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Institute: search.filters.UBSInstitut.Institut für Mechanik (Bauwesen)Subject: search.filters.subject.620Start date: 2021End date: 2021

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Now showing 1 - 6 of 6
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    Permeability estimation of regular porous structures : a benchmark for comparison of methods
    (2021) Wagner, Arndt; Eggenweiler, Elissa; Weinhardt, Felix; Trivedi, Zubin; Krach, David; Lohrmann, Christoph; Jain, Kartik; Karadimitriou, Nikolaos; Bringedal, Carina; Voland, Paul; Holm, Christian; Class, Holger; Steeb, Holger; Rybak, Iryna
    The intrinsic permeability is a crucial parameter to characterise and quantify fluid flow through porous media. However, this parameter is typically uncertain, even if the geometry of the pore structure is available. In this paper, we perform a comparative study of experimental, semi-analytical and numerical methods to calculate the permeability of a regular porous structure. In particular, we use the Kozeny-Carman relation, different homogenisation approaches (3D, 2D, very thin porous media and pseudo 2D/3D), pore-scale simulations (lattice Boltzmann method, Smoothed Particle Hydrodynamics and finite-element method) and pore-scale experiments (microfluidics). A conceptual design of a periodic porous structure with regularly positioned solid cylinders is set up as a benchmark problem and treated with all considered methods. The results are discussed with regard to the individual strengths and limitations of the used methods. The applicable homogenisation approaches as well as all considered pore-scale models prove their ability to predict the permeability of the benchmark problem. The underestimation obtained by the microfluidic experiments is analysed in detail using the lattice Boltzmann method, which makes it possible to quantify the influence of experimental setup restrictions.
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    Finite strain hyperelastic multiscale homogenization via projection, efficient sampling and concentric interpolation
    (Stuttgart : Institute of Applied Mechanics, 2021) Kunc, Oliver; Fritzen, Felix (Prof. Dr.-Ing. Dipl.-Math. techn.)
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    Simulation of coupled transfer and transport phenomena in multi-phase materials with application to polymer gels
    (Stuttgart : Institute of Applied Mechanics, 2021) Sauerwein, Malte; Steeb, Holger (Prof. Dr.-Ing.)
    The use of polymers in fluid-saturated porous media has increased in relevance during the last years. Polymers, which exist in the pore space of a solid skeleton, are able to interact with the pore fluid as well as with the solid. The interactions cause changes in the macroscopic behavior, while especially transport and transfer processes within the pore space are affected. The precise knowledge of these processes over time is a key factor for developing innovative applications in petroleum engineering but also for innovative building materials. Therefore, the aim of this thesis is to develop a multi-phase model for simulating the coupled processes in such kind of material. With such model, the physical behavior of water-soluble polymers in petroleum engineering and the swelling behavior of hydrogels in polymer-enhanced building materials can be predicted over time. The coupled processes are simulated by solving the system's governing equations in a finite element framework and are validated through experimental results.
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    Continuum mechanics of multicomponent materials : modelling, numerics and applications for biological materials in the framework of the theory of porous media
    (Stuttgart : Institut für Mechanik (Bauwesen), Lehrstuhl für Kontinuumsmechanik, Universität Stuttgart, 2021) Wagner, Arndt; Ehlers, Wolfgang (Prof. Dr.-Ing. Dr. h. c.)
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    Variational methods for dissipative multifield problems in solid mechanics
    (Stuttgart : Institute of Applied Mechanics, 2021) Teichtmeister, Stephan; Keip, Marc-Andre (Prof. Dr.-Ing.)
    In many engineering applications, solid materials undergo processes that cause an irreversible change in their microstructure. Such dissipative phenomena usually have a multifield character which means that, besides the macro-deformation, also other physical fields such as temperature, species concentration or plastic and damage variables are involved. Practical applications include, for example, hot sheet metal forming, diffusion processes or brittle as well as ductile fracturing. The focus of this work is to develop a general and versatile modeling framework for dissipative multifield processes in solids undergoing large deformations. This framework is provided by incremental variational principles which fully describe the evolution of the system under consideration. Special attention is paid to the coupling of the involved physical fields in accordance with the fundamental laws of thermodynamics. The major contribution of this work is the development of new models and formulations for brittle and ductile fracturing in isotropic and anisotropic materials, diffusion in solids and the thermomechanics of gradient-extended continua including aspects of stability.
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    A portable intuitive haptic device on a desk for user-friendly teleoperation of a cable-driven parallel robot
    (2021) Park, Jae-Hyun; Kim, Min-Cheol; Böhi, Ralf; Gommel, Sebastian Alexander; Kim, Eui-Sun; Choi, Eunpyo; Park, Jong-Oh; Kim, Chang-Sei
    This paper presents a compact-sized haptic device based on a cable-driven parallel robot (CDPR) mechanism for teleoperation. CDPRs characteristically have large workspaces and lightweight actuators. An intuitive and user-friendly remote control has not yet been achieved, owing to the unfamiliar multiple-cable configuration of CDPRs. To address this, we constructed a portable compact-sized CDPR with the same configuration as that of a larger fully constrained slave CDPR. The haptic device is controlled by an admittance control for stiffness adjustment and implemented in an embedded microprocessor-based controller for easy installation on an operator’s desk. To validate the performance of the device, we constructed an experimental teleoperation setup by using the prototyped portable CDPR as a master and larger-size CDPR as a slave robot. Experimental results showed that a human operator can successfully control the master device from a remote site and synchronized motion between the master and slave device was performed. Moreover, the user-friendly teleoperation could intuitively address situations at a remote site and provide an operator with realistic force during the motion of the slave CDPR.