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21 results on '"Kudela, László"'

1. Direct structural analysis of domains defined by point clouds

Author

Kudela, László, Kollmannsberger, Stefan, Almac, Umut, and Rank, Ernst

Subjects
Computer Science - Computational Engineering, Finance, and Science, Computer Science - Computational Geometry, Mathematics - Numerical Analysis
Abstract

This contribution presents a method that aims at the numerical analysis of solids represented by oriented point clouds. The proposed approach is based on the Finite Cell Method, a high-order immersed boundary technique that computes on a regular background grid of finite elements and requires only inside-outside information from the geometric model. It is shown that oriented point clouds provide sufficient information for these point-membership classifications. Further, we address a tessellation-free formulation of contour integrals that allows to apply Neumann boundary conditions on point clouds without having to recover the underlying surface. Two-dimensional linear elastic benchmark examples demonstrate that the method is able to provide the same accuracy as those computed with conventional, continuous surface descriptions, because the associated error can be controlled by the density of the cloud. Three-dimensional examples computed on point clouds of historical structures show how the method can be employed to establish seamless connections between digital shape measurement techniques and numerical analyses.

Published
2019
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2. Integrating CAD and Numerical Analysis: 'Dirty Geometry' handling using the Finite Cell Method

Author

Wassermann, Benjamin, Kollmannsberger, Stefan, Yin, Shuohui, Kudela, László, and Rank, Ernst

Subjects
Computer Science - Computational Engineering, Finance, and Science
Abstract

This paper proposes a computational methodology for the integration of Computer Aided Design (CAD) and the Finite Cell Method (FCM) for models with "dirty geometries". FCM, being a fictitious domain approach based on higher order finite elements, embeds the physical model into a fictitious domain, which can be discretized without having to take into account the boundary of the physical domain. The true geometry is captured by a precise numerical integration of elements cut by the boundary. Thus, an effective Point Membership Classification algorithm that determines the inside-outside state of an integration point with respect to the physical domain is a core operation in FCM. To treat also "dirty geometries", i.e. imprecise or flawed geometric models, a combination of a segment-triangle intersection algorithm and a flood fill algorithm being insensitive to most CAD model flaws is proposed to identify the affiliation of the integration points. The present method thus allows direct computations on geometrically and topologically flawed models. The potential and merit for practical applications of the proposed method is demonstrated by several numerical examples., Comment: Accepted Manuscript

Published
2018
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3. An Immersed Boundary Approach for the Numerical Analysis of Objects Represented by Oriented Point Clouds

Author

Kudela, László, Kollmannsberger, Stefan, Rank, Ernst, Hutchison, David, Editorial Board Member, Kanade, Takeo, Editorial Board Member, Kittler, Josef, Editorial Board Member, Kleinberg, Jon M., Editorial Board Member, Mattern, Friedemann, Editorial Board Member, Mitchell, John C., Editorial Board Member, Naor, Moni, Editorial Board Member, Pandu Rangan, C., Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Terzopoulos, Demetri, Editorial Board Member, Tygar, Doug, Editorial Board Member, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Barneva, Reneta P., editor, Brimkov, Valentin E., editor, Kulczycki, Piotr, editor, and Tavares, João Manuel R. S., editor

Published
2019
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5. Direct Numerical Analysis of Historical Structures Represented by Point Clouds

Author

Kudela, László, Almac, Umut, Kollmannsberger, Stefan, Rank, Ernst, Hutchison, David, Series Editor, Kanade, Takeo, Series Editor, Kittler, Josef, Series Editor, Kleinberg, Jon M., Series Editor, Mattern, Friedemann, Series Editor, Mitchell, John C., Series Editor, Naor, Moni, Series Editor, Pandu Rangan, C., Series Editor, Steffen, Bernhard, Series Editor, Terzopoulos, Demetri, Series Editor, Tygar, Doug, Series Editor, Ioannides, Marinos, editor, Fink, Eleanor, editor, Brumana, Raffaella, editor, Patias, Petros, editor, Doulamis, Anastasios, editor, Martins, João, editor, and Wallace, Manolis, editor

Published
2018
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13. Bildbasierte Finite Elemente Analyse

Author

Kudela, László, Rank, Ernst (Prof. Dr.), Stilla, Uwe (Prof. Dr.), and Yosibash, Zohar (Prof., D.Sc.)

Subjects
Ingenieurwissenschaften, ddc:620
Abstract

This work demonstrates the steps of creating a finite element model for objects that do not possess a CAD representation. The complete process is demonstrated through an application that creates finite element models for objects that are immersed in a refractive medium. Further, a combination of the finite cell method and point-cloud-based geometry descriptions is proposed, allowing for direct numerical analysis of objects that are represented by point clouds, drastically simplifying the image-based analysis process. Diese Arbeit stellt die Schritte zum Erstellen eines Finiten Element (FE) Modells für Geometrien vor, die über keine CAD-Darstellung verfügen. Der gesamte Prozess wird anhand einer Beispielanwendung demonstriert, in der FE-Modelle für Objekte erzeugt werden, die in einem lichtbrechenden Medium eingetaucht sind. Des Weiteren wird eine Kombination der Methode der finiten Zellen mit punktwolkenbasierten Geometriedarstellungen vorgestellt. Dadurch wird der bildbasierte Simulationsprozess drastisch simplifiziert.

Published
2020

14. Image-based finite element analysis

Author

Rank, Ernst (Prof. Dr.), Yosibash, Zohar (Prof., D.Sc.), Stilla, Uwe (Prof. Dr.), Kudela, László, Rank, Ernst (Prof. Dr.), Yosibash, Zohar (Prof., D.Sc.), Stilla, Uwe (Prof. Dr.), and Kudela, László

Abstract

This work demonstrates the steps of creating a finite element model for objects that do not possess a CAD representation. The complete process is demonstrated through an application that creates finite element models for objects that are immersed in a refractive medium. Further, a combination of the finite cell method and point-cloud-based geometry descriptions is proposed, allowing for direct numerical analysis of objects that are represented by point clouds, drastically simplifying the image-based analysis process., Diese Arbeit stellt die Schritte zum Erstellen eines Finiten Element (FE) Modells für Geometrien vor, die über keine CAD-Darstellung verfügen. Der gesamte Prozess wird anhand einer Beispielanwendung demonstriert, in der FE-Modelle für Objekte erzeugt werden, die in einem lichtbrechenden Medium eingetaucht sind. Des Weiteren wird eine Kombination der Methode der finiten Zellen mit punktwolkenbasierten Geometriedarstellungen vorgestellt. Dadurch wird der bildbasierte Simulationsprozess drastisch simplifiziert.

Published
2020

15. Multi-level hp-finite cell method for embedded interface problems with application in biomechanics

Author

Elhaddad, Mohamed, Zander, Nils, Bog, Tino, Kudela, László, Kollmannsberger, Stefan, Kirschke, Jan S., Baum, Thomas, Ruess, Martin, and Rank, Ernst

Abstract

This work presents a numerical discretization technique for solving three-dimensional material interface problems involving complex geometry without conforming mesh generation. The finite cell method (FCM), which is a high-order fictitious domain approach, is used for the numerical approximation of the solution without a boundary-conforming mesh. Weak discontinuities at material interfaces are resolved by using separate FCM meshes for each material sub-domain, and weakly enforcing the interface conditions between the different meshes. Additionally, a recently developed hierarchical hp-refinement scheme is employed to locally refine the FCM meshes in order to resolve singularities and local solution features at the interfaces. Thereby, higher convergence rates are achievable for non-smooth problems. A series of numerical experiments with two- and three-dimensional benchmark problems is presented, showing that the proposed hp-refinement scheme in conjunction with the weak enforcement of the interface conditions leads to a significant improvement of the convergence rates, even in the presence of singularities. Finally, the proposed technique is applied to simulate a vertebra-implant model. The application showcases the method's potential as an accurate simulation tool for biomechanical problems involving complex geometry, and it demonstrates its flexibility in dealing with different types of geometric description.

Published
2018

21. Multi-level hp-finite cell method for embedded interface problems with application in biomechanics.

Author

Elhaddad M, Zander N, Bog T, Kudela L, Kollmannsberger S, Kirschke J, Baum T, Ruess M, and Rank E

Subjects
Biomechanical Phenomena, Numerical Analysis, Computer-Assisted, Pedicle Screws, Spine surgery, Stress, Mechanical, Finite Element Analysis
Abstract

This work presents a numerical discretization technique for solving 3-dimensional material interface problems involving complex geometry without conforming mesh generation. The finite cell method (FCM), which is a high-order fictitious domain approach, is used for the numerical approximation of the solution without a boundary-conforming mesh. Weak discontinuities at material interfaces are resolved by using separate FCM meshes for each material sub-domain and weakly enforcing the interface conditions between the different meshes. Additionally, a recently developed hierarchical hp-refinement scheme is used to locally refine the FCM meshes to resolve singularities and local solution features at the interfaces. Thereby, higher convergence rates are achievable for nonsmooth problems. A series of numerical experiments with 2- and 3-dimensional benchmark problems is presented, showing that the proposed hp-refinement scheme in conjunction with the weak enforcement of the interface conditions leads to a significant improvement of the convergence rates, even in the presence of singularities. Finally, the proposed technique is applied to simulate a vertebra-implant model. The application showcases the method's potential as an accurate simulation tool for biomechanical problems involving complex geometry, and it demonstrates its flexibility in dealing with different types of geometric description., (Copyright © 2017 John Wiley & Sons, Ltd.)

Published
2018
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