Optimal orientation estimators for detection of cylindrical objects

International audienceThis paper introduces low level operators in the context of detecting cylindrical axis in 3 D images. Knowing the axis of a cylinder is particularly useful since cylinder location, length and curvature derive from this knowledge. This paper introduces a new gradient-based optimal operator dedicated to accurate estimation of the direction toward the axis. The operator relies on Finite Impulse Response filters. The approach is presented first in a 2-D context, thus providing optimal gradient masks for locating the center of circular objects. Then, a 3-D extension is provided, allowing the exact estimation of the orientation toward the axis of cylindrical objects when this axis coincides with one of the mask reference axes. Applied to more general cylinders and to noisy data, the operator still provides accurate estimation and outperforms classical gradient operators

Contribution of X-ray CMT and image processing to the modelling of pyrocarbon Chemical Vapour Infiltration

International audienceThe Chemical Vapour Infiltration (CVI) process is used to fabricate the pyrocarbon matrices of C/C composites. This process involves complex physico-chemical phenomena such as the transport of precursor, carrier, and by-product gases in the reactor and inside a fibrous preform, heat transfer, chemical reactions (pyrolysis and deposition), and the structural evolution of the preform. It is able to provide high-quality materials because the processing conditions are rather mild with respect to the fibres; however it is expensive and sometimes difficult to optimize. This process has been the object of extensive modelling efforts, because of imperative optimization needs. The present work presents an approach suited to the exploitation of computerized microtomographs of C/C composites, which features image acquisition, computation of geometrical and transport properties, and infiltration modelling, as applied to the infiltration of needled carbon fibre fabrics. Another application to the reinforcement of carbon foams is also presented, as an example of inserting this approach in a global modelling strategy

Modelling Chemical Vapour Infiltration in C/C composites: numerical tools based on µ-CT images

ISBN 978-3-00-032049-1International audienceIn the production of high-quality Ceramic-Matrix Composites, matrix preparation is often made by Chemical Vapor Infiltration (CVI), a process which involves many phenomena such as gas transport, chemical reactions, and structural evolution of the preform. Control and optimization of this high-tech process are demanding for modeling tools.In this context, a numerical simulation of CVI in complex 3D images, acquired e.g. by X-ray Computerized Microtomography, has been developed. The approach addresses the two length scales which are inherent to a composite with woven textile reinforcement (i.e. inter- and intra-bundle), with two numerical tools.The small-scale program allows direct simulation of CVI in small intra-bundle pores. Effective laws for porosity, surface and transport properties as infiltration proceeds are produced by averaging. They are an input for the next modeling step.The second code is a large-scale solver which accounts for the locally heterogeneous and anisotropic character of the pore space. Simulation of the infiltration of a whole composite material part is possible with this program.Validation of these tools on test cases, as well as some examples on actual materials, are shown and discussed

Détection, caractérisation d'objets 3D et simulation d'évolution morphologique appliquée à l'infiltrabilité de préformes fibreuses

This thesis connects image processing and physicochemical modeling to characterize the infiltrability of porous media. Infiltrability means “ability of a porous medium to receive a solid deposit brought by penetration of a carrier fluid”. A practical case is the preparation of ceramic-matrix composites by Chemical Vapor Infiltration (CVI). Various studies have proved that the fiber arrangement in preforms of composite materials affects the density of the material at the final stage. In this work, the morphological evolution of complex 3D porous media during the gas-phase infiltration is studied. The first step consists in the segmentation and characterization X-ray Micro Tomography of the infiltrated composite. The objects to be segmented are quasi cylindrical fibers. Two tools have been developed: an optimal estimator of the orientation toward the axis; and an algorithm to detect and characterize quasi cylindrical objects. Applied on images of fiber-reinforced composites, this approach makes it possible to obtain the block containing the fibers. This block is the complex porous medium used for infiltrability characterization. The second step addresses the fiber-scale modeling of CVI. It is based on Ran walkers and fluid / solid interface management by a simplified marching cube. Our algorithm is innovative since it handles simultaneously chemical reactions, gas transport in rarefied and continuum regimes, and the morphological evolution of porous structure. By combining these two steps, we can compare the deposit obtained by segmentation to simulated deposits obtained in various physicochemical regimes. This allows performing an inverse analysis of the actual deposition conditions from the morphology of the deposit. The provided computational approach also allows the comparison of different porous textures with respect to their infiltrability.Cette thèse associe analyse d’image et modélisation physico-chimique afin de caractériser l’infiltrabilité d’un milieu poreux. Infiltrabilité signifie : « propension d’un milieu poreux à se laisser pénétrer par un fluide apportant un dépôt solide ». Une application est la fabrication de composites à matrice céramique par dépôt chimique en phase gazeuse (CVI). Des études ont montré que l’agencement des fibres d’un matériau composite a un impact sur sa densité finale. Nous proposons d’étudier l’évolution du milieu poreux au cours de l’infiltration pour des architectures complexes. La première étape consiste en la segmentation et la caractérisation de composites déjà densifiés obtenus par micro-tomographie. Les objets à segmenter sont des fibres quasi-cylindriques. Deux outils ont été développés : un estimateur optimal de l’orientation vers l’axe de cylindres, et un algorithme de détection et de caractérisation d’objets quasi-cylindriques. Appliquée aux composites fibreux, cette étape fournit un bloc contenant les fibres. Il constitue le milieu poreux complexe dont on cherche à caractériser l’infiltrabilité. La seconde étape est la modélisation à l’échelle des fibres du procédé CVI. Elle utilise des marcheurs aléatoires, avec une gestion de l’interface du solide par « marching cube simplifié». L’algorithme proposé est novateur car il prend en compte simultanément les réactions chimiques, le transport de gaz en régime raréfié ou continu et l’évolution temporelle de la morphologie d’un milieu poreux. Le couplage des deux étapes permet de comparer le dépôt issu de la segmentation à celui résultant de la simulation dans divers régimes physiques. Il est alors possible d’effectuer une analyse inverse des conditions d’élaboration à partir de la morphologie du dépôt. Les outils proposés permettent aussi de comparer l’infiltrabilité de différentes architectures fibreuses

Détection, caractérisation d'objets 3D et simulation d'évolution morphologique appliquée à l'infiltrabilité de préformes fibreuses

This thesis connects image processing and physicochemical modeling to characterize the infiltrability of porous media. Infiltrability means “ability of a porous medium to receive a solid deposit brought by penetration of a carrier fluid”. A practical case is the preparation of ceramic-matrix composites by Chemical Vapor Infiltration (CVI). Various studies have proved that the fiber arrangement in preforms of composite materials affects the density of the material at the final stage. In this work, the morphological evolution of complex 3D porous media during the gas-phase infiltration is studied. The first step consists in the segmentation and characterization X-ray Micro Tomography of the infiltrated composite. The objects to be segmented are quasi cylindrical fibers. Two tools have been developed: an optimal estimator of the orientation toward the axis; and an algorithm to detect and characterize quasi cylindrical objects. Applied on images of fiber-reinforced composites, this approach makes it possible to obtain the block containing the fibers. This block is the complex porous medium used for infiltrability characterization. The second step addresses the fiber-scale modeling of CVI. It is based on random walkers and fluid / solid interface management by a simplified marching cube. Our algorithm is innovative since it handles simultaneously chemical reactions, gas transport in rarefied and continuum regimes, and the morphological evolution of porous structure. By combining these two steps, we can compare the deposit obtained by segmentation to simulated deposits obtained in various physicochemical regimes. This allows performing an inverse analysis of the actual deposition conditions from the morphology of the deposit. The provided computational approach also allows the comparison of different porous textures with respect to their infiltrability.Cette thèse associe analyse d’image et modélisation physico-chimique afin de caractériser l’infiltrabilité d’un milieu poreux. Infiltrabilité signifie : « propension d’un milieu poreux à se laisser pénétrer par un fluide apportant un dépôt solide ». Une application est la fabrication de composites à matrice céramique par dépôt chimique en phase gazeuse (CVI). Des études ont montré que l’agencement des fibres d’un matériau composite a un impact sur sa densité finale. Nous proposons d’étudier l’évolution du milieu poreux au cours de l’infiltration pour des architectures complexes. La première étape consiste en la segmentation et la caractérisation de composites déjà densifiés obtenus par micro-tomographie. Les objets à segmenter sont des fibres quasi-cylindriques. Deux outils ont été développés : un estimateur optimal de l’orientation vers l’axe de cylindres, et un algorithme de détection et de caractérisation d’objets quasi-cylindriques. Appliquée aux composites fibreux, cette étape fournit un bloc contenant les fibres. Il constitue le milieu poreux complexe dont on cherche à caractériser l’infiltrabilité. La seconde étape est la modélisation à l’échelle des fibres du procédé CVI. Elle utilise des marcheurs aléatoires, avec une gestion de l’interface du solide par « marching cube simplifié». L’algorithme proposé est novateur car il prend en compte simultanément les réactions chimiques, le transport de gaz en régime raréfié ou continu et l’évolution temporelle de la morphologie d’un milieu poreux. Le couplage des deux étapes permet de comparer le dépôt issu de la segmentation à celui résultant de la simulation dans divers régimes physiques. Il est alors possible d’effectuer une analyse inverse des conditions d’élaboration à partir de la morphologie du dépôt. Les outils proposés permettent aussi de comparer l’infiltrabilité de différentes architectures fibreuses

Détection, caractérisation d'objets 3D et simulation d'évolution morphologique appliquée à l'infiltrabilité de préformes fibreuses

Cette thèse associe analyse d image et modélisation physico-chimique afin de caractériser l infiltrabilité d un milieu poreux. Infiltrabilité signifie : propension d un milieu poreux à se laisser pénétrer par un fluide apportant un dépôt solide . Une application est la fabrication de composites à matrice céramique par dépôt chimique en phase gazeuse (CVI). Des études ont montré que l agencement des fibres d un matériau composite a un impact sur sa densité finale. Nous proposons d étudier l évolution du milieu poreux au cours de l infiltration pour des architectures complexes. La première étape consiste en la segmentation et la caractérisation de composites déjà densifiés obtenus par micro-tomographie. Les objets à segmenter sont des fibres quasi-cylindriques. Deux outils ont été développés : un estimateur optimal de l orientation vers l axe de cylindres, et un algorithme de détection et de caractérisation d objets quasi-cylindriques. Appliquée aux composites fibreux, cette étape fournit un bloc contenant les fibres. Il constitue le milieu poreux complexe dont on cherche à caractériser l infiltrabilité. La seconde étape est la modélisation à l échelle des fibres du procédé CVI. Elle utilise des marcheurs aléatoires, avec une gestion de l interface du solide par marching cube simplifié . L algorithme proposé est novateur car il prend en compte simultanément les réactions chimiques, le transport de gaz en régime raréfié ou continu et l évolution temporelle de la morphologie d un milieu poreux. Le couplage des deux étapes permet de comparer le dépôt issu de la segmentation à celui résultant de la simulation dans divers régimes physiques. Il est alors possible d effectuer une analyse inverse des conditions d élaboration à partir de la morphologie du dépôt. Les outils proposés permettent aussi de comparer l infiltrabilité de différentes architectures fibreuses.This thesis connects image processing and physicochemical modeling to characterize the infiltrability of porous media. Infiltrability means ability of a porous medium to receive a solid deposit brought by penetration of a carrier fluid . A practical case is the preparation of ceramic-matrix composites by Chemical Vapor Infiltration (CVI). Various studies have proved that the fiber arrangement in preforms of composite materials affects the density of the material at the final stage. In this work, the morphological evolution of complex 3D porous media during the gas-phase infiltration is studied. The first step consists in the segmentation and characterization X-ray Micro Tomography of the infiltrated composite. The objects to be segmented are quasi cylindrical fibers. Two tools have been developed: an optimal estimator of the orientation toward the axis; and an algorithm to detect and characterize quasi cylindrical objects. Applied on images of fiber-reinforced composites, this approach makes it possible to obtain the block containing the fibers. This block is the complex porous medium used for infiltrability characterization. The second step addresses the fiber-scale modeling of CVI. It is based on random walkers and fluid / solid interface management by a simplified marching cube. Our algorithm is innovative since it handles simultaneously chemical reactions, gas transport in rarefied and continuum regimes, and the morphological evolution of porous structure. By combining these two steps, we can compare the deposit obtained by segmentation to simulated deposits obtained in various physicochemical regimes. This allows performing an inverse analysis of the actual deposition conditions from the morphology of the deposit. The provided computational approach also allows the comparison of different porous textures with respect to their infiltrability.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Infiltrability properties of porous media using X-ray CMT of thermostructural material

International audienceThermostructural composites are increasingly used in many industrial applications that require materials with excellent thermo-mechanical properties at high temperature. These materials usually consist in the combination of a matrix embedding a reinforcement made of cylindrical fibers. The quality of the composites depends partly on the matrix infiltration step, in our case performed by Chemical Vapor Infiltration (CVI) process, because it is decisive on the residual porosity and the matrix quality. Experimental determination of the optimal processing parameters is expensive and time-consuming, so it seems interesting to model this process. The morphological evolution of the preform has an impact on the infiltration through various phenomena (gas transport, chemical reactions). To understand the influence of the pore shapes on infiltration quality, an approach has been developed, which is based on 3D images acquired by synchrotron X-ray microtomography. Image processing allows separating the raw fibers from the matrix and the remaining voids; then, morphological parameters (pore and fiber diameters, matrix thickness, etc ...) become accessible. A computer code based on a Monte Carlo/Random Walks algorithm with surface discretization by Simplified Marching Cubes makes it possible to model the infiltration. The comparison of the segmented and the simulated matrix blocks gives information on the infiltrability of the preform. Then, it becomes possible to relate infiltrability to physicochemical parameters and to the fiber arrangement, and also to predict optimal infiltration conditions of a given new texture

Impact de la texture d'une préforme sur son infiltrabilité : Evolution morphologique du matériau poreux au cours de la densification

La CVI (Chemical Vapor Infiltration) est un procédé d'élaboration des composites thermostruturaux. La préforme fibreuse est placée dans une enceinte chauffée à haute température dans laquelle un gaz est introduit. Celui-ci pénètre grâce aux différents types de transports de gaz (convection, diffusion...) dans le milieu poreux. La densification s'effectue par réaction chimique hétérogène du gaz avec la texture solide. La qualité d'un composite thermostructural dépend en partie du déroulement du procédé CVI. En particulier, les différents phénomènes intervenant au cours de la densification du milieu poreux sont régis par des lois qui dépendent de l'évolution de la géométrie de la préforme et de sa porosité. Il semble donc intéressant de connaître l'effet de la texture de la préforme sur son infiltrabilité, ce qui permettra par la suite de modéliser le processus de CVI. Le travail présenté s'inscrit dans cette étude en l'abordant à partir d'images 3D de matériaux réels obtenues par tomographie synchrotron à différents stades de densification. Le traitement de ces images associé à la simulation physico-chimique permettront de comprendre l'évolution de la texture de la préforme et de caractériser son effet sur l'infiltrabilité et donc le processus de densification. La démarche globale de validation est de segmenter les blocs d'images de matériaux densifiés, c'est-à-dire de récupérer l'architecture fibreuse et le dépôt de matrice séparément, pour ensuite comparer le dépôt réel à celui simuler à partir de la texture segmentée. Ce papier présente les différentes étapes de l'approche ainsi que les premiers résultats obtenus sur des extraits de blocs 3D

Axis detection method for cylindrical objects

International audienceThis paper introduces an algorithm dedicated to the detection of the axes of cylindrical objects in a 3-D block. The proposed algorithm performs the 3-D axis detection without prior segmentation of the block. This approach is specifically appropriate when the grey levels of the cylindrical object are not homogeneous and thus difficult to distinguish from the background. The method relies on gradient and curvature estimation and operates in two main steps. The first one selects candidate voxels for the axis and the second one refines the determination of the axis of each cylindrical object. Applied to fiber reinforced composite materials, this algorithm allows detecting the axes of fibers in order to obtain the geometrical characteristics of the reinforcement. Knowing the reinforcement characteristics is an important issue in the quality control of the material but also in the prediction of the thermal and mechanical behavior. In this paper, the various steps of the algorithm are detailed. Then, results obtained with synthetic blocks and with blocks acquired by synchrotron X-ray microtomography on actual carbon-fiber reinforced carbon (C/C) composites are presented

Axis detection of cylindrical objects in 3-D images

This paper introduces an algorithm dedicated to the detection of the axes of cylindrical objects in a 3-D block. The proposed algorithm performs the 3-D axis detection without prior segmentation of the block. This approach is specifically appropriate when the grey levels of the cylindrical objects are not homogeneous and thus difficult to distinguish from the background. The method relies on gradient and curvature estimation and operates in two main steps. The first one selects candidate voxels for the axes and the second one refines the determination of the axis of each cylindrical object. Applied to fiber reinforced composite materials, this algorithm allows detecting the axes of fibers in order to obtain the geometrical characteristics of the reinforcement. Knowing the reinforcement characteristics is an important issue in the quality control of the material but also in the prediction of the thermal and mechanical performance. In this paper, the various steps of the algorithm are detailed. Then, some results are presented, obtained with both synthetic blocks and real data acquired by synchrotron X-ray micro tomography on carbon-fiber reinforced carbon composites. 2 hal-00326703, version 1- 5 Oct 2008 1