Academic literature on the topic 'Tissu orthotrope'

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Journal articles on the topic "Tissu orthotrope"

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Cowin, S. C. "Torsion of Cylinders With Shape Intrinsic Orthotropy." Journal of Applied Mechanics 54, no. 4 (December 1, 1987): 778–82. http://dx.doi.org/10.1115/1.3173116.

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Shape intrinsic orthotropy may be thought of as the type of elastic material symmetry possessed by the wood tissue of a tree. Each year’s new growth rings form a laminate around a central core. The axes of material symmetry lie in the directions tangent and normal to the growth rings or laminates and along the axis of the cylinder. Let Gtz denote the linear elastic orthotropic shear modulus associated with the axial and tangential directions, the tangent plane of a laminate. It is shown here that, for a certain class of elastic cylinders with shape intrinsic orthotropy, the solution to the torsion problem is the same as the solution to the torsion problem for the isotropic cylinder of the same shape if the isotropic shear modulus G were replaced by the orthotropic shear modulus Gtz.
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Kawamura, Koji, and Hiroshi Takeda. "Rules of crown development in the clonal shrub Vaccinium hirtum in a low-light understory: a quantitative analysis of architecture." Canadian Journal of Botany 82, no. 3 (March 1, 2004): 329–39. http://dx.doi.org/10.1139/b04-001.

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The rules of crown development in the clonal shrub Vaccinium hirtum Thunb. in a low-light understory were identified by architectural analysis, and the structure and dynamics of current-year shoots were quantified. Development started from an initial orthotropic axis, which forked into plagiotropic axes; consequently, arched stems were formed. Subsequently, a new orthotropic shoot arose from the dormant meristem on the stem. The process from orthotrophy to plagiotrophy was then repeated. Ramets developed vertically as a result of the repeated formation of such orthotropic shoots and reached a maximum height of about 2 m. These processes were mainly characterized by the sequential change from orthotrophy to plagiotrophy in stem orientation and by a sequential reduction in shoot growth, in which a long shoot forked into shorter shoots with increasing allocation to leaves relative to stems. These rules may be adaptive for efficient light capture under conditions of low light availability, in terms of a low degree of self-shading and low cost of supporting tissue. Simultaneously, these rules worked to restrict the developmental potential of crowns, including the lateral expansion of crowns and the longevity of branch systems. This may be associated with a shrub-specific, throwaway design for stems that are expendable in high-stress environments.Key words: crown architecture, branching, leaf display, architectural unit, reiteration.
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Zysset, P. K., R. W. Goulet, and S. J. Hollister. "A Global Relationship Between Trabecular Bone Morphology and Homogenized Elastic Properties." Journal of Biomechanical Engineering 120, no. 5 (October 1, 1998): 640–46. http://dx.doi.org/10.1115/1.2834756.

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An alternative concept of the relationship between morphological and elastic properties of trabecular bone is presented and applied to human tissue from several anatomical locations using a digital approach. The three-dimensional morphology of trabecular bone was assessed with a microcomputed tomography system and the method of directed secants as well as the star volume procedure were used to compute mean intercept length (MIL) and average bone length (ABL) of 4 mm cubic specimens. Assuming isotropic elastic properties for the trabecular tissue, the general elastic tensors of the bone specimens were determined using the homogenization method and the closest orthotropic tensors were calculated with an optimization algorithm. The assumption of orthotropy for trabecular bone was found to improve with specimen size and hold within 6.1 percent for a 4 mm cube size. A strong global relationship (r2 = 0.95) was obtained between fabric and the orthotropic elastic tensor with a minimal set of five constants. Mean intercept length and average bone length provided an equivalent power of prediction. These results support the hypothesis that the elastic properties of human trabecular bone from an arbitrary anatomical location can be estimated from an approximation of the anisotropic morphology and a prior knowledge of tissue properties.
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Benson, Alan P., Olivier Bernus, Hans Dierckx, Stephen H. Gilbert, John P. Greenwood, Arun V. Holden, Kevin Mohee, et al. "Construction and validation of anisotropic and orthotropic ventricular geometries for quantitative predictive cardiac electrophysiology." Interface Focus 1, no. 1 (December 3, 2010): 101–16. http://dx.doi.org/10.1098/rsfs.2010.0005.

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Reaction–diffusion computational models of cardiac electrophysiology require both dynamic excitation models that reconstruct the action potentials of myocytes as well as datasets of cardiac geometry and architecture that provide the electrical diffusion tensor D , which determines how excitation spreads through the tissue. We illustrate an experimental pipeline we have developed in our laboratories for constructing and validating such datasets. The tensor D changes with location in the myocardium, and is determined by tissue architecture. Diffusion tensor magnetic resonance imaging (DT-MRI) provides three eigenvectors e i and eigenvalues λ i at each voxel throughout the tissue that can be used to reconstruct this architecture. The primary eigenvector e 1 is a histologically validated measure of myocyte orientation (responsible for anisotropic propagation). The secondary and tertiary eigenvectors ( e 2 and e 3 ) specify the directions of any orthotropic structure if λ 2 is significantly greater than λ 3 —this orthotropy has been identified with sheets or cleavage planes. For simulations, the components of D are scaled in the fibre and cross-fibre directions for anisotropic simulations (or fibre, sheet and sheet normal directions for orthotropic tissues) so that simulated conduction velocities match values from optical imaging or plunge electrode experiments. The simulated pattern of propagation of action potentials in the models is partially validated by optical recordings of spatio-temporal activity on the surfaces of hearts. We also describe several techniques that enhance components of the pipeline, or that allow the pipeline to be applied to different areas of research: Q ball imaging provides evidence for multi-modal orientation distributions within a fraction of voxels, infarcts can be identified by changes in the anisotropic structure—irregularity in myocyte orientation and a decrease in fractional anisotropy, clinical imaging provides human ventricular geometry and can identify ischaemic and infarcted regions, and simulations in human geometries examine the roles of anisotropic and orthotropic architecture in the initiation of arrhythmias.
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Holzapfel, Gerhard A., and Ray W. Ogden. "Constitutive modelling of passive myocardium: a structurally based framework for material characterization." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1902 (September 13, 2009): 3445–75. http://dx.doi.org/10.1098/rsta.2009.0091.

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In this paper, we first of all review the morphology and structure of the myocardium and discuss the main features of the mechanical response of passive myocardium tissue, which is an orthotropic material. Locally within the architecture of the myocardium three mutually orthogonal directions can be identified, forming planes with distinct material responses. We treat the left ventricular myocardium as a non-homogeneous, thick-walled, nonlinearly elastic and incompressible material and develop a general theoretical framework based on invariants associated with the three directions. Within this framework we review existing constitutive models and then develop a structurally based model that accounts for the muscle fibre direction and the myocyte sheet structure. The model is applied to simple shear and biaxial deformations and a specific form fitted to the existing (and somewhat limited) experimental data, emphasizing the orthotropy and the limitations of biaxial tests. The need for additional data is highlighted. A brief discussion of issues of convexity of the model and related matters concludes the paper.
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Semenova, Elena, Nikita Kharin, Pavel Bolshakov, Anastasiya Ivanova, and Viktoriya Yaikova. "Automatic processing and analysis of the structural properties of bone tissue." MATEC Web of Conferences 329 (2020): 03077. http://dx.doi.org/10.1051/matecconf/202032903077.

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The volumetric distribution of bone tissue can be analysed in terms of orthotropic medium. In this case, it is important to define the orthotropic directions. Nowadays, computed tomography methods allow getting such information. The method for automation such analysis is presented. Firstly, the threshold of binarization should be calculated. Then the sample should be meshed and each element should be binarized. After that fabric tensor, eigenvalues, eigenvectors and fractional anisotropy can be calculated for each element. Statistical methods were used to analyse the field of the obtained data. Described methods were used on a bone sample. It was shown that for a sample the fabric tensor is constant and the fractional anisotropy is close to zero. That’s means that the medium in the sample was isotropic.
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Turner, C. H., and S. C. Cowin. "Errors Induced by Off-Axis Measurement of the Elastic Properties of Bone." Journal of Biomechanical Engineering 110, no. 3 (August 1, 1988): 213–15. http://dx.doi.org/10.1115/1.3108433.

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Misalignment between the axes of measurement and the material symmetry axes of bone causes error in anisotropic elastic property measurements. Measurements of Poisson’s ratio were strongly affected by misalignment errors. The mean errors in the measured Young’s moduli were 9.5 and 1.3 percent for cancellous and cortical bone, respectively, at a misalignment angle of 10 degrees. Mean errors of 1.1 and 5.0 percent in the measured shear moduli for cancellous and cortical bone, respectively, were found at a misalignment angle of 10 degrees. Although, cancellous bone tissue was assumed to have orthotropic elastic symmetry, the possibility of the greater symmetry of transverse isotropy was investigated. When the nine orthotropic elastic constants were forced to approximate the five transverse isotropic elastic constants, errors of over 60 percent were introduced. Therefore, it was concluded that cancellous bone is truly orthotropic and not transversely isotropic. A similar but less strong result for cortical bone tissue was obtained.
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Ruiz-Baier, Ricardo. "Modelling Thermo-Electro-Mechanical Effects in Orthotropic Cardiac Tissue." Communications in Computational Physics 27, no. 1 (June 2020): 87–115. http://dx.doi.org/10.4208/cicp.oa-2018-0253.

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Koombua, Kittisak, and Ramana M. Pidaparti. "Inhalation Induced Stresses and Flow Characteristics in Human Airways through Fluid-Structure Interaction Analysis." Modelling and Simulation in Engineering 2008 (2008): 1–8. http://dx.doi.org/10.1155/2008/358748.

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Better understanding of stresses and flow characteristics in the human airways is very important for many clinical applications such as aerosol drug therapy, inhalation toxicology, and airway remodeling process. The bifurcation geometry of airway generations 3 to 5 based on the ICRP tracheobronchial model was chosen to analyze the flow characteristics and stresses during inhalation. A computational model was developed to investigate the airway tissue flexibility effect on stresses and flow characteristics in the airways. The finite-element method with the fluid-structure interaction analysis was employed to investigate the transient responses of the flow characteristics and stresses in the airways during inhalation. The simulation results showed that tissue flexibility affected the maximum airflow velocity, airway pressure, and wall shear stress about 2%, 7%, and 6%, respectively. The simulation results also showed that the differences between the orthotropic and isotropic material models on the airway stresses were in the ranges of 25–52%. The results from the present study suggest that it is very important to incorporate the orthotropic tissue properties into a computational model for studying flow characteristics and stresses in the airways.
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Pervolaraki, Eleftheria, Richard A. Anderson, Alan P. Benson, Barrie Hayes-Gill, Arun V. Holden, Benjamin J. R. Moore, Martyn N. Paley, and Henggui Zhang. "Antenatal architecture and activity of the human heart." Interface Focus 3, no. 2 (April 6, 2013): 20120065. http://dx.doi.org/10.1098/rsfs.2012.0065.

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We construct the components for a family of computational models of the electrophysiology of the human foetal heart from 60 days gestational age (DGA) to full term. This requires both cell excitation models that reconstruct the myocyte action potentials, and datasets of cardiac geometry and architecture. Fast low-angle shot and diffusion tensor magnetic resonance imaging (DT-MRI) of foetal hearts provides cardiac geometry with voxel resolution of approximately 100 μm. DT-MRI measures the relative diffusion of protons and provides a measure of the average intravoxel myocyte orientation, and the orientation of any higher order orthotropic organization of the tissue. Such orthotropic organization in the adult mammalian heart has been identified with myocardial sheets and cleavage planes between them. During gestation, the architecture of the human ventricular wall changes from being irregular and isotropic at 100 DGA to an anisotropic and orthotropic architecture by 140 DGA, when it has the smooth, approximately 120° transmural change in myocyte orientation that is characteristic of the adult mammalian ventricle. The DT obtained from DT-MRI provides the conductivity tensor that determines the spread of potential within computational models of cardiac tissue electrophysiology. The foetal electrocardiogram (fECG) can be recorded from approximately 60 DGA, and RR, PR and QT intervals between the P, R, Q and T waves of the fECG can be extracted by averaging from approximately 90 DGA. The RR intervals provide a measure of the pacemaker rate, the QT intervals an index of ventricular action potential duration, and its rate-dependence, and so these intervals constrain and inform models of cell electrophysiology. The parameters of models of adult human sinostrial node and ventricular cells that are based on adult cell electrophysiology and tissue molecular mapping have been modified to construct preliminary models of foetal cell electrophysiology, which reproduce these intervals from fECG recordings. The PR and QR intervals provide an index of conduction times, and hence propagation velocities (approx. 1–10 cm s −1 , increasing during gestation) and so inform models of tissue electrophysiology. Although the developing foetal heart is small and the cells are weakly coupled, it can support potentially lethal re-entrant arrhythmia.
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Dissertations / Theses on the topic "Tissu orthotrope"

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Nguyen, Thanh Truong. "Numerical modeling and buckling analysis of inflatable structures." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10123.

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L’objectif principal de cette thèse est de modéliser en flambement des poutres pressurisées en tissu souple homogène orthotrope (THO) composite. La première partie détaille les études expérimentales qui ont été menées sur des poutres gonflables à certain niveaux de pression afin de caractériser les propriétés mécaniques du matériau et le comportement en flambement de la structure. Dans une deuxième partie, une approche analytique a été envisagée afin d’étudier le flambement ainsi que le comportement d’une poutre gonflable orthotrope. Un modèle 3D gonflables poutre orthotrope basé sur la cinématique de Timoshenko a été présenté brièvement. La charge critique a été étudiée pour différents cas de charge avec différentes conditions aux limites. Les résultats ont été confrontés aux résultats théoriques disponibles. Pour vérifier la limite de validité des résultats, la charge d’apparition des plis a également fait l’objet d’une étude pour chacun des cas. La dernière partie est consacrée à une étude linéaire et à une analyse non-linéaire du flambement de la poutre gonflable en THO composite. Le modèle éléments finis (MEF) établi ici implique un élément poutre de Timoshenko à trois-nœuds avec une continuité de type C0. Un test de convergence du maillage sur la force critique de la poutre a été réalisé par la résolution du problème aux valeurs propres. En outre, un MEF non-linéaire a été développé en utilisant la procédure itérative de quasi-Newton avec incréments de chargement adaptatif permettant le tracé pas à pas de la réponse charge-déflexion de la poutre. Les résultats ont été validés à partir d’un certain niveau de pression par des résultats expérimentaux et numériques
The main goals of this thesis are to modeling and to perform the buckling study of inflatable beams made from homogeneous orthotropic woven fabric (HOWF) composite. Three main scenarios were investigated in this thesis. The first is the experimental studies which were performed on HOWF inflatable beam in various inflation pressures for characterizing the orthotropic mechanical properties and buckling behaviors of the beam. In the second scenario, an analytical approach was considered to study the buckling and the behavior of an inflatable orthotropic beam. A 3D inflatable orthotropic beam model based on the Timoshenko's kinematics was briefly introduced: the nonlinearities (finite rotation, follower forces) were included in this model. The results were compared with theoretical results available in the literature. To check the limit of validity of the results, the wrinkling load was also presented in every case. The last scenario is devoted to the linear eigen and non-linear buckling analysis of inflatable beam made of HOWF. The finite element (FE) model established here involves a three-noded Timoshenko beam element with C0-type continuity for the transverse displacement and quadratic shape functions for the bending rotation and the axial displacement. In the linear buckling analysis, a mesh convergence test on the beam critical load was carried out by solving the linearized eigenvalue problem. In addition, a nonlinear FE model was developed by using the quasi-Newton iteration with adaptive load stepping for tracing load-deflection response of the beam. The results were validated from a certain pressure level by experimental and thin-shell FE results
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Apedo, Komla Lolonyo. "Numerical modelling of inflatable structures made of orthotropic technical textiles : application to the frames of inflatable tents." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10145.

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L'objectif principal visé par cette thèse est de modéliser les poutres gonflables en textiles techniques orthotropes. Les approches statiques font l'objet de ce rapport. Avant d'aborder ce problème, nous avons été amenés à identifier tous les paramètres qui ont un effet direct sur les propriétés mécaniques effectives de ces composites. Ainsi, nous avons développé un modèle micro mécanique de prédiction de ces propriétés mécaniques. Le modèle proposé est basé sur l’analyse d'un volume élémentaire représentatif (VER) prenant en compte non seulement les propriétés mécaniques et la. fraction de volume de chaque phase dans le VER mais également leur géométrie et leur architecture. Chaque fil dans le VER a été modélisé comme un matériau isotrope transverse (contenant les fibres et la résine). La méthode dite d’assemblage de cylindres a été utilisée pour l’homogénéisation au niveau des fils. Une deuxième homogénéisation est ensuite réalisée. Elle prend en compte la fraction de volume de chaque constituant (fils de chaîne, fils de trame et résine non prise en compte dans les fils). Le modèle a été validé par des résultats expérimentaux existant dans la littérature. Une élude paramétrique a été menée afin d'étudier les effets des divers paramètres géométriques et mécaniques sur ces propriétés mécaniques. Dans l'analyse structurale, un modèle poutre gonflable 3D de Timoshenko en tissu orthotrope a été proposé. Il prend en compte les non-linéarités géométriques et l'effet de la force suiveuse générée par la pression de gonflage. Les équations d'équilibre non-linéaires dérivent du principe des travaux virtuels en configuration lagrangienne totale. Dans une première approche, une linéarisation a été faite autour de la configuration de référence précontrainte pour obtenir les équations adaptées aux problèmes linéaires. A titre d'exemple, le problème de flexion plane a été abordé. Quatre cas de conditions aux limites ont été traités et les résultats obtenus améliorent les modèles existants dans le cas de tissu isotrope. Les charges de plissage ont été également proposées dans chaque cas traité. Dans une deuxième approche, les équations non-linéaires ont été discrétisées par la méthode des éléments finis. Deux types de solutions ont été alors proposées : les solutions aux problèmes éléments finis linéaires obtenues par une linéarisation des équations discrétisées autour de la configuration de référence précontrainte et les solutions aux problèmes éléments finis non-linéaires réalisées en adoptant une méthode Quasi-Newton sous sa forme incrémentale. A titre d’exemple, la flexion d’une poutre encastrée-libre a été étudiée et les résultats améliorent les modèles théoriques. Le modèle éléments finis non-linéaire a été comparé favorablement à un modèle éléments finis coque mince 3D. Une étude paramétrique a été ensuite effectuée. Elle a porté sur l'influence des propriétés mécaniques et sur de la pression de gonflage sur la réponse de la poutre. Les solutions éléments finis linéaires se sont avérées proches des résultats théoriques linéarisés d'une part et les résultats du modèle éléments finis non-linéaire se sont avérés proches des résultats du modèle linéaire dans le cas des propriétés mécaniques élevées alors que le modèle éléments finis non-linéaire est indispensable pour modéliser ces poutres lorsque les propriétés mécaniques du tissu sont faibles
The main objective of this thesis was to model inflatable beams made frorn orthotropic woven fabric composites. The static aspects were investigated in this report. Before planning to develop these models, it was necessary to know all the parameters which have a direct effect on the effective mechanical properties these composites. Thus, a micro­ mechanical model was performed for predicting the effective mechanical properties. The proposed model was based on the analysis of the representative volume element (RVE). The model took into account not only the mechanical properties and volume fraction of each components in the RVE but also their geometry and architecture. Each yarn in the RVE was modelled as a transversely isotropic material (containing fibres and resin) using the concentric cylinders model (CCIVI). A second volumetric averaging which took into account the volume fraction of each constituent (warp yarn, weft yarn and resin), was performed. The model was validated favorably against experimental available data. A parametric study was conducted in order to investigate the effects of various geometrical and mechanical parameters on the elastic properties of these composites. ln the structural analysis, a 3D Timoshenko airbeam with a homogeneous orthotropic woven fabric (OWF) was addressed. The model took into account the geometrical nonlinearities and the inflation pressure follower force effect. The analytical equilibrium equations were performed using the total Lagrangian form of the virtual work principle. As these equations were nonlinear, in a first approach, a linearization was performed at the prestressed reference configuration to obtain the equations devoted to linearized problems. As example, the bending problem was investigated. Four cases of boundary conditions were treated and the deflections and rotations results improved the existing models in the case of isotropic fabric. The wrinkling load in every case was also proposed. In a second approach, the nonlinear equilibrium equations of the 3DTimoshenko airbeam were discretized by the finite element method. Two finite element solutions were then investigated : finite element solutions for linearized problems which were obtained by the means of the linearization around the prestressed reference configuration of the nonlinear equations and nonlinear finite element solutions which were performed by the use of an optimization algorithm based on the Qua.si-Newton method. As an example, the bending problem of a cantilever inflated beam under concentrated load was considered and the deflection results improve the theoretical models. As these beams are made from fabric, the beam models were validated through their comparison with a 3D thin-shell finite element model. The influence of the material effective properties and the inflation pressure on the beam response was also investigated through a parametric study. The finite element solutions for linearized problems were found to be close to the theoretical linearized results. On the other hand, the results for the nonlinear finite element model were shown to be close to the results for the linearized finite element model in the case of high mechanical properties and the non linear finite element model was used to improve the linearized model when the mechanical properties of the fabric are low
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Mailler, Philippe. "Rhéologie des membranes composites souples orthotropes sous chargement multi-axial." Lyon 1, 1996. http://www.theses.fr/1996LYO10143.

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La recherche aborde l'identification et la modelisation du comportement rheologique de composites souples (tissu de fibres de polyester enduit de polychlorure de vinyle) utilises sous forme de membranes pour l'architecture tensible. Le bilan bibliographique met en evidence l'absence de methodes de caracterisation de ces composites orthotropes sous sollicitations multiaxiales et l'absence de methodes previsionnelles pour decrire le comportement rheologique de ces materiaux et prevoir l'evolution du comportement en rigidite et a rupture en fonction du temps et de l'environnement. La premiere partie de la these est consacree a la conception et a la validation d'une machine d'essai de traction biaxiale regulee en charge et en deplacement. La methodologie experimentale porte d'une part sur des mesures de champs de deplacement par des techniques d'extensometrie optique et sur l'analyse des champs de contraintes corriges en fonction des geometries des eprouvettes et de l'anisotropie du materiau. L'etude du comportement rheologique et l'identification des fonctions fluage et relaxation des membranes est abordee en realisant des essais de fluage thermostimules et en appliquant le principe d'equivalence temps temperatures. Parallelement a partir de la mesure des proprietes viscoelastiques des fibres et de la matrice et de l'identification de modeles rheologiques ou de derivees fractionnaires, en appliquant des expressions previsionnelles de calcul des caracteristiques en rigidite des structures textiles considerees a l'echelle microscopique, nous proposons une formulation des fonctions fluage et relaxation. La validation de ces methodologies theorico-experimentales est faite par une confrontation avec des resultats de fluage obtenus dans des bases de temps et dans des conditions d'environnement reelles
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Chatain, Szostkiewicz Catherine. "Méthodes mixtes numériques et expérimentales pour la caractérisation en rigidité et la fissuration de membranes composites orthotropes." Lyon 1, 1998. http://www.theses.fr/1998LYO10288.

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L'etude du comportement pathologique des membranes composites orthotropes mises en uvre en architecture tensible met en evidence des singularites de comportement induites par les effets d'anisotropie propres aux renforts multidirectionnels textiles et des mecanismes de rupture localises dans des zones a forte concentration de contraintes se traduisant par des amorcages et des propagations de fissures. Dans une premiere partie, nous avons developpe une methode mixte numerique et experimentale d'identification de la matrice de rigidite de membrane d'un materiau orthotrope. Le champ de deformations, en partie centrale de l'eprouvette cruciforme, est mesure par un dispositif optique adapte aux grands deplacements. Le champ de contraintes correspondant est evalue avec un code de calcul aux elements finis (ansys). La matrice de rigidite est ensuite determinee par un calcul inverse combinant les resultats issus d'essais de traction bi-axiale, controles en force ou en deplacement, avec differents rapports de chargement. Les resultats obtenus sont confrontes a ceux deduits de calculs previsionnels (modeles multicouches et unidirectionnel a ondulations). Dans une seconde partie, nous avons observe et analyse les mecanismes de ruine d'une eprouvette entaillee, notamment par l'evaluation de l'influence de la longueur et de l'orientation initiales de la fissure sur sa propagation (mode i). L'application de la mecanique lineaire elastique de la rupture et de ses extensions ont permis la determination de valeurs caracteristiques de la propagation de fissures (tenacite k i c). Parallelement, nous etudions deux solutions numeriques au probleme de fissuration pose : la premiere comprenant un macro-element fissurant et la seconde, plus classique, un raffinement du maillage en fond d'entaille. En conclusion, nous sommes en mesure de proposer des lois de comportement et des criteres de rupture plus realistes pour effectuer le dimensionnement des structures tensibles.
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Book chapters on the topic "Tissu orthotrope"

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S. Kulkarni, Mrudula. "Mechanical Properties and Elasticity Model for Bovine Hard Tissue." In Bovine Science [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98410.

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This chapter aims at establishing engineering material properties of bovine hard tissue cut out of long bone. The study and design of implants, medical devices, and their bone material necessitate the knowledge of mechanical properties of bone to be evaluated. Braces or steel plates are used as fixation devices in animals who are treated for the fracture to bone or cracked bone. Braces or steel plates are fixed to the bone by rods and screws. For checking the stability of these inserted metallic parts, they have to be compatible with bone. The metal and bone form composite action for the load transfer mechanism. To ensure proper biomechanics and design of these inserts and accessories, we need to know the elastic properties of bone. This chapter establishes the modulus of elasticity, poisons ratio of Bovine femur bone. The experimental study establishes the orthotropic behavior of Bovidae femur bone. This experimental research provides comprehensive mechanical properties of Bovidae femur bone, through series of mechanical tests. By performing compression tests on a bone specimen, stress, strain, elastic modulus, poison’s ratio, and yielding point of bone are established. The bovine long bone exhibits orthotropic or transversely isotropic nature of femur bone as expected. The data presented here is for samples derived from goat and water buffalo. The solid mechanics approach using stiffness matrix is adopted to establish elastic constants. The data of elastic constants, compliance, and stiffness coefficients obtained can be used for finite element analysis to simulate stability of composite, femur bone, and metallic fixation. The values of compression strength, Young’s modulus, Poisson’s ratio, and shear modulus are higher for water buffalo male than that of female showing gender difference. This may be attributed to lower bone density in females due to hormone secretion.
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Mohan Vasu, Ram. "Quantitative vibro-acoustography from measurement of modal frequencies: characterisation of isotropic and orthotropic tissue-like objects." In Ultrasound-Mediated Imaging of Soft Materials. IOP Publishing, 2019. http://dx.doi.org/10.1088/2053-2563/aae893ch4.

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Conference papers on the topic "Tissu orthotrope"

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Klisch, Stephen M., Suzanne E. Holtrichter, Robert L. Sah, and Andrew Davol. "A Bimodular Second-Order Orthotropic Stress Constitutive Equation for Cartilage." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59475.

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The design of tissue-engineered constructs grown in vitro is a promising treatment strategy for degenerated cartilaginous tissues. Cartilaginous tissues such as articular cartilage and the annulus fibrosus are collagen fiber-reinforced composites that exhibit orthotropic behavior and highly asymmetric tensile-compressive responses. They also experience finite deformations in vivo. Successful integration with surrounding tissue upon implantation likely will require cartilage constructs to have similar structural and functional properties as native tissue. Reliable stress constitutive equations that accurately characterize the tissue’s mechanical properties must be developed to achieve this aim. Recent studies have successfully implemented bimodular theories for infinitesimal strains (Soltz et al., 2000; Wang et al., 2003); those models were based on the theory of Curnier et al. (1995).
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Murali, Adithyavairavan, Siddarth Sen, Ben Kehoe, Animesh Garg, Seth McFarland, Sachin Patil, W. Douglas Boyd, Susan Lim, Pieter Abbeel, and Ken Goldberg. "Learning by observation for surgical subtasks: Multilateral cutting of 3D viscoelastic and 2D Orthotropic Tissue Phantoms." In 2015 IEEE International Conference on Robotics and Automation (ICRA). IEEE, 2015. http://dx.doi.org/10.1109/icra.2015.7139344.

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3

Deuerling, Justin M., Weimin Yue, Alejandro A. Espinoza, and Ryan K. Roeder. "Specimen Specific Multiscale Model for the Anisotropic Elastic Properties of Human Cortical Bone Tissue." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-175240.

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The elastic constants of cortical bone are orthotropic or transversely isotropic depending on the anatomic origin of the tissue. Micromechanical models have been developed to predict anisotropic elastic properties from structural information. Many have utilized microstructural features such as osteons, cement lines and Haversian canals to model the tissue properties [1]. Others have utilized nanoscale features to model the mineralized collagen fibril [2]. Quantitative texture analysis using x-ray diffraction techniques has shown that elongated apatite crystals exhibit a preferred orientation in the longitudinal axis of the bone [3]. The orientation distribution of apatite crystals provides fundamental information influencing the anisotropy of the extracellular matrix (ECM) but has not been utilized in existing micromechanical models.
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4

Amabili, Marco, Kostas Karazis, Rosaire Mongrain, and Nastaran Shahmansouri. "A Model for the Nonlinear Buckling of Human Aorta." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89141.

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Human aortas are subjected to large mechanical stresses due to blood flow pressurization and through contact with the surrounding tissue. It is essential that the aorta does not lose stability by buckling for its proper functioning to ensure proper blood flow. A refined reduced-order bifurcation analysis model is employed to examine the stability of an aortic segment subjected to internal blood flow. The structural model is based on a nonlinear cylindrical orthotropic laminated composite shell theory that assumes three aortic wall layers representing the tunica intima, media and adventitia. The fluid model contains the unsteady effects obtained from linear potential flow theory and the steady viscous effects obtained from the time-averaged Navier-Stokes equations. Residual stresses due to pressurization are evaluated and included in the model. The aortic segment loses stability by divergence with deformation of the cross-section at a critical flow velocity for a given static pressure, exhibiting a strong subcritical behaviour with partial or total collapse of the inner wall. Subsequent analyses including the effect of geometric wall imperfections indicate that imperfections in the axial direction have a more profound effect on the stability of the aorta decreasing the critical flow velocity for buckling.
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Wu, Xuehai, and Assimina A. Pelegri. "Deep 3D Convolution Neural Network Methods for Brain White Matter Hybrid Computational Simulations." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-24664.

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Abstract Material properties of brain white matter (BWM) show high anisotropy due to the complicated internal three-dimensional microstructure and variant interaction between heterogeneous brain-tissue (axon, myelin, and glia). From our previous study, finite element methods were used to merge micro-scale Representative Volume Elements (RVE) with orthotropic frequency domain viscoelasticity to an integral macro-scale BWM. Quantification of the micro-scale RVE with anisotropic frequency domain viscoelasticity is the core challenge in this study. The RVE behavior is expressed by a viscoelastic constitutive material model, in which the frequency-related viscoelastic properties are imparted as storage modulus and loss modulus for the composite comprised of axonal fibers and extracellular glia. Using finite elements to build RVEs with anisotropic frequency domain viscoelastic material properties is computationally very consuming and resource-draining. Additionally, it is very challenging to build every single RVE using finite elements since the architecture of each RVE is arbitrary in an infinite data set. The architecture information encoded in the voxelized location is employed as input data and is consequently incorporated into a deep 3D convolution neural network (CNN) model that cross-references the RVEs’ material properties (output data). The output data (RVEs’ material properties) is calculated in parallel using an in-house developed finite element method, which models RVE samples of axon-myelin-glia composites. This novel combination of the CNN-RVE method achieved a dramatic reduction in the computation time compared with directly using finite element methods currently present in the literature.
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