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Artykuły w czasopismach na temat "Orthotropic Elastic Moduli"
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SOFIYEV, A. H., E. SCHNACK, V. C. HACIYEV i N. KURUOGLU. "EFFECT OF THE TWO-PARAMETER ELASTIC FOUNDATION ON THE CRITICAL PARAMETERS OF NONHOMOGENEOUS ORTHOTROPIC SHELLS". International Journal of Structural Stability and Dynamics 12, nr 05 (październik 2012): 1250041. http://dx.doi.org/10.1142/s0219455412500411.
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A theoretical analysis is presented for determining the free vibrational and buckling characteristics of the nonhomogeneous, orthotropic, thin-walled, circular cylindrical and conical shells under a hydrostatic pressure and resting on a two-parameter elastic foundation. The basic relations have been obtained for the orthotropic truncated conical shell, the Young's moduli and density of which vary continuously in the thickness direction. By applying the Galerkin method, the buckling hydrostatic pressure and dimensionless frequency parameter of the homogeneous and nonhomogeneous orthotropic truncated conical shells with or without elastic foundations are obtained. Finally, the effects of the Winkler and Pasternak-type elastic foundations, the variations of shell characteristics, the effects of the nonhomogeneity and orthotropy on the critical parameters have been studied. The results are presented in tables, figures and compared with other works.
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Diaco, Marina. "On Torsion of Functionally Graded Elastic Beams". Modelling and Simulation in Engineering 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/8464205.
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The evaluation of tangential stress fields in linearly elastic orthotropic Saint-Venant beams under torsion is based on the solution of Neumann and Dirichlet boundary value problems for the cross-sectional warping and for Prandtl stress function, respectively. A skillful solution method has been recently proposed by Ecsedi for a class of inhomogeneous beams with shear moduli defined in terms of Prandtl stress function of corresponding homogeneous beams. An alternative reasoning is followed in the present paper for orthotropic functionally graded beams with shear moduli tensors defined in terms of the stress function and of the elasticity of reference inhomogeneous beams. An innovative result of invariance on twist centre is also contributed. Examples of functionally graded elliptic cross sections of orthotropic beams are developed, detecting thus new benchmarks for computational mechanics.
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Turner, C. H., i S. C. Cowin. "Errors Induced by Off-Axis Measurement of the Elastic Properties of Bone". Journal of Biomechanical Engineering 110, nr 3 (1.08.1988): 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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Ozyhar, Tomasz, Stefan Hering i Peter Niemz. "Moisture-dependent orthotropic tension-compression asymmetry of wood". Holzforschung 67, nr 4 (1.05.2013): 395–404. http://dx.doi.org/10.1515/hf-2012-0089.
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Abstract The influence of moisture content (MC) on the tension-compression (Te-Co) asymmetry of beech wood has been examined. The elastic and strength parameters, including Te and Co Young’s moduli, Poisson’s ratios, and ultimate and yield stress values, were determined and compared in terms of different MCs for all orthotropic directions. The results reveal a distinctive Te-Co strength asymmetry with a moisture dependency that is visualized clearly by the Te to Co yield stress ratio. The Te-Co asymmetry is further shown by the inequality of the elastic properties, known as the “bimodular behavior”. The latter is proven for the Young’s moduli values in the radial and tangential directions and for individual Poisson’s ratios. Although the bimodularity of the Young’s moduli is significant at low MC levels, there is no evidence of moisture dependency on the Te-Co asymmetry of the Poisson’s ratios.
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Vorobyev, Alexey, Olivier Arnould, Didier Laux, Roberto Longo, Nico P. van Dijk i E. Kristofer Gamstedt. "Characterisation of cubic oak specimens from the Vasa ship and recent wood by means of quasi-static loading and resonance ultrasound spectroscopy (RUS)". Holzforschung 70, nr 5 (1.05.2016): 457–65. http://dx.doi.org/10.1515/hf-2015-0073.
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Abstract The cylindrical orthotropy, inherent time-dependency response, and variation between and within samples make the stiffness characterisation of wood more challenging than most other structural materials. The purpose of the present study is to compare static loading with resonant ultrasound spectroscopy (RUS) and to investigate how to combine the advantages of each of these two methods to improve the estimation of the full set of elastic parameters of a unique sample. The behavior of wood as an orthotropic mechanical material was quantified by elastic engineering parameters, i.e. Poisson’s ratios and Young’s and shear moduli. Recent and waterlogged archaeological oak impregnated with polyethylene glycol (PEG) from the Vasa warship built in 1628 was in focus. The experimental results were compared, and the difference between RUS and static loading was studied. This study contributes additional information on the influence of PEG and degradation on the elastic engineering parameters of wood. Finally, the shear moduli and Poisson’s ratios were experimentally determined for Vasa archaeological oak for the first time.
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Subhani, Mahbube, Jian Chun Li, Hauke Gravenkamp i Bijan Samali. "Effect of Elastic Modulus and Poisson's Ratio on Guided Wave Dispersion Using Transversely Isotropic Material Modelling". Advanced Materials Research 778 (wrzesień 2013): 303–11. http://dx.doi.org/10.4028/www.scientific.net/amr.778.303.
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Timber poles are commonly used for telecommunication and power distribution networks, wharves or jetties, piling or as a substructure of short span bridges. Most of the available techniques currently used for non-destructive testing (NDT) of timber structures are based on one-dimensional wave theory. If it is essential to detect small sized damage, it becomes necessary to consider guided wave (GW) propagation as the behaviour of different propagating modes cannot be represented by one-dimensional approximations. However, due to the orthotropic material properties of timber, the modelling of guided waves can be complex. No analytical solution can be found for plotting dispersion curves for orthotropic thick cylindrical waveguides even though very few literatures can be found on the theory of GW for anisotropic cylindrical waveguide. In addition, purely numerical approaches are available for solving these curves. In this paper, dispersion curves for orthotropic cylinders are computed using the scaled boundary finite element method (SBFEM) and compared with an isotropic material model to indicate the importance of considering timber as an anisotropic material. Moreover, some simplification is made on orthotropic behaviour of timber to make it transversely isotropic due to the fact that, analytical approaches for transversely isotropic cylinder are widely available in the literature. Also, the applicability of considering timber as a transversely isotropic material is discussed. As an orthotropic material, most material testing results of timber found in the literature include 9 elastic constants (three elastic moduli and six Poisson's ratios), hence it is essential to select the appropriate material properties for transversely isotropic material which includes only 5 elastic constants. Therefore, comparison between orthotropic and transversely isotropic material model is also presented in this article to reveal the effect of elastic moduli and Poisson's ratios on dispersion curves. Based on this study, some suggestions are proposed on selecting the parameters from an orthotropic model to transversely isotropic condition.
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Adibaskoro, Tito, Michalina Makowska, Aleksi Rinta-Paavola, Stefania Fortino i Simo Hostikka. "Elastic Modulus, Thermal Expansion, and Pyrolysis Shrinkage of Norway Spruce Under High Temperature". Fire Technology 57, nr 5 (30.04.2021): 2451–90. http://dx.doi.org/10.1007/s10694-021-01123-z.
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AbstractThe orthotropic and temperature-dependent nature of the mechanical properties of wood is well recognized. However, past studies of mechanical properties at elevated temperatures are either limited to temperatures below 200 °C or focus only on the direction parallel to grain. The effect of time-dependent pyrolysis during measurement is often neglected. This paper presents a novel method for determining elastic modulus at high temperatures and thermal expansion coefficient in different orthotropic directions via Dynamic Mechanical-Thermal Analyser (DMTA). The method allows for drying, drying verification, and measurement in one chamber, eliminating the possibility of moisture reabsorption from ambient air. The repeatable measurements can be carried out in temperatures up to 325°C, adequate for observing time-dependent pyrolysis during measurement. Results of the measurements of Norway Spruce provide data of its mechanical response at temperature range previously not explored widely, as well as in the orthotropic direction. Time-dependent behaviour was observed in the thermal expansion and shrinkage experiment, where above 250°C the amount of shrinkage depends on heating rate. At such temperature, elastic moduli measurement also shows time dependence, where longer heating at certain temperature slightly increases the measured elastic modulus. Additionally, bilinear regression of the relationship between elastic moduli and temperature shows quantitatively good fit. Numerical simulation of the DMTA temperature history and wood chemical components mass losses show the onset of shrinkage and onset of hemicellulose mass loss occurring at around the same time, while decomposition of cellulose correlate with the sudden loss of elastic moduli.
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Tokovyy, Yuriy V., Anatoliy V. Yasinskyy, Sebastian Lubowicki i Dariusz M. Perkowski. "Elastic and Thermoelastic Responses of Orthotropic Half-Planes". Materials 15, nr 1 (31.12.2021): 297. http://dx.doi.org/10.3390/ma15010297.
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A unified approach is presented for constructing explicit solutions to the plane elasticity and thermoelasticity problems for orthotropic half-planes. The solutions are constructed in forms which decrease the distance from the loaded segments of the boundary for any feasible relationship between the elastic moduli of orthotropic materials. For the construction, the direct integration method was employed to reduce the formulated problems to a governing equation for a key function. In turn, the governing equation was reduced to an integral equation of the second kind, whose explicit analytical solution was constructed by using the resolvent-kernel algorithm.
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Zhao, Aihong, i Jilin Yu. "The overall elastic moduli of orthotropic composite and description of orthotropic damage of materials". International Journal of Solids and Structures 37, nr 45 (listopad 2000): 6755–71. http://dx.doi.org/10.1016/s0020-7683(99)00226-7.
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Gotkhindi, Tejas P., i K. R. Y. Simha. "Transverse orthotropic elastic moduli of bundled coated thin elliptical tubes". Composite Structures 118 (grudzień 2014): 178–99. http://dx.doi.org/10.1016/j.compstruct.2014.07.030.
Pełny tekst źródłaRozprawy doktorskie na temat "Orthotropic Elastic Moduli"
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Moussu, Florent. "Développement d'une méthode de détermination des constantes élastiques d'un matériau orthotrope". Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL033N.
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Le développement de nouveaux matériaux pose le problème de la connaissance de leurs constantes élastiques. Les méthodes de mesure des constantes élastiques sont nombreuses, mais ne permettent que très rarement de déterminer simultanément et de façon non destructive un grand nombre des composantes du tenseur des rigidités élastiques. Grâce l'essor des outils de calcul numérique et de traitement du signal, une nouvelle méthode est développée, basée sur l'analyse du comportement dynamique d'une plaque rectangulaire complètement libre à orthotropie spéciale. Deux modèles théoriques sont décrits selon que la plaque est mince ou épaisse conduisant aux équations aux dérivées partielles du mouvement et à l'expression des conditions aux limites. La résolution en terme de fréquences propres et modes propres de ces équations n'est pas simple, et par souci d'économie de temps calcul, une méthode semi-analytique originale est développée: il s'agit de la méthode dite de superposition qui permet de décomposer un problème qui n'admet pas de solution analytique, en deux sous problèmes dont la solution peut être décrite grâce à des développements en séries trigonométriques. Par ailleurs, un dispositif expérimental est mis au point, permettant, grâce à une bonne simulation des conditions aux limites complètement libres et à l'utilisation d'une métrologie sans contact, de déterminer avec précision les fréquences propres et modes propres d'une plaque. Sachant calculer théoriquement et mesurer expérimentalement les fréquences propres de la plaque, un algorithme est développé afin de déterminer les quatre ou six constantes élastiques (selon qu'elle est mince ou épaisse) régissant au mieux au sens des moindres carrés son comportement dynamique. Finalement, des résultats expérimentaux valident la méthodologie proposée et montrent sa précision et sa sensibilité
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Grédé, Audrey. "Modélisation des chocs d’origine pyrotechnique dans les structures d’Ariane5 : développement de modèles de propagation et d'outils de modélisation". Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2009. http://www.theses.fr/2009ECAP0006/document.
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La compréhension et l’amélioration de l’environnement vibratoire des charges utiles demande la mise au point de démarches prédictives maîtrisées qui permettent de comprendre les phénomènes de transmission des ondes de chocs d’origine pyrotechnique dans le lanceur Ariane5. Plus particulièrement, la maîtrise du comportement transitoire des coques sandwichs en nid d’abeilles, principaux constituants de l’Adaptateur de Charges Utiles – structure porteuse des satellites, est nécessaire pour prédire les vibrations au pied des équipements électroniques des satellites et des lanceurs. Cette problématique présente un caractère multi-échelle tant d’un point de vue temporel (charge mobile supersonique, temps d’analyse) que spatial (dimensions des structures du lanceur, taille des cellules en nid d’abeilles, longueurs d’ondes liées aux hautes fréquences). Celui-ci a été traité dans cette thèse en s’appuyant d’une part, sur une qualification à la fois analytique et numérique des modèles classiques homogénéisés des plaques sandwichs en nid d’abeilles pour la gamme de fréquence mise en jeu et d’autre part, sur une application des stratégies de remaillage adaptatif pour la propagation des ondes développées dans le cadre de la méthode de Galerkin espace-temps discontinue en temps. Deux catégories de modèles de plaques épaisses ont été ainsi construites dans le but d’enrichir la cinématique classique de plaques épaisses de Mindlin-Reissner qui s’est avérée être insuffisante pour correctement représenter le comportement dynamique hors-plan des plaques sandwich en nid d’abeilles. Ainsi ont été analysés les modèles dits monocouches basés sur un enrichissement de la cinématique par ajout de degrés de liberté dans l’épaisseur, et les modèles multicouches composés d’une superposition de trois plaques avec une homogénéisation séparée des matériaux. Il a été montré que ces deux sortes de modèles améliorent la description des phénomènes de hautes fréquences, notamment ceux de flexion et de cisaillement transverse qui sont plus délicats à retranscrire. Toutes les études numériques ont été effectuées avec un code éléments finis qui emploie des solveurs adaptatifs dynamiques basés sur la méthode de Galerkin espace-temps discontinue en temps. Cette méthode d’intégration en temps introduit un amortissement numérique dépendant du pas de temps et qui peut interférer avec un amortissement physique susceptible d’être introduit dans un modèle numérique et conduire au final à un amortissement total différent de celui qui est attendu. Cette interaction a été analysée et mise en évidence dans ce travail à travers l’introduction de l’amortissement de Rayleigh dans les modèles de propagation de chocs. Les outils et les modèles de propagation ainsi développés ont été validés sur plusieurs structures académiques et industrielles. Des comparaisons avec des données expérimentales sur des structures industrielles de grande taille, plus particulièrement sur un Adaptateur de Charges Utiles d’Ariane5, sont effectuées et soulignent la cohérence de notre approche ainsi que la fiabilité et l’efficacité des modèles de propagation proposésReliable and efficient numerical models for the pyrotechnic shock wave propagation in structures of the Ariane5 launcher are necessary for a good understanding and a predictive analysis of the payload vibration environment. More precisely, the correct modeling of the dynamic behaviour of the honeycomb sandwich shells, the main material composing the payload adaptor, is essential to control the vibration environment of the payload and the embarked electronic equipments and so to prevent them from damages caused by the shock wave propagation. The topic is obviously a multi-scale problem from both temporal and spatial points of view : short time intervals imposed by supersonic moving loads vs. large total time interval that the slowest waves need to travel throughout the adaptor ; very short wavelengths of high frequency waves, and very small size of the honeycomb cells vs. large structure dimensions. To take into account all involved space-time scales in a reliable and efficient way, the herein study is based both on the analytical and numerical qualification of the classical homogenized models of honeycomb sandwich shells for the frequency range introduced by the pyrotechnic shock wave, and on a dynamic solver based on the well-known space-time discontinuous Galerkin method, allowing the use of adaptive remeshes for the wave propagation. The classical Mindlin-Reissner’s kinematics of thick plates being inefficient to correctly represent the dynamic out-of-plane behaviour of the honeycomb sandwich plates, two kinds of its enrichment are considered : One-layered models based on an enrichment of the kinematics by adding degrees of freedom in the thickness, and multi-layered models composed of a superposition of three plates with separated material homogenisations. It has been shown theoretically and numerically that, both types of enrichment allow more precise descriptions of flexure and transverse shear modes in the high frequency range. However, the multi-layered models give much more promising results, as the important role played by the honeycomb core for the transverse shear behaviour of the whole sandwich is not “smeared” in a one-layered homogenized model. All the numerical studies were conducted with a finite element code which uses a dynamic solverbased on the time discontinuous space-time Galerkin method. The built-in numerical damping of this solver can interfere with a physical damping potentially introduced by the numerical model and results in a global damping totally unexpected. This interaction has been analysed and underlined in this work thanks to the introduction of the Rayleigh damping in the shock wave propagation models. Theoretical and numerical tools and propagating models thus developed have been validated on several academic and industrial structures. Comparison with experimental data on large size industrial structures, especially a real size payload adaptor, is performed and emphasizes the coherence of our approach and the reliability and the efficiency of the proposed propagating models
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Burela, Ramesh Gupta. "Asymptotically Correct Dimensional Reduction of Nonlinear Material Models". Thesis, 2011. http://etd.iisc.ernet.in/2005/3909.
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This work aims at dimensional reduction of nonlinear material models in an asymptotically accurate manner. The three-dimensional(3-D) nonlinear material models considered include isotropic, orthotropic and dielectric compressible hyperelastic material models. Hyperelastic materials have potential applications in space-based inflatable structures, pneumatic membranes, replacements for soft biological tissues, prosthetic devices, compliant robots, high-altitude airships and artificial blood pumps, to name a few. Such structures have special engineering properties like high strength-to-mass ratio, low deflated volume and low inflated density. The majority of these applications imply a thin shell form-factor, rendering the problem geometrically nonlinear as well. Despite their superior engineering properties and potential uses, there are no proper analysis tools available to analyze these structures accurately yet efficiently. The development of a unified analytical model for both material and geometric nonlinearities encounters mathematical difficulties in the theory but its results have considerable scope. Therefore, a novel tool is needed to dimensionally reduce these nonlinear material models.
In this thesis, Prof. Berdichevsky’s Variational Asymptotic Method(VAM) has been applied rigorously to alleviate the difficulties faced in modeling thin shell structures(made of such nonlinear materials for the first time in the history of VAM) which inherently exhibit geometric small parameters(such as the ratio of thickness to shortest wavelength of the deformation along the shell reference surface) and physical small parameters(such as moderate strains in certain applications).
Saint Venant-Kirchhoff and neo-Hookean 3-D strain energy functions are considered for isotropic hyperelastic material modeling. Further, these two material models are augmented with electromechanical coupling term through Maxwell stress tensor for dielectric hyperelastic material modeling. A polyconvex 3-D strain energy function is used for the orthotropic hyperelastic model. Upon the application of VAM, in each of the above cases, the original 3-D nonlinear electroelastic problem splits into a nonlinear one-dimensional (1-D) through-the-thickness analysis and a nonlinear two-dimensional(2-D) shell analysis. This greatly reduces the computational cost compared to a full 3-D analysis. Through-the-thickness analysis provides a 2-D nonlinear constitutive law for the shell equations and a set of recovery relations that expresses the 3-D field variables (displacements, strains and stresses) through thethicknessintermsof2-D shell variables calculated in the shell analysis (2-D).
Analytical expressions (asymptotically accurate) are derived for stiffness, strains, stresses and 3-D warping field for all three material types. Consistent with the three types of 2-D nonlinear constitutive laws,2-D shell theories and corresponding finite element programs have been developed.
Validation of present theory is carried out with a few standard test cases for isotropic hyperelastic material model. For two additional test cases, 3-Dfinite element analysis results for isotropic hyperelastic material model are provided as further proofs of the simultaneous accuracy and computational efficiency of the current asymptotically-correct dimensionally-reduced approach. Application of the dimensionally-reduced dielectric hyperelastic material model is demonstrated through the actuation of a clamped membrane subjected to an electric field. Finally, the through-the-thickness and shell analysis procedures are outlined for the orthotropic nonlinear material model.
Części książek na temat "Orthotropic Elastic Moduli"
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Acosta Flores, Mario, Eusebio Jiménez López i Marta Lilia Eraña Díaz. "Obtaining of a Constitutive Models of Laminate Composite Materials". W Elasticity of Materials [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.100607.
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The study of the mechanical behavior of composite materials has acquired great importance due to the innumerable number of applications in new technological developments. As a result, many theories and analytical models have been developed with which its mechanical behavior is predicted; these models require knowledge of elastic properties. This work describes a basic theoretical framework, based on linear elasticity theory and classical lamination theory, to generate constitutive models of laminated materials made up of orthotropic layers. Thus, the models of three orthotropic laminated composite materials made up of layers of epoxy resin reinforced with fiberglass were also obtained. Finally, by means of experimental axial load tests, the constants of the orthotropic layers were determined.
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S. Kulkarni, Mrudula. "Mechanical Properties and Elasticity Model for Bovine Hard Tissue". W 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.
Streszczenia konferencji na temat "Orthotropic Elastic Moduli"
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Lipton, Robert P., i James Northrup. "Bounds on shear moduli for orthotropic elastic composites". W 1993 North American Conference on Smart Structures and Materials, redaktor H. Thomas Banks. SPIE, 1993. http://dx.doi.org/10.1117/12.148411.
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Behfar, K., R. Naghdabadi, A. Vafai i H. E. Estekanchi. "Nanoscale Vibrational Analysis of an Embedded Multi-Layered Graphene Sheet". W ASME 7th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2004. http://dx.doi.org/10.1115/esda2004-58629.
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In this paper, nanoscale vibrational analysis of a multilayered graphene sheet embedded in an elastic medium is investigated and the corresponding resonant modes and frequencies are determined. It is known that the elastic moduli of a graphene sheet in two orientations x, y are different, so the graphene sheet is assumed to be a general form of an orthotropic plate. The orthotropic sheets stacking at the top of each other bond with carbon-carbon van der Waals forces, also the whole multi-layered graphene sheet is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium.
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Zhang, Yiqing, i Lifeng Wang. "Vibration of Rectangular Single-Layered Black Phosphorus". W ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71056.
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Two-dimensional layered crystal material black phosphorus (BP) has attracted extensive attention due to its excellent property and practical applications. Single-layered BP has a characteristic puckered structure which leads to two anisotropic in-plane directions. The vibration properties of this puckered structure material would be very interesting. Thermal vibration of a rectangular single-layered BP is studied by using continuum orthotropic plate models together with molecular dynamics (MD) simulation. Five elastic constants including two bending moduli, two Poisson’s ratios, and one shear modulus of BP are calculated by using MD method. The natural frequencies of BP are obtained by orthotropic plate models and MD simulation via fast Fourier transformation (FFT). The result of MD simulation shows that continuum orthotropic plate models can predict the natural frequencies well.
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DiCarlo, Anthony A., i John A. Gallagher. "An Adaptive Structure Topology Optimization Approach Applied to Vertebral Bone Architecture". W ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/smasis2018-8131.
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Bone is a highly adaptive biological structure. Following Wolff’s law, bone realigns and grows to adapt to its mechanical environment. This leads to structural heterogeneity of trabecular bone and orthotropic symmetry of the elastic properties. Determining the bone alignment and material properties for living patients is difficult and involves implantation of force and displacement sensors on the bone to determine the compliance and stiffness properties. Micro-computed tomography along with finite element modeling have been limited to the vertebrae of donor cadavers to evaluate trabecular architecture, material properties, and density. Here, an adaptive structure topology optimization algorithm is presented and used to predict trabecular architecture. The algorithm predicts the optimal structure by minimizing the global compliance. The lumbar 1 (L1) vertebra is used as an example. Loads common to L1 vertebrae are applied and bone volume fraction measurements that can be taken easily from living patients through bone mineral density scans are used as the only inputs. The mathematical model is an adaptation of “99 Line Topology Optimization Code Written in Matlab” developed by Sigmund (2001). Bone is locally assumed to be isotropic with an elastic modulus of 13 GPa and the Poisson ratio of 0.3 applied to each element. The resulting structural heterogeneity results in global orthotropic relations. The model uses bone volume fraction and the loading orientation as inputs and gives the corresponding ideal bone structure geometry as an output. The trabecular structure can be predicted solely from the results of a bone mineral density scan. Finite element analysis of the optimized structure is then conducted and the global material properties are determined. While this model is for two-dimensional examples representing planes within the vertebral bone, it is extended to three-dimensional modeling to develop the cortical bone geometry and define the total volume. Matlab is then used to run the topology optimization simulation. The ideal structure is defined by optimizing for a prescribed displacement field of the system following the implementation of a gradient descent optimization method. The results are compared to published values from a combined experimental and numerical procedure. The procedure on sectioned vertebrae reported average ratios between elastic moduli of E1/E2 = 5.2, E1/E3 = 8.8, and E2/E3 = 1.4. Results between the models and the previously published data yield similar transversely isotropic symmetry in the elastic moduli of trabecular bone. However, the elastic moduli ratios are not quite in agreement. Improving the accuracy of the boundary conditions and loading of the finite element model may improve the correlation between the optimization models and published data.
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Somireddy, Madhukar, i Aleksander Czekanski. "Characterization of Material Behavior of the Fused Deposition Modeling Processed Parts". W ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-2949.
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In the present research, one of the additive manufacturing techniques, fused deposition modeling (FDM) fabricated parts are considered for investigation of their material behavior. The FDM process is a layer upon layer deposition of a material to build three dimensional parts and such parts behave as laminated composite structures. Each layer of the part acts as a unidirectional fiber reinforced lamina, which is treated as an orthotropic material. The mesostructure of a part fabricated via fused deposition modeling process is accounted for in the investigation of its mechanical behavior. The finite element (FE) procedure for characterization of a material constitutive law for the FDM processed parts is presented. In the analysis, the mesostructure of the part obtained via FDM process is replicated in the finite element models. Finite element models of tensile specimens are developed with mesostructure that would be obtained from FDM process, then uniaxial tensile test simulations are conducted. The elastic moduli of a lamina are calculated from the linear analysis and the strength parameters are obtained from the nonlinear finite element analysis. The present work provides a FE methodology to find elastic moduli and strength parameters of a FDM processed part by accounting its mesostructure in the analysis.
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Liu, Yu Cheng, i Jin Huang Huang. "Modes of Wave Propagation and Dispersion Relations in Inclusion Reinforced Composite Plates". W ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24246.
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This paper mainly analyzes the wave dispersion relations and associated modal pattens in the inclusion-reinforced composite plates including the effect of inclusion shapes, inclusion contents, inclusion elastic constants, and plate thickness. The shape of inclusion is modeled as spheroid that enables the composite reinforcement geometrical configurations ranging from sphere to short and continuous fiber. Using the Mori-Tanaka mean-field theory, the effective elastic moduli which are able to elucidate the effect of inclusion’s shape, stiffness, and volume fraction on the composite’s anisotropic elastic behavior can be predicted explicitly. Then, the dispersion relations and the modal patterns of Lamb waves determined from the effective elastic moduli can be obtained by using the dynamic stiffness matrix method. Numerical simulations have been given for the various inclusion types and the resulting dispersions in various wave types on the composite plate. The types (symmetric or antisymmetric) of Lamb waves in an isotropic plate can be classified according to the wave motions about the midplane of the plate. For an orthotropic composite plate, it can also be classified as either symmetric or antisymmetric waves by analyzing the dispersion curves and inspecting the calculated modal patterns. It is also found that the inclusion contents, aspect ratios and plate thickness affect propagation velocities, higher-order mode cutoff frequencies, and modal patterns.
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Quek, Shu Ching, Anthony M. Waas, Venkatesh Agaram i Khaled Shahwan. "Compressive Instabilities in Braided Textile Composites". W ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/ad-25306.
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Abstract This paper discusses the results of a finite element (FE) based study of the compressive instabilities of braided glass fiber composites. The micromodel was based on a 2-unitcell size 3-D FE model. Computational tests were carried out to first determine the elastic moduli of the system. Once the computational model was validated with experimental data for the elastic moduli, the compressive response of the micromodel was established using the RIKS method option available in the ABAQUS commercial FE code. The present approach is different from that reported in the literature where classical methods based on the technique of homogenization is used to model the elastic and inelastic response of braided composites. In the present work, explicit account of the braid microstructure (geometry and packing) and the inelastic properties of the matrix are accounted for via the use of the FE method. The macromechanical data pertaining to the braided composites were obtained through traditional means. Tensile tests were performed on the composites through the usage of ASTM D 3039 standard to obtain the macroscopic orthotropic moduli and response. For each test, 3 samples were used to ensure accuracy and the average data is reported in this paper. A separate test was conducted to obtain the in-situ matrix properties of the glass braided composites. The computational model provides a means to assess the compressive strength of braided composites and its dependence on various microstructural parameters. It also serves as a tool to assess the most significant parameter that affects compressive strength. Furthermore, the model is useful to understand the response of braided composites under multiaxial loads.
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Ju, J. W., i K. Yanase. "Elastoplastic Micromechanical Damage Mechanics for Composites With Progressive Partial Fiber Debonding and Thermal Residual Stress". W ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42744.
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By incorporating interfacial damage and thermal residual stress, a novel elastoplastic damage model is proposed to predict the overall transverse mechanical behavior of fiber-reinforced ductile matrix composites within the framework of micromechanics. Based on the concept of fictitious inclusion, and taking the debonding angle into consideration, partially debonded isotropic fibers are replaced by equivalent orthotropic yet perfectly bonded elastic fibers. Up to three interfacial damage modes (no debonding, partial debonding and complete debonding) are considered. The Weibull’s probabilistic function is employed to describe the varying probability of progressive partial fiber debonding. The effective elastic moduli of four-phase composites, composed of a ductile matrix and randomly located yet unidirectionally aligned fibers (undamaged/damaged) are derived by a micromechanical formulation. Thermal residual stress is taken into account through the concept of thermal eigenstrain to study the effect of the manufacturing process-induced residual stress. Further, explicit exact formulation on the exterior point Eshelby’s tensor for elliptical fiber is utilized to investigate the effect on the inelastic mechanical responses of the composites due to the aspect ratio of elliptical fiber.
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Shen, Chuanchuan, Li Ma i Jinyang Zheng. "A Novel Assessment Method for Wrinkle Defects in Composites". W ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21177.
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Abstract Fiber reinforced composite structures have been increasingly used in the field of pressure vessels and piping. Various process-induced defects of composite structures are accumulated during their manufacture processes for the variations of environment temperature and humidity, pre-stress of fiber and curing temperature. Wrinkle defect is one of the most frequently encountered defects in fiber reinforced composite structures. In this paper, a new method for detecting wrinkle defects based on the relation of the displacement fields between flawed and flawless areas is proposed. The orthotropic finite element analysis codes combined with wrinkle model were developed based on Matlab platform to predict structural responses of laminates under three different loading types, including transverse compression, axial tension and bending. The effective elastic moduli disturbed by wrinkles were determined based on a mesomechanics model and a two-step homogenization procedure. Two different wrinkle models including definite and heterogeneous distributed models were considered. It is found that the out-of-plane displacement obviously increases at the wrinkle region under the axial load. The fluctuant displacement fields under axial tensile load can be clearly observed when the heterogeneity wrinkle model is considered. However, the transverse compression cannot produce any displacement distortion. All the results bring us a new idea of non-destructive evaluation for composites, wherein the defects that mainly weakening the stiffness can be detected by measuring the displacement distribution under some specified loads.
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Yang, H. D., i L. Y. Fu. "Acoustoelastic Simulation of Wave Propagation in Different Prestressed Media". W International Geomechanics Symposium. ARMA, 2022. http://dx.doi.org/10.56952/igs-2022-005.
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Abstract Insight into wave propagation in prestressed media is of importance to geophysical applications such as monitoring changes in geopressure and tectonic stress. This issue can be approached by the theory of acoustoelasticity that accounts for nonlinear strain responses due to stresses of finite magnitude. In this study, a rotated staggered-grid finite-difference (RSG-FD) method with an unsplit convolutional perfectly matched layer (CPML) absorbing boundary is used to solve the relevant acoustoelastic equations with third-order elastic constants for elastic wave propagation in prestressed media. Numerical acoustoelasticity simulations for wave propagation in single- and double-layer models are performed under four states of prestresses, confining, uniaxial, pure-shear, and simple-shear. The results display the effective anisotropy of elastic wave propagation in acoustoelastic media, illustrating that the prestress-induced velocity anisotropy is of orthotropic features that are strongly related to the orientation of prestresses. These examples demonstrate the significant impact of prestress conditions on seismic responses in both phase and amplitude. Introduction The impact of prestressed zones on seismic waves is an important issue that affects the interpretation of the results by seismic imaging and inversion. It is well known that acoustic velocities in rocks are sensitive to prestresses. The theory of acoustoelasticity, as an extension of the classical theory of elasticity, is set up under the framework of hyperelasticity (Shams et al., 2011). The theory relates elastic moduli to prestresses (or residual stresses) in solids (Pao and Gamer, 1985), resulting in an effective anisotropy for wave propagation in acoustoelastic media. It has been used to account for stress-induced velocity variations in rocks (Johnson and Shankland, 1989), therefore perhaps providing the potential to understand the acoustic response to in-situ stresses (Sinha and Kostek, 1996; Huang et al., 2001) and, in turn, to monitor changes in geopressure and tectonic stress. Theoretical and experimental investigations of acoustoelasticity for wave propagation in prestressed rocks have made great signs of progress, but with limited literature on numerical simulations for acoustoelastic wave propagation. As a useful complement to the theoretical solutions of acoustoelastic equations, numerical acoustoelasticity simulations are thought to provide further insights into the stress-induced variations in velocity and anisotropy.
Raporty organizacyjne na temat "Orthotropic Elastic Moduli"
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English, Shawn Allen, i Arthur A. Brown. A 3D Orthotropic Elastic Continuum Damage Material Model. Office of Scientific and Technical Information (OSTI), sierpień 2013. http://dx.doi.org/10.2172/1113865.
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English, Shawn Allen. A 3D Orthotropic Strain-Rate Dependent Elastic Damage Material Model. Office of Scientific and Technical Information (OSTI), wrzesień 2014. http://dx.doi.org/10.2172/1156935.
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