1,011 research outputs found
A multi-level interface model for damaged masonry
No full textThe aim of the present work is to propose a new micro-mechanical model in the context of the deductive approach used to derive interface models. This model, based on a previous study introduced previously by A. Rekik and F. Lebon, is used to reproduce the damage in masonry by combining structural analysis and homogenization methods. The focal point of this method is to assume the existence of a third material, called interphase, which is a mixture of the two principal constituents of masonry, brick and mortar, and that is the interface between them. This new element presents a low thickness, a low stiffness and a given damage ratio. The mechanical problem of masonry, initially a 3D problem, is solved numerically as a 2D problem using finite element methods. The properties of the interface brick-mortar material are obtained using three essentials steps. First of all, an exact homogenisation of a laminates is used to define a first homogeneous equivalent medium named HEM-1. After, the assumption of damaged material is taken into account by using the general framework given by M. Kachanov to evaluate the global behaviour of the damaged HEM-1 defining thus a second equivalent homogeneous medium noted HEM-2. The last step consists in using an asymptotic analysis technique which is performed to model HEM-2 as an interface or a joint. The properties of this joint are deduced from those of the HEM-2 material as proposed in former papers. Particularly, through the second homogenization are taken into account the variability of microcracks oriented family and simultaneously the opening-closure effects (unilateral behaviour). Numerically this interface is modelled with connector finite elements. Numerical results are compared to experimental ones available in the literature
Formulation en contraintes pour le contact frottant
No full textInternational audienceL'objet de cet exposé est de montrer la faisabilité et l'efficacité de méthodes numériques de résolution et de contrôle d'erreur basées sur une formulation en contrainte de problèmes de contact frottant en élasticité statique. Dans ce travail, on entendra par contact, loi de Signorini et par frottement, loi de Coulomb. Dans un premier temps, on formulera le problème sous forme d'une inéquation quasi-variationnelle. On montrera que les difficultés introduites par le contact frottant sont circonscrites à l'ensemble des champs statiquement admissibles. On développera ensuite une méthode d'éléments finis " équilibre " apte à résoudre le problème approché. On proposera plusieurs méthodes de résolution du problème discret et on comparera leurs efficacités respectives. On s'intéressera ensuite à la mise en en place d'un estimateur d'erreur a posteriori " approché " basé sur une " comparaison " primal-dual. On montrera que cet estimateur permet de déterminer avec précision les zones du maillage à raffiner ou à remailler. On terminera l'exposé par l'analyse de deux méthodes de décomposition de domaine de type Schwarz additive et multiplicative. On montrera que l'ordre de convergence de ces méthodes dépend, comme dans des cas usuels, de la taille du " chevauchement " entre les domaines. [1] Bisegna, P., Lebon, F., Maceri, F. The unilateral frictional contact of a piezoelectric body with a rigid support, Solids Mechanics and its Applications Series, J.A.C. Martins Ed., Kluwer, pp. 347-354, 2002. [2] Bisegna P., Lebon F., Maceri F. : D-PANA: a convergent block-relaxation solution method for the discretized dual formulation of the Signorini-Coulomb contact problem, Comptes Rendus Académie des Sciences, Série I, vol. 333, pp. 1053-1058, 2001 [3] Bisegna, P., Lebon F., Maceri, F. : Relaxation procedures for solving Signorini-Coulomb contact problems, Advances in Engineering Software, Vol 35, pp 595-600, 2004. [4] Kuss, F., Lebon, F. : Méthodes duales pour le contact frottant, European Journal of Computational Mechanics, Revue Européenne de Mécanique Numérique, vol. 16, pp. 33-51, 2007. [5] Kuss F., Lebon F. : Comparison of numerical procedures for dual contact problems, Advances in Engineering Software, Vol. 40, pp. 697-706, 2009. [6] Kuss F., Lebon F. : Error Estimation and Mesh Adaptation for Signorini-Coulomb Problems using E-FEM, Computers and Structures, Vol. 89, pp. 1148-1154, 2011. [7] Badea, L., Lebon, F. : Schwarz methods for dual contact problems, Journal of Computational and Applied Mathematics, soumis, 2012
Formulation en contraintes pour le contact frottant
No full textInternational audienceL'objet de cet exposé est de montrer la faisabilité et l'efficacité de méthodes numériques de résolution et de contrôle d'erreur basées sur une formulation en contrainte de problèmes de contact frottant en élasticité statique. Dans ce travail, on entendra par contact, loi de Signorini et par frottement, loi de Coulomb. Dans un premier temps, on formulera le problème sous forme d'une inéquation quasi-variationnelle. On montrera que les difficultés introduites par le contact frottant sont circonscrites à l'ensemble des champs statiquement admissibles. On développera ensuite une méthode d'éléments finis " équilibre " apte à résoudre le problème approché. On proposera plusieurs méthodes de résolution du problème discret et on comparera leurs efficacités respectives. On s'intéressera ensuite à la mise en en place d'un estimateur d'erreur a posteriori " approché " basé sur une " comparaison " primal-dual. On montrera que cet estimateur permet de déterminer avec précision les zones du maillage à raffiner ou à remailler. On terminera l'exposé par l'analyse de deux méthodes de décomposition de domaine de type Schwarz additive et multiplicative. On montrera que l'ordre de convergence de ces méthodes dépend, comme dans des cas usuels, de la taille du " chevauchement " entre les domaines. [1] Bisegna, P., Lebon, F., Maceri, F. The unilateral frictional contact of a piezoelectric body with a rigid support, Solids Mechanics and its Applications Series, J.A.C. Martins Ed., Kluwer, pp. 347-354, 2002. [2] Bisegna P., Lebon F., Maceri F. : D-PANA: a convergent block-relaxation solution method for the discretized dual formulation of the Signorini-Coulomb contact problem, Comptes Rendus Académie des Sciences, Série I, vol. 333, pp. 1053-1058, 2001 [3] Bisegna, P., Lebon F., Maceri, F. : Relaxation procedures for solving Signorini-Coulomb contact problems, Advances in Engineering Software, Vol 35, pp 595-600, 2004. [4] Kuss, F., Lebon, F. : Méthodes duales pour le contact frottant, European Journal of Computational Mechanics, Revue Européenne de Mécanique Numérique, vol. 16, pp. 33-51, 2007. [5] Kuss F., Lebon F. : Comparison of numerical procedures for dual contact problems, Advances in Engineering Software, Vol. 40, pp. 697-706, 2009. [6] Kuss F., Lebon F. : Error Estimation and Mesh Adaptation for Signorini-Coulomb Problems using E-FEM, Computers and Structures, Vol. 89, pp. 1148-1154, 2011. [7] Badea, L., Lebon, F. : Schwarz methods for dual contact problems, Journal of Computational and Applied Mathematics, soumis, 2012
Modeling of stiff interfaces: from statics to dynamics
No full textIn this paper, some results on the asymptotic behavior of stiff thin interfaces in elasto-
statics are recalled. A specific study of stiff interfaces in elastodynamics is presented
and a numerical procedure is given
Numerical Validation of Multiphysic Imperfect Interfaces Models
No full textWe investigate some mathematical and numerical methods based on asymptotic expansions for the modeling of bonding interfaces in the presence of linear coupled multiphysic phenomena. After reviewing new recently proposed imperfect contact conditions (Serpilli et al., 2019), we present some numerical examples designed to show the efficiency of the proposed methodology. The examples are framed within two different multiphysic theories, piezoelectricity and thermo-mechanical coupling. The numerical investigations are based on a finite element approach generalizing to multiphysic problems the procedure developed in Dumont et al. (2018)
Ultraviolet, Circular Dichroism, Fluorescence, and Circularly Polarized Luminescence Spectra of Regioregular Poly-[3-((S)-2-Methylbutyl)-Thiophene] in Solution.
No full textUltraviolet (UV), Circular Dichroism(CD), Fluorescence, and Circularly Polarized
Luminescence (CPL) spectra were recorded for mixed chloroform/methanol and chloroform/
butanol solutions of regioregular poly[3-((S)-2-methylbutyl)-thiophene]. An evaluation of the chiral
and nonchiral components in solution is proposed on the basis of the UV and CD spectra. The
fluorescence and CPL spectra are observed in a wavelength range where some UV and CD activity
still appears. For this reason, the observed CPL features are strongly influenced by CD. A general
procedure for evaluating true CPL spectra is proposed, when absorption and emission coexist
Development of a quantification method to specific Anti-ORF2 antibody using a blocking ELISA
No full textGuillossou, S.; Lebon, E.; Mieli, L.; Bonnard, M.; Thomson, D.. (2007). Development of a quantification method to specific Anti-ORF2 antibody using a blocking ELISA. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/155566
Vibrational Circular Dichroism (VCD): a Valuable Tool for Conformational Analysis and Absolute Configuration Assignment of Chiral 1-([2.2]Paracyclophan-4-yl)-2,2,2-trifluoroethanols
No full textThe IR and Near infrared (NIR) vibrational circular dichroism (VCD) spectra of molecules endowed with noncentral chirality have been investigated. Data for fundamental, first, and second overtone regions of (S)-2,3-pentadiene, exhibiting axial chirality, and methyl-d(3) (R)- and (S)-[ 2.2] paracyclophane-4-carboxylate, exhibiting planar chirality have been measured and analyzed. The analysis of NIR and IR VCD spectra was based on the local-mode model and the use of density functional theory (DFT), providing mechanical and electrical anharmonic terms for all CH-bonds. The comparison of experimental and calculated spectra is satisfactory and allows one to monitor fine details in the asymmetric charge distribution in the molecules: these details consist in the harmonic frequencies, in the principal anharmonicity constants, in both the atomic polar and axial tensors and in their first and second derivatives with respect to the CH-stretching coordinates
Combined use of three forms of chiroptical spectroscopies in the study of the absolute configuration and conformational properties of 3-phenylcyclopentanone, 3-phenylcyclohexanone, and 3-phenylcycloheptanone
No full textThree forms of chiroptical spectroscopies, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) have been employed to study the configuration and conformational properties of the three molecules: (S)-3-phenylcyclopentanone, (S)-3-phenylcyclohexanone, and (S)-3-phenylcycloheptanone (including (S)-3-phenylcyclopentanone-2,2,5,5-d4 and (S)-3-phenylcyclohexanone-2,2,6,6-d4). ECD and VCD spectra in the mid-IR for the three molecular systems are marginally dependent on fine conformational details, as interpreted in terms of standard DFT computational methods, with common spectroscopic features to the three systems clearly identified. Accounting for vibronic coupling mechanisms reproduces the structuring of ECD n→π∗ band. The ORD curves are quite similar for the three types of molecules, but their interpretation highlights a crucial role played by conformations of the cycloalkanone ring in the case of (S)-3-phenylcycloheptanone. The same conclusions are reached by considering the VCD spectra in the CH-stretching region
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