Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen
OPUS4-3466 Konferenzveröffentlichung Häfner, Stefan; Kessel, Marco; Könke, Carsten Multiphase B-spline finite elements of variable order in the mechanical analysis of heterogeneous solids Multiphase B-spline finite elements of variable order in the mechanical analysis of heterogeneous solids Institut für Strukturmechanik
OPUS4-2964 Konferenzveröffentlichung Häfner, Stefan; Kessel, Marco; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten MULTIPHASE B-SPLINE FINITE ELEMENTS OF VARIABLE ORDER IN THE MECHANICAL ANALYSIS OF HETEROGENEOUS SOLIDS Advanced finite elements are proposed for the mechanical analysis of heterogeneous materials. The approximation quality of these finite elements can be controlled by a variable order of B-spline shape functions. An element-based formulation is developed such that the finite element problem can iteratively be solved without storing a global stiffness matrix. This memory saving allows for an essential increase of problem size. The heterogeneous material is modelled by projection onto a uniform, orthogonal grid of elements. Conventional, strictly grid-based finite element models show severe oscillating defects in the stress solutions at material interfaces. This problem is cured by the extension to multiphase finite elements. This concept enables to define a heterogeneous material distribution within the finite element. This is possible by a variable number of integration points to each of which individual material properties can be assigned. Based on an interpolation of material properties at nodes and further smooth interpolation within the finite elements, a continuous material function is established. With both, continuous B-spline shape function and continuous material function, also the stress solution will be continuous in the domain. The inaccuracy implied by the continuous material field is by far less defective than the prior oscillating behaviour of stresses. One- and two-dimensional numerical examples are presented. 37 urn:nbn:de:gbv:wim2-20170327-29643 10.25643/bauhaus-universitaet.2964 Institut für Strukturmechanik
OPUS4-3467 Konferenzveröffentlichung Häfner, Stefan; Könke, Carsten Multigrid preconditioned conjugate gradient method in the mechanical analysis of heterogeneous solids Multigrid preconditioned conjugate gradient method in the mechanical analysis of heterogeneous solids Institut für Strukturmechanik
OPUS4-2962 Konferenzveröffentlichung Häfner, Stefan; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten MULTIGRID PRECONDITIONED CONJUGATE GRADIENT METHOD IN THE MECHANICAL ANALYSIS OF HETEROGENEOUS SOLIDS A fast solver method called the multigrid preconditioned conjugate gradient method is proposed for the mechanical analysis of heterogeneous materials on the mesoscale. Even small samples of a heterogeneous material such as concrete show a complex geometry of different phases. These materials can be modelled by projection onto a uniform, orthogonal grid of elements. As one major problem the possible resolution of the concrete specimen is generally restricted due to (a) computation times and even more critical (b) memory demand. Iterative solvers can be based on a local element-based formulation while orthogonal grids consist of geometrical identical elements. The element-based formulation is short and transparent, and therefore efficient in implementation. A variation of the material properties in elements or integration points is possible. The multigrid method is a fast iterative solver method, where ideally the computational effort only increases linear with problem size. This is an optimal property which is almost reached in the implementation presented here. In fact no other method is known which scales better than linear. Therefore the multigrid method gains in importance the larger the problem becomes. But for heterogeneous models with very large ratios of Young's moduli the multigrid method considerably slows down by a constant factor. Such large ratios occur in certain heterogeneous solids, as well as in the damage analysis of solids. As solution to this problem the multigrid preconditioned conjugate gradient method is proposed. A benchmark highlights the multigrid preconditioned conjugate gradient method as the method of choice for very large ratio's of Young's modulus. A proposed modified multigrid cycle shows good results, in the application as stand-alone solver or as preconditioner. 29 urn:nbn:de:gbv:wim2-20170327-29626 10.25643/bauhaus-universitaet.2962 Institut für Strukturmechanik
OPUS4-3452 Konferenzveröffentlichung Luther, Torsten; Könke, Carsten Multi-scale strategies for simulating brittle fracture in metallic materials Multi-scale strategies for simulating brittle fracture in metallic materials Institut für Strukturmechanik
OPUS4-3446 Wissenschaftlicher Artikel Unger, Jörg F.; Eckardt, Stefan; Könke, Carsten Modelling of cohesive crack growth in concrete structures with the extended finite element method Modelling of cohesive crack growth in concrete structures with the extended finite element method 13 Computer Methods in Applied Mechanics and Engineering 4087 4100 Institut für Strukturmechanik
OPUS4-3495 Konferenzveröffentlichung Luther, Torsten; Könke, Carsten Micro-Mesoscale Analysis of Crack Initiation and Propagation in Metallic Polycrystals Micro-Mesoscale Analysis of Crack Initiation and Propagation in Metallic Polycrystals Institut für Strukturmechanik
OPUS4-3426 Konferenzveröffentlichung Luther, Torsten; Könke, Carsten Micro and Meso Scale Analysis of Brittle Grain Boundary Damage in Polycrystalline Materials Micro and Meso Scale Analysis of Brittle Grain Boundary Damage in Polycrystalline Materials Institut für Strukturmechanik
OPUS4-3460 Wissenschaftlicher Artikel Häfner, Stefan; Eckardt, Stefan; Luther, Torsten; Könke, Carsten Mesoscale modeling of concrete: Geometry and numerics Mesoscale modeling of concrete: Geometry and numerics 11 Computers and Structures 450 461 Institut für Strukturmechanik
OPUS4-3472 Konferenzveröffentlichung Luther, Torsten; Könke, Carsten Investigation of crack growth in polycrystalline mesostructures Investigation of crack growth in polycrystalline mesostructures Institut für Strukturmechanik
OPUS4-2988 Konferenzveröffentlichung Luther, Torsten; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten INVESTIGATION OF CRACK GROWTH IN POLYCRYSTALLINE MESOSTRUCTURES The design and application of high performance materials demands extensive knowledge of the materials damage behavior, which significantly depends on the meso- and microstructural complexity. Numerical simulations of crack growth on multiple length scales are promising tools to understand the damage phenomena in complex materials. In polycrystalline materials it has been observed that the grain boundary decohesion is one important mechanism that leads to micro crack initiation. Following this observation the paper presents a polycrystal mesoscale model consisting of grains with orthotropic material behavior and cohesive interfaces along grain boundaries, which is able to reproduce the crack initiation and propagation along grain boundaries in polycrystalline materials. With respect to the importance of modeling the geometry of the grain structure an advanced Voronoi algorithm is proposed to generate realistic polycrystalline material structures based on measured grain size distribution. The polycrystal model is applied to investigate the crack initiation and propagation in statically loaded representative volume elements of aluminum on the mesoscale without the necessity of initial damage definition. Future research work is planned to include the mesoscale model into a multiscale model for the damage analysis in polycrystalline materials. 11 urn:nbn:de:gbv:wim2-20170327-29886 10.25643/bauhaus-universitaet.2988 Institut für Strukturmechanik
OPUS4-3417 Konferenzveröffentlichung Schwedler, Michael; Könke, Carsten Integrierte Tragwerksanalysen mittels Bauwerksinformationsmodellen und isogeometrischer FE-Methoden Integrierte Tragwerksanalysen mittels Bauwerksinformationsmodellen und isogeometrischer FE-Methoden 978-3-00-041256-1 Institut für Strukturmechanik
OPUS4-3338 Wissenschaftlicher Artikel Luu, M.; Martinez-Rodrigo, M.D.; Zabel, Volkmar; Könke, Carsten H∞ optimization of fluid viscous dampers for reducing vibrations of high-speed railway bridges H∞ optimization of fluid viscous dampers for reducing vibrations of high-speed railway bridges 21 Journal of Sound and Vibration 2421 2442 Institut für Strukturmechanik
OPUS4-3399 Wissenschaftlicher Artikel Schrader, Kai; Könke, Carsten Hybrid computing models for large-scale heterogeneous 3d microstructures Hybrid computing models for large-scale heterogeneous 3d microstructures 12 International Journal for Multiscale Computational Engineering 365 377 Institut für Strukturmechanik
OPUS4-2848 Konferenzveröffentlichung Häfner, Stefan; Vogel, Frank; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten FINITE ELEMENT ANALYSIS OF TORSION FOR ARBITRARY CROSS-SECTIONS The present article proposes an alternative way to compute the torsional stiffness based on three-dimensional continuum mechanics instead of applying a specific theory of torsion. A thin, representative beam slice is discretized by solid finite elements. Adequate boundary conditions and coupling conditions are integrated into the numerical model to obtain a proper answer on the torsion behaviour, thus on shear center, shear stress and torsional stiffness. This finite element approach only includes general assumptions of beam torsion which are independent of cross-section geometry. These assumptions essentially are: no in-plane deformation, constant torsion and free warping. Thus it is possible to achieve numerical solutions of high accuracy for arbitrary cross-sections. Due to the direct link to three-dimensional continuum mechanics, it is possible to extend the range of torsion analysis to sections which are composed of different materials or even to heterogeneous beams on a high scale of resolution. A brief study follows to validate the implementation and results are compared to analytical solutions. 11 urn:nbn:de:gbv:wim2-20170314-28483 10.25643/bauhaus-universitaet.2848 Institut für Strukturmechanik
OPUS4-2841 Konferenzveröffentlichung Eckardt, Stefan; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten ENERGY RELEASE CONTROL FOR NONLINEAR MESOSCALE SIMULATIONS In nonlinear simulations the loading is, in general, applied in an incremental way. Path-following algorithms are used to trace the equilibrium path during the failure process. Standard displacement controlled solution strategies fail if snap-back phenomena occur. In this contribution, a path-following algorithm based on the dissipation of the inelastic energy is presented which allows for the simulation of snap-backs. Since the constraint is defined in terms of the internal energy, the algorithm is not restricted to continuum damage models. Furthermore, no a priori knowledge about the final damage distribution is required. The performance of the proposed algorithm is illustrated using nonlinear mesoscale simulations. 5 urn:nbn:de:gbv:wim2-20170314-28414 10.25643/bauhaus-universitaet.2841 Institut für Strukturmechanik
OPUS4-3424 Konferenzveröffentlichung Nasser, Mourad; Schwedler, Michael; Wuttke, Frank; Könke, Carsten; Schanz, Tom Dynamic Soil-Structure Interaction Models: Theory and Application Dynamic Soil-Structure Interaction Models: Theory and Application Institut für Strukturmechanik
OPUS4-3350 Wissenschaftlicher Artikel Schrader, Kai; Könke, Carsten Distributed computing for the nonlinear analysis of multiphase composites Distributed computing for the nonlinear analysis of multiphase composites 12 Advances in Engineering Software 20 32 Institut für Strukturmechanik
OPUS4-3030 Konferenzveröffentlichung Unger, Jörg F.; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten DISCRETE CRACK SIMULATION OF CONCRETE USING THE EXTENDED FINITE ELEMENTMETHOD The extended finite element method (XFEM) offers an elegant tool to model material discontinuities and cracks within a regular mesh, so that the element edges do not necessarily coincide with the discontinuities. This allows the modeling of propagating cracks without the requirement to adapt the mesh incrementally. Using a regular mesh offers the advantage, that simple refinement strategies based on the quadtree data structure can be used to refine the mesh in regions, that require a high mesh density. An additional benefit of the XFEM is, that the transmission of cohesive forces through a crack can be modeled in a straightforward way without introducing additional interface elements. Finally different criteria for the determination of the crack propagation angle are investigated and applied to numerical tests of cracked concrete specimens, which are compared with experimental results. 12 urn:nbn:de:gbv:wim2-20170327-30303 10.25643/bauhaus-universitaet.3030 Institut für Strukturmechanik
OPUS4-1970 Konferenzveröffentlichung Theiler, Michael; Könke, Carsten Maia, Nuno Damping in Bolted Joints With the help of modern CAE-based simulation processes, it is possible to predict the dynamic behavior of fatigue strength problems in order to improve products of many industries, e.g. the building, the machine construction or the automotive industry. Amongst others, it can be used to improve the acoustic design of automobiles in an early development stage. Nowadays, the acoustics of automobiles plays a crucial role in the process of vehicle development. Because of the advanced demand of comfort and due to statutory rules the manufacturers are faced with the challenge of optimizing their car's sound emissions. The optimization includes not only the reduction of noises. Lately with the trend to hybrid and electric cars, it has been shown that vehicles can become too quiet. Thus, the prediction of structural and acoustic properties based on FE-simulations is becoming increasingly important before any experimental prototype is examined. With the state of the art, qualitative comparisons between different implementations are possible. However, an accurate and reliable quantitative prediction is still a challenge. One aspect in the context of increasing the prediction quality of acoustic (or general oscillating) problems - especially in power-trains of automobiles - is the more accurate implementation of damping in joint structures. While material damping occurs globally and homogenous in a structural system, the damping due to joints is a very local problem, since energy is especially dissipated in the vicinity of joints. This paper focusses on experimental and numerical studies performed on a single (extracted) screw connection. Starting with experimental studies that are used to identify the underlying physical model of the energy loss, the locally influencing parameters (e.g. the damping factor) should be identified. In contrast to similar research projects, the approach tends to a more local consideration within the joint interface. Tangential stiffness and energy loss within the interface are spatially distributed and interactions between the influencing parameters are regarded. As a result, the damping matrix is no longer proportional to mass or stiffness matrix, since it is composed of the global material damping and the local joint damping. With this new approach, the prediction quality can be increased, since the local distribution of the physical parameters within the joint interface corresponds much closer to the reality. 8 Proceedings of International Conference on Structural Engineering Dynamics (ICEDyn) 2013 978-989-96276-4-2 urn:nbn:de:gbv:wim2-20130701-19709 10.25643/bauhaus-universitaet.1970 Institut für Strukturmechanik