Modelling the microstructure and the viscoelastic behaviour of carbon black filled rubber materials from 3D simulations

International audienceVolume fraction and spatial repartition of fillers impact the physical properties of rubber. Extended percolating networks of nano-sized fillers significantly modify the macroscopic mechanical properties of rubbers. Random models that describe the multiscale microstructure of rubber and efficient Fourier-based numerical algorithms are combined to predict the material’s mechanical properties. From TEM image analysis, various types of multiscale models were proposed and validated, accounting for the non-homogeneous distribution of fillers: in the present work, aggregates are located outside of an exclusion polymer simulated by two families of random models. The first model generates the exclusion polymer by a Boolean model of spheres. In the second model, the exclusion polymer is a mosaic model built from a Johnson-Mehl tessellation. Here the exclusion polymer and the polymer containing the filler show a similar morphology, contrary to the Boolean model. Aggregates are then described as the intersection of a Boolean model of spheres and of the complementary of the exclusion polymer. Carbon black particles are simulated by a Cox model of spheres in the aggregates. The models rely on a limited number of parameters fitted from experimental covariance and cumulative granulometry. The influence of the model parameters on percolation properties of the models is studied numerically from 3D simulations. Finally, a novel Fourier-based algorithm is proposed to estimate the viscoelastic properties of linear heterogeneous media, in the harmonic regime. The method is compared to analytical results and to a different, time-discretized FFT scheme. As shown in this work, the proposed numerical method is efficient for computing the viscoelastic response of microstructures containing rubbers and fillers

3D Morphological modeling of a polycrystaline microstructure with non-convex, anisotropic grains

International audienceTATB (1,3,5-triamino-2,4,6-trinitrobenzene) is an energetic molecular crystal that combines high energetic performance and good thermal stability. By adding a small amount of a polymer acting as a binder between TATB grains, it is possible to obtain exceptionally safe explosives displaying good mechanical properties. A first step toward the understanding of the influence of the microstructure on the mechanical properties of TATB is the development of stochastic models to describe the microstructure of the material

Waterpixels

International audience— Many approaches for image segmentation rely on a 1 first low-level segmentation step, where an image is partitioned 2 into homogeneous regions with enforced regularity and adherence 3 to object boundaries. Methods to generate these superpixels have 4 gained substantial interest in the last few years, but only a few 5 have made it into applications in practice, in particular because 6 the requirements on the processing time are essential but are not 7 met by most of them. Here, we propose waterpixels as a general 8 strategy for generating superpixels which relies on the marker 9 controlled watershed transformation. We introduce a spatially 10 regularized gradient to achieve a tunable tradeoff between the 11 superpixel regularity and the adherence to object boundaries. 12 The complexity of the resulting methods is linear with respect 13 to the number of image pixels. We quantitatively evaluate our 14 approach on the Berkeley segmentation database and compare 15 it against the state-of-the-art

Modelling mesoporous alumina microstructure with 3D random models of platelets

International audienceThis work focuses on a mesoporous material made of nanometric alumina "platelets" of unknown shape. We develop a 3D random microstructure to model the porous material , based on 2D Transmission Electron Microscopy (TEM) images, without prior knowledge on the spatial distribution of alumina inside the material. The TEM images , acquired on samples with thickness 300 nm, a scale much larger than the platelets's size, are too blurry and noisy to allow one to distinguish platelets or platelets aggregates individually. In a first step, the TEM images correlation function and integral range are estimated. The presence of long-range fluctuations, due to the TEM inhomogeneous detection , is detected and corrected by filtering. The corrected correlation function is used as a morphological descriptor for the model. After testing a Boolean model of platelets, a two-scales model of microstructure is introduced to replicate the statistical dispersion of platelets observed on TEM images. Accordingly a set of two-scales Boolean models with varying physically-admissible platelets shapes is proposed. Upon optimization, the model takes into account the dispersion of platelets in the microstructure as observed on TEM images. Comparing it to X-ray diffraction and nitrogen porosimetry data, the model is found to be in good agreement with the material in terms of specific surface area

SMIL: Simple Morphological Image Library

International audienceSMIL est une bibliothèque de traitement d'images 2D/3D. Elle a été développée pour répondre à une demande de plus en plus forte (en particulier dans le cas de projets industriels) en termes de performances : taille d'images (2D ou 3D) et temps d'exécution. Développée en C++ et utilisant les templates, elle peut être utilisée avec n'importe quel type standard de données. Un effort important a été porté sur la factorisation du code (par le biais de functors), d'une part, pour faciliter l'intégration de nouvelles fonctions, et d'autre part pour concentrer les parties du code permettant l'optimisation. Ces "briques" communes optimisées utilisent le code SIMD généré par l'auto-vectorisation de gcc et sont également parallélisées grâce à l'utilisation d'OpenMP

Segmentation of 3D microtomographic images of granular materials with the stochastic watershed

International audienceSegmentation of 3D images of granular materials obtained by microtomography is not an easy task. Because of the conditions of acquisition and the nature of the media, the available images are not exploitable without a reliable method of extraction of the grains. The high connectivity in the medium, the disparity of the object's shape and the presence of image imperfections make classical segmentation methods (using image gradient and watershed constrained by markers) extremely difficult to perform efficiently. In this paper, we propose a non-parametric method using the stochastic watershed, allowing to estimate a 3D probability map of contours. Procedures allowing to extract final segmentation from this function are then presented

Modélisation 3D de réseaux fibreux (un outil pour l'étude des interactions microstructure-propriétés de panneaux de fibres)

Le but de ce travail de recherche est de proposer des outils de représentation de structures fibreuses aléatoires par des modèles probabiliste, en s'appuyant sur l'analyse de milieux réels observés en microtomographie X. Compte tenu de la complexité des matériaux analysés, la reconstruction tridimensionnelle d'un milieu "équivalent", du point de vue de ses propriétés morphologiques (porosité, connectivité), constitue une étape fondamentale. Cette démarche conditionne la possibilité de généraliser à d'autres microstructures fibreuses des interactions entre caractéristiques morphologiques et propriétés physiquesBORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

TOUCHING GRAIN KERNELS SEPARATION BY GAP-FILLING

Separation of touching grain kernels is a recurring problem in image analysis. Morphological methods to separatemerged objects in binary images are generally based on the watershed transformapplied to the inverse of the distance function. This method is efficient with roughly circular objects, but cannot separate objects beyond a certain elliptic shape nor when the contact zones are too numerous or too large. This paper presents a gap-filling method applied to the skeleton of the image background as an alternative technique to go further in the fused objects separation process. Open lines resulting from skeletonization are prolonged according to their direction from corresponding end points. If the distance between two lines is smaller than a certain value, their respective end points are connected. Results of combined use of watershed and gap-filling based methods are presented on sample binary images. An example of its use on an particularly complex image containing rice grains shows that it allows to segment up to 90% of the grains when classical watershed methods allow only to segment 25% of the grains. An application to breakage and cracks assessing of parboiled rice kernels is presented

3D MULTISCALE VECTORIAL SIMULATIONS OF RANDOM MODELS

International audienceWe present here a method using level sets as primary grains to generate 3D simulations of random models in the continuous space. Primary grains of any shape can be used as long as we are able to represent them by an implicit function. Simulations are generated using Boolean combinations of the primary implicit functions. This approach allows us to build complex combinations of simulations that we could not obtain with a pixel based method. Furthermore, vectorial simulations do not require a large amount of computer resources, which allows us to obtain fast generations of microstructures with very large sizes and numbers of primary grains

Assessing Breakage and Cracks of Parboiled Rice Kernels by Image Analysis Techniques

International audienceThis paper deals with the measurement of breakage ratio and the estimation of fissures on parboiled rice by image analysis on unarranged grain samples. Hardware cost of the apparatus is low since it is based on standard off-the-shelf scanner. In addition, open source (free) software is used to complete the experimental setup. An innovative technique for segmentation of touching kernels is used, combined with breakage estimation based on geometric properties and crack estimation using a new image analysis technique. This inexpensive system is validated with reference measurements for breakage and visual inspection for cracks