45 results on '"Marcos Arndt"'
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2. Accurate assessment of natural frequencies for uniform and non-uniform Euler-Bernoulli beams and frames by adaptive generalized finite element method
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Marcos Arndt, Roberto Dalledone Machado, and Adriano Scremin
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- 2016
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3. An enriched formulation of isogeometric analysis applied to the dynamical response of bars and trusses
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Marcos Arndt, Mateus Rauen, and Roberto Dalledone Machado
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General Engineering ,Truss ,02 engineering and technology ,Isogeometric analysis ,01 natural sciences ,Finite element method ,Computer Science Applications ,010101 applied mathematics ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Computational Theory and Mathematics ,Partition of unity ,Rate of convergence ,Convergence (routing) ,Applied mathematics ,0101 mathematics ,Software ,Mathematics ,Extended finite element method ,Parametric statistics - Abstract
Purpose This study aims to present a new hybrid formulation based on non-uniform rational b-splines functions and enrichment strategies applied to free and forced vibration of straight bars and trusses. Design/methodology/approach Based on the idea of enrichment from generalized finite element method (GFEM)/extended finite element method (XFEM), an extended isogeometric formulation (partition of unity isogeometric analysis [PUIGA]) is conceived. By numerical examples the methods are tested and compared with isogeometric analysis, finite element method and GFEM in terms of convergence, error spectrum, conditioning and adaptivity capacity. Findings The results show a high convergence rate and accuracy for PUIGA and the advantage of input enrichment functions and material parameters on parametric space. Originality/value The enrichment strategies demonstrated considerable improvements in numerical solutions. The applications of computer-aided design mapped enrichments applied to structural dynamics are not known in the literature.
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- 2020
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4. Modelling of cathodic protection developed to different underwater structures configurations
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Priscilla Mengarda, Heloisa Nunes Da Motta, Luiz Alkimin De Lacerda, Marcos Arndt, Luan Zeszotko Cristovao Da Silva, Igor De Lacerda, Leonardo Oliveira De Barros, Rene Thiago Capelari Orlowski, and Camila Pesqueira
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Aerospace Engineering - Published
- 2022
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5. ANÁLISE DINÂMICA TRANSIENTE DE BARRAS PELO MÉTODO DOS ELEMENTOS FINITOS GENERALIZADOS UTILIZANDO SUPERPOSIÇÃO MODAL
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Marcos Arndt, Roberto Dalledone Machado, and Leticia Col Debella
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Pharmacology - Abstract
O Método dos Elementos Finitos (MEF), embora amplamente utilizado como um método de solução aproximada, possui algumas limitações quando aplicado na análise dinâmica. Como alternativa para melhorar a resposta dinâmica da estrutura, o Método dos Elementos Finitos Generalizados (MEFG) pode ser usado para enriquecer o espaço de aproximação com funções apropriadas de acordo com o problema em estudo. Uma vez que a literatura mostra que o MEFG é um método eficaz na análise dinâmica, o presente trabalho tem como objetivo analisar um procedimento capaz de aumentar a precisão e eficiência computacional do método. Para tanto, a matriz modal, responsável pelo desacoplamento do sistema das equações de equilíbrio dinâmico, é utilizada com a presença apenas dos modos de vibração mais preponderantes do problema, que são identificados a partir de um proposto coeficiente capaz de indicar a influência de cada um desses modos. As análises foram feitas em elementos de barra e foi possível obter resultados transientes de deslocamento mais precisos, e mais eficientes computacionalmente.
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- 2019
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6. Transient dynamic analysis of bars and trusses by the adaptive generalized finite element method
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Leticia Col Debella, Marcos Arndt, Roberto Dalledone Machado, and Carolina Castro Cittadin
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Computer science ,business.industry ,Modal analysis ,General Engineering ,Truss ,02 engineering and technology ,Structural engineering ,01 natural sciences ,Finite element method ,Displacement (vector) ,Computer Science Applications ,010101 applied mathematics ,Vibration ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Computational Theory and Mathematics ,Dynamic problem ,Modal matrix ,Transient (oscillation) ,0101 mathematics ,business ,Software - Abstract
PurposeThis paper aims to present an adaptive approach of the generalized finite element method (GFEM) for transient dynamic analysis of bars and trusses. The adaptive GFEM, previously proposed for free vibration analysis, is used with the modal superposition method to obtain precise time-history responses.Design/methodology/approachThe adaptive GFEM is applied to the transient analysis of bars and trusses. To increase the precision of the results and computational efficiency, the modal matrix is responsible for the decoupling of the dynamic equilibrium equations in the modal superposition method, which is used with only the presence of the problem’s most preponderant modes of vibration. These modes of vibration are identified by a proposed coefficient capable of indicating the influence of each mode on the transient response.FindingsThe proposed approach leads to more accurate results of displacement, velocity and acceleration when compared to the traditional finite element method.Originality/valueIn this paper, the application of the adaptive GFEM to the transient analysis of bars and trusses is presented for the first time. A methodology of identification of the preponderant modes to be retained in the modal matrix is proposed to improve the quality of the solution. The examples showed that the method has a strong potential to solve dynamic analysis problems, as the approach had already proved to be efficient in the modal analysis of different framed structures. A simple way to performh-refinement of truss elements to obtain reference solutions for dynamic problems is also proposed.
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- 2019
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7. Free Vibration of Curved beams with Hierarchical Finite Element Method
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Roberto Dalledone, Ramon Macedo, and Marcos Arndt
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Vibration ,business.industry ,Computer science ,Structural engineering ,business ,Finite element method - Published
- 2019
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8. Linear static analysis of cables by the Generalized Finite Element Method
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Leonardo Basso and Marcos Arndt
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- 2021
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9. Selective enrichment and modal matrix reduction in the generalized / eXtended Finite Element Method applied to dynamic analysis of plane state problems
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Carolina Castro Cittadin, Ramon Macedo Corrêa, Roberto Dalledone Machado, and Marcos Arndt
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Offset (computer science) ,Plane (geometry) ,Mechanical Engineering ,Degrees of freedom (statistics) ,General Physics and Astronomy ,Vibration ,Mechanics of Materials ,Convergence (routing) ,Modal matrix ,Applied mathematics ,General Materials Science ,Reduction (mathematics) ,Mathematics ,Extended finite element method - Abstract
The Generalized/eXtended Finite Element Method (G/XFEM) has successfully been applied in the dynamic analysis of a variety of structures such as bars, trusses, beams, and two-dimensional (2D) problems. The G/XFEM has shown high convergence rates to approximate displacements and stresses in many problems, such as in Fracture Mechanics . For free vibration analyses, the G/XFEM also shows high convergence rates to approximate most of the natural frequencies but the error is still considerable for the highest ones. Dealing with transient analysis, the enrichment has usually been done for all elements of the mesh, which requires high computational efforts. Further, those frequencies that were poorly approximated, pollute and affect the final solution precision of the time response. To reduce such issues, a compound strategy is adopted joining selective enrichment and modal matrix reduction. Friberg Indicator is taken in the selective process. The proposed technique is examined for dynamic analysis of plane state problems. Some examples show that, even with a reduced number of degrees of freedom, more accurate approximations are obtained. The additional time for computation of selective parameters is offset by the reduction of the total time solution. Thus, all results have less total computational running time than the traditional G/XFEM.
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- 2022
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10. Isogeometric analysis of free vibration of framed structures: comparative problems
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Marcos Arndt, Roberto Dalledone Machado, and Mateus Rauen
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business.industry ,General Engineering ,Phase error ,Truss ,02 engineering and technology ,Isogeometric analysis ,Structural engineering ,01 natural sciences ,Finite element method ,Computer Science Applications ,010101 applied mathematics ,Vibration ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Computational Theory and Mathematics ,Normal mode ,Convergence (routing) ,Elastic rods ,0101 mathematics ,business ,Software ,Mathematics - Abstract
Purpose The purpose of this paper is to check the efficiency of isogeometric analysis (IGA) by comparing its results with classical finite element method (FEM), generalized finite element method (GFEM) and other enriched versions of FEM through numerical examples of free vibration problems. Design/methodology/approach Since its conception, IGA was widely applied in several problems. In this paper, IGA is applied for free vibration of elastic rods, beams and trusses. The results are compared with FEM, GFEM and the enriched methods, concerning frequency spectra and convergence rates. Findings The results show advantages of IGA over FEM and GFEM in the frequency error spectra, mostly in the higher frequencies. Originality/value Isogeometric analysis shows a feasible tool in structural analysis, with emphasis for problems that requires a high amount of vibration modes.
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- 2017
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11. Numerical analysis of plane stress free vibration in severely distorted mesh by Generalized Finite Element Method
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Marcos Arndt, Roberto Dalledone Machado, João Elias Abdalla Filho, and Hsu Yang Shang
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Quadrilateral ,business.industry ,Mechanical Engineering ,Numerical analysis ,Mathematical analysis ,General Physics and Astronomy ,02 engineering and technology ,Mixed finite element method ,Structural engineering ,01 natural sciences ,Finite element method ,Numerical integration ,Exponential function ,010101 applied mathematics ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,General Materials Science ,0101 mathematics ,business ,Mathematics ,Plane stress ,Extended finite element method - Abstract
This paper presents a C0 quadrilateral enriched element by the Generalized Finite Element Method, having trigonometric and exponential functions as enrichment functions, applied in free vibration analysis with distorted mesh. The stiffness and mass matrices are obtained by subintervals numerical integration. The efficiency of the enriched C0 element is observed by solving several plane stress free vibrations problems. The analyses include uniform and non-uniform mesh models, and severely distorted meshes. Furthermore, the sensitivity of the enriched C0 element is also analyzed. The results of the analyses are compared with other numerical formulations and show that the enriched C0 element proposed in this paper has good performance.
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- 2017
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12. Free in-plane vibration analysis of curved beams by the generalized/extended finite element method
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Marcos Arndt, Ramon Macedo Corrêa, and Roberto Dalledone Machado
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Physics ,Mechanical Engineering ,Mathematical analysis ,General Physics and Astronomy ,Stiffness ,Context (language use) ,Computer Science::Numerical Analysis ,Finite element method ,Vibration ,symbols.namesake ,Fourier transform ,Mechanics of Materials ,Convergence (routing) ,symbols ,medicine ,General Materials Science ,medicine.symptom ,Focus (optics) ,Extended finite element method - Abstract
Arches and curved beams are solved here by the G/XFEM in the context of free vibration problems. This hierarchical enrichment method has been used in many complex applications, however it has not been examined for dynamic of curved beams yet. The focus of the present work is to apply the G/XFEM for free vibration analysis of thin and thick curved beam models. The accuracy of frequencies values, the convergence to reach them, and the frequency spectrum are some of the points to be discussed. Four examples are carried out and the results are compared with standard FEM, the p -Fourier Method and analytical solutions. Even with coarse meshes, G/XFEM presents competitiveness and can reach good precision for large range of frequencies with few enrichment levels. It is also shown that the ill conditioning of mass and stiffness matrices for higher enrichment levels does not affect the G/XFEM competitiveness, since it converges faster with few enrichment levels.
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- 2021
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13. Accurate assessment of natural frequencies for uniform and non-uniform Euler-Bernoulli beams and frames by adaptive generalized finite element method
- Author
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Roberto Dalledone Machado, Marcos Arndt, and Adriano Scremin
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Basis (linear algebra) ,business.industry ,Frame (networking) ,General Engineering ,02 engineering and technology ,Structural engineering ,01 natural sciences ,Finite element method ,Computer Science Applications ,010101 applied mathematics ,Vibration ,symbols.namesake ,Bernoulli's principle ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Computational Theory and Mathematics ,Partition of unity ,Convergence (routing) ,Euler's formula ,symbols ,Applied mathematics ,0101 mathematics ,business ,Software ,Mathematics - Abstract
Purpose – The purpose of this paper is devoted to present an accurate assessment for determine natural frequencies for uniform and non-uniform Euler-Bernoulli beams and frames by an adaptive generalized finite element method (GFEM). The present paper concentrates on developing the C1 element of the adaptive GFEM for vibration analysis of Euler-Bernoulli beams and frames. Design/methodology/approach – The variational problem of free vibration is formulated and the main aspects of the adaptive GFEM are presented and discussed. The efficiency and convergence of the proposed method in vibration analysis of uniform and non-uniform Euler-Bernoulli beams are checked. The application of this technique in a frame is also presented. Findings – The present paper concentrates on developing the C1 element of the adaptive GFEM for vibration analysis of Euler-Bernoulli beams and frames. The GFEM, which was conceived on the basis of the partition of unity method, allows the inclusion of enrichment functions that contain a priori knowledge about the fundamental solution of the governing differential equation. The proposed enrichment functions are dependent on the geometric and mechanical properties of the element. This approach converges very fast and is able to approximate the frequency related to any vibration mode. Originality/value – The main contribution of the present study consisted in proposing an adaptive GFEM for vibration analysis of Euler-Bernoulli uniform and non-uniform beams and frames. The GFEM results were compared with those obtained by the h and p-versions of FEM and the c-version of the CEM. The adaptive GFEM has shown to be efficient in the vibration analysis of beams and has indicated that it can be applied even for a coarse discretization scheme in complex practical problems.
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- 2016
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14. Hierarchical methods for free vibration of thin curved beams
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Roberto Dalledone Machado, Ramon Macedo Corrêa, and Marcos Arndt
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Vibration ,Materials science ,Acoustics - Published
- 2019
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15. Isogeometric Shell Analysis based on Kirchhoff-Love theory
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Marcos Arndt, Jorge Luis Garcia zuñiga, and Roberto Dalledone Machado
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Physics ,Classical mechanics ,Shell (structure) - Published
- 2019
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16. GFEM for modal analysis of 2D wave equation
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Marcos Arndt, André Jacomel Torii, and Roberto Dalledone Machado
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Polynomial ,Modal analysis using FEM ,Modal analysis ,Mathematical analysis ,General Engineering ,Wave equation ,Finite element method ,Computer Science Applications ,Computational Theory and Mathematics ,Normal mode ,Trigonometric functions ,Sine ,Software ,Mathematics - Abstract
Purpose – The purpose of this paper is to present an application of the Generalized Finite Element Method (GFEM) for modal analysis of 2D wave equation. Design/methodology/approach – The GFEM can be viewed as an extension of the standard Finite Element Method (FEM) that allows non-polynomial enrichment of the approximation space. In this paper the authors enrich the approximation space with sine e cosine functions, since these functions frequently appear in the analytical solution of the problem under study. The results are compared with the ones obtained with the polynomial FEM using higher order elements. Findings – The results indicate that the proposed approach is able to obtain more accurate results for higher vibration modes than standard polynomial FEM. Originality/value – The examples studied in this paper indicate a strong potential of the GFEM for the approximation of higher vibration modes of structures, analysis of structures subject to high frequency excitations and other problems that concern high frequency oscillatory phenomena.
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- 2015
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17. Comportamento Dinâmico Linear de Pontes com Veículos em Movimento
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Carlos Rossigali, Marcos Arndt, Roberto Dalledone Machado, and Diego Gabriel Metz
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- 2018
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18. DYNAMIC ANALYSIS OF TIMOSHENKO BEAMS USING THE GENERALIZED FINITE ELEMENT METHOD
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Paulo de Oliveira Weinhardt, Roberto Dalledone Machado, Marcos Arndt, and Patricia Luiza Moscon Freisleben
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Physics ,Mathematical analysis ,Finite element method - Published
- 2017
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19. ANALYSIS OF THE NONLINEAR DYNAMIC BEHAVIOUR OF REINFORCED CONCRETE BRIDGE BEAMS WITH VARIABLE REINFORCEMENT DISTRIBUTION THROUGH THE VEHICLE-BRIDGE INTERACTION AND THE DAMAGE MECHANICS
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Marcos Arndt, Ana Paula Imai, Roberto Dalledone Machado, and Thiago de Oliveira Abeche
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Nonlinear system ,Variable (computer science) ,business.industry ,Computer science ,Damage mechanics ,Structural engineering ,Reinforced concrete ,Reinforcement ,business ,Bridge (interpersonal) ,Distribution (differential geometry) - Published
- 2017
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20. ADAPTIVE ENRICHMENT OF THE GENERALIZED FINITE ELEMENT METHOD BASED ON THE FRIBERG ERROR INDICATOR
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Paulo de Oliveira Weinhardt, Marcos Arndt, Maicon Felipe Malacarne, Roberto Dalledone Machado, and Thamara Petroli
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Physics ,Applied mathematics ,Finite element method - Published
- 2017
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21. Free Vibration Isogeometric Analysis of CAD Mapped Trusses
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Marcos Arndt, Mateus Rauen, and Roberto Dalledone Machado
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Vibration ,business.industry ,Computer science ,Truss ,CAD ,Structural engineering ,Isogeometric analysis ,business - Published
- 2017
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22. THE GENERALIZED FINITE ELEMENT METHOD APPLIED IN FREE VIBRATION ANALYSIS UNDER PLANE STRESS
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Ricardo Custódio and Marcos Arndt
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Vibration ,Physics ,Mathematical analysis ,Finite element method ,Plane stress - Published
- 2017
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23. Enriched Techniques applied to Modified Local Green's Function Method in Dynamic Modal Analysis
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Roberto Dalledone Machado, Marcos Arndt, and Paulo de Oliveira Weinhardt
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symbols.namesake ,Modal analysis ,Green's function ,symbols ,Applied mathematics ,Mathematics - Published
- 2017
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24. The Generalized Finite Element Method applied to dynamic transient analysis
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Marcos Arndt, Roberto Dalledone Machado, and Leticia Col Debella
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Physics ,Mathematical analysis ,Transient analysis ,Finite element method - Published
- 2017
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25. COMPARISON OF NONLINAR DYNAMIC RESPONSES OF EULER-BERNOULLI BEAMS AND TWO-DIMENSIONAL PLANE STRESS STATE OBTAINED FROM VEHICLE, IRREGULARITIES AND REINFORCED CONCRETE BRIDGE DYNAMIC INTERACTION SYSTEM
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Ana Paula Imai, Thiago de Oliveira Abeche, Roberto Dalledone Machado, and Marcos Arndt
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Physics ,Bernoulli's principle ,symbols.namesake ,business.industry ,Euler's formula ,symbols ,Structural engineering ,State (functional analysis) ,Reinforced concrete ,business ,Bridge (interpersonal) ,Plane stress - Published
- 2017
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26. INFLUENCES OF CURVE MOMENT ROTATION MODELS IN STATIC AND DYNAMIC ANALYSIS OF STEEL STRUCTURES WITH BEAM-COLUMN AND COLUMN-BASE SEMI-RIGID CONNECTIONS
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Vinícius Hanser de Souza, Cladilson Nardino, and Marcos Arndt
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Moment (mathematics) ,Materials science ,Base (geometry) ,Beam column ,Steel structures ,Geometry ,Rotation ,Column (database) - Published
- 2017
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27. AN ENRICHED AND ADAPTIVE ALGORITHM FOR FREE VIBRATION OF BARS USING NURBS APROACH
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Marcos Arndt, Roberto Dalledone Machado, and Mateus Rauen
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Vibration ,Adaptive algorithm ,Control theory ,Computer science - Published
- 2017
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28. GFEM STABILIZATION TECHNIQUES APPLIED TO DYNAMIC ANALYSIS OF NON-UNIFORM SECTION BARS
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Roberto Dalledone Machado, Paulo de Oliveira Weinhardt, Leticia Col Debella, and Marcos Arndt
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GFEM ,business.industry ,Mechanical Engineering ,Aerospace Engineering ,Ocean Engineering ,Numerical Stability ,02 engineering and technology ,Dynamic Analysis ,Structural engineering ,01 natural sciences ,010101 applied mathematics ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Section (archaeology) ,Automotive Engineering ,General Materials Science ,0101 mathematics ,business ,Geology ,Civil and Structural Engineering ,Mathematics - Abstract
The Finite Element Method (FEM), although widely used as an approximate solution method, has some limitations when applied in dynamic analysis. As the loads excite the high frequency and modes, the method may lose precision and accuracy. To improve the representation of these high-frequency modes, we can use the Generalized Finite Element Method (GFEM) to enrich the approach space with appropriate functions according to the problem under study. However, there are still some aspects that limit the GFEM applicability in problems of dynamics of structures, as numerical instability associated with the process of enrichment. Due to numerical instability, the GFEM may lose precision and even result in numerically singular matrices. In this context, this paper presents the application of two proposals to minimize the problem of sensitivity of the GFEM: an adaptation of the Stable Generalized Finite Element Method for dynamic analysis and a stabilization strategy based on preconditioning of enrichment. Examples of one-dimensional modal and transient analysis are presented as bars with cross section area variation. Numerical results obtained are discussed analyzing the effects of the adoption of preconditioning techniques on the approximation and the stability of GFEM in dynamic analysis.
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- 2017
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29. On the damage evolution of reinforced concrete I-beam bridges due to dynamic vehicle-structure interaction
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Marcos Arndt, Thiago de Oliveira Abeche, Ana Imai, and Roberto Dalledone Machado
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I-beam ,Materials science ,business.industry ,Structure (category theory) ,Dynamic vehicle ,Structural engineering ,Reinforced concrete ,business - Published
- 2017
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30. DYNAMIC ANALYSIS OF PLANE STEEL FRAMES WITH SEMI-RIGID CONNECTIONS BY THE GENERALIZED FINITE ELEMENT METHOD
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Marcos Arndt and Vinícius Hanser de Souza
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Physics ,Plane (geometry) ,Mathematical analysis ,Finite element method - Published
- 2017
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31. A mesh generation algorithm for NURBS based methods through image analysis
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Marcos Arndt, Mateus Rauen, and Roberto Dalledone Machado
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Mesh generation ,Computer science ,Algorithm ,Image (mathematics) - Published
- 2017
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32. FREE VIBRATION ANALYSIS OF TRUSSES APPLYING THE GENERALIZED FINITE ELEMENT METHOD WITH A SELECTIVE MESH ENRICHMENT
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Maicon Felipe Malacarne, Paulo de Oliveira Weinhardt, Roberto Dalledone Machado, and Marcos Arndt
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Vibration ,Physics ,business.industry ,Truss ,Structural engineering ,business ,Finite element method - Published
- 2017
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33. Numerical Stability of GFEM Evaluation for Free Vibration Analysis in Trussed Structures
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Marcos Arndt, Paulo de Oliveira Weinhardt, Thamara Petroli, and Roberto Dalledone Machado
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Vibration ,Materials science ,business.industry ,Structural engineering ,business ,Numerical stability - Published
- 2017
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34. Condicionamento do problema de autovalores obtido da aplicação do Método dos Elementos Finitos Generalizados na dinâmica das estruturas
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Thamara Petroli, Marcos Arndt, Paulo de Oliveira Weinhardt, and Roberto Dalledone Machado
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- 2015
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35. ISOGEOMETRIC ANALYSIS OF FREE VIBRATION OF TRUSSES AND PLANE STRESS
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Marcos Arndt, Roberto Dalledone Machado, and Mateus Rauen
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Vibration ,Materials science ,business.industry ,Truss ,Isogeometric analysis ,Structural engineering ,business ,Plane stress - Published
- 2015
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36. Análise estrutural das etapas construtivas de um edifício associada ao modelo BIM 4D
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Marcos Arndt, Sérgio Scheer, and Éric Flôr
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- 2015
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37. O Método dos Elementos Finitos Generalizados aplicado a análise dinâmica: tipos de enriquecimento, escolha da partição da unidade e técnicas de pré condicionamento
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Paulo de Oliveira Weinhardt, Marcos Arndt, and Roberto Dalledone Machado
- Published
- 2015
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38. DYNAMIC ANALYSIS OF TIMOSHENKO BEAMS USING THE GENERALIZED FINITE ELEMENT METHOD
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Moscon, Freisleben, Patricia Luiza, primary, Marcos, Arndt,, additional, de Oliveira, Weinhardt, Paulo, additional, and Dalledone, Machado, Roberto, additional
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- 2017
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39. Comparative analysis between damage models applicable to concrete structures using Positional-FEM
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Sergiomar Israel do Nascimento Filho, Rogério Carrazedo, Marcos Arndt, and Caio Gorla Nogueira
- Abstract
A Mecânica do Dano Contínuo se apresenta como uma importante ferramenta na previsão de respostas não-lineares dos materiais frágeis e quase-frágeis submetidos a carregamentos, através do estudo do comportamento das estruturas a partir do estado de microfissuração observado em média escala. O presente trabalho se propõe a comparar o desempenho dos modelos de dano de Mazars (1984) e Kurumatani et al. (2016) aplicados a estruturas de concreto, no que diz respeito à sensibilidade de seus parâmetros e ao grau de discretização da malha. São analisadas estruturas planas bidimensionais com o uso do Método dos Elementos Finitos Posicional (MEF-Posicional), que levam em consideração naturalmente os efeitos de Não-Linearidade Geométrica (NLG). Para o concreto, são utilizados elementos de chapa de interpolação cúbica e para o aço são utilizados elementos de treliça. A aderência entre os dois materiais é simulada através do método de embutimento fibra-matriz, que possui como vantagem não acrescentar graus de liberdade ao problema. Foram simulados seis exemplos no total: dois para validar os elementos de chapa e de treliça com a formulação do MEF-Posicional, e quatro exemplos de vigas em concreto armado em que as análises e comparações dos modelos de dano são realizadas. A partir das análises, foi possível concluir que o modelo de Mazars (1984) apresentou melhor desempenho dentre os exemplos utilizados, e que o modelo de Kurumatani et al. (2016) possui a vantagem de utilizar parâmetros de interpretação física direta, no entanto possui o parâmetro de comprimento característico dependente da malha de elementos finitos. The Continuous Damage Mechanics is presented as an important tool in the prediction of non- linear responses of brittle and quasi-brittle materials subjected to loads, through the study of the behavior of structures from the microcracking state observed on a mesoscale. The present work proposes to compare the performance of the damage models of Mazars (1984) and Kurumatani et al. (2016) applied to concrete structures, with regard to the sensitivity of their parameters and the degree of discretization of the mesh. Two-dimensional plane structures are analyzed using the Positional Finite Element Method (Positional-FEM), which naturally takes into account the effects of Geometric Non-Linearity (GNL). For concrete, cubic interpolation plate elements are used and for steel truss elements are used. The adhesion between the two materials is simulated using the fiber-matrix embedding method, which has the advantage of not adding degrees of freedom to the problem. Six examples were simulated in total: two to validate the plate and truss elements with the Positional-FEM formulation, and four examples of reinforced concrete beams in which the analyzes and comparisons of the damage models are performed. Based on the analyses, it was possible to conclude that the model by Mazars (1984) presented the best performance among the examples used, and that the model by Kurumatani et al. (2016) has the advantage of using parameters of direct physical interpretation, however it has the characteristic length parameter dependent on the finite element mesh.
- Published
- 2022
40. Integração numérica por decomposição de elementos no contexto do método dos elementos finitos generalizados
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Bruna Caroline Campos, Felício Bruzzi Barros, Samuel Silva Penna, Rodrigo Guerra Peixoto, and Marcos Arndt
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Mecânica da fratura ,Integração numérica ,Método dos elementos finitos generalizados - Abstract
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior O presente trabalho apresenta a utilização de estratégias de integração numérica alternativas às convencionais a serem aplicadas no contexto do Método dos Elementos Finitos Generalizados (MEFG), especificamente em modelos bidimensionais da Mecânica da Fratura. Propõe-se o emprego da subdivisão de elementos e mapeamento dos pontos de integração em elementos da malha contendo descontinuidades ou singularidades, representando assim de forma mais realista os campos de deslocamentos e tensões. Busca-se validar as estratégias implementadas por meio da análise da energia de deformação e da rigidez calculadas em exemplos variados, comparando-as com casos onde é empregada a quadratura de Gauss convencional. As estratégias citadas são aplicadas também no âmbito do Método dos Elementos Finitos Generalizados Estável (MEFGE), da metodologia global-local (MEFGgl) e da Análise Fisicamente Não-Linear. Obtém-se resultados mais precisos e tempos de processamento reduzidos devido à diminuição do número de pontos de integração, que passam a ser posicionados levando em conta as especificidades do problema. As implementações computacionais foram realizadas como parte da expansão do sistema INSANE (INteractive Structural ANalysis Environment), um projeto de software livre desenvolvido pelo Departamento de Engenharia de Estruturas da Universidade Federal de Minas Gerais. The current work presents the employment of alternative numerical integration strategies over the conventional ones to be applied in the Generalized Finite Element Method context, specifically in two-dimensional Fracture Mechanics models. It is suggested to utilize the subdivision of elements and mapping of the integration points in mesh elements containing discontinuities or singularities, therefore representing the displacements and stress fields more precisely. It is aimed to validate the implemented strategies by analysing the strain energy and stiffness computed in a range of examples, comparing them to conventional Gauss quadrature situations. The cited strategies are also applied in cases modelled by the Stable Generalized Finite Element Method (GFEM), the global-local methodology (GFEMgl) and the Physically Non-Linear Analysis. It is achieved good results and reduced processing times due to the decrease in the number of integration points, which are allocated taking into account problems particularities. Computational implementations were performed as part of the expansion of INSANE (INteractive Structural ANalysis Environment), an open-source software project developed by the Structural Department of the Federal University of Minas Gerais.
- Published
- 2020
41. Uma nova metodologia para solução de modelos não linearesutilizando estratégia global-local
- Author
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Larissa Novelli, Roque Luiz da Silva Pitangueira, Felicio Bruzzi Barros, Marcos Arndt, and Ramon Pereira da Silva
- Subjects
Enriquecimento global-local ,Análise fisicamente não linear ,Engenharia de estruturas ,Método dos elementos finitos ,Método dos elementos finitos generalizados - Abstract
O presente trabalho apresenta uma nova metodologia de soluc~ao para problemas que possuem n~ao linearidade material utilizando o Metodo dos Elementos Finitos Generalizados (MEFG) aliado a estrategia global-local de analise. Neste processo, a analise n~ao linear se da no problema global e ao nal de cada passo incremental convergido um problema local e resolvido. O problema local, com uma malha mais renada, e extrado do problema global na regi~ao onde encontra-se uma maior con- centrac~ao de deformac~oes, e sobre ele s~ao impostas condic~oes de contorno oriundas da soluc~ao do problema global. Para a soluc~ao local, utiliza-se a rigidez aproximada por sua parcela secante e o estado corrente do meio material, resultante da transfe- r^encia das variaveis constitutivas entre os dois modelos considerados. A soluc~ao local obtida enriquece o problema global valendo-se das prerrogativas do MEFG. Adota-se o metodo de Newton-Raphson como processo incremental-iterativo. Diferentes me- todos de controle podem ser utilizados, assim como diversos modelos constitutivos e leis materiais apropriados para representac~ao de meios com degradac~ao elastica. As implementac~oes computacionais foram realizadas no sistema INSANE (INterac- tive Structural ANalysis Environment), um projeto de software livre desenvolvido pelo Departamento de Engenharia de Estruturas da Universidade Federal de Minas Gerais. The present work presents a new solution methodology for problems that have material non-linearity using the Generalized Finite Element Method (GFEM) allied to the global-local analysis strategy. In this process, the nonlinear analysis occurs in the global problem and at the end of each convergent incremental step a local problem is solved. The local problem, with a ner mesh, is extracted from the global problem in the region where there is a greater concentration of deformations, and on the local domain, boundary conditions, coming from the numerical solution of the global problem, are imposed. For the local solution, it is used the stiness approxi- mate by its secant portion and the current state of the material medium, resulting from the transfer of the constitutive variables between the two models considered. The local solution obtained enriches the global problem using the prerogatives of GFEM. The Newton-Raphson method is adopted as an incremental-iterative pro- cess. Dierent control methods can be used, as well as several constitutive models and appropriate material laws for representing elastically degraded media. The com- putational implementations were performed in the INSANE (INteractive Structural ANALYSIS Environment) system, a free software project developed by the Depart- ment of Structural Engineering of the Federal University of Minas Gerais.
- Published
- 2019
42. Análise numérica bidimensional de interação fluido-estrutura: uma formulação posicional baseada em elementos finitos e partículas
- Author
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Giovane Avancini, Rodolfo André Kuche Sanches, Marcos Arndt, and Fabrício Simeoni de Sousa
- Abstract
Problemas envolvendo interação entre fluido e estrutura são desafiadores para a engenharia e, ao mesmo tempo em que abrangem dois meios com características físicas distintas, demandam uma descrição matemática para cada um deles que seja compatível, de forma a permitir o acoplamento. Assim, este trabalho apresenta uma formulação em descrição Lagrangeana para análises dinâmicas de sólidos, fluidos incompressíveis e interação fluido-estrutura (IFE). Nos problemas de IFE é comum a estrutura apresentar grandes deslocamentos, o que torna imprescindível considerar o efeito da não-linearidade geométrica. Levando isso em consideração, é empregada uma formulação do método dos elementos finitos (MEF) baseada em posições, cuja aplicação em análises dinâmicas de estruturas em regime de grandes deslocamentos vem se mostrando bastante robusta. Já no âmbito da dinâmica dos fluidos, sabe-se que uma descrição Lagrangeana acaba por eliminar os termos convectivos das equações de Navier-Stokes, dispensando o uso de métodos estabilizantes nessas equações. Por outro lado, a dificuldade é então transferida para o uso de técnicas eficientes de remesh, preservação da qualidade da malha e de identificação do contorno, uma vez que os fluidos podem deformar-se indefinidamente quando submetidos a forças de cisalhamento. Assim, uma combinação do método dos elementos finitos e do método de partículas é utilizada, onde as forças de interação entre as partículas de fluido são calculadas por meio de uma malha de elementos finitos que é renovada para cada passo de tempo. Por meio de técnicas que reconstroem automaticamente o contorno, é possível simular problemas de superfície livre que sofram severas alterações e, até mesmo, uma eventual separação de partículas do domínio inicial, representando, por exemplo, a formação de gotas. Por fim, o sistema de acoplamento entre o fluido e o sólido é simplificado devido a ambos os domínios serem descritos através de um referencial Lagrangeano, não necessitando de métodos para a adaptação da malha do fluido de modo a acompanhar o movimento da estrutura. Problems involving fluid-structure interaction are challenging for engineering and, while involving two different materials with distinct physical properties, they require a compatible mathematical description for both solid and fluid domain in order to allow the coupling. Thus, this work introduces a formulation, under Lagrangian description, for the solution of solid, incompressible fluid dynamics and fluid-structure interaction (FSI). In FSI problems, the structure usually presents large displacements thus making mandatory a geometric non-linear analysis. Considering it, we adopt a position based formulation of the finite element method (FEM) which has been shown to be very robust when applied to large displacement solid dynamics. For the fluid mechanics problem it is well known that a Lagrangian description eliminates the convective terms from the Navier-Stokes equations and thus, no stabilization technique is required. However, the difficulty is then transferred to the need of efficient re-meshing, mesh quality and external boundary identification techniques, since the fluid presents no resistance to shear stresses and may deform indefinitely. In this sense, we employ a combination of finite element and particle methods in which the particle interaction forces are computed by mean of a finite element mesh which is re-constructed at every time step. Free surface flows are simulated by a boundary recognition technique enabling large domain distortions or even the particles separation from the main domain, representing for instance a water drop. Finally, the fluid-structure coupling is simplified due to the Lagrangian description adopted for both materials, with no need for extra adaptive mesh-moving technique for the fluid computational domain to follow the structure motion.
- Published
- 2018
- Full Text
- View/download PDF
43. Análise da influência do campo higrométrico sobre a reação álcali-agregado
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Rafael Corrêa Salomão, Rogério Carrazedo, Marcos Arndt, and Gláucia Maria Dalfré
- Abstract
A reação álcali-sílica é uma patologia de origem química que ocorre em estruturas de concreto. A partir desta reação há a formação de um gel de álcali-sílica que em contato com a água provoca expansão e deformação da estrutura. Esta patologia traz muitos transtornos e prejuízos, principalmente em obras que estão em contato direto com a água (barragens, pontes, piers, etc) e a possibilidade de prever o comportamento e deformações em uma estrutura desse porte é de grande valia. Neste trabalho é feita a modelagem da percolação d\'água em meio poroso por meio do método dos elementos finitos, sem movimentação de malha e fazendo uso de função Heaviside contínua para a percolação. A modelagem da reação álcali-sílica é feita por meio de um modelo paramétrico, com alteração para contemplar regimes não uniformes de umidade e sua interferência na taxa de expansão. A modelagem do campo mecânico é feita pelo Método dos Elementos Finitos Posicional. The alkali-silica reaction (ASR) is a pathology that occurs in concrete structures. Such pathology creates an alkali-silica gel that when in contact to water promotes expansion and strain on a affected structure. Most buildings that are susceptible to this fenomena are the ones in contact with water, such as dams, piers and bridges. The possibility to predict the ASR behavior and total strain developed would be helpful. In this work, finite element method with fixed mesh is employed to model seepage in a porous media. Also, it\'s used a Heaviside function for the percolation coefficient. The modeling of the alkali-silica reaction is done by a parametric model, modified to non-uniform humidity conditions and it\'s interference on the expansion rate. The modeling of the mechanical field is done by the Positional Finite Element method.
- Published
- 2018
- Full Text
- View/download PDF
44. Experimentos numéricos com versões estáveis do Método dos Elementos Finitos Generalizados
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Fernando Massami Sato, Sergio Persival Baroncini Proença, Marcos Arndt, and Leandro Palermo Junior
- Subjects
Finite element limit analysis ,Mathematical analysis ,Spectral element method ,hp-FEM ,Smoothed finite element method ,Mixed finite element method ,Boundary knot method ,Finite element method ,Mathematics ,Extended finite element method - Abstract
The Generalized Finite Element Method (GFEM) is essentially a partition of unity based method (PUM) that explores the Partition of Unity (PoU) concept to match a set of functions chosen to efficiently approximate the solution locally. Despite its well-known advantages, the method may present some drawbacks. For instance, increasing the approximation space through enrichment functions may introduce linear dependences in the solving system of equations, as well as the appearance of blending elements. To address the drawbacks pointed out above, some improved versions of the GFEM were developed. The Stable GFEM (SGFEM) is a first version hereby considered in which the GFEM enrichment functions are modified. The Higher Order SGFEM proposes an additional modification for generating the shape functions attached to the enriched patch. This research aims to present and numerically test these new versions recently proposed for the GFEM. In addition to highlighting its main features, some aspects about the numerical integration when using the higher order SGFEM, in particular are also addressed. Hence, a splitting rule of the quadrilateral element area, guided by the PoU definition itself is described in detail. The examples chosen for the numerical experiments consist of 2-D panels that present favorable geometries to explore the advantages of each method. Essentially, singular functions with good properties to approximate the solution near corner points and polynomial functions for approximating smooth solutions are examined. Moreover, a comparison among the conventional FEM and the methods herein described is made taking into consideration the scaled condition number and rates of convergence of the relative errors on displacements. Finally, the numerical experiments show that the Higher Order SGFEM is the more robust and reliable among the versions of the GFEM tested. O Método dos Elementos Finitos Generalizados (MEFG) é essencialmente baseado no método da partição da unidade, que explora o conceito de partição da unidade para compatibilizar um conjunto de funções escolhidas para localmente aproximar de forma eficiente a solução. Apesar de suas vantagens bem conhecidas, o método pode apresentar algumas desvantagens. Por exemplo, o aumento do espaço de aproximação por meio das funções de enriquecimento pode introduzir dependências lineares no sistema de equações resolvente, assim como o aparecimento de elementos de mistura. Para contornar as desvantagens apontadas acima, algumas versões aprimoradas do MEFG foram desenvolvidas. O MEFG Estável é uma primeira versão aqui considerada na qual as funções de enriquecimento do MEFG são modificadas. O MEFG Estável de ordem superior propõe uma modificação adicional para a geração das funções de forma atreladas ao espaço enriquecido. Esta pesquisa visa apresentar e testar numericamente essas novas versões do MEFG recentemente propostas. Além de destacar suas principais características, alguns aspectos sobre a integração numérica quando usado o MEFG Estável de ordem superior, em particular, são também abordados. Por exemplo, detalha-se uma regra de divisão da área do elemento quadrilateral, guiada pela própria definição de sua partição da unidade. Os exemplos escolhidos para os experimentos numéricos consistem em chapas com geometrias favoráveis para explorar as vantagens de cada método. Essencialmente, examinam-se funções singulares com boas propriedades de aproximar a solução nas vizinhanças de vértices de cantos, bem como funções polinomiais para aproximar soluções suaves. Ademais, uma comparação entre o MEF convencional e os métodos aqui descritos é feita levando-se em consideração o número de condição do sistema escalonado e as razões de convergência do erro relativo em deslocamento. Finalmente, os experimentos numéricos mostram que o MEFG Estável de ordem superior é a mais robusta e confiável entre as versões do MEFG testadas.
- Published
- 2017
45. Incompressible fluid-structure interaction using the finite element method
- Author
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Jeferson Wilian Dossa Fernandes, Rodolfo André Kuche Sanches, Marcos Arndt, and Fabrício Simeoni de Sousa
- Abstract
A interação entre fluidos e estruturas caracteriza um problema multi-físico não linear e está presente numa grande variedade de áreas da engenharia. Este trabalho apresenta o desenvolvi mento de ferramentas computacionais com base no Método dos Elementos Finitos (MEF) para a análise de interação fluido-estrutura (IFE) considerando escoamentos com baixas velocidades. Dada a interdisciplinaridade do tema, se faz necessário o estudo em três diferentes assuntos: a dinâmica das estruturas computacional, a dinâmica dos fluidos computacional, e o problema de acoplamento. No caso da dinâmica das estruturas empregar-se um elemento finito que seja adequado para a simulação de problemas de IFE, que claramente demandam uma análise não linear geométrica, optando-se pelo emprego de uma formulação descrita em posições, a qual evita problemas relativos à aproximação de rotações finitas. Quanto à dinâmica dos fluidos computacional, é empregado um método estável e ao mesmo tempo sensível à movimentação da estrutura, utilizando a descrição Lagrangeana-Euleriana Arbitrária (ALE). Os casos considerados neste trabalho, assim como muitos dos problemas de engenharia, ocorrem com escoamentos em baixas velocidades, implicando na incompressibilidade do fluido, o que demanda, para um método estável, a utilização de elementos que atendam à condição de Ladyzhenskaya-Babuska-Brezzi (LBB). Além disso, é necessário também o emprego de métodos que consigam neutralizar as variações espúrias decorrentes da não-linearidade de possíveis escoamentos com convecção dominante e que surgem com a aplicação do processo clássico de Galerkin. Para superar esse problema, é aplicado o método Streamline-Upwind/Petrov-Galerkin (SUPG), que adiciona difusividade artificial na direção do escoamento, controlando a amplitude dos termos convectivos. No que se refere ao acoplamento fluido-casca, buscam-se modularidade e versatilidade adotando-se o modelo particionado. O modelo de acoplamento implementado garante ainda a utilização de malhas do fluido e da estrutura sem a necessidade de coincidência de nós. Interaction between fluids and structures characterizes a nonlinear multi-physics problem presente in a wide range of engineering fields. This works presets the development of computational tools based on finite element method (FEM) for fluid-structure interaction (FSI) analysis considering low speed flows (incompressible), as a great part of the engineering problems. Given the topic multidisciplinary nature, it is necessary to study three different subjects: the computational structural dynamics, the computational fluid mechanics and the coupling problem. Regarding structural mechanics, we seek to employ a finite element adequate to FSI simulation, what clearly demands a geometric nonlinear analysis. We chose to employ shell elements with formulation in terms of positions, which avoids problems related to finite rotations approximations. Concerning computational fluid dynamics, we employ a stable method, at same time sensible o structural movements, which is written in the arbitrary Lagrangian-Eulerian (ALE) description. The flow incompressibility demands, for a stable method, the use of elements according to the Ladyzhenskaya-Bbuska-Brezzi (LBB) condition. It is also necessary to employ methods able to neutralize the spurious variations that appears from convection dominated flows when applying the standard Galerking method. In order to overcome this problem, we apply the Streamline-Upwind/Petrov-Galerkin (SUPG) method, which adds artificial diffusivity to the streamline direction, controlling spurious variations. Considering the fluid-shell coupling, we seek modularity and versatility, adopting the partitioned model. The developed coupling model ensure the use of fluid and structure meshes with no need for matching nodes.
- Published
- 2016
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