Дисертації з теми "Hybrid finite element"
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1
Kang, David Sung-Soo. "Hybrid stress finite element method." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14973.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO
Bibliography: leaves 257-264.
by David Sung-Soo Kang.
Ph.D.
2
Liu, Yunshan. "P-adaptive hybrid/mixed finite element method /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487950153602937.
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3
Demirhisar, Umut. "A Hybrid-stress Nonuniform Timoshenko Beam Finite Element." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608992/index.pdf.
Повний текст джерелаАнотація:
In this thesis, a hybrid-stress finite element is developed for nonuniform Timoshenko beams. The element stiffness matrix is obtained by assuming a stress field only. Since element boundaries are simply the element nodes, a displacement assumption is not necessary. Geometric and mass stiffness matrices are obtained via equilibrium and kinematics of deformation equations which are derived in the beam arbitrary cross-section. Utilizing this method eliminates the displacement assumption for the geometric and mass stiffness matrices. The element has six degrees of freedom at each node. Axial, flexural and torsional effects are considered. The torsional and distortional warping effects are omitted. Deformations due to shear is also taken into account.
Finally, some sample problems are solved with the element and results are compared with the solutions in the literature and commercial finite element programs (i.e. MSC/NASTRAN®).
4
Liu, Xiao Bin. "Finite element analysis of hybrid thermoplastic composite structures." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493330.
Повний текст джерелаАнотація:
A wide range of thermoplastic composites (TPC) are now being used in automotive applications including vehicle front-end structures, load floors, seat backs, door cassettes and instrument panels. Long fibre thermoplastics (LFT), glass mat thermoplastics (GMT) and fully structural materials such as woven commingled fabric TPCs, e.g. Twintex®, provide a range of properties and mouldability appropriate to specific applications.
5
Quinelato, Thiago de Oliveira. "Mixed hybrid finite element method in elasticity and poroelasticity." Laboratório Nacional de Computação Científica, 2017. https://tede.lncc.br/handle/tede/273.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Esta tese é focada no desenvolvimento e na análise de aproximações em dimensão finita das equações que descrevem problemas de elasticidade linear e poroelasticidade. A estratégia de aproximação é baseada em formulações de elementos finitos mistas hibridas desses problemas e a construção dos espaços de dimensão finita é guiada por várias propriedades desejadas: continuidade das trações (conservação do momento linear), simetria do tensor de tensão (conservação do momento angular), número reduzido de graus de liberdade globais e robustez sob distorção de malha. A principal dificuldade está relacionada com o atendimento simultâneo da condição inf-sup e da simetria do tensor de tensão. O ultimo requisito é relaxado, sendo satisfeito de maneira fraca pela introdução de um multiplicador de Lagrange. A maior contribuição é o desenvolvimento e a análise de espaços de dimensão finita estáveis para aproximação mista dos problemas de elasticidade linear e poroelasticidade em malhas quadrilaterais arbitrárias. Esses espaços são capazes de fornecer convergência com taxa ótima do campo de tensão na norma H(div) em malhas de quadriláteros arbitrários, o que é provado pela análise numérica e confirmado por experimentação.
This thesis is focused on the development and analysis of finite dimensional approximations of the equations describing linear elasticity and poroelasticity problems. The approximation strategy is based on mixed hybrid finite element formulations of those problems and the construction of the finite dimensional spaces is guided by several desired properties: continuity of the tractions (conservation of linear momentum), symmetry of the stress tensor (conservation of angular momentum), reduced number of global degrees of freedom, and robustness under mesh distortion. The main difficulty is related with the simultaneous fulfillment of the inf-sup condition and the symmetry of the stress tensor. The last requirement is relaxed, being enforced in the weak sense through the introduction of a Lagrange multiplier. The main contribution is the development and analysis of stable finite dimensional spaces for mixed approximation of linear elasticity and poroelasticity problems on arbitrary quadrilateral meshes. These spaces are capable of providing optimal order convergence of the stress field in the H(div)-norm on meshes of arbitrary quadrilaterals, which is proved by numerical analysis and confirmed by experimentation.
6
Fan, Yuanji. "3D Finite Element Analysis of a Hybrid Stepper Motor." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278496.
Повний текст джерелаАнотація:
Hybrid stepper motors are being applied to more and more industrial regionsdue to their low cost compared with servo motors and prominent performance.Many industrial applications require accurate and eective methods for predictinga motor’s performance at the design stage. The geometry of the motorsis complicated and the magnetic saturation eect is also serious, giving riseto the diculty of understanding the transient behavior of the motors. Furthermore,the drive circuit and control algorithm are more sophisticated thanthose of traditional AC or DC motors. Lastly, the losses of the motors createthe rising of temperature, while the thermal eect and dynamic performanceaect each other.All these factors can be solved by simulating a hybrid stepper motor witha model combining the eect of electromagnetic field, control algorithm, andmotor loss together. In this thesis, a three-dimension (3D) finite elementmodel is developed in the software Maxwell for studying motor characteristics.The electromagnetic field is analyzed in a static state. The simulatedback electromagnetic force is verified by experiments. The feasibility of fullstepcontrol algorithm is analyzed. The vector control algorithm is applied tothe model through co-simulation of Simulink and Maxwell in Simplorer. The3D model is proved to be unrealistic for co-simulation. In the end, this thesissummarizes the modeling experience and gives recommendations on thetransient simulation of the motor.Hybridstegsmotorer appliceras i fler ochfler industriapplikationer tack vare deras låga kostnad och förbättrad prestanda jämfört med servomotorer. Många branschapplikationer kräver exakta och effektiva metoder för att förutsäga motorns prestanda redan i konstruktionsstadiet. Motorns geometri är komplicerad och den magnetiska mättnadseffekten är också betydande, vilket försvårar modelleringen. Dessutom är drivkretsen och styralgoritmen mer sofistikerad än den för traditionella växeleller likströmsmotorer. Vidare så resulterar motorns förluster i temperaturökningar vilka påverkar dynamiska.Alla dessa faktorer kan studeras genom att simulera hybrida stegmotorer med en modell som kombinerar effekten av elektromagnetiskt fält, kontrollalgoritm och motorförluster tillsammans. I detta examensarbete utvecklas en tredimensionell finit elementmodell i programvaran Maxwell för att studera motorns elektromagnetiska egenskaper. Det elektromagnetiska fältet analyseras i ett statiskt tillstånd. Den beräknade mot-EMK:n har verifieras genom experiment. Vektorkontrollalgoritmen tillämpas på modellen genom samsimulering i Simulink och Maxwell i Simplorer. Den tredimensionella modellen visade sig vara orealistisk för samsimulering. Till sist summeras uppnådaerfarenheter och rekommendationer för fortsatt arbete ges.
7
Tsoi, Sai Hong. "On a hybrid finite element with weak Kirchhoff assumption." HKBU Institutional Repository, 2000. http://repository.hkbu.edu.hk/etd_ra/218.
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Meyer, Frans J. C. (Frans Johannes Christiaan). "Hybrid Finite Element/Boundary Element solutions of general two dimensional electromagnetic scattering problems." Thesis, Stellenbosch : Stellenbosch University, 1991. http://hdl.handle.net/10019.1/69271.
Повний текст джерелаАнотація:
Thesis (MEng) -- University of Stellenbosch, 1991.ENGLISH ABSTRACT: A two-dimensional Coupled Element Method (CEM) for solving electromagnetic scattering problems involving lossy, inhomogeneous, arbitrarily shaped cylinders, was investigated and implemented. The CEM uses the Finite Element Method (FEM) to approximate the fields in and around the scatterer and the Boundary Element Method (BEM) to approximate the far-field values. The basic CEM theory is explained using the special, static electric field problem involving the solution of Laplace's equation. This theory is expanded to incorporate scattering problems, involving the solution of the Helmholtz equation. This is done for linear as well as quadratic elements. Some of the important algorithms used to implement the CEM theory are discussed. Analytical solutions for a round, homogeneous- and one layer coated PC cylinder are discussed and obtained. The materials used in these analytical solutions can be lossy as well as chiral. The CEM is validated by comparing near- and far-field results to the analytical solution. A comparison between linear and quadratic elements is also made. The theory of the CEM is further expanded to incorporate scattering from chiral media
AFRIKAANSE OPSOMMING: 'n Gekoppelde Element Metode (GEM) wat elektromagnetiese weerkaatsingsprobleme, van verlieserige, nie-homogene, arbitrere voorwerpe kan oplos, is ondersoek en geimplimenteer. Die GEM gebruik die Eindige Element Metode (EEM) om die velde in en om die voorwerp te benader. 'n Grenselementmetode word gebruik om die vervelde te benader. Die basiese teorie van die GEM word verduidelik deur die toepassing daarvan op die spesiale geval van 'n statiese elektriese veld- probleem. Hierdie probleem verlang die oplossing van Laplace se vergelyking. Die teorie word uitgebrei om weerkaatsingsprobleme te kan hanteer. Die weerkaatsingsprobleme verlang die oplossing van 'n Helmholtz-vergelyking. Hierdie teorie word ontwikkel vir lineere sowel as kwadratiese elemente. Van die belangrike algoritmes wat gebruik is om die GEM-teorie te implimenteer, word bespreek. Analietise oplossings vir ronde, homogene en eenlaag bedekte perfek geleidende silinders word bespreek en verkry. Die material wat in die oplossings gebruik word, kan verlieserig of kiraal wees. Die GEM word bekragtig deur naby- en verveld resultate te vergelyk met ooreenkomstige aitalitiese oplossings. Die lineere en kwadratiese element- resultate word ook met mekaar vergelyk. Die GEM-teorie is verder uitgebrei sodat weerkaatsing vanaf kirale materiale ook hanteer kan word.
9
Zheng, Hui. "Application of the hybrid finite element procedure to crack band propagation." Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183125160.
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Riyait, Navtej Singh. "Anisotropic scattering, voids and hybrid principles in finite element neutron transport." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47228.
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11
Girgis, Alexi M. "Finite Element Method Modeling of Optoconductance in Metal-Semiconductor Hybrid Devices." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/401.
Повний текст джерелаАнотація:
"A numerical description of the extraordinary optoconductance (EOC) effect is presented using two separate models. Extraordinary optoconductance is part of a general class of EXX geometric effects involving the external perturbation of the properties of a 2D electron gas in a macroscopic semiconductor or metal-semiconductor hybrid structure. The addition of metallic inclusions, has been shown to increase the sensitivity of devices relying on EXX effects. Following the discovery of the first EXX effect, extraordinary magneto-resistance (EMR), an optical equivalent was suggested. Unlike EMR, where the external perturbation is an applied magnetic field, EOC results from the modification of the local charge density in the semiconductor by a focused laser. The first model assumes Gaussian charge densities for the photo-generated electron-hole pairs while the second model directly solves the semiconductor drift-diffusion equations using the finite element method (FEM). Results from both models are shown to agree with experimental EOC data, both as a function of the laser spot position and temperature. The FEM model has the ability to describe EOC in more complex geometries making it useful in designing EOC devices geared for particular applications. "
12
Li, Ming-Sang. "Higher order laminated composite plate analysis by hybrid finite element method." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/40145.
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Kehl, Richard Eugene. "Application of unified constitutive relations to hybrid stress finite element formulation." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/39022.
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Mbanga, Badel L. "HYBRID PARTICLE-FINITE ELEMENT ELASTODYNAMICS SIMULATIONS OF NEMATIC LIQUID CRYSTAL ELASTOMERS." Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1334607477.
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Zhang, Jinmiao. "A Hybrid Finite Element Method for Heterogeneous Media With Random Microstructures /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487931512621134.
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Sun, Mingkun Sun. "MULTISCALE HYBRID ELEMENT MODELING OF TRIAXIAL BRAIDED COMPOSITE." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1533550804106857.
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Citrain, Aurélien. "Hybrid finite element methods for seismic wave simulation : coupling of discontinuous Galerkin and spectral element discretizations." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR28.
Повний текст джерелаАнотація:
Pour résoudre des équations d’ondes posées dans des milieux hétérogènes avec des éléments finis et un coût numérique raisonnable, nous couplons la méthode Discontinue de Galerkine (DGm) avec des éléments finis spectraux (SEm). Nous utilisons des maillages hybrides composés de tétraèdres et d’hexaèdres structurés. Le couplage est réalisé en partant d’une formulation DG mixte primale posée dans un maillage hybride composé d’un macro-élément hexaédrique et d’un sous-maillage composé de tétraèdres. La SEm est appliquée dans le macro-élément découpé en hexaèdres structurés et le couplage est assuré par les flux numériques de la DGm appliqués sur les faces internes du macro-élément communes avec le maillage tétraédrique. La stabilité de la méthode couplée est démontrée quand l’intégration en temps est effectuée avec un schéma Saute-Mouton. Les performances de la méthode couplée sont étudiées numériquement et on montre que le couplage permet de réduire les coûts numériques avec un très bon niveau de précision. On montre aussi que la formulation couplée peut stabiliser la méthode DG appliquée dans des domaines incluant des couches parfaitement adaptéesTo solve wave equations in heterogeneous media with finite elements with a reasonable numerical cost, we couple the Discontinuous Galerkin method (DGm) with Spectral Elements method (SEm). We use hybrid meshes composed of tetrahedra and structured hexahedra. The coupling is carried out starting from a mixed-primal DG formulation applied on a hybrid mesh composed of a hexahedral macro-element and a sub-mesh composed of tetrahedra. The SEm is applied in the macro-element paved with structured hexahedrons and the coupling is ensured by the DGm numerical fluxes applied on the internal faces of the macro-element common with the tetrahedral mesh. The stability of the coupled method is demonstrated when time integration is performed with a Leap-Frog scheme. The performance of the coupled method is studied numerically and it is shown that the coupling reduces numerical costs while keeping a high level of accuracy. It is also shown that the coupled formulation can stabilize the DGm applied in areas that include Perfectly Matched Layers
18
Dang, Weidong. "Finite element modelling of hybrid (spot welded/bonded) joints under service conditions." Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2187/document.
Повний текст джерелаАнотація:
Le soudage par point et le collage sont largement utilisés dans la jonction des tôles, telles que l'assemblage de caisses de voiture. Récemment, le soudage par point et le collage ont été combinés pour faire le joint hybride soudé-collé, qui est utilisé pour joindre les aciers à hautes résistances et améliorer la rigidité et la résistance aux chocs des corps de voiture. Dans l'industrie, l'évaluation de la conception avant prototype nécessite des modèles fiables de comportement en termes de prédiction des comportements mécaniques. Le modèle élément finis de joint soudé-collé est un nouveau défi car il doit combiner les modèles de soudage par points et les modèles de collage.Cette thèse se concentre sur la modélisation du joint soudé-collé par de l'acier DP600 et avec l’adhésif structurel SikaPower®-498. La modélisation peur utiliser un modèle solide ou un modèle simplifié (élément coque plus élément de connexion). Le modèle solide permet de prédire le comportement de spécimen à petite échelle: KS2 et cisaillement. Le modèle simplifié peut être utilisé pour prédire la performance des composants de grande dimension avec un coût de calcul acceptable.En ce qui concerne le modèle solide, le comportement du joint soudé et du joint collé sont identifiés séparément calibrés sur un spécimen KS2 sous trajets de chargement différents. Les inhomogénéités dans la zone de fusion et la zone affectée par la chaleur du soudage par point sont prises en compte par l'intermédiaire de facteurs d'échelle applique à la contrainte d'écoulement du métal de base. Les facteurs d'échelle sont determinés par identification inverse. Le modèle de Gurson est utilisé pour prédire la rupture ductile en zone affectée par le chaleur et dans le métal base tandis que le modèle de zone cohésive est utilisé pour simuler la rupture quasi-fragile dans l'interface de la zone de fusion. Les paramètres du modèle de zone cohésive sont identifiés par l'intégrale J à la pointe de fissure de la soudure. Des éléments de zone cohésive avec une loi traction-séparation sont également utilisés pour prédire le décollement adhésif. Les paramètres du modèle sont identifiés par des essais du type « Double Cantilevered Beam » et « End Notched Flexure », correspondant aux mode I et mode II respectivement. Le modèle élaboré pour le soudage par est associé avec le modèle de collage pour prédire le comportement et la rupture du joint soudé-collé.En ce qui concerne le modèle simplifié, des éléments de connexion sont utilisés pour prédire les endommagement des soudure par point. Les paramètres de l'élément de connexion sont identifiés par des tests de KS2 sous différents trajets de chargement. Enfin, les modèles simplifiés d'un soudage, d'un collage, et d'un soudé-collé sont validés sur une jonction en T qui peut représenter le pilier-B de carrosserie de la voitureSpot welding and adhesive bonding are widely used in joining of sheet metals, such as assembling of car body-in-white. Recently, spot weld and adhesive are combined to make weld bonded joint, which is employed to join Advanced High Strength Steel to improve the stiffness and crashworthiness of car body. In industry, the assessment of designing prior to prototype requires reliable constitutive models in terms of the prediction of the mechanical behaviors. The FE model of weld bonded joint is a new challenge as it should combine the models of spot welding and the models of adhesive. This thesis focuses on the modeling of weld bonded joint by DP600 steel and structural adhesive SikaPower®-498. The model of weld bonded joint consists of solid model and simplified model. The former is devoted to predict the behavior of weld bonded joint on small-scale specimen: KS2 and lap-shear. The latter can be used to predict the performance of large components with acceptable computational cost. As regards solid model, spot welded joint and adhesive bonded joint behaviors are separately identified by KS2 specimen under different loading path. The inhomogeneities in fusion zone and heat affected zone of spot weld are taken into account via the scaling of the flow stress of base metal. The scaling factors are calibrated by inverse identification. Gurson model is used to predict ductile fracture in heat affected zone and base metal while cohesive zone model is employed to simulate quasi-brittle fracture in the interface of fusion zone. The parameters of cohesive zone model are identified by the J-integral at the notch tip of spot weld crack. Cohesive zone elements with traction-separation-laws are also used to predict adhesive debonding. Model parameters are calibrated by Double Cantilevered Beam and End Notched Flexure specimens, corresponding to Mode-I and Mode-II fracture respectively. The model developed for spot weld is associated with adhesive model to predict weld bonded joint. As regards simplified model, connector elements are employed to predict the damage of spot weld. The parameters of connector element are identified by KS2 tests under different loading paths. Finally, the simplified model of spot welding, adhesive bonding, and weld-bonding are validated by T-joint which can represent the B-pillar of car body
19
Nanneh, Mohammad Majed. "A synthesis method based on hybrid principles for finite element neutron transport." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46465.
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20
Lee, Soon Gie. "Hybrid Damage Identification Based on Wavelet Transform and Finite Element Model Updating." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333676433.
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Zeng, Dan. "Development of the hybrid finite element method for applications to heterogeneous materials /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu148820315882678.
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Jolliffe, Clifford Mark. "The design of hybrid stepping motors aided by three dimensional finite element analysis." Thesis, University of Warwick, 1999. http://wrap.warwick.ac.uk/3842/.
Повний текст джерелаАнотація:
Though the hybrid stepping motor has a long and proven history, in terms of toughness, accuracy of position and the ability to operate in open loop, motor performance improvements can still be made in terms of the physical structure of the motor's components. It is impossible to build a complete solution of the hybrid stepping motor using simple analytical functions or equivalent circuit representations. This is due to the difficulties introduced by the motor's highly non-linear three dimensional magnetic structure, of which the doubly salient tooth structure, axial magnet, and back iron all complicate the situation. However, with the recent advances in three dimensional finite element software a comprehensive study of the motor has been achieved in this thesis. This has allowed improvements to simpler two dimensional based mathematical models, which allow faster computation of the motor's electromagnetic performance. To aid modelling, novel equations which accurately model today's high permeability steels have been developed. These are shown to be more accurate than the established Jiles-Atherton method. Inductance calculations of the steel's flux paths have been comprehensively improved by the use of elliptical functions. The thesis concludes with the design of two quite individual new machines. The first dramatically improves a motor's power output, smoothness, noise levels, and resonance by modifying the tooth structure. The second uses soft magnetic composite materials to provide an isotropic path for cross lamination flux which flows in a stator's back iron. Both new designs are shown to offer a significant improvements to the high speed torque capability of the hybrid stepping motor.
23
Wang, Xinfei. "Multiscale Modeling of friction Mechanisms with Hybrid Methods." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78169.
Повний текст джерелаАнотація:
This thesis presents a simulation model of sliding process of friction, which combines Newtonian particle dynamics and finite element method to study friction mechanisms that bridging micro and macro scales. In the thesis, it first reviews the importance of studying pavement friction that is associated to safety of drivers, society economics and environmental impact. Then, the hybrid numerical methods of Newtonian particle dynamics and finite element method have been introduced, and the rules to bridge these two methods also have been discussed for solid material that assumes the forces and displacements are continuous at the interface of these two methods. The fundamental theories of friction mechanisms are built upon the surface roughness, adhesion and deformation at the contact between two surfaces. At last, the simulation model of sliding process is presented with the hybrid method, and its visualization and result analysis has been given. At the same time, this thesis also includes the procedures of establishing the simulation of the hybrid methods with C++ programming like the program framework, structure and the major pieces of the program.Master of Science
24
Akman, Mehmet Nazim. "Analysis Of Thin Walled Open Section Tapered Beams Using Hybrid Stress Finite Element Method." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609246/index.pdf.
Повний текст джерелаАнотація:
In this thesis, hybrid stress finite element is formulated for the analysis of the isotropic, thin walled, open section beams with variable cross sections. The beam element has two nodes each having seven degrees of freedom. Assumption of stress field is sufficient to determine the element stiffness matrix. Axial, flexural and torsional effects are taken into account in the analysis. The methodology can be applied both to the tapered and the uniform beams. Throughout this study, firstly element cross-sectional properties are computed using the flow analogy of the inter-connected elements which may have different thicknesses. Then another computer program calculates the displacements and stresses at the nodes along the beam. The results obtained are compared to the results taken from literature and commercial FEM program Nastran.
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Zhao, Jianzhao. "Evaluation of efficiency of partial hybrid finite element method using composite laminates with crack." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/MQ39482.pdf.
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Wagner, James Michael. "A hybrid finite element analysis of shot peen contour forming using residual stress measurements." Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/7049.
Повний текст джерелаАнотація:
In order to develop surfaces that have the proper curvature for aerospace structures, it is
sometimes necessary to use shot peen forming, also known as contour forming, to create the
desired shape in a piece of metal. Since the preferred metal in aerospace continues to be
aluminum and its alloys, this study will concentrate on the effects of shot peening on aluminum.
Typically, shot intensity is measured using standard Almen strips made from cold rolled
SAE 1070 spring steel. Since the effects of the shot on aluminum is the chief concern of this
study, aluminum strips of the same size and thickness will be used to determine the intensity of
the shot on aluminum parts. These strips will be exposed for different amounts of time to
different intensities, measured using the steel Almen strips, and then the intensity (or arc height)
will be measured on the aluminum strips. The residual stresses in these strips will then be
measured using the hole drill method (ASTM E837).
The stresses from the residual stress test will then be used to develop a finite element
model that simulates the aluminum strips and the deformation in them. The model will then be
calibrated with the empirical data. From there, it will be the goal of this study to be able to
predict the deformation of aluminum parts when exposed to certain shot peen intensities. This
will enable more efficient contour forming processes with less rework. Furthermore, the trial
and error of a manual process can be avoided with the use of robotics. Robotics/Automation can
also help in creating more consistent results.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Momoh, Osman Aliu. "Application of the hybrid stress finite element method in stability analysis of mine excavations." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74234.
Повний текст джерелаАнотація:
This thesis reports the formulation and implementation of a finite element model, which is based on the so called Hybrid Stress Finite Element Method. The proposed formulation is based on stress as the primary unknown and is radically different from displacement-based finite element models.Among the special features of the model are the casting of the element stiffness equations in terms of local rather than global coordinate system, the use of the active column method known as the "Skyline technique for the solution of equilibrium equations", and the use of fast and efficient mesh generation and alteration routines developed specially for geotechnical applications.
Verification tests carried out on problems in elasticity with closed form solutions show that the proposed method is accurate and that it requires relatively fewer elements than displacement-based finite element method to achieve the same accuracy. Results of case history studies done on two mine design problems matched those from other numerical modelling procedures within acceptable limits and showed that the proposed method can be used to solve geomechanics problems efficiently and realistically.
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Keat, William D. "Surface integral and finite element hybrid method for the analysis of three-dimensional fractures." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14294.
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Suliman, Basem Saoud. "A hybrid exact strip and finite element method for modelling damage in composite plates." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/114326/.
Повний текст джерелаАнотація:
Delamination is a frequent cause of failure in laminated structures, particularly under compressive loads. The presence of delaminations in composite laminates reduces their overall stiffness. In addition, delaminations tend to grow rapidly under postbuckling loads, causing further reductions in the structural strength and leading ultimately to a sudden structural failure. Recently, many studies have been carried out to investigate the effects of delaminations on the buckling and vibration behaviour of composite structures. Finite element analysis is often used to perform these due to its ability to model complex geometries, loading and boundary conditions, but this comes at a high computational cost. The exact strip method provides an efficient alternative approach using an exact dynamic stiffness matrix based on a continuous distribution of stiffness and mass over the structure, so avoiding the discretization to nodal points that is implicit in finite element analysis. However due to its prismatic requirements, the exact strip method can model damaged plates directly only if the damaged region extends along the whole length of the plate. This thesis introduces a novel combination of exact strip and finite element analysis which can be used to model more complex cases of damaged plates. Comparisons with pure finite element analysis and a previous technique based on the exact strip method demonstrate the capability and efficiency of this hybrid method for a range of isotropic and composite plates.
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Tongtoe, Samruam. "A comparison of displacement and hybrid stress models for two dimensional finite element analysis." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/80094.
Повний текст джерелаАнотація:
An eight-node isoparametric hybrid stress element is developed for two dimensional plane stress and plane strain analyses. The assumed stresses are represented by 18 unknown parameters. An eight-node isoparametric displacement element is implemented in an existing finite element program [10]. Several example problems are solved to compare the results of the hybrid and the displacement elements.Master of Science
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ELKILANI, YASSER SHAWKI. "A HYBRID ELASTICITY AND FINITE ELEMENT METHOD FOR THREE-DIMENSIONAL CONTACT PROBLEMS WITH FRICTION." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1055167472.
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Kung, Christopher W. "Development of a time domain hybrid finite difference/finite element method for solutions to Maxwell's equations in anisotropic media." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1238024768.
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Suliman, Ridhwaan. "Development of parallel strongly coupled hybrid fluid-structure interaction technology involving thin geometrically non-linear structures." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/24288.
Повний текст джерелаАнотація:
This work details the development of a computational tool that can accurately model strongly-coupled fluid-structure-interaction (FSI) problems, with a particular focus on thin-walled structures undergoing large, geometrically non-linear deformations, which has a major interest in, amongst others, the aerospace and biomedical industries. The first part of this work investigates improving the efficiency with which a stable and robust in-house code, Elemental, models thin structures undergoing dynamic fluid-induced bending deformations. Variations of the existing finite volume formulation as well as linear and higher-order finite element formulations are implemented. The governing equations for the solid domain are formulated in a total Lagrangian or undeformed conguration and large geometrically non-linear deformations are accounted for. The set of equations is solved via a single-step Jacobi iterative scheme which is implemented such as to ensure a matrix-free and robust solution. Second-order accurate temporal discretisation is achieved via dual-timestepping, with both consistent and lumped mass matrices and with a Jacobi pseudo-time iteration method employed for solution purposes. The matrix-free approach makes the scheme particularly well-suited for distributed memory parallel hardware architectures. Three key outcomes, not well documented in literature, are highlighted: the issue of shear locking or sensitivity to element aspect ratio, which is a common problem with the linear Q4 finite element formulation when subjected to bending, is evaluated on the finite volume formulations; a rigorous comparison of finite element vs. finite volume methods on geometrically non-linear structures is done; a higher-order finite volume solid mechanics procedure is developed and evaluated. The second part of this work is concerned with fluid-structure interaction (FSI) modelling. It considers the implementation and coupling of a higher order finite element structural solver with the existing finite volume fluid-flow solver in Elemental. To the author’s knowledge, this is the first instance in which a strongly-coupled hybrid finite element–finite volume FSI formulation is developed. The coupling between the fluid and structural components with non-matching nodes is rigorously assessed. A new partitioned fluid-solid interface coupling methodology is also developed, which ensures stable partitioned solution for strongly-coupled problems without any additional computational overhead. The solver is parallelised for distributed memory parallel hardware architectures. The developed technology is successfully validated through rigorous temporal and mesh independent studies of representative two-dimensional strongly-coupled large-displacement FSI test problems for which analytical or benchmark solutions exist.Dissertation (MEng)--University of Pretoria, 2012.
Mechanical and Aeronautical Engineering
unrestricted
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Góis, Wesley. "Elementos finitos híbridos e híbrido-mistos de tensão com enriquecimento nodal." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-15062009-092448/.
Повний текст джерелаАнотація:
Neste trabalho, a técnica de enriquecimento da partição da unidade é estendida e adaptada para duas formulações não-convencionais para a elasticidade plana: a formulação híbrida de tensão (FHT) e a formulação híbrido-mista de tensão (FHMT). Estas formulações são ditas não-convencionais, pois não recorrem a princípios variacionais clássicos. Elementos finitos triangulares e quadrilaterais com enriquecimento nodal são desenvolvidos para avaliação da forma discreta das duas formulações estudadas. Na FHMT, três campos são aproximados de forma independente: tensões e deslocamentos no domínio e deslocamentos no contorno. O conceito de partição da unidade é então utilizado para garantir continuidade de cada um dos campos envolvidos na FHMT e realizar o procedimento de enriquecimento nodal. Funções polinomiais são utilizadas para enriquecer cada uma das aproximações dos campos da FHMT. A sensibilidade das respostas em relação a redes distorcidas é avaliada. Além disso, abordam-se aspectos relativos à convergência e estabilidade da solução numérica. Especificamente para a FHT, dois campos são independentemente aproximados: tensões no domínio e deslocamentos na fronteira estática. As aproximações das tensões, que por definição não estão atreladas a nós, devem primeiramente satisfazer a condição de equilíbrio no domínio. O conceito de partição da unidade é empregado, neste caso, para dar continuidade aos deslocamentos entre as fronteiras dos elementos. O enriquecimento polinomial da partição de unidade é então aplicado às aproximações dos deslocamentos no contorno. Para o campo de tensões no domínio, desenvolve-se uma técnica específica de enriquecimento nodal. Mais uma vez, aspectos relativos à sensibilidade à distorção de redes e convergência são estudados e avaliados. Finalmente, alguns exemplos numéricos são apresentados para ilustrar o desempenho de ambas as abordagens, especialmente quando a técnica de enriquecimento é aplicada.In the present work, the partition of unity enrichment concept is basically applied to non-conventional stress hybrid-mixed and hybrid formulations in plane elasticity. These formulations are referred to as non-conventional because no variational principles are explored. From these, triangular and quadrilateral finite elements with selective nodal enrichment are then derived. In the stress hybrid-mixed approach, three independent fields are approximated: stress and displacement fields in the domain and displacement fields on the static boundary. The partition of unity concept is then used to provide continuity to all the fields involved. Afterwards, the nodal enrichment feature is explored. Polynomial functions are employed to enrich each one of the approximation fields. Besides, some aspects concerning convergence and stability of the numerical solutions obtained are addressed. On the other hand, in the hybrid approach, two independent fields are approximated: stress fields in the domain and displacement fields on the static boundary. However, the approximation of the stress field must first satisfy the equilibrium condition in the domain without involving nodal values in its definition. Hence, the partition of unity concept is used to provide continuity of displacements between the boundaries of the elements. The partition of unity based nodal enrichment is then applied to the boundary displacement fields. Nevertheless, enrichment of the stress field can also be carried out with exploring a specific and original technique that permits applied the partition of unity concept but in such way as to preserve satisfaction of the equilibrium condition in the domain. Again, convergence and stability aspects of the hybrid approach are briefly addressed. Finally, some numerical examples are presented to illustrate the performance of both approaches derived, especially when combined possibilities of enrichment are explored.
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Chandrashaker, Rajagopalan Carleton University Dissertation Engineering Civil. "Seismic analysis of gravity dam-reservoir-foundation system using an effective hybrid technique." Ottawa, 1992.
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Ayoub, Sherif Fathy. "Analysis of elastic-plastic continuum at large deformation using hybrid descriptions and finite element method /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487265555439612.
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Mohamed, Kamal. "STIFFNESS ASSESSMENT OF TRANSITION PIECE ON HYBRID WIND TOWER : EIGENFREQUENCY ANALYSIS OF FINITE ELEMENT MODELS." Thesis, Luleå tekniska universitet, Byggkonstruktion och -produktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65308.
Повний текст джерелаАнотація:
A transition piece has responsibility to transmit forces from one member to another member. But when doing it, the transition piece must be stiff enough. Studying what parameter of the transition piece is contributing to the stiffness the most, will give economic advantages. Studies on the stiffness when introducing a transition piece on a hybrid tower will be carried out with an analytical procedure through Finite element method, with the software Abaqus. A linear perturbation, with a frequency step where extraction of the eigenfrequency value will be obtained. The value will reflect the stiffness of the structure, because it has a linear relation between each other. Higher eigenfrequency means higher stiffness and vice versa. The first model (Case A) is model of a fixed tubular tower. The frequency of case A is desired because it’s stiff at the bottom. Therefore a comparison has been made when introducing the transition piece.The eigenfrequency of the tubular tower (Case A) is 0,36765 Hz. And The eigenfrequency of the structure (Case D) is 0,21964 Hz, which make a stiffness reduction of 40,3 % when introducing the transition piece. 60,6 % of the total reduction is due to the bridging ring. The most efficient change on the bridging ring that will obtain a higher stiffness on the entire structure is to increase mid-plates layers.
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Dow, Douglas Donald. "Finite Element and Experimental Analyses of Hybrid Joints Subjected to Fully Reversed Flexure Fatigue Loading." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/DowDD2008.pdf.
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Loehr, John Erik. "Development of a hybrid limit equilibrium-finite element procedure for three-dimensional slope stability analysis /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Usner, Brian C. "Generalized hybrid methods for modeling complex electromagnetic structures." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1135004394.
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Ledfelt, Gunnar. "Hybrid Time-Domain Methods and Wire Models for Computational Electromagnetics." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3115.
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Edelvik, Fredrik. "Hybrid Solvers for the Maxwell Equations in Time-Domain." Doctoral thesis, Uppsala universitet, Avdelningen för teknisk databehandling, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2156.
Повний текст джерелаАнотація:
The most commonly used method for the time-domain Maxwell equations is the Finite-Difference Time-Domain method (FDTD). This is an explicit, second-order accurate method, which is used on a staggered Cartesian grid. The main drawback with the FDTD method is its inability to accurately model curved objects and small geometrical features. This is due to the Cartesian grid, which leads to a staircase approximation of the geometry and small details are not resolved at all. This thesis presents different ways to circumvent this drawback, but still take advantage of the benefits of the FDTD method. An approach to avoid staircasing errors but still retain the efficiency of the FDTD method is to use a hybrid grid. A few layers of unstructured cells are used close to curved objects and a Cartesian grid is used for the rest of the domain. For the choice of solver on the unstructured grid two different alternatives are compared: an explicit Finite-Volume Time-Domain (FVTD) solver and an implicit Finite-Element Time-Domain (FETD) solver. The hybrid solvers calculate the scattering from complex objects much more efficiently compared to using FDTD on highly resolved Cartesian grids. For the same accuracy in the solution roughly a factor of 10 in memory requirements and a factor of 20 in execution time are gained. The ability to model features that are small relative to the cell size is often important in electromagnetic simulations. In this thesis a technique to generalize a well-known subcell model for thin wires, in order to take arbitrarily oriented wires in FETD and FDTD into account, is proposed. The method gives considerable modeling flexibility compared to earlier methods and is proven stable. The results show excellent consistency and very good accuracy on different antenna configurations. The recursive convolution method is often used to model frequency dispersive materials in FDTD. This method is used to enable modeling of such materials in the unstructured FVTD and FETD solvers. The stability of both solvers is analyzed and their accuracy is demonstrated by computing the radar cross section for homogeneous as well as layered spheres with frequency dependent permittivity.
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Marais, Neilen. "Efficient high-order time domain finite element methods in electromagnetics." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1499.
Повний текст джерелаАнотація:
Thesis (DEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.The Finite Element Method (FEM) as applied to Computational Electromagnetics (CEM), can beused to solve a large class of Electromagnetics problems with high accuracy and good computational efficiency. For solving wide-band problems time domain solutions are often preferred; while time domain FEM methods are feasible, the Finite Difference Time Domain (FDTD) method is more commonly applied. The FDTD is popular both for its efficiency and its simplicity. The efficiency of the FDTD stems from the fact that it is both explicit (i.e. no matrices need to be solved) and second order accurate in both time and space. The FDTD has limitations when dealing with certain geometrical shapes and when electrically large structures are analysed. The former limitation is caused by stair-casing in the geometrical modelling, the latter by accumulated dispersion error throughout the mesh. The FEM can be seen as a general mathematical framework describing families of concrete numerical method implementations; in fact the FDTD can be described as a particular FETD (Finite Element Time Domain) method. To date the most commonly described FETD CEM methods make use of unstructured, conforming meshes and implicit time stepping schemes. Such meshes deal well with complex geometries while implicit time stepping is required for practical numerical stability. Compared to the FDTD, these methods have the advantages of computational efficiency when dealing with complex geometries and the conceptually straight forward extension to higher orders of accuracy. On the downside, they are much more complicated to implement and less computationally efficient when dealing with regular geometries. The FDTD and implicit FETD have been combined in an implicit/explicit hybrid. By using the implicit FETD in regions of complex geometry and the FDTD elsewhere the advantages of both are combined. However, previous work only addressed mixed first order (i.e. second order accurate) methods. For electrically large problems or when very accurate solutions are required, higher order methods are attractive. In this thesis a novel higher order implicit/explicit FETD method of arbitrary order in space is presented. A higher order explicit FETD method is implemented using Gauss-Lobatto lumping on regular Cartesian hexahedra with central differencing in time applied to a coupled Maxwell’s equation FEM formulation. This can be seen as a spatially higher order generalisation of the FDTD. A convolution-free perfectly matched layer (PML) method is adapted from the FDTD literature to provide mesh termination. A curl conforming hybrid mesh allowing the interconnection of arbitrary order tetrahedra and hexahedra without using intermediate pyramidal or prismatic elements is presented. An unconditionally stable implicit FETD method is implemented using Newmark-Beta time integration and the standard curl-curl FEM formulation. The implicit/explicit hybrid is constructed on the hybrid hexahedral/tetrahedral mesh using the equivalence between the coupled Maxwell’s formulation with central differences and the Newmark-Beta method with Beta = 0 and the element-wise implicitness method. The accuracy and efficiency of this hybrid is numerically demonstrated using several test-problems.
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Dechamps, Xavier. "Numerical simulation of incompressible magnetohydrodynamic duct and channel flows by a hybrid spectral, finite element solver." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209203.
Повний текст джерелаАнотація:
In this dissertation, we are concerned with the numerical simulation for flows of electrically conducting fluids exposed to an external magnetic field (also known as magnetohydrodynamics or in short MHD). The aim of the present dissertation is twofold. First, the in-house CFD hydrodynamic solver SFELES is extended to MHD problems. Second, MHD turbulence is studied in the simple configuration of a MHD pipe flow within an external transverse magnetic field. Chapter 2 of this dissertation aims at reminding the physical equations that govern incompressible MHD problems. Two equivalent formulations are put forward in the particular case of quasi-static MHD. Chapter 3 is devoted to the detailed development of the hybrid spectral - stabilized finite element methods for quasi-static MHD problems. The extension of SFELES is made for both Cartesian and axisymmetric systems of coordinates. The short chapter 4 follows to provide the performances of SFELES executed by several processes in a parallel environment. The addition of a parallel direct solver is studied in regards with the memory and time requirements. The extension of SFELES is then validated in chapter 5 with test cases of increasing complexity. For this purpose, laminar flows with an existing analytical-asymptotic solution are considered. The subject of chapter 6 is the MHD turbulent pipe flow within an external transverse and uniform magnetic field. The results are partially compared with the corresponding hydrodynamic flow and with a few data available in the literature. / Le thème de cette thèse de doctorat est la simulation numérique d'écoulements de fluides conducteurs d'électricité qui sont exposés à un champ magnétique extérieur (également connu sous le nom de magnétohydrodynamique ou encore MHD). L'objectif de ce travail est double. Premièrement, le code CFD maison SFELES est étendu aux problèmes MHD. Deuxièmement, la turbulence MHD est étudiée dans la configuration de l'écoulement en conduite cylindrique à l'intérieur d'un champ magnétique transverse. Le chapitre 2 de cette thèse a pour but de rappeler les équations qui gouvernent les problèmes de MHD incompressible. Deux formulations équivalente sont mises en évidence dans le cas particulier de la MHD quasi-statique. Le chapitre 3 est dévoué au développement détaillé des méthodes spectrale - éléments finis pour la MHD quasi-statique. L'extension de SFELES est réalisée dans les systèmes de coordonnées cartésiennes et axisymétriques. Le court chapitre 4 suit pour fournir les performances de SFELES exécuté sur plusieurs processeurs dans un environnement parallèle. L'ajout d'un solveur parallèle direct est étudié en ce qui concerne les demandes en temps et mémoire. L'extension de SFELES est alors validée dans le chapitre 5 avec des cas d'étude de complexité croissante. Dans ce but, des écoulements laminaires avec solution théorique-asymptotique sont envisagés. Le sujet du chapitre 6 est l'écoulement MHD turbulent en conduite cylindrique à l'intérieur d'un champ magnétique transverse et uniforme. Les résultats sont partiellement comparés avec l'écoulement hydrodynamique correspondant et avec des données disponibles dans la littérature.Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Kuloglu, Mustafa. "Development of a Hybrid Finite Element/Rigorous Coupled Wave Analysis for Light Scattering From Periodic Structures." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228185511.
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Briers, William Jennings. "Design and analysis of a hybrid steel/composite pipe for high pressure applications." Morgantown, W. Va. : [West Virginia University Libraries], 2001. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=2005.
Повний текст джерелаАнотація:
Thesis (M.S.)--West Virginia University, 2001Title from document title page. Document formatted into pages; contains xvi, 175 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 115-116).
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Passarelli, Garrett J. "A Feasiblity Study on the Fatigue Performance of Laser Beam Welds and Hybrid-Laser Arc Welds Used in an Innovative Modular Steel Sandwich Panel Bridge Deck SyStem." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/45149.
Повний текст джерелаАнотація:
This research investigation explores the feasibility of implementing a laser welded
sandwich steel panel bridge deck system as a viable alternative to standardized reinforced
concrete bridge decks. Generally used in naval ship building applications, steel sandwich
panels possess attractive characteristics towards the integration with bridge infrastructure such
as service life in excess of 100 plus years, dead load reduction, rapid construction, decreased
closure time, and automated mass production. The lack of fatigue data for the laser â stakeâ
welds used to create the enclosed sandwich panel geometry raised concerns with respect to
fatigue life. The primary focus of this study was to determine whether or not infinite fatigue life
was possible. Two different laser welding technologies were investigated, Laser Beam
Welding (LBW) and Hybrid-Laser Arc Welding (HLAW). Test specimens were fabricated and
tested in order to examine fatigue resistance based on a localized load effect between adjacent
core stiffeners. Finite element models were used to obtain the stress range for each individual
test due to complex geometry and partially restrained boundary conditions. In order to assess
the fatigue performance of the overall deck system, additional finite element models were
created to study the local and global behavior of different sandwich panel configurations. As a
whole the investigation yielded promising results. Infinite fatigue life is achievable due to
outstanding fatigue performance. The HLAW stake welds demonstrated superior fatigue
resistance in comparison to the LBW process. Localized load effects can be minimized
through the modification of different panel parameters. Pushing forward, full scale testing is
essential to the future employment of this innovative bridge deck system.Master of Science
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Shetty, Sandeep Kumar Lankarani Hamid M. "Finite element modeling of energy absorption characteristic of hybrid structure - composite wrapped on a square metal tube." Diss., Click here for available full-text of this thesis, 2006. http://library.wichita.edu/digitallibrary/etd/2006/t067.pdf.
Повний текст джерелаАнотація:
Thesis (M.S.)--Wichita State University, Dept. of Mechanical Engineering."May 2006." Title from PDF title page (viewed on October 29, 2006). Thesis adviser: Hamid Lankarani. Includes bibliographic references (leaves 47-51).
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Horton, Brandon Alexander. "Comprehensive Multi-Scale Progressive Failure Analysis for Damage Arresting Advanced Aerospace Hybrid Structures." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/93961.
Повний текст джерелаАнотація:
In recent years, the prevalence and application of composite materials has exploded. Due to the demands of commercial transportation, the aviation industry has taken a leading role in the integration of composite structures. Among the leading concepts to develop lighter, more fuel-efficient commercial transport is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. The highly integrated structure of PRSEUS allows pressurized, non-circular fuselage designs to be implemented, enabling the feasibility of Hybrid Wing Body (HWB) aircraft. In addition to its unique fabrication process, the through-thickness stitching utilized by PRSEUS overcomes the low post-damage strength present in typical composites. Although many proof-of-concept tests have been performed that demonstrate the potential for PRSEUS, efficient computational tools must be developed before the concept can be commercially certified and implemented.
In an attempt to address this need, a comprehensive modeling approach is developed that investigates PRSEUS at multiple scales. The majority of available experiments for comparison have been conducted at the coupon level. Therefore, a computational methodology is progressively developed based on physically realistic concepts without the use of tuning parameters. A thorough verification study is performed to identify the most effective approach to model PRSEUS, including the effect of element type, boundary conditions, bonding properties, and model fidelity. Using the results of this baseline study, a high fidelity stringer model is created at the component scale and validated against the existing experiments. Finally, the validated model is extended to larger scales to compare PRSEUS to the current state-of-the-art.
Throughout the current work, the developed methodology is demonstrated to make accurate predictions that are well beyond the capability of existing predictive models. While using commercially available predictive tools, the methodology developed herein can accurately predict local behavior up to and beyond failure for stitched structures such as PRSEUS for the first time. Additionally, by extending the methodology to a large scale fuselage section drop scenario, the dynamic behavior of PRSEUS was investigated for the first time. With the predictive capabilities and unique insight provided, the work herein may serve to benefit future iteration of PRSEUS as well as certification by analysis efforts for future airframe development.PHD
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Redmond, Laura M. "Seismic performance, analysis, and design of hybrid concrete-masonry." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53497.
Повний текст джерелаАнотація:
Caribbean-style hybrid concrete-masonry structures consist of a reinforced concrete frame with partially grouted and reinforced infill masonry walls. The infill walls are typically connected to the RC frame with cast-in-place dowel reinforcement along one or more edges of the wall. There is limited guidance in masonry codes to design these types of structures, and their seismic performance has not been characterized with experimental tests. In this work, an experimental program characterized the seismic behavior of hybrid concrete-masonry frames and showed they do not exhibit the typical strut mechanism observed in unreinforced masonry infill structures. In addition, a detailed finite element modeling scheme and calibration methodology was developed for modeling partially grouted masonry. This model includes a novel calibration method to account for the difference in the shear and tensile behavior of bed joints with grouted and ungrouted cells, and a method to account for the contribution of vertical reinforcement to the shear capacity of the bed joints with grouted cells. Finally, simplified models were proposed for use in engineering design. A modification of the TMS 402 strut model for hybrid concrete-masonry was suggested to incorporate the effects of the masonry infill and connections in large models.