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 OPUS4-301 Konferenzveröffentlichung Häfner, Stefan; Eckardt, Stefan; Könke, Carsten A geometrical inclusion-matrix model for the finite element analysis of concrete at multiple scales This paper introduces a method to generate adequate inclusion-matrix geometries of concrete in two and three dimensions, which are independent of any specific numerical discretization. The article starts with an analysis on shapes of natural aggregates and discusses corresponding mathematical realizations. As a first prototype a two-dimensional generation of a mesoscale model is introduced. Particle size distribution functions are analysed and prepared for simulating an adequate three-dimensional representation of the aggregates within a concrete structure. A sample geometry of a three-dimensional test cube is generated and the finite element analysis of its heterogeneous geometry by a uniform mesh is presented. Concluding, aspects of a multiscale analysis are discussed and possible enhancements are proposed. 2003 urn:nbn:de:gbv:wim2-20111215-3018 10.25643/bauhaus-universitaet.301 Professur Informatik im Bauwesen OPUS4-3409 Wissenschaftlicher Artikel Eckardt, Stefan; Könke, Carsten Adaptive damage simulation of concrete using heterogeneous multiscale models Adaptive damage simulation of concrete using heterogeneous multiscale models 22 Journal of Algorithms & Computational Technology 275 297 Institut für Strukturmechanik (ISM) OPUS4-2947 Konferenzveröffentlichung Eckardt, Stefan; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten ADAPTIVE SIMULATION OF THE DAMAGE BEHAVIOR OF CONCRETE USING HETEROGENEOUS MULTISCALE MODELS In this paper an adaptive heterogeneous multiscale model, which couples two substructures with different length scales into one numerical model is introduced for the simulation of damage in concrete. In the presented approach the initiation, propagation and coalescence of microcracks is simulated using a mesoscale model, which explicitly represents the heterogeneous material structure of concrete. The mesoscale model is restricted to the damaged parts of the structure, whereas the undamaged regions are simulated on the macroscale. As a result an adaptive enlargement of the mesoscale model during the simulation is necessary. In the first part of the paper the generation of the heterogeneous mesoscopic structure of concrete, the finite element discretization of the mesoscale model, the applied isotropic damage model and the cohesive zone model are briefly introduced. Furthermore the mesoscale simulation of a uniaxial tension test of a concrete prism is presented and own obtained numerical results are compared to experimental results. The second part is focused on the adaptive heterogeneous multiscale approach. Indicators for the model adaptation and for the coupling between the different numerical models will be introduced. The transfer from the macroscale to the mesoscale and the adaptive enlargement of the mesoscale substructure will be presented in detail. A nonlinear simulation of a realistic structure using an adaptive heterogeneous multiscale model is presented at the end of the paper to show the applicability of the proposed approach to large-scale structures. 15 urn:nbn:de:gbv:wim2-20170327-29478 10.25643/bauhaus-universitaet.2947 Institut für Strukturmechanik (ISM) OPUS4-3403 Wissenschaftlicher Artikel Luther, Torsten; Könke, Carsten Coupled cohesive zone representations from 3D quasicontinuum simulation on aluminum grain boundaries Coupled cohesive zone representations from 3D quasicontinuum simulation on aluminum grain boundaries International Journal for Multiscale Computational Engineering Institut für Strukturmechanik (ISM) OPUS4-3413 Wissenschaftlicher Artikel Unger, Jörg F.; Könke, Carsten Coupling of scales in a multiscale simulation using neural networks Coupling of scales in a multiscale simulation using neural networks Computers & Structures Institut für Strukturmechanik (ISM) OPUS4-2963 Konferenzveröffentlichung Häfner, Stefan; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten DAMAGE SIMULATION OF HETEROGENEOUS SOLIDS BY NONLOCAL FORMULATIONS ON ORTHOGONAL GRIDS The present paper is part of a comprehensive approach of grid-based modelling. This approach includes geometrical modelling by pixel or voxel models, advanced multiphase B-spline finite elements of variable order and fast iterative solver methods based on the multigrid method. So far, we have only presented these grid-based methods in connection with linear elastic analysis of heterogeneous materials. Damage simulation demands further considerations. The direct stress solution of standard bilinear finite elements is severly defective, especially along material interfaces. Besides achieving objective constitutive modelling, various nonlocal formulations are applied to improve the stress solution. Such a corrective data processing can either refer to input data in terms of Young's modulus or to the attained finite element stress solution, as well as to a combination of both. A damage-controlled sequentially linear analysis is applied in connection with an isotropic damage law. Essentially by a high resolution of the heterogeneous solid, local isotropic damage on the material subscale allows to simulate complex damage topologies such as cracks. Therefore anisotropic degradation of a material sample can be simulated. Based on an effectively secantial global stiffness the analysis is numerically stable. The iteration step size is controlled for an adequate simulation of the damage path. This requires many steps, but in the iterative solution process each new step starts with the solution of the prior step. Therefore this method is quite effective. The present paper provides an introduction of the proposed concept for a stable simulation of damage in heterogeneous solids. 15 urn:nbn:de:gbv:wim2-20170327-29638 10.25643/bauhaus-universitaet.2963 Institut für Strukturmechanik (ISM) 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 (ISM) 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 (ISM) 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 (ISM) 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 (ISM)