Tesis sobre el tema "Finite element (FE) method"
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Nishiyama, Kenta. "Analysis of Soil-Tire Interaction Using a Two-Dimensional Finite Element-Discrete Element Method". Kyoto University, 2019. http://hdl.handle.net/2433/245298.
Texto completoBambal, Ashish S. "Mechanical evaluation and FE modeling of composite sandwich panels". Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5379.
Texto completoTitle from document title page. Document formatted into pages; contains xviii, 141 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 140-141).
Chilton, Ryan Austin. "H-, P- and T-Refinement Strategies for the Finite-Difference-Time-Domain (FDTD) Method Developed via Finite-Element (FE) Principles". The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1219064270.
Texto completoGunnarsdóttir, Aðalheiður. "Evaluation of Test Methods for Football Helmets Using Finite Element Simulations". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-255278.
Texto completoVuchi, Aditya. "Graphical user interface for three-dimensional FE modeling of composite steel bridges". Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4389.
Texto completoTitle from document title page. Document formatted into pages; contains xi, 188 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 111-115).
Gunbring, Freddie. "Prediction and Modelling of Fastener Flexibility Using FE". Thesis, Linköping University, Department of Management and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11428.
Texto completoThis report investigates the feasibility and accuracy of determining fastener flexibility with 3D FE and representing fasteners in FE load distribution models with simple elements such as springs or beams. A detailed study of 3D models compared to experimental data is followed by a parametric study of different shell modelling techniques. These are evaluated and compared with industry semi-empirical equations.
The evaluated 3D models were found to match the experimental values with good precision. Simulations based on these types of 3D models may replace experimental tests. Two different modelling techniques were also evaluated for use in load distribution models. Both were verified to work very well with representing fastener installations in lap-joints using the ABAQUS/Standard solver. Further improvement of one of the models was made through a modification scale factor. Finally, the same modelling technique was verified using the NASTRAN solver.
To summarize, it is concluded that:
• Detailed 3D-models with material properties defined from stress-strain curves correspond well to experiments and simulations may replace actual flexibility tests.
• At mid-surface modelling of the connecting parts, beam elements with a circular cross section as a connector between shell elements is an easy and accurate modelling technique, with the only data input of bolt material and dimension.
• Using connector elements is accurate only if the connecting parts are modelled in the same plane, i.e. with no offset. Secondary bending due to offset should only be accounted for once and only once throughout the analysis, and it is already included in the flexibility input.
Karaagacli, Taylan. "Determination Of Dynamically Equivalent Fe Models Of Aircraft Structures By Using Modal Test Data". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612522/index.pdf.
Texto completoUsner, 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.
Texto completoRoubin, Emmanuel. "Meso-scale FE and morphological modeling of heterogeneous media : applications to cementitious materials "". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00957377.
Texto completoBotha, Matthys Michiel. "Efficient finite element electromagnetic analysis of antennas and microwave devices : the FE-BI-FMM formulation and a posteriori error estimation for p adaptive analysis". Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52818.
Texto completoENGLISH ABSTRACT: This document presents a Galerkin FE formulation for the full-wave, frequency domain, electromagnetic analysis of three dimensional structures relevant to microwave engineering, together with the investigation of two techniques to enhance the formulation's computational efficiency. The first technique considered is the fast multi pole method (FMM) and the second technique is adaptive refinement of the discretization, based on a posteriori error estimation. Thus, the motivation for the work presented in this document is to increase the computational efficiency of the FE formulation considered. The FE formulation considered is widely used within the microwave engineering, finite element community. Tetrahedral, rectilinear, curl-conforming, mixed- and full order, hierarchical vector elements are used. The formulation is extended to incorporate a cavity backed aperture employing the appropriate half-space Green function within a BI boundary condition, which represents a specific member of a large class of hybrid FE-BI formulations. The formulation is also extended to model coaxial ports via a Neumann boundary condition, using a priori knowledge of the dominant modal fields. Results are presented in support of the formulation and its extensions, including novel results on the coupling between microstrip patch antennas on a perforated substrate. The FMM is investigated first, with the purpose of optimizing the non-local BI component of the cavity FE-BI formulation, in light of its coupling with the differential equation based, sparse FEM. The FMM results in a partly sparse factorization of the BI contribution to the system matrix. Error control schemes for the FMM are thoroughly reviewed and an additional, novel scheme is empirically devised. The second technique investigated, which is more directly related to the FEM and larger in scope, is the use of a posteriori error estimation, in order to optimize the FE discretization through adaptive refinement. A overview of available a posteriori error estimation techniques in the general FE literature is given as well as a survey of available techniques that are specifically tailored to Maxwell's equations. Two known approaches within the applied mathematics literature are adapted to the FE formulation at hand, resulting in two novel, residual based error estimation procedures for this FE formulation - one explicit in nature and the other implicit. The two error estimators are then used to drive a single p adaptive analysis cycle of the FE formulation, experimentally demonstrating their effectiveness. A quasi-static condition is introduced and successfully used to enhance the adaptive algorithm's effectiveness, independently of the error estimation procedure employed. The novel error estimation schemes and adaptive results represent the main research contributions of this study.
AFRIKAANSE OPSOMMING: Hierdie dokument beskryf 'n Galerkin eindige element (EE) formulering vir die volgolf, frekwensiegebied, elektromagnetiese analise van driedimensionele strukture relevant vir mikrogolfingenieurwese, saam met die ondersoek van twee tegnieke om die numeriese effektiwiteit van die formulering te verbeter. Die eerste tegniek wat ondersoek word, is die vinnige multipooi metode (VMM) en die tweede is die aanpasbare verfyning van die EE diskretisering, gebaseer op a posteriori foutberaming. Dus, die motivering vir hierdie werk is om die numeriese effektiwiteit van die genoemde EE formulering te verbeter. Die bogenoemde EE formulering word algemeen gebruik deur die mikrogolfingenieurswese, eindige element-gemeenskap. Tetrahedriese, reglynige, curl-ondersteunende, hierargiese vektorelemente van gemengde- en volledige ordes word gebruik. Die formulering word uitgebrei om holtes in 'n oneindige grondvlak te kan hanteer, deur gebruik te maak van die toepaslike Green funksie binne 'n grensintegraal (GI) grensvoorwaarde, wat 'n spesifieke lid is van 'n groot klas, hibriede, EE-GI formulerings. Die formulering word ook uitgebrei om koaksiale poorte to modelleer via 'n Neumann grensvoorwaarde, deur die gebruik van a priori kennis van die koaksiale, dominante modus-velde. Resultate word gelewer om die formulering, saam met die uitbreidings daarvan, te ondersteun, insluitende oorspronklike resultate in verband met die koppeling tussen mikrostrook plakantennes op 'n geperforeerde substraat. Die VMM word eerste ondersoek, met die doelom die nie-lokale, GI komponent van die EEGI formulering vir holtes te optimeer, weens die koppeling daarvan met die yl, differensiaalvergelyking- gebaseerde, eindige element-metode. Die VMM lei tot 'n gedeeltelik-yl faktorisering van die GI bydrae tot die algehele matriksvergelyking. Skemas om die VMM fout te beheer word deeglik ondersoek en 'n addisionele, oorspronklike skema word empiries ontwikkel. Die tweede tegniek wat ondersoek word, wat meer direk verband hou met die eindige elementmetode, en van groter omvang is, is die gebruik van a posteriori foutberaming om die EE diskretisasie te optimeer deur middel van aanpasbare verfyning. 'n Oorsig van beskikbare, a posteriori foutberamingstegnieke in die algemene EE literatuur word gegee, asook 'n opname van beskikbare tegnieke wat spesifiek gerig is op Maxwell se vergelykings. Twee bekende benaderings binne die toegepaste wiskunde-literatuur word aangepas by die bogenoemde EE formulering, wat lei tot twee oorspronklike residu-gebaseerde foutberamingstegnieke vir hierdie formulering - een van 'n eksplisiete aard en die ander implisiet. Die twee foutberamingstegnieke word gebruik om 'n enkel, p-aanpasbare analisesiklus aan te dryf, wat die effektiwiteit van die foutberamingstegnieke eksperimenteel demonstreer. 'n Kwasi-statiese vereiste word beskryf en suksesvol gebruik om die aanpasbare algoritme se effektiwiteit te verhoog, onafhanklik van die foutberamingstegniek wat gebruik word. Die oorspronklike foutberamingstegnieke en aanpasbare algoritme-resultate verteenwoordig die hoof navorsingsbydraes van hierdie studie.
Eisenträger, Almut. "FE Simulations for the Plate Equation on Large Deformations". Master's thesis, Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200801312.
Texto completoThe aim of this thesis is a model for the plate deformations, under consideration of large strains, and the implementation of a suitable FE simulation. Starting from nonlinear static 3D elasticity theory and introducing the Kirchhoff assumptions, the total energy of a deformed plate is described solely by the displacements of its midsurface. Minimizing this energy leads to a nonlinear variational problem, which can be solved numerically, using Newton's method and the finite element method. For this purpose, the formulae of the energy functional and its necessary two linearizations are provided. With the further assumption that the normal of the midsurface does not change, an FE implementation is derived, with bilinear element functions in the in-plane-direction and bicubic element functions, from the Bogner-Fox-Schmidt-element, in the out-of-plane-direction
Skoog, Adam y Alahmad Yaseen Mohamad. "FE-Analysis of stress variation during diamond cutting of prestressed concrete sleepers". Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-46016.
Texto completoFigiel, Lukasz. "Sensitivity Analysis of Interface Fatigue Crack Propagation in Elastic Composite Laminates". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1102358246078-89903.
Texto completoLiu, Bing 1975. "FE analysis of plastic buckling of plates with initial imperfections and simulation of experiments". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100251.
Texto completoThis thesis presents finite element analyses of plastic buckling and postbuckling behaviour of columns and plates, taking into account the presence of initial out-of-plane imperfections. The FE programs constructed by the author for this purpose are used to analyze the imperfection growth of such columns and plates under axial loading and simply supported edge conditions. The material behaviour is modeled according to both the incremental and the deformation theories of strain-hardening plasticity. The programs combine both the geometric and material nonlinearities to trace the load-deflection behaviours of these structures in prebuckling (up to the maximum load) as well as postbuckling ranges. The results of the analyses for plates show the extreme sensitivity of the incremental theory, and the relative insensitivity of the deformation theory, to the initial imperfections.
The programs are used to simulate the plastic buckling experiments on Aluminum tubes, taking into account their measured imperfections. The imperfection growth analyses demonstrate that the maximum load predictions of the incremental theory are quite close to those recorded in the experiments.
Lindqvist, Petter. "Validering av solida temperaturer i FDS genom jämförelse mot FE-beräkningar". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79973.
Texto completoFDS (Fire Dynamics Simulator) uses a version of the Navier-Stokes equations to make accurate calculations of heat and gas flow through enclosures exposed to fire. The developers of FDS have, and continue to, validate it as new features get added in an attempt to increase its accuracy and broaden its potential applications. However, little of this effort is focused on FDS’ conductive heat transfer model, based on the one-dimensional Crank-Nicolson method. Thus, this study aims to test the accuracy of FDS’ conduction model by comparing it to calculations using FEM (Finite Element Method). FDS simulations were created so as to facilitate the study of a wall and its boundary conditions with as little interference from other factors as possible. This to create a controlled environment which easily could be replicated in the subsequent FE-calculations of the conductive heat flow through the solid obstructions. Three different walls (10 cm concrete, 20 cm concrete and 1 mm steel), each with the three different boundary conditions for the rear surface (Exposed, Void and Insulated), were exposed to three different temperatures (100 °C, 500 °C and 1000 °C) for a total of 27 FDS simulations. The adiabatic surface temperature was measured in each simulation in FDS and used as input for the corresponding FE-calculations. The results showed no clear inconsistencies in the boundary conditions, given enough time for thermal penetration they affected the resulting temperatures as expected. Save a slight deviation in the steel walls exposed to 100 °C and 500 °C with boundary conditions Exposed and Void where FDS slightly underestimated the temperature relative to the FE-calculations. The gas temperatures in the grid cells closest to the wall were found to be unreliable as they tended to undergo substantial fluctuations, likely as a result of how FDS handles the discretization of non-solid space for the Navier-Stokes calculations. These fluctuations were however not found to affect the solid temperatures as the mean gas temperature was accurate. FDS was also found to have a tendency to slightly overestimate the surface temperature in the first few minutes of the simulations relative to the FE-calculations. Though the resulting temperatures from the two methods converged after a few minutes at most in all tests. These deviations were considered to have too minor an impact on the solid temperature to justify claims of inaccuracy in FDS. Thus, the general conclusion of this study is that FDS’ predictions of solid phase temperatures are sufficiently accurate within these delimitations.
Kolchuzhin, Vladimir. "Methods and Tools for Parametric Modeling and Simulation of Microsystems based on Finite Element Methods and Order Reduction Technologies". Doctoral thesis, Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-201000550.
Texto completoThe thesis deals with advanced parametric modeling technologies based on differentiation of the finite element equations which account for parameter variations in a single FE run. The key idea of the new approach is to compute not only the governing system matrices of the FE problem but also high order partial derivatives with regard to design parameters by means of automatic differentiation. As result, Taylor vectors of the system’s response can be expanded in the vicinity of the initial position capturing dimensions and physical parameter. A novel approaches for the parametric MEMS simulation have been investigated for mechanical, electrostatic and fluidic domains in order to improve the computational efficiency. Objective of reduced order modeling is to construct a simplified model which approximates the original system with reasonable accuracy for system level design of MEMS. The modal superposition technique is most suitable for system with flexible mechanical components because the deformation state of any flexible system can be accurately described by a linear combination of its lowest eigenvectors. The developed simulation approach using parametric FE analyses to extract basis functions have been applied for parametric reduced order modeling. The successful implementation of a derivatives based technique for parameterization of macromodel by the example of microbeam and for exporting this macromodel into MATLAB/Similink to simulate dynamical behavior has been reported
Graziano, Maria. "Updating of Finite Element Models using static and dynamic optical strains with application to damage assessment". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
Buscar texto completoNunez, Ramirez Jorge. "A multi time-step partitioned approach for the coupling of SPH and FE methods for nonlinear FSI problems". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI040/document.
Texto completoA method to couple smoothed particle hydrodynamics and finite elements methods for nonlinear transient fluid–structure interaction simulations by adopting different time-steps depending on the fluid or solid sub-domains is proposed. These developments were motivated by the need to simulate highly non-linear and sudden phenomena that take into acount solid impacts and hence require the use of explicit time integrators on both sub-domains (explicit Newmark for the solid and Runge–Kutta 2 for the fluid). However, due to critical time-step required for the stability of the explicit time integrators in, it becomes important to be able to integrate each sub-domain with a different time-step while respecting the features that a previously developed mono time-step coupling algorithm offered. For this matter, a dual-Schur decomposition method originally proposed for structural dynamics was considered, allowing to couple time integrators of the Newmark family with different time-steps with the use of Lagrange multipliers
Wu, Xiaoyue. "Simulation Study of Epitaxially Regrown Vertical-Cavity Surface-Emitting Lasers". Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-52896.
Texto completoAbdinasser, Ahmed y Sara Tabatabaei. "Samverkan av jord och ovanliggande struktur i FEM-program : En studie av nya jordmodeller I FE-programmet 3D- Structure". Thesis, KTH, Byggteknik och design, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-213840.
Texto completoIn recent years, there have been various companies that produced advanced software in the construction industry. A part of software is designed to create 2D drawings and 3D models. With the help of these tools, engineers and architects have been able to quickly create drawings and models for estimation of designs. Development in this area is called BIM. Building Information Modeling, BIM, supports design of a building through all phases and enables better design, manufacturing and purchasing activities. Other software is intended to predict how a structure responds to real loads, vibration, heat and other physical effects. For this, finite element method is used, where the structure will be analyzed in elements for more accurate results. Development in this area has also taken place. Strusoft AB develops FE tools for structural analysis and the latest product is a module for calculating the interaction between structure, foundation and subsoil in the form of soil. The module is called 3D-Soil and is used by Strusoft for modeling and analysis of geo-constructions. In this report, modeling of a structure and underlying soil with the finite element analysis program, FEM-Design, is provided with the new 3D-Soil module for geotechnical calculations. The goal is to compare the results for moment based on interaction forces between soil and structure in FEM-Design with another FEM program, Lusas. Unlike FEM-Design, soil and water pressure is applied as a distributed load in Lusas. The results show that there are significant differences between the results of the analysis programs and there are limitations in the modeling tool that needs further development.
Takahashi, Bruno Ximenes. "Metodologia moderna para análise de fadiga baseada em elementos finitos de componentes sujeitos a fadiga uni e multiaxial". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-19032015-173219/.
Texto completoMost of mechanical components and structures are subjected to time varying loading and therefore often present fatigue failure. Therefore, it is essential to consider the fatigue failure mode in the project of components, machines and structures under cyclic loading. Design of Machine Elements books are still the most used in industry as theoretical and practical reference for designing products against fatigue. However, many of them still do not include the latest findings and methodologies used in fatigue life assessment of structures. Additionally, overall, most of the specialized fatigue books also do not include detailed information about fatigue life assessment in a mechanical project view, as the fatigue analysis using Multiaxial Fatigue criteria and the fatigue life prediction using the Finite Element Method (FE-Based Fatigue Analysis). Based on this fact, this thesis proposes a procedure for predicting component and structures fatigue life, gathering together the most recent methods used in the fatigue area. Among the several subjects included in this procedure, we can highlight: the important contributions of the German Engineering Research Council (FKM-Guideline); the use of Finite Element Analysis (FEA) in the fatigue life assessment; the calculation of the mean stress factor using the pseudo stresses from FEA; the computation of the notch eect in geometrically complex components using the Relative Stress Gradient Method in conjunction with FEA, method which can be applied both in uniaxial loading and multiaxial loading; the estimation of the fatigue damage in structures under variable amplitude multiaxial fatigue loading; the selection of an adequate Finite Element mesh density to use in computational fatigue; and the aplication of the Multiaxial Fatigue theory and criteria, specially in FE-Based Fatigue Analyses, of which use is essential in structures under ciclic stresses in 2 or 3 directions (x,y,z).
Capron, Adélie. "Towards the predictive FE analysis of a metal/composite booster casing’s thermomechanical integrity". Doctoral thesis, Universite Libre de Bruxelles, 2020. https://dipot.ulb.ac.be/dspace/bitstream/2013/314767/5/contratAC.pdf.
Texto completoDoctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
Berglund, Anders. "Criteria for Machinability Evaluation of Compacted Graphite Iron Materials : Design and Production Planning Perspective on Cylinder Block Manufacturing". Doctoral thesis, KTH, Industriell produktion, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-48430.
Texto completoQC 20111121
MERA - OPTIMA CGI
FFI - OPTIMA phase two
Benkert, Katharina. "Effiziente FE-Approximation bei komplizierten Geometrien durch Materialfunktionen". [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11481994.
Texto completoKang, David Sung-Soo. "Hybrid stress finite element method". Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14973.
Texto completoMICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO
Bibliography: leaves 257-264.
by David Sung-Soo Kang.
Ph.D.
Xu, Guohe. "Finite element analysis using fe-based neural networks". Thesis, Southampton Solent University, 2001. http://ssudl.solent.ac.uk/1158/.
Texto completoSevilla, Cárdenas Rubén. "NURBS-Enhanced Finite Element Method (NEFEM)". Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/5857.
Texto completoLa implementació i aplicació de NEFEM a problemes que requereixen una descripció acurada del contorn són, també, objectius prioritaris d'aquesta tesi. Per exemple, la solució numèrica de les equacions de Maxwell és molt sensible a la descripció geomètrica. Es presenta l'aplicació de NEFEM a problemes d'scattering d'ones electromagnètiques amb una formulació de Galerkin discontinu. S'investiga l'habilitat de NEFEM per obtenir solucions precises amb malles grolleres i aproximacions d'alt ordre, i s'exploren les possibilitats de les anomenades malles NEFEM, amb elements que contenen singularitats dintre d'una cara o aresta d'un element. Utilitzant NEFEM, la mida de la malla no està controlada per la complexitat de la geometria. Això implica una dràstica diferència en la mida dels elements i, per tant, suposa un gran estalvi tant des del punt de vista de requeriments de memòria com de cost computacional. Per tant, NEFEM és una eina poderosa per la simulació de problemes tridimensionals a gran escala amb geometries complexes. D'altra banda, la simulació de problemes d'scattering d'ones electromagnètiques requereix mecanismes per aconseguir una absorció eficient de les ones scattered. En aquesta tesi es discuteixen, optimitzen i comparen dues tècniques en el context de mètodes de Galerkin discontinu amb aproximacions d'alt ordre.
La resolució numèrica de les equacions d'Euler de la dinàmica de gasos és també molt sensible a la representació geomètrica. Quan es considera una formulació de Galerkin discontinu i elements isoparamètrics lineals, una producció espúria d'entropia pot evitar la convergència cap a la solució correcta. Amb NEFEM, l'acurada imposició de la condició de contorn en contorns impenetrables proporciona resultats precisos inclús amb una aproximació lineal de la solució. A més, la representació exacta del contorn permet una imposició adequada de les condicions de contorn amb malles grolleres i graus d'interpolació alts. Una propietat atractiva de la implementació proposada és que moltes de les rutines usuals en un codi d'elements finits poden ser aprofitades, per exemple rutines per realitzar el càlcul de les matrius elementals, assemblatge, etc. Només és necessari implementar noves rutines per calcular les quadratures numèriques en elements corbs i emmagatzemar el valor de les funciones de forma en els punts d'integració. S'han proposat vàries tècniques d'elements finits corbs a la literatura. En aquesta tesi, es compara NEFEM amb altres tècniques populars d'elements finits corbs (isoparamètics, cartesians i p-FEM), des de tres punts de vista diferents: aspectes teòrics, implementació i eficiència numèrica. En els exemples numèrics, NEFEM és, com a mínim, un ordre de magnitud més precís comparat amb altres tècniques. A més, per una precisió desitjada NEFEM és també més eficient: necessita un 50% dels graus de llibertat que fan servir els elements isoparamètrics o p-FEM per aconseguir la mateixa precisió. Per tant, l'ús de NEFEM és altament recomanable en presència de contorns corbs i/o quan el contorn té detalls geomètrics complexes.
This thesis proposes an improvement of the classical finite element method (FEM) for an efficient treatment of curved boundaries: the NURBSenhanced FEM (NEFEM). It is able to exactly represent the geometry by means of the usual CAD boundary representation with non-uniform rational Bsplines (NURBS), while the solution is approximated with a standard piecewise polynomial interpolation. Therefore, in the vast majority of the domain, interpolation and numerical integration are standard, preserving the classical finite element (FE) convergence properties, and allowing a seamless coupling with standard FEs on the domain interior. Specifically designed polynomial interpolation and numerical integration are designed only for those elements affected by the NURBS boundary representation.
The implementation and application of NEFEM to problems demanding an accurate boundary representation are also primary goals of this thesis. For instance, the numerical solution of Maxwell's equations is highly sensitive to geometry description. The application of NEFEM to electromagnetic scattering problems using a discontinuous Galerkin formulation is presented. The ability of NEFEM to compute an accurate solution with coarse meshes and high-order approximations is investigated, and the possibilities of NEFEM meshes, with elements containing edge or corner singularities, are explored. With NEFEM, the mesh size is no longer subsidiary to geometry complexity, and depends only on the accuracy requirements on the solution, whereas standard FEs require mesh refinement to properly capture the geometry. This implies a drastic difference in mesh size that results in drastic memory savings, and also important savings in computational cost. Thus, NEFEM is a powerful tool for large-scale scattering simulations with complex geometries in three dimensions. Another key issue in the numerical solution of electromagnetic scattering problems is using a mechanism to perform the absorption of outgoing waves. Two perfectly matched layers are discussed, optimized and compared in a high-order discontinuous Galerkin framework.
The numerical solution of Euler equations of gas dynamics is also very sensitive to geometry description. Using a discontinuous Galerkin formulation and linear isoparametric elements, a spurious entropy production may prevent convergence to the correct solution. With NEFEM, the exact imposition of the solid wall boundary condition provides accurate results even with a linear approximation of the solution. Furthermore, the exact boundary representation allows using coarse meshes, but ensuring the proper implementation of the solid wall boundary condition. An attractive feature of the proposed implementation is that the usual routines of a standard FE code can be directly used, namely routines for the computation of elemental matrices and vectors, assembly, etc. It is only necessary to implement new routines for the computation of numerical quadratures in curved elements and to store the value of shape functions at integration points.
Several curved FE techniques have been proposed in the literature. In this thesis, NEFEM is compared with some popular curved FE techniques (namely isoparametric FEs, cartesian FEs and p-FEM), from three different perspectives: theoretical aspects, implementation and performance. In every example shown, NEFEM is at least one order of magnitude more accurate compared to other techniques. Moreover, for a desired accuracy NEFEM is also computationally more efficient. In some examples, NEFEM needs only 50% of the number of degrees of freedom required by isoparametric FEs or p-FEM. Thus, the use of NEFEM is strongly recommended in the presence of curved boundaries and/or when the boundary of the domain has complex geometric details.
Valivarthi, Mohan Varma y Hema Chandra Babu Muthyala. "A Finite Element Time Relaxation Method". Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-17728.
Texto completoMüller, Stephan. "Entwicklung eines Werkstoffmodells zur FE-Simulation des Tragverhaltens neuartiger Befestigungsmittel in Spanplatten". Aachen Shaker, 2005. http://d-nb.info/988332167/04.
Texto completo梁耀華 y Yew-wah Leung. "Finite element solution on microcomputers". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31209300.
Texto completoLeung, Yew-wah. "Finite element solution on microcomputers /". [Hong Kong] : University of Hong Kong, 1989. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12754948.
Texto completoMüller, Björn. "Parallel Finite Element Method with FEAP 8.2". Darmstadt TU, Fachgebiet Numerische Berechnungsverfahren im Maschinenbau, 2009. http://tuprints.ulb.tu-darmstadt.de/1336/.
Texto completoZhang, Lin. "Generalized finite element method for multiscale analysis". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1141.
Texto completoVu, Thu Hang. "Enhancing the scaled boundary finite element method". University of Western Australia. School of Civil and Resource Engineering, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0068.
Texto completoDavidsson, Johan. "Sobolev Spaces and the Finite Element Method". Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-67470.
Texto completoPack, Peter Michael Walter. "The finite element method in underwater acoustics". Thesis, University of Southampton, 1986. https://eprints.soton.ac.uk/52298/.
Texto completoLiu, Yunshan. "P-adaptive hybrid/mixed finite element method /". The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487950153602937.
Texto completoLu, Chuan. "Generalized finite element method for electromagnetic analysis". Diss., Connect to online resource - MSU authorized users, 2008.
Buscar texto completoTitle from PDF t.p. (viewed on Apr. 8, 2009) Includes bibliographical references (p. 148-153). Also issued in print.
Gundu, Krishna Mohan. "hp-Finite Element Method for Photonics Applications". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195940.
Texto completoFotsch, Daniel Wesley. "Development of valid FE models for structural dynamic design". Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367597.
Texto completoOlivier, Albertus Hendrik. "Object-oriented finite element framework". Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52971.
Texto completoENGLISH ABSTRACT: The role of the computer has changed from a calculation tool to a tool that supports human thinking. In this thesis fundamental aspects of the Finite Element method are mapped to an object model with a well defined structure which provides for local and distributed analysis work. To achieve this the following was investigated: • An object-oriented framework for the Finite Element analysis method • An associated graphical user interface that enables the user to create and modify Finite Element models in an effective way • Requirements for the sharing of analysis information in a communication network Proposed solutions are implemented in a pilot application which indicates their potential.
AFRIKAANSE OPSOMMING: Die rol van die rekenaar het verander vanaf 'n gereedskapstuk wat berekening doen na 'n gereedskapstuk wat menslike denke ondersteun. In hierdie tesis word die fundamentele aspekte van die Eindige Element metode oorgedra na 'n objek model met 'n goed gedefinieerde struktuur wat lokale en verspreide analisering werk ondersteun. Om dit te bereik is die volgende ondesoek: • 'n Objek orienteerde raamwerk vir die Eindige Element metode • 'n Geassosieerde grafiese raamwerk wat die gebruiker in staat stelom objekte te skep en te verander • Vereistes vir die deel van analise inligting in 'n kommunikasie netwerk Die voorgestelde oplossing is geimplimenteer in 'n loodsimplementering wat die voordele van die benadering uitlig.
Chiocchetti, Simone. "High order numerical methods for a unified theory of fluid and solid mechanics". Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/346999.
Texto completoXiao, Dong Wen. "Efficiency analysis on element decomposition method for stochastic finite element analysis". Thesis, University of Macau, 2000. http://umaclib3.umac.mo/record=b1636334.
Texto completoIrfanoglu, Bulent. "Boundary Element-finite Element Acoustic Analysis Of Coupled Domains". Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605360/index.pdf.
Texto completoPerry, William H. "Finite element analysis of polymer flows". Ohio : Ohio University, 1985. http://www.ohiolink.edu/etd/view.cgi?ohiou1184072781.
Texto completoAyers, Christopher Lee. "Concurrent processing of finite element calculations". Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/13072.
Texto completoLentzen, Sven. "Nonlinearly coupled thermopiezoelectric modelling and FE simulation of smart structures". Düsseldorf VDI-Verl, 2009. http://d-nb.info/993098843/04.
Texto completoHeinrich, Bernd y Beate Jung. "The Fourier-finite-element method with Nitsche-mortaring". Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601493.
Texto completoStarkloff, Hans-Jörg. "Stochastic finite element method with simple random elements". Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200800596.
Texto completoAhlbert, Gabriella. "Method Evaluation of Global-Local Finite Element Analysis". Thesis, Linköpings universitet, Hållfasthetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78103.
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