The Experts below are selected from a list of 10707 Experts worldwide ranked by ideXlab platform

Pierré Jean-emmanuel - One of the best experts on this subject based on the ideXlab platform.

  • Stéréo corrélation d'images numériques éléments finis : application à la validation de modèles de structures composites sous sollicitations complexes
    2016
    Co-Authors: Pierré Jean-emmanuel
    Abstract:

    Le projet VERTEX, dans lequel s'inscrivent ces travaux, a pour objectif de valider des modèles composites par essais statiques multi-axiaux sur des éprouvettes à l'échelle des détails structuraux. Le positionnement à cette échelle nécessite de développer de nouveaux outils d'instrumentation et de dialogue essais/calculs, qui sont au cœur de cette thèse. Compte-tenu de la complexité de ce type d'essai, nous nous intéressons ici à la Stéréo Corrélation d'Images Numériques (SCIN) puisqu'elle permet d'accéder à un champ de déplacement 3D à la surface du spécimen. Néanmoins, si l'on s'en tient à des approches classiques, il est difficile de faire une comparaison quantitative entre un champ mesuré et un champ simulé par Éléments Finis (EF). Ainsi dans ce travail, un formalisme est développé pour réaliser une mesure par SCIN dans l'espace physique en se basant sur un modèle EF (calibration de modèles non-linéaires de caméra, mesure de forme EF, mesure de champs EF). Cette méthode donne accès à un champ de déplacement expérimental directement exprimé dans les repère et support EF de la simulation, ce qui simplifie considérablement la validation. Pour valider un modèle à l'échelle des détails structuraux, la question des conditions aux limites est fondamentale. Cette question est d'autant plus complexe que la mesure cinématique se limite à la surface visible. En plus de cette mesure surfacique, il est envisagé ici d'estimer les conditions aux limites dans l'épaisseur en s'appuyant sur un modèle de type plaque/coque (classique ou volumique) et en y accordant plus ou moins de confiance (approches régularisée ou intégrée dans tout ou partie de l'éprouvette). La méthodologie est implémentée dans un logiciel académique et est appliquée sur des essais synthétiques. Une instrumentation adaptée au banc VERTEX a également permis l'analyse des essais réalisés dans le projet.VERTEX Project, to which this thesis belongs, aims to validate composite models by multi-axial static tests on specimens at the level of structural details. The positioning on this scale requires the development of both new instrumentation techniques and tools for the test/simulation dialogue, which are at the heart of this thesis. Given the complexity of this type of experiments, we focus here on Stereo Digital Image Correlation (SDIC) since it yields 3D displacement fields on the surface of the specimen. However, if we stick to conventional approaches, it is difficult to make quantitative comparisons between a measured field and a Finite Element (FE) simulated field. Thus, in this work, a framework is developed to make a measurement by SDIC in the Physical Coordinate System based on an FE model (calibration of non-linear camera models , FE shape measurement, FE field measurement). This method gives access to experimental displacement fields directly expressed both in the Coordinate System and support of the FE simulation, which considerably simplifies validation. To validate a model at the scale of structural details, the question of boundary conditions is fundamental. This question is even more complex since the kinematic measurement is limited to the visible surface. In addition to this surface measurement, it is here envisioned to estimate additionally the boundary conditions in the thickness of the specimen relying on a plate/shell-like model (classic or volume). Different approaches are considered depending on the confidence giving to this model. This methodology is implemented in an academic software and is applied to synthetic tests. The development of a dedicated instrumentation also allowed the analysis of tests performed on the VERTEX bench

  • Finite element based stereo digital image correlation : application to the validation of composite structures models complex loading
    2016
    Co-Authors: Pierré Jean-emmanuel
    Abstract:

    Le projet VERTEX, dans lequel s'inscrivent ces travaux, a pour objectif de valider des modèles composites par essais statiques multi-axiaux sur des éprouvettes à l'échelle des détails structuraux. Le positionnement à cette échelle nécessite de développer de nouveaux outils d'instrumentation et de dialogue essais/calculs, qui sont au cœur de cette thèse. Compte-tenu de la complexité de ce type d'essai, nous nous intéressons ici à la Stéréo Corrélation d'Images Numériques (SCIN) puisqu'elle permet d'accéder à un champ de déplacement 3D à la surface du spécimen. Néanmoins, si l'on s'en tient à des approches classiques, il est difficile de faire une comparaison quantitative entre un champ mesuré et un champ simulé par Éléments Finis (EF). Ainsi dans ce travail, un formalisme est développé pour réaliser une mesure par SCIN dans l'espace physique en se basant sur un modèle EF (calibration de modèles non-linéaires de caméra, mesure de forme EF, mesure de champs EF). Cette méthode donne accès à un champ de déplacement expérimental directement exprimé dans les repère et support EF de la simulation, ce qui simplifie considérablement la validation. Pour valider un modèle à l'échelle des détails structuraux, la question des conditions aux limites est fondamentale. Cette question est d'autant plus complexe que la mesure cinématique se limite à la surface visible. En plus de cette mesure surfacique, il est envisagé ici d'estimer les conditions aux limites dans l'épaisseur en s'appuyant sur un modèle de type plaque/coque (classique ou volumique) et en y accordant plus ou moins de confiance (approches régularisée ou intégrée dans tout ou partie de l'éprouvette). La méthodologie est implémentée dans un logiciel académique et est appliquée sur des essais synthétiques. Une instrumentation adaptée au banc VERTEX a également permis l'analyse des essais réalisés dans le projet.VERTEX Project, to which this thesis belongs, aims to validate composite models by multi-axial static tests on specimens at the level of structural details. The positioning on this scale requires the development of both new instrumentation techniques and tools for the test/simulation dialogue, which are at the heart of this thesis. Given the complexity of this type of experiments, we focus here on Stereo Digital Image Correlation (SDIC) since it yields 3D displacement fields on the surface of the specimen. However, if we stick to conventional approaches, it is difficult to make quantitative comparisons between a measured field and a Finite Element (FE) simulated field. Thus, in this work, a framework is developed to make a measurement by SDIC in the Physical Coordinate System based on an FE model (calibration of non-linear camera models , FE shape measurement, FE field measurement). This method gives access to experimental displacement fields directly expressed both in the Coordinate System and support of the FE simulation, which considerably simplifies validation. To validate a model at the scale of structural details, the question of boundary conditions is fundamental. This question is even more complex since the kinematic measurement is limited to the visible surface. In addition to this surface measurement, it is here envisioned to estimate additionally the boundary conditions in the thickness of the specimen relying on a plate/shell-like model (classic or volume). Different approaches are considered depending on the confidence giving to this model. This methodology is implemented in an academic software and is applied to synthetic tests. The development of a dedicated instrumentation also allowed the analysis of tests performed on the VERTEX bench

  • Stéréo Corrélation d’Images Numériques Éléments Finis: application à la validation de modèles de structures composites sous sollicitations complexes
    HAL CCSD, 2016
    Co-Authors: Pierré Jean-emmanuel
    Abstract:

    VERTEX Project, to which this thesis belongs, aims to validate composite models bymulti-axial static tests on specimens at the level of structural details. The positioning onthis scale requires the development of both new instrumentation techniques and tools forthe test/simulation dialogue, which are at the heart of this thesis. Given the complexityof this type of experiments, we focus here on Stereo Digital Image Correlation (SDIC )since it yields 3D displacement fields on the surface of the specimen. However, if we stickto conventional approaches, it is difficult to make quantitative comparisons between ameasured field and a Finite Element (FE) simulated field.Thus, in this work, a framework is developed to make a measurement by SDIC inthe Physical Coordinate System based on an FE model (calibration of non-linear cameramodels, FE shape measurement, FE field measurement). This method gives access toexperimental displacement fields directly expressed both in the Coordinate System andsupport of the FE simulation, which considerably simplifies validation.To validate a model at the scale of structural details, the question of boundary condi-tions is fundamental. This question is even more complex since the kinematic measurementis limited to the visible surface. In addition to this surface measurement, it is here envi-sioned to estimate the boundary conditions in the thickness of the specimen relying on aplate/shell-like model (classic or volume). Different approaches are considered dependingon the confidence giving to this model.This methodology is implemented in an academic software and is applied to synthetictests. The development of a dedicated instrumentation also allowed the analysis of testsperformed on the VERTEX bench.Le projet VERTEX, dans lequel s’inscrivent ces travaux, a pour objectif de valider desmodèles composites par essais statiques multi-axiaux sur des éprouvettes à l’échelle desdétails structuraux. Le positionnement à cette échelle nécessite de développer de nouveauxoutils d’instrumentation et de dialogue essais/calculs, qui sont au cœur de cette thèse.Compte-tenu de la complexité de ce type d’essai, nous nous intéressons ici à la StéréoCorrélation d’Images Numériques (SCIN ) puisqu’elle permet d’accéder à un champ dedéplacement 3D à la surface du spécimen. Néanmoins, si l’on s’en tient à des approchesclassiques, il est difficile de faire une comparaison quantitative entre un champ mesuré etun champ simulé par Éléments Finis (EF ).Ainsi dans ce travail, un formalisme est développé pour réaliser une mesure par SCINdans l’espace physique en se basant sur un modèle EF (calibration de modèles non-linéaires de caméra, mesure de forme EF, mesure de champs EF ). Cette méthode donneaccès à un champ de déplacement expérimental directement exprimé dans le repère et surle support EF de la simulation, ce qui simplifie considérablement la validation.Pour valider un modèle à l’échelle des détails structuraux, la question des conditionsaux limites est fondamentale. Cette question est d’autant plus complexe que la mesurecinématique se limite à la surface visible. En plus de cette mesure surfacique, il est envisagéici d’estimer les conditions aux limites dans l’épaisseur en s’appuyant sur un modèle detype plaque/coque (classique ou volumique) et en y accordant plus ou moins de confiance(approches régularisée ou intégrée dans tout ou partie de l’éprouvette).La méthodologie est implémentée dans un logiciel académique et est appliquée sur desessais synthétiques. Une instrumentation adaptée au banc VERTEX a également permisl’analyse des essais réalisés dans le projet

C. Sikorski - One of the best experts on this subject based on the ideXlab platform.

  • Efficient streamline, streamribbon, and streamtube constructions on unstructured grids
    IEEE Transactions on Visualization and Computer Graphics, 1996
    Co-Authors: Shyh-kuang Ueng, C. Sikorski
    Abstract:

    Streamline construction is one of the most fundamental techniques for visualizing steady flow fields. Streamribbons and streamtubes are extensions for visualizing the rotation and the expansion of the flow. The paper presents efficient algorithms for constructing streamlines, streamribbons, and streamtubes on unstructured grids. A specialized Runge-Kutta method is developed to speed up the tracing of streamlines. Explicit solutions are derived for calculating the angular rotation rates of streamribbons and the radii of streamtubes. In order to simplify mathematical formulations and reduce computational costs, all calculations are carried out in the canonical Coordinate System instead of the Physical Coordinate System. The resulting speed up in overall performance helps explore large flow fields.

Jean-emmanuel Pierré - One of the best experts on this subject based on the ideXlab platform.

  • Finite Element Stereo Digital Image Correlation: Framework and Mechanical Regularization
    Experimental Mechanics, 2017
    Co-Authors: Jean-emmanuel Pierré, Jean-charles Passieux, Jean-noël Périé
    Abstract:

    The use of Finite Element meshes in Digital Image Correlation (FE-DIC) is now widespread in experimental mechanics. Up to now FE have been much less used in Stereo-DIC. The first goal of this paper is to explain in details how to use FE in Stereo-DIC using a formulation in the Physical Coordinate System. More precisely, it is shown how to perform the calibration of possibly nonlinear models, shape and displacement measurement based on a FE mesh. In addition it is shown that with such a framework it is possible to regularise the measurement with a FE model based on the same mesh. For instance, using this technique, it is shown that it is possible to measure the rotation field of a bending plate in addition to its displacement.

  • Unstructured finite element-based digital image correlation with enhanced management of quadrature and lens distortions
    Optics and Lasers in Engineering, 2016
    Co-Authors: Jean-emmanuel Pierré, Jean-charles Passieux, Jean-noël Périé, Florian Bugarin, Laurent Robert
    Abstract:

    Like subset-based methods, the very first finite element versions of digital image correlation were closely related to the regular structure of images, as they were based on regular quadrilateral elements corresponding to an integer number of pixels. The use of unstructured meshes, to exploit the full potential of FE-DIC in structural mechanics, is now widespread. Most of the time, the formulation, the quadrature and the definition of the region of interest still rely on the pixels grid. In this paper, a formulation in the Physical Coordinate System and not in the image frame is proposed for 2D digital image correlation. In addition to a more precise definition of the region of interest, it allows the use of a more accurate quadrature rule. It is also shown that lens distortions can be successfully taken into account directly with such a formalism.

Laurent Robert - One of the best experts on this subject based on the ideXlab platform.

  • Unstructured finite element-based digital image correlation with enhanced management of quadrature and lens distortions
    Optics and Lasers in Engineering, 2016
    Co-Authors: Jean-emmanuel Pierré, Jean-charles Passieux, Jean-noël Périé, Florian Bugarin, Laurent Robert
    Abstract:

    Like subset-based methods, the very first finite element versions of digital image correlation were closely related to the regular structure of images, as they were based on regular quadrilateral elements corresponding to an integer number of pixels. The use of unstructured meshes, to exploit the full potential of FE-DIC in structural mechanics, is now widespread. Most of the time, the formulation, the quadrature and the definition of the region of interest still rely on the pixels grid. In this paper, a formulation in the Physical Coordinate System and not in the image frame is proposed for 2D digital image correlation. In addition to a more precise definition of the region of interest, it allows the use of a more accurate quadrature rule. It is also shown that lens distortions can be successfully taken into account directly with such a formalism.

Jean-noël Périé - One of the best experts on this subject based on the ideXlab platform.

  • Finite Element Stereo Digital Image Correlation: Framework and Mechanical Regularization
    Experimental Mechanics, 2017
    Co-Authors: Jean-emmanuel Pierré, Jean-charles Passieux, Jean-noël Périé
    Abstract:

    The use of Finite Element meshes in Digital Image Correlation (FE-DIC) is now widespread in experimental mechanics. Up to now FE have been much less used in Stereo-DIC. The first goal of this paper is to explain in details how to use FE in Stereo-DIC using a formulation in the Physical Coordinate System. More precisely, it is shown how to perform the calibration of possibly nonlinear models, shape and displacement measurement based on a FE mesh. In addition it is shown that with such a framework it is possible to regularise the measurement with a FE model based on the same mesh. For instance, using this technique, it is shown that it is possible to measure the rotation field of a bending plate in addition to its displacement.

  • Unstructured finite element-based digital image correlation with enhanced management of quadrature and lens distortions
    Optics and Lasers in Engineering, 2016
    Co-Authors: Jean-emmanuel Pierré, Jean-charles Passieux, Jean-noël Périé, Florian Bugarin, Laurent Robert
    Abstract:

    Like subset-based methods, the very first finite element versions of digital image correlation were closely related to the regular structure of images, as they were based on regular quadrilateral elements corresponding to an integer number of pixels. The use of unstructured meshes, to exploit the full potential of FE-DIC in structural mechanics, is now widespread. Most of the time, the formulation, the quadrature and the definition of the region of interest still rely on the pixels grid. In this paper, a formulation in the Physical Coordinate System and not in the image frame is proposed for 2D digital image correlation. In addition to a more precise definition of the region of interest, it allows the use of a more accurate quadrature rule. It is also shown that lens distortions can be successfully taken into account directly with such a formalism.