based on the followingmorphological criteria [2]:— basic measures: volume fraction, surface areas of phases— sizing: distributions of pores or grains size— spatial distribution: estimation of characteristic length scale, geometrical dispersion, anisotropy— connectivity: which highly influence on permeability (existence of percolation)Sandstones are products of a series of complex geological and hydrodynamical processes. Insimplified way it can be described by sandgrains transport, deposit, compaction and diagenesis. Inthis work we reconstructed the 3D sandstone geometry by simulating the way of the sandstoneformingprocesses. The reconstruction method consists of three main steps [3]:— sedimentation: grain deposit— compaction: bulk volume reduction and pore space extension— diagenesis: decrease of the characteristic size of the porous phase.Generated samples satisfy aforementioned morphological and statistical informations which wereobtained by 3D image analysis of Xray tomography of the natural rock sample.The chemical degradation of the material is taken into account by performing the numerical erosionof the microstructure by using 26neighbourhood structuring element. We proposed two scenarii ofnumerical dissolution:— the first scenario (isotropic dissolution): consists in dissolving all the pore space— the second scenario: consists in dissolving only percolated porous network.The proposed modelling is universal in the sense that it uses nondimensional time scale that can beadjusted to a particular timedependent process.Some numerical upscaling techniques (linear homogenization, effective Darcy's law) are used inorder to estimate evolution of elastic effective behaviour and permeability, triggered by progressivedissolution of microstructure. A new methodology enabling imposing periodic boundary conditions,in order to estimate mechanical properties, on nonperiodic geometry is proposed. A link betweeneffective elastic moduli and permeability is proposed.




Chemical degradation of a numerical material  application to Fontainebleau sandstone
Auteur(s): Wojtacki K., Daridon L., Monerie Y.
Conference: European Mechanics of Materials Conference (EMMC15) (Bruxelles, BE, 20160907)
Ref HAL: hal01511172_v1
Exporter : BibTex  endNote
Résumé: The carbon capture and storage consists in injecting large quantities of CO2 in supercritical form directly into deeply located geological formations. During the geological storage, chemical reactions may induce some important and irreversible changes of the rock properties [1].The morphology of the pore network and solid skeleton defines important macroscopic properties of the rock (permeability, stiffness). The proposed micromechanical approach is based on the following morphological criteria [2]: basic measures: volume fraction, surface areas of phases sizing: distributions of pores or grains size spatial distribution: estimation of characteristic length scale, geometrical dispersion, anisotropy connectivity: which highly influence on permeability (existence of percolation)Sandstones are products of a series of complex geological and hydrodynamical processes. In simplified way it can be described by sandgrains transport, deposit, compaction and diagenesis. In this work we reconstructed the 3D sandstone geometry by simulating the way of the sandstoneforming processes. The reconstruction method consists of three main steps [3]: sedimentation: grain deposit compaction: bulk volume reduction and pore space extension diagenesis: decrease of the characteristic size of the porous phase.Generated samples satisfy aforementioned morphological and statistical informations which were obtained by 3D image analysis of Xray tomography of the natural rock sample.The chemical degradation of the material is taken into account by performing the numerical erosion of the microstructure by using 26neighbourhood structuring element. We proposed two scenarii of numerical dissolution: the first scenario (isotropic dissolution): consists in dissolving all the pore space the second scenario: consists in dissolving only percolated porous network.The proposed modelling is universal in the sense that it uses nondimensional time scale that can be adjusted to a particular timedependent process. Some numerical upscaling techniques (linear homogenization, effective Darcy’s law) are used in order to estimate evolution of elastic effective behaviour and permeability, triggered by progressive dissolution of microstructure. A new methodology enabling imposing periodic boundary conditions, in order to estimate mechanical properties, on nonperiodic geometry is proposed. A link between effective elastic moduli and permeability is proposed.



Prise en compte de l'anisotropie dans la détermination des coefficients de variations hygroscopiques des bois
Auteur(s): Montero C., Burgers A., Arnould O., Wattrisse B., Gril J.
Conference: 5èmes journées du GDR Sciences du Bois  Les usages du bois : enjeux et opportunités (Bordeaux, FR, 20161108)
Actes de conférence: , vol. p. ()
Ref HAL: hal01464541_v1
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Résumé: Les interactions entre l'eau et le bois ont des conséquences importantes dans tous les usages des bois. Elles induisent entre autres des variations dimensionnelles pouvant nuire à la fabrication ou l'emploi des éléments bois. Par exemple, dans le domaine de la construction, les protocoles de séchages doivent être maîtrisés pour fournir des pièces de bois de dimension précises à une teneur en eau contrôlée que ce soit pour des emplois en bois massifs ou pour la fabrication de produits dérivés structurels tels des poutres lamelléscollés, des panneaux lamellés croisés etc. Les unités de transformations réalisent pour cela des prédébits des sciages ainsi que des protocoles de séchages naturels ou artificiels. Ces deux étapes sont importantes pour une bonne utilisation des bois et nécessitent un bonne connaissance des propriétés hygromécaniques des essences de bois employées.




Modeling of the effective elastic behavior of nanoporous materials with spherical and ellipsoidal in shape bubbles: application to irradiated uranium dioxide
Auteur(s): Haller Xavier, Monerie Y., Pagano S., Vincent PierreGuy
(Affiches/Poster)
NuMat2016: The Nuclear Materials Conference (Montpellier, FR), 20161107
Ref HAL: hal01409659_v1
Exporter : BibTex  endNote
Résumé: This work is devoted to the modeling of the effective elastic behavior of nanoporous materials containing both spherical and ellipsoidal in shape bubbles, typically the irradiated uranium dioxide (UO2) studied by the French “Institut de Radioprotection et de Sûreté Nucléaire” to investigate the response of fuel rods under reactivity initiated accident (RIA) conditions. As a first approximation, this material exhibits at least two populations of bubbles: (1) intragranular bubbles, almost spherical in shape with a typical diameter of a few nanometers, (2) intergranular bubbles, roughly lenticular in shape whose size ranges from tens to several hundred nanometers. Molecular dynamics results of [Colbert, 2012] and [Jelea et al., 2011] show the existence of a nonneglectible surface effect on the effective elastic behavior for UO2 at the intragranular bubbles scale, particularly when the surface/volume ratio of these bubbles increases.Analytical micromechanical models ([Duan et al., 2005], [Brisard et al., 2010]) concerning materials with an isotropic distribution of nanosized spherical inclusions have been extended to the case of materials with two populations of pressurized bubbles, one relative to spherical bubbles and the other relative to ellipsoidal bubbles. The proposed model follows the general framework of the socalled ‘morphologically representative patternbased approach’ of [Stolz and Zaoui, 1991] and is compared to existing models (with or without surface effects). The relevance of the analytical model has been assessed by comparison with finite elements simulations. A preliminary study has been performed on the evolution of the elastic moduli of the irradiated UO2 fuel obtained from this model during a RIA test condition.



Thermomechanical analysis of the onset of strain concentration zones in wet polyamide 6.6 subjected to cyclic loading
Auteur(s): Benaarbia A., Chrysochoos A., Robert Gilles
(Article) Publié:
Mechanics Of Materials, vol. 99 p.925 (2016)
Ref HAL: hal01325033_v1
DOI: 10.1016/j.mechmat.2016.04.011
Exporter : BibTex  endNote
Résumé: In the present paper, we put forward some experimental results on the local thermomechanical behavior of a wet PA6.6 matrix subjected to cyclic loading. We used photomechanical techniques to assess the creep and cyclic strain rate fields, as well as the associated dissipation and coupling heat source fields. This thermomechanical analysis enabled us, from the very beginning of the cyclic test, to track the onset of strain concentration zones and note their limited development. Moreover, this analysis helped us to highlight the coexistence of glassy, rubber and mixed thermal responses. This revealed that wet PA6.6 was a graded material whose property variations surely promoted the development of strain concentration.

