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Статті в журналах з теми "Hyperelastic anisotropic material"
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Gurvich, Mark R. "On Characterization of Anisotropic Elastomeric Materials for Structural Analysis." Rubber Chemistry and Technology 77, no. 1 (March 1, 2004): 115–30. http://dx.doi.org/10.5254/1.3547805.
Повний текст джерелаАнотація:
Abstract Existing efforts in constitutive modeling of elastomers are primarily focused on isotropic materials. On the other hand, anisotropic elastic models were successfully developed for traditional composites with relatively small strains, where geometrical non-linearity of deformation may be ignored. There are, however, certain materials where neither large deformation and incompressibility nor anisotropy of material stiffness may be neglected. This study proposes a general constitutive approach to model both hyperelasticity (including incompressibility) and full anisotropy of material deformation in structural analysis. According to the proposed approach, an original hyperelastic anisotropic body is modeled as a combination of two hypothetical components (hyperelastic isotropic and elastic anisotropic ones). The proposed approach shows simplicity and convenience of practical application along with high accuracy of analysis. It may be easily implemented in computational analysis of 2- and 3-D problems using commercially available FEA codes without additional programming efforts. Analytical and computational implementation of the approach is considered on representative examples of elastomeric structures and rubber-based composites. Analytical solutions are shown for examples of biaxial tension of composites and inflation of a toroidal anisotropic tube. FEA solutions are discussed on examples of an inflated anisotropic sphere and non-uniform deformation of a composite layer. Obtained results are discussed to emphasize benefits of the proposed approach. Finally, a methodology to evaluate material parameters using corresponding test results is considered according to the proposed approach.
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Chanda, Arnab, Subhodip Chatterjee, and Vivek Gupta. "Soft composite based hyperelastic model for anisotropic tissue characterization." Journal of Composite Materials 54, no. 28 (June 23, 2020): 4525–34. http://dx.doi.org/10.1177/0021998320935560.
Повний текст джерелаАнотація:
Soft tissues are complex anisotropic composite systems comprising of multiple differently oriented layers of fiber embedded within a soft matrix. To date, soft tissues have been mainly characterized using simplified linear elastic material models, isotropic viscoelastic and hyperelastic models, and transversely isotropic models. In such models, the effect of fiber volume fraction (FVF), fiber orientation, and fiber-matrix interactions are missing, inhibiting accurate characterization of anisotropic tissue properties. The current work addresses this literature gap with the development of a novel soft composite based material framework to model tissue anisotropy. In this model, the fiber and matrix are considered as separate hyperelastic materials, and fiber-matrix interaction is modeled using multiplicative decomposition of the deformation gradient. The effect of the individual contribution of the fibers and matrix are introduced into the numerical framework for a single soft composite layer, and fiber orientation effects are incorporated into the strain energy functions. Also, strain energy formulations are developed for multiple soft composite layers with varying fiber orientations and contributions, describing the biomechanical behavior of an entire anisotropic tissue block. Stress-strain relationships were derived from the strain energy equations for a uniaxial mechanical test condition. To validate the model parameters, experimental models of soft composites tested under uniaxial tension were characterized using the novel anisotropic hyperelastic model (R2 = 0.983). To date, such a robust anisotropic hyperelastic composite framework has not been developed, which would be indispensable for experimental characterization of tissues and for improving the fidelity of computational biological models in future.
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Ansari, Mohd Zahid, Sang Kyo Lee, and Chong Du Cho. "Hyperelastic Muscle Simulation." Key Engineering Materials 345-346 (August 2007): 1241–44. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.1241.
Повний текст джерелаАнотація:
Biological soft tissues like muscles and cartilages are anisotropic, inhomogeneous, and nearly incompressible. The incompressible material behavior may lead to some difficulties in numerical simulation, such as volumetric locking and solution divergence. Mixed u-P formulations can be used to overcome incompressible material problems. The hyperelastic materials can be used to describe the biological skeletal muscle behavior. In this study, experiments are conducted to obtain the stress-strain behavior of a solid silicone rubber tube. It is used to emulate the skeletal muscle tensile behavior. The stress-strain behavior of silicone is compared with that of muscles. A commercial finite element analysis package ABAQUS is used to simulate the stress-strain behavior of silicone rubber. Results show that mixed u-P formulations with hyperelastic material model can be used to successfully simulate the muscle material behavior. Such an analysis can be used to simulate and analyze other soft tissues that show similar behavior.
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Cudny, Marcin, and Katarzyna Staszewska. "A hyperelastic model for soils with stress-induced and inherent anisotropy." Acta Geotechnica 16, no. 7 (March 5, 2021): 1983–2001. http://dx.doi.org/10.1007/s11440-021-01159-z.
Повний текст джерелаАнотація:
AbstractIn this paper, modelling of the superposition of stress-induced and inherent anisotropy of soil small strain stiffness is presented in the framework of hyperelasticity. A simple hyperelastic model, capable of reproducing variable stress-induced anisotropy of stiffness, is extended by replacement of the stress invariant with mixed stress–microstructure invariant to introduce constant inherent cross-anisotropic component. A convenient feature of the new model is low number of material constants directly related to the parameters commonly used in the literature. The proposed description can be incorporated as a small strain elastic core in the development of some more sophisticated hyperelastic-plastic models of overconsolidated soils. It can also be used as an independent model in analyses involving small strain problems, such as dynamic simulations of the elastic wave propagation. Various options and features of the proposed anisotropic hyperelastic model are investigated. The directional model response is compared with experimental data available in the literature.
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Nam, Tran Huu. "Using FEM for large deformation analysis of inflated air-spring cylindrical shell made of rubber-textile cord composite." Vietnam Journal of Mechanics 28, no. 1 (April 17, 2006): 10–20. http://dx.doi.org/10.15625/0866-7136/28/1/5474.
Повний текст джерелаАнотація:
An orthotropic hyperelastic constitutive model is presented for large deformation analysis of the nonlinear anisotropic hyperelastic material of the cylindrical air-spring shell used in vibroisolation of driver's seat. Nonlinear hyperelastic constitutive equations of orthotropic composite material are incorporated into the finite strain analysis by finite element method (FEM). The results of deformation analysis of the inflated air-spring shell made of composite with rubber matrix reinforced by textile cords are given. Obtained numerical results of deformation corresponding to the experimentally measured deformation of the inflated cylindrical air-spring.
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Chanda, Arnab, and Christian Callaway. "Tissue Anisotropy Modeling Using Soft Composite Materials." Applied Bionics and Biomechanics 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/4838157.
Повний текст джерелаАнотація:
Soft tissues in general exhibit anisotropic mechanical behavior, which varies in three dimensions based on the location of the tissue in the body. In the past, there have been few attempts to numerically model tissue anisotropy using composite-based formulations (involving fibers embedded within a matrix material). However, so far, tissue anisotropy has not been modeled experimentally. In the current work, novel elastomer-based soft composite materials were developed in the form of experimental test coupons, to model the macroscopic anisotropy in tissue mechanical properties. A soft elastomer matrix was fabricated, and fibers made of a stiffer elastomer material were embedded within the matrix material to generate the test coupons. The coupons were tested on a mechanical testing machine, and the resulting stress-versus-stretch responses were studied. The fiber volume fraction (FVF), fiber spacing, and orientations were varied to estimate the changes in the mechanical responses. The mechanical behavior of the soft composites was characterized using hyperelastic material models such as Mooney-Rivlin’s, Humphrey’s, and Veronda-Westmann’s model and also compared with the anisotropic mechanical behavior of the human skin, pelvic tissues, and brain tissues. This work lays the foundation for the experimental modelling of tissue anisotropy, which combined with microscopic studies on tissues can lead to refinements in the simulation of localized fiber distribution and orientations, and enable the development of biofidelic anisotropic tissue phantom materials for various tissue engineering and testing applications.
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Sokolova, M. Yu, and D. V. Khristich. "FINITE STRAINS OF NONLINEAR ELASTIC ANISOTROPIC MATERIALS." Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mekhanika, no. 70 (2021): 103–16. http://dx.doi.org/10.17223/19988621/70/9.
Повний текст джерелаАнотація:
Anisotropic materials with the symmetry of elastic properties inherent in crystals of cubic syngony are considered. Cubic materials are close to isotropic ones by their mechanical properties. For a cubic material, the elasticity tensor written in an arbitrary (laboratory) coordinate system, in the general case, has 21 non-zero components that are not independent. An experimental method is proposed for determining such a coordinate system, called canonical, in which a tensor of elastic properties includes only three nonzero independent constants. The nonlinear model of the mechanical behavior of cubic materials is developed, taking into account geometric and physical nonlinearities. The specific potential strain energy for a hyperelastic cubic material is written as a function of the tensor invariants, which are projections of the Cauchy-Green strain tensor into eigensubspaces of the cubic material. Expansions of elasticity tensors of the fourth and sixth ranks in tensor bases in eigensubspaces are determined for the cubic material. Relations between stresses and finite strains containing the second degree of deformations are obtained. The expressions for the stress tensor reflect the mutual influence of the processes occurring in various eigensubspaces of the material under consideration.
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Vladimirov, Ivaylo N., Michael P. Pietryga, Yalin Kiliclar, Vivian Tini, and Stefanie Reese. "Failure modelling in metal forming by means of an anisotropic hyperelastic-plasticity model with damage." International Journal of Damage Mechanics 23, no. 8 (January 16, 2014): 1096–132. http://dx.doi.org/10.1177/1056789513518953.
Повний текст джерелаАнотація:
In metal forming, formability is limited by the evolution of ductile damage in the work piece. The accurate prediction of material failure requires, in addition to the description of anisotropic plasticity, the inclusion of damage in the finite element simulation. This paper discusses the application of an anisotropic hyperelastic-plasticity model with isotropic damage to the numerical simulation of fracture limits in metal forming. The model incorporates plastic anisotropy, nonlinear kinematic and isotropic hardening and ductile damage. The constitutive equations of the proposed model are numerically integrated both implicitly and explicitly, and the model is implemented as a user material subroutine UMAT in the commercial solvers ABAQUS/Standard and LS-DYNA, respectively. The numerical examples investigate the potential of the constitutive framework regarding the prediction of failure in metal forming processes such as, e.g. cross-die deep drawing. In particular, simulations of the Nakazima stretching test with varying specimen geometry are utilized to simulate the forming limit diagram at fracture and the numerical results are compared to experimental data for aluminium alloy sheets.
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Hashemi, Sanaz S., Masoud Asgari, and Akbar Rasoulian. "An experimental study of nonlinear rate-dependent behaviour of skeletal muscle to obtain passive mechanical properties." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 234, no. 6 (March 5, 2020): 590–602. http://dx.doi.org/10.1177/0954411920909705.
Повний текст джерелаАнотація:
Accurate modelling of biological tissues has been a significant need for analysis of the human body. In this article, a comprehensive in vitro experimental study has been done on the fresh bovine skeletal muscle before the onset of rigour mortis in order to provide an experimental description of passive skeletal muscle properties in three dimensions. Different situations including various deformation modes, different loading rates and loading directions are tested to consider all features of skeletal muscle behaviour. Based on the nonlinear continuum mechanics, a three-dimensional visco-hyperelastic model is introduced which considers all aspects of skeletal muscle’s features such as nonlinear hyperelastic, time-dependent behaviour, anisotropy and quasi-incompressibility. Visco-hyperelastic material constants are obtained for passive behaviour of the muscle based on genetic algorithm optimization method via comparing the theoretical and experimental results. Experiments show that the rate of loading affects the configuration of experimental curves considerably. It could be also concluded that compression–tension asymmetry, as well as anisotropic behaviour, of the muscle is due to fibres orientation. Obtained experimental results help to achieve a better understanding of mechanical properties and nonlinear behaviour of the skeletal muscles.
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Chatelin, Simon, Caroline Deck, and Rémy Willinger. "An anisotropic viscous hyperelastic constitutive law for brain material finite-element modeling." Journal of Biorheology 27, no. 1-2 (December 6, 2012): 26–37. http://dx.doi.org/10.1007/s12573-012-0055-6.
Повний текст джерелаДисертації з теми "Hyperelastic anisotropic material"
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Hu, Lianxin. "Micromechanics of granular materials : Modeling anisotropy by a hyperelastic-plastic model." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI133.
Повний текст джерелаАнотація:
Afin de modéliser le comportement des géométariaux sous des charges complexes, plusieurs études et travaux expérimentaux ont été réalisées afin d’établir des modèles constitutifs relatifs. Une caractéristique importante des matériaux granulaires est que la relation entre la contrainte et la déformation et ce même dans le domaine élastique n’est pas linéaire, contrairement aux réponses du métal. Il a également été constaté que la réponse contrainte-déformation des matériaux granulaires montre les caractéristiques de l’anisotropie induite, ainsi que les non-linéarités. En outre, l’anisotropie induite par la contrainte se produit pendant le processus de chargement sur les sols, par exemple, les charges ou les déplacements. Dans ce travail, un nouveau modèle qui est une combinaison de modèle hyperélastique Houlsby et modèle élastoplastique Plasol a été proposé. Ce nouveau modèle a pris en compte la réponse non linéaire de la contrainte dans le domaine élastique et plastique, et l’élasticité anisotrope a également été bien considérée. En outre, les problèmes de l’écoulement de la déformation plastique a été calibré par un algorithme d’intégration approprié. Plus tard, le nouveau modèle a été vérifié en utilisant la méthode numérique et comparé aux expériences de laboratoire dans des conditions triaxiales axisymmétriques. Les résultats de comparaison ont montré un bon effet de simulation du nouveau modèle qui a juste utilisé un seul ensemble de paramètres pour un sol spécifique dans différentes situations de contraintes. Ensuite, l’analyse de la nouvelle variable interne du modèle, c’est-à-dire l’exposant de pression, a montré que la valeur de l’exposant de pression qui correspond au degré d’anisotropie a eu un effet évident sur la réponse contrainte-déformation. De plus, ce type d’effet est également affecté par la densité et l’état de drainage des échantillons. En s’appuyant sur un nouveau modèle, un facteur de sécurité qui fait référence au critère de travail de deuxième ordre a été adopté et testé dans un modèle axisymétrique et un modèle de pente réel. Il a montré que la valeur négative ou la diminution spectaculaire du travail global normalisé de second ordre se produit lors d’une défaillance locale ou globale avec apparition d’énergie cinétique. Cette caractéristique du travail du second ordre peut également être affectée par l’exposant à pression variable. Enfin, un nouveau modèle a également été comparé à un modèle élastoplastique qui considère à la fois l’anisotropie élastique et la dilatation anisotrope, c’est-à-dire le modèle SANISAND modifié. Les avantages et les inconvénients ont été illustrés dans les résultats de comparaisonIn order to model the behavior of geometarials under complex loadings, several researches have done numerous experimental works and established relative constitutive models for decades. An important feature of granular materials is that the relationship between stress and strain especially in elastic domain is not linear, unlike the responses of typical metal or rubber. It has been also found that the stress-strain response of granular materials shows the characteristics of cross-anisotropy, as well as the non-linearities. Besides, the stress-induced anisotropy occurs expectedly during the process of disturbance on soils, for example, the loads or displacements. In this work, a new model which is a combination of Houlsby hyperelastic model and elastoplastic Plasol model was proposed. This new model took into account the non-linear response of stress and strain in both elastic and plastic domain, and the anisotropic elasticity was also well considered. Moreover, the overflow problem of plastic strain in plastic part was calibrated by a proper integration algorithm. Later, new model was verified by using numerical method and compared with laboratory experiments in axisymmetric triaxial conditions. The comparison results showed a good simulation effect of new model which just used one single set of parameters for a specific soil in different confining pressure situations. Then the analysis of new model internal variable, i.e., pressure exponent, illustrated that the value of pressure exponent which corresponds to the degree of anisotropy had an obvious effect on the stress-strain response. Moreover, this kind of effect is also affected by the density and drainage condition of samples. Basing on new model, a safety factor which refers to the second-order work criterion was adopted and tested in axisymmetric model and actual slope model. It showed that the negative value or dramatic decreasing of global normalized second-order work occurs accompanying with a local or global failure with a burst of kinetic energy. This feature of second-order work can also be affected by the variable pressure exponent. At last, new model was also compared with an elastoplastic model which considers both anisotropic elastic and anisotropic dilatancy, i.e., modified SANISAND model. Both advantages and disadvantages were illustrated in the comparison results
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Grilo, Tiago Jordão. "Development of computational anisotropic hypoelastic- and hyperelastic-based models including nonlinear kinematic hardening." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14428.
Повний текст джерелаАнотація:
Doutoramento em Engenharia MecânicaIn the present work, finite strain elastoplastic constitutive formulations suitable for advanced metallic materials are developed. The main goals are the correct description of the elastoplastic behaviour, including strong plastic anisotropy and cyclic hardening phenomena, in the large strain regime, as well as the development of numerically efficient algorithmic procedures for numerical implementation of the constitutive models into codes of numerical simulation by the Finite Element Method. Two different approaches are used in the derivation of the finite strain constitutive formulations, namely, hypoelasticity and hyperelasticity. On the one hand, regarding the hypoelastic-based model, particular attention is given to the development of computationally effcient forward- and backward-Euler algorithms considering distinct techniques. On the other hand, concerning the hyperelastic-based model, the focus is on the possibility of using any (quadratic or nonquadratic) yield criteria and on a new procedure that ensures that the anisotropy is correctly described in the finite strain regime. Moreover, the constitutive relations are solely expressed in the reference configuration, hence yielding symmetric tensor-valued quantities only. This symmetry, allied to an algorithm that preserves it, is crucial for the computational efficiency of the model's implementation since it reduces the storage effort and the required solver capacities when compared to the model's standard counterparts. For a better description of cyclic hardening phenomena, the developed models and corresponding algorithms, are extended to include several back stresses. This extension is carried out by considering a modified rheological model of nonlinear kinematic hardening and using additional state variables. The capabilities of the developed models for accurate reproduction of the plastic anisotropy and cyclic hardening phenomena are assessed by means of their implementation into material user subroutines of the commercial code Abaqus. The accuracy and computational efficiency of the models and numerical algorithms are compared by means of simulations of benchmarks. These benchmarks allow the models' assessment in the description of, e.g., metal forming defects such as earing and springback, as well as the comparison of the stability and precision of the numerical algorithms.
No presente trabalho, são desenvolvidas formulações constitutivas elastoplásticas para grandes deformações, adequadas a materiais metálicos avançados. Os principais objectivos deste estudo consistem na correcta descrição do comportamento elastoplástico, incluindo anisotropia plástica acentuada e fenómenos de endurecimento cíclico, no regime de grandes deformações, bem como o desenvolvimento de procedimentos algorítmicos eficientes para a implementação numérica dos modelos constitutivos em códigos de simulação numérica pelo Método dos Elementos Finitos. São usadas duas metodologias diferentes na derivação das formulações constitutivas de grandes deformações, nomeadamente, hipoelasticidade e hiperelasticidade. Por um lado, relativamente ao modelo baseado em hipoelasticidade, é dada particular atenção ao desenvolvimento de algoritmos eficientes do ponto de vista computacional, considerando técnicas particulares. Por outro lado, em relação ao modelo baseado em hiperelasticidade, a possibilidade de usar qualquer critério de cedência (quadrático ou não-quadrático) e a apresentação de um procedimento inovador, que garante a correcta descrição da anisotropia na presença de grandes deformaçães, são destacadas. Além disso, as relações constitutivas são expressas unicamente na configuração de referência, resultando no uso de apenas variáveis simétricas de segunda ordem. Esta simetria e o uso de um algoritmo que a preserva são cruciais no que diz respeito à eficiência numérica da implementação do modelo, uma vez que reduz significativamente o espaço de armazenamento e o custo computacional de cálculo, relativamente aos modelos hiperelásticos convencionais. Os modelos, e respectivos algoritmos de integração, são posteriormente alargados ao uso de múltiplos tensores das tensões inversas de modo a permitir uma melhor descrição dos fenómenos de endurecimento cíclico. Para tal, foi considerado um modelo reológico modificado de endurecimento cinemático e usadas variáveis de estado adicionais. O desempenho dos modelos desenvolvidos na reprodução precisa de anisotropia plástica e fenómenos de endurecimento cíclico é avaliado através da sua implementação no código comercial Abaqus usando subrotinas de utilizador. A precisão e eficiência computacional dos modelos e algoritmos desenvolvidos são comparados entre si através de simulações de benchmarks. Estes benchmarks permitem a avaliação dos modelos na descrição de, por exemplo, defeitos na conformação de chapas metálicas, tais como a formação de orelhas e o retorno elástico, bem como a comparação da estabilidade e precisão dos algoritmos numéricos.
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Alleau, Thibaut. "Development of a numerical platform to model the mitral valve." Thesis, Compiègne, 2021. http://www.theses.fr/2021COMP2649.
Повний текст джерелаАнотація:
L’insuffisance mitrale est la valvulopathie mondiale la plus fréquente avec une prévalence de 2%. Lorsque le patient n’est pas en mesure d’être opéré à cœur ouvert, un implant percutané est utilisé pour aider la fermeture des feuillets. Le seul implant actuellement disponible est basé sur la réparation bord à bord de la valve mitrale. Il réduit le reflux vers l’oreillette lors de la systole, mais n’est pas adapté pour les patients souffrant d’insuffisance mitrale fonctionnelle, chez qui la pathologie provient du ventricule et non des éléments de la valve. L’objectif de la thèse est de fournir une plateforme numérique permettant d’aider au développement d’un implant adapté pour ces patients. Plusieurs géométries de valve ont été réalisées au moyen d’un modèle paramétrique, en utilisant des données anatomiques. La dynamique de la valve a été modélisée avec le logiciel ADINA par des simulations éléments finis en grandes déformations. Des modèles structurels de la valve ont permis de représenter la fermeture de la valve sous une pression uniforme. Les lois de comportement de matériaux ont été développé dans le but d’obtenir une fermeture réaliste de la valve. Cela a nécessité la prise en compte de l’hyperélasticité et de l’anisotropie des tissus. Des pathologies valvulaires, telles que la dilatation de l’anneau mitrale ou la rupture des cordages tendineux ont été modélisées, et plusieurs méthodes ont été testées pour y apposer des systèmes médicaux. En utilisant une description ALE et un couplage monolithique, les interactions fluide-structure ont été simulées pour une valve mitrale bi-dimensionnelle. La fermeture hermétique de la valve pendant la systole a pu être reproduite et l’ouverture de la valve étudiée pendant la diastole. La plateforme numérique développée permet de modéliser la fonction de la valve mitrale et peut être utilisée pour aider au développement d’un implant mitral grâce au modèle paramétrique reproduisant différentes géométries de valve et aux lois matériaux anisotropes. Une perspective reste la création d’un modèle 3D des interactions fluide-structure de la valve mitraleMitral insufficiency is the first valvular disease worldwide, with a 2% prevalence. When open-heartsurgery is impossible for the patient, surgeons use percutaneous devices to help the mitral leaflets coapt. However, the only device currently available is based on the edge-to-edge mitral valve repair technique. This type of implant is not adapted for patients suffering from functional mitral insufficiency, where the ventricle is responsible for the lack of coaptation of the leaflets. This thesis aims to provide a numerical platform to help the development of a mitral valve implant adapted for those patients. Several mitral valve geometries were created from a parametric model using anatomical measurements. Finite element simulations of the mitral valve were performed using ADINA to determine the valve closure under constant pressure. Several material models were developed in large strain and large deformation to model the valve closure accurately. Pathological behaviour such as annulus dilatation and chordae rupture were modelled, and several methods were tested to implement medical devices. Fluid-structure interaction of a 2D mitral valve was obtained using an ALE description and a monolithic coupling approach. Both the systole and the diastole were reproduced and studied, and the hermetic seal of the valve was detailed. The numerical platform developed is suited to model mitral valve function and can be used to help the development of mitral implants. In addition, the parametric geometry model and the anisotropic material model will be useful to depict with realism the valve function. A 3D fluid-structure interaction of the mitral valve could be developed
Тези доповідей конференцій з теми "Hyperelastic anisotropic material"
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Ahsanizadeh, Sahand, and LePing Li. "Strain-Rate Sensitive Constitutive Modeling of Anisotropic Visco-Hyperelastic Materials." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88608.
Повний текст джерелаАнотація:
Integral-based formulations of viscoelasticity have been widely used to describe the mechanical behavior of soft biological tissues and polymers. However, it is suggested that they are not suitable to be used under high strain rates. On the other hand, strain-rate sensitive models with an explicit dependence on the strain-rate have been developed for a certain class of materials. They predict the viscoelastic behavior during ramp loading more accurately while fail to account for the relaxation response. In order to overcome these drawbacks, a viscoelastic constitutive model has been proposed in this study based on the concept of internal variables. While the behavior of elastic materials is uniquely determined by the current state of deformation or external variables, the mechanical response of inelastic materials are regulated also by internal variables. The internal variables are associated with the dissipative mechanisms in the material and along with the evolution equations introduce the effect of history of the deformation to the current configuration. The current study employs short-term and long-term internal variables to account for the viscoelastic response during loading and relaxation respectively.
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Luo, Yun-Mei, Luc Chevalier, and Eric Monteiro. "An anisotropic visco-hyperelastic model for PET behavior under ISBM process conditions." In ESAFORM 2016: Proceedings of the 19th International ESAFORM Conference on Material Forming. Author(s), 2016. http://dx.doi.org/10.1063/1.4963407.
Повний текст джерела
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Forsell, Caroline, and T. Christian Gasser. "Impact of Material Anisotropy on Deformation of Myocardial Tissue due to Pacemaker Electrodes." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53383.
Повний текст джерелаАнотація:
A Pacemaker electrode can penetrate the heart wall, and to design a penetration-resistent lead tip sound knowledge regarding failure of ventricular tissue is required. Numerical simulations can be particular helpful in that respect, but depend on a reliable constitutive description for ventricular tissue. In this study an anisotropic hyperelastic model for the myocardium has been implemented and compared to predictions from an isotropic description. Specifically, the response due to pushing a rigid punch into the myocardium was studied. Results between anisotropic and isotropic descriptions of the myocardium differed significantly, which justified the implementation of an anisotropic model for the myocardium.
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Kao, Philip, H. Jerry Qi, Steve Lammers, and Robin Shandas. "A Comparative Study of Mechanical Properties of Fresh and Elastic-Network Only Proximal Artery Tissues." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176546.
Повний текст джерелаАнотація:
The contribution of the elastic network to the mechanical behavior of arterial tissues is not well quantified. This paper focuses on the quantification of the behavior of fresh and elastic-network-only (digested) calf arterial tissues in uniaxial deformation using the anisotropic hyperelastic model proposed by Bischoff et al. ([1]). This model characterizes an orthotropic, hyperelastic response, which is well-suited for the modeling of arterial tissues ([2],[3]). For this paper, we attempt to match the material constants associated with the Bischoff-Arruda anisotropic hyperelastic model to our experimental data from arterial tissues including the ascending aortic arch, descending aorta, main, left, and right pulmonary arteries, using a least-squares method. The material parameters obtained from the data fit provide a quantitative comparison of mechanical properties of fresh artery tissues and elastin networks.
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O’Connell, Grace D., Heather L. Guerin, and Dawn M. Elliott. "An Anisotropic Hyperelastic Model Applied to Nondegenerate and Degenerate Annulus Fibrosus." In ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-192890.
Повний текст джерелаАнотація:
The intervertebral disc is comprised of complex components that provide the disc with nonlinear, viscoelastic and anisotropic mechanical properties. The annulus fibrosus (AF) is a highly organized structure composed of concentric layers of collagen fibers embedded in a proteoglycan matrix. The AF has a high tensile stiffness and supports the large loads encountered by the disc. Mathematical models are needed to interpret and elucidate the meaning of experimental measurements made in mechanical tests. Based upon the classic work of Spencer [1], the AF has been modeled as a fiber-induced anisotropic hyperelastic material [e.g.,2–6], using the principle invariants of the Green deformation tensor and structural tensors representing the collagen fiber populations. Contributions of other AF components to mechanical behaviors are less understood than the fibers or matrix and may include connections between collagens and proteoglycans that can be incorporated into models through fiber-matrix interactions [2–4]. The previous models, however, have not been applied to experimental data from both nondegenerate and degenerate tissue. Constitutive modeling applied to nondegenerate and degenerate AF may elucidate microstructural changes with degeneration, will be useful for finite element models [5], and provide targets for disc treatments, such as tissue engineered constructs [7].
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Okamoto, Ruth J., Yuan Feng, Guy M. Genin, and Philip V. Bayly. "Anisotropic Behavior of White Matter in Shear and Implications for Transversely Isotropic Models." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14039.
Повний текст джерелаАнотація:
Experimental studies [1] have shown that white matter (WM) in the brain is mechanically anisotropic. Based on its fibrous structure, transversely isotropic (TI) material models have been suggested to capture WM behavior. TI hyperelastic material models involve strain energy density functions that depend on the I4 and I5 pseudo-invariants of the Cauchy-Green strain tensor to account for the effects of stiff fibers. The pseudo-invariant I4 is the square of the stretch ratio in the fiber direction; I5 contains contributions of shear strain in planes parallel to the fiber axis. Most, if not all, published models of WM depend on I4 but not on I5.
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Mortier, Peter, Benedict Verhegghe, Matthieu De Beule, Pascal Verdonck, and Gerhard A. Holzapfel. "Biomechanical Analysis of Stent Placement in a Coronary Bifurcation Considering the Anisotropic Response of the Wall." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206611.
Повний текст джерелаАнотація:
The role of finite element simulations during the design and evaluation of medical devices is gaining importance. Such simulations provide insights into the mechanical behaviour of medical devices and help to identify the critical design parameters. One important category are vascular implants such as stents, stent grafts, aortic valve stents among others. A realistic vascular geometry and an adequate constitutive model are basic requirements in order to accurately assess the behaviour of such vascular implants during and after implantation by numerical analysis. Many recently described vascular models, for example in the field of stenting, contain rather severe simplifications both on the geometrical and the constitutive level, although the feasibility of using accurate models has been demonstrated recently by, for example, Kiousis et al. [1]. This observation may be explained by the fact that specific anisotropic material models suitable to describe the large deformations of vascular tissue are not available in standard material libraries of some of the widely used finite element solvers. For example, the ABAQUS’ material library only contains two forms of anisotropic hyperelastic materials.
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Beblo, Richard, Michael Settle, Tyler Guin, Timothy White, and Gregory Reich. "Constitutive Modeling of Patterned Liquid Crystal Elastomer for Active Flow Control." In ASME 2017 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/smasis2017-3891.
Повний текст джерелаАнотація:
Patterned liquid crystal elastomer (LCE) has been shown to have significant promise in surface topography control. Large and diverse shapes and surface adaptive responses have been shown using LCE materials with patterned director profiles. Using various techniques, crystal orientation across the surface of the material as well as through the thickness can be achieved yielding the capability to design out-of-plane deformation. These topological features can be used as active flow effectors manipulating, among other things, drag on an object in cross-flow. It is well known that surface topography can have a large effect on skin friction drag by effecting the boundary layer transition, separation, and interfering with the shedding of vortices. In regards to a cylinder in a cross-flow, spatially manipulating surface topography, and thus drag, in this way gives rise to forces exerted by the fluid on the body. An imbalance of forces due to non-uniform surface topography can then be used to control the cylinder. Designing such a system requires optimization of the surface topography via optimization of the crystal orientation pattern over a wide range of environments. Key to this optimization, described in detail in the presented work, is an accurate material model validated against experimental data. By representing the strain energy of the material as a combination of contributions of the elastomer backbone and the liquid crystals separately, unique material properties can be properly modeled. This is achieved by combining a traditional isotropic 3 chain Arruda-Boyce hyperelastic equation modeling the elastomer backbone with an anisotropic extension modeling the patterned liquid crystals, resulting in an anisotropic hyperelastic material model. The model can then be used to predict the material response of various patterns and investigate the design space of possible surface topographies.
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Natali, Arturo N., Emanuele L. Carniel, Piero G. Pavan, Alessio Gasparetto, Franz G. Sander, Christina Dorow, and Martin Geiger. "Constitutive Formulation for Numerical Analysis of Visco-Hyperelastic Damage Phenomena in Soft Biological Tissues." In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95254.
Повний текст джерелаАнотація:
Soft biological tissues show a strongly non linear and time-dependent mechanical response and undergo large strains under physiological loads. The microstructural arrangement determines specific anisotropic macroscopic properties that must be considered within a constitutive formulation. The characterization of the mechanical behaviour of soft tissues entails the definition of constitutive models capable of accounting for geometric and material non linearity. In the model presented here a hyperelastic anisotropic formulation is adopted as the basis for the development of constitutive models for soft tissues and can be properly arranged for the investigation of viscous and damage phenomena as well to interpret significant aspects pertaining to ordinary and degenerative conditions. Visco-hyperelastic models are used to analyze the time-dependent mechanical response, while elasto-damage models account for the stiffness and strength decrease that can develop under significant loading or degenerative conditions. Experimental testing points out that damage response is affected by the strain rate associated with loading, showing a decrease in the damage limits as the strain rate increases. This phenomena can be investigated by means of a model capable of accounting for damage phenomena in relation to viscous effects. The visco-hyperelastic damage model developed is defined on the basis of a Helmholtz free energy function depending on the strain-damage history. In particular, a specific damage criterion is formulated in order to evaluate the influence of the strain rate on damage. The model can be implemented in a general purpose finite element code. This makes it possible to perform numerical analyses of the mechanical response considering time-dependent effects and damage phenomena. The experimental tests develop investigated tissue response for different strain rate conditions, accounting for stretch situations capable of inducing damage phenomena. The reliability of the formulation is evaluated by a comparison with the results of experimental tests performed on pig periodontal ligament.
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Kadlowec, Jennifer A., Spencer P. Lake, Kristin S. Miller, Louis J. Soslowsky, and Dawn M. Elliott. "A Hyperelastic Model With Distributed Fibers to Describe Human Supraspinatus Tendon Tensile Mechanics." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206509.
Повний текст джерелаАнотація:
Tendon tissue is composed of collagen fibers in a hydrated proteoglycan matrix. Although many tendons have fibers that are highly aligned (e.g. flexor tendon), the supraspinatus tendon (SST) of the shoulder has significant distribution of fiber alignment [1]. The alignment and distribution of the fibers likely contributes to the nonlinear and anisotropic mechanical behavior, however this has not been demonstrated. Understanding the role of fiber structure on tendon mechanical behavior, that is, characterizing the structure-function relationships, is critical to evaluate the function of injured, degenerated, or healing tendons and would be invaluable in the design and assessment of tissue engineered tendon replacements. While a structurally based hyperelastic model has been developed for tendon [2], this model contained only a single fiber orientation, which is not adequate for the more distributed fiber structure in the SST. We have recently applied a hyperelastic model formulation that has distributed collagen fiber orientation developed by Gasser and colleagues for the arterial wall [3] to model a tendon analog made from nanofibrous scaffolds [4]. The objective of this study was to build on previous work to apply a hyperelastic fiber-reinforced constitutive model that includes a specific term for fiber distribution to the tensile mechanics of human SST and to evaluate the site-specific model material properties.