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Multifunktionale Strukturen sind heute in verschiedenen Fachbereichen von Wissenschaft und Technik von großer Bedeutung. Die Integration von Zusatzfunktionen in existierende Strukturen und Maschinenelemente ermöglicht die Entwicklung neuer innovativer Produkte, die nicht nur kostengünstig, sondern auch platzsparend hergestellt werden können oder vollkommen neue Funktion erfüllen. Das Kunststoffgleitlager mit inte-grierter Verschleißsensorik, das derzeit an der Professur Intelligente Maschinensysteme der Hochschule Mittweida erforscht wird, ist ein beispielhaftes Forschungsprojekt im Bereich multifunktionaler Strukturen. Das Kunststoffgleitlager bietet dem Anwender die Möglichkeit, dank der integrierten Verschleißsensorik aus elektrisch leitfähigem thermoplastischem Kunststoff, Betriebsdaten in Echtzeit zu ermitteln. Diese Innovation ermöglicht die Erfassung des Verschleißgrades des Lagers während des Betriebs, was wiederum eine effektivere Planung von Wartungsintervallen erlaubt. Durch die Vermeidung des vorbeugenden Austauschs noch funktionsfähiger Lager können erhebliche Ressourcen und Kosten eingespart werden. Zur Analyse des Betriebsverhaltens der Sensorelemente wurden umfangreiche numerische Untersuchungen zum mechanischen, thermischen und elektrischen Verhalten des Kunststoffgleitlagers durchgeführt. Ein gekoppeltes Modell wurde in Ansys entwickelt, und mittels einer Parameterstudie verschiedene Szenarien simuliert. Die erzielten Ergebnisse bieten einen detaillierten Einblick in das Betriebsverhalten und die Funktion des Lagers inkl. Sensorik. Mit diesen Erkenntnissen konnte ein Verschleißmodell erstellt werden, welches auf Basis der Sensorwerte kraft- richtungsunabhängig den Verschleißzustand des Lagers ermittelt. Weiterhin kann mit den ermittelten Daten ein passgenauer Messverstärker effizient entwickelt werden. / Multifunctional structures are of great importance in various fields of science and technology today. The integration of additional functions into existing structures and machine elements enables the development of new innovative products that can be manufactured not only cost-effectively but also in a space-saving manner or fulfill entirely new functions. The plastic plain bearing with integrated wear sensing, currently being researched at the Chair of Intelligent Machine Systems at Mittweida University of Applied Sciences, is an exemplary research project in the field of multifunctional structures. The plastic plain bearing provides the user with the ability to determine operating data in real-time thanks to the integrated wear sensing made of electrically conductive thermoplastic material. This innovation enables the monitoring of the degree of wear of the bearing during operation, which in turn allows for more effective planning of maintenance intervals. By avoiding the preventive replacement of still functional bearings, significant resources and costs can be saved. Extensive numerical investigations into the mechanical, thermal, and electrical behavior of the plastic plain bearing were conducted to analyze the operational behavior of the sensor elements. A coupled model was developed in Ansys, and various scenarios were simulated through a parameter study. The results obtained provide a detailed insight into the operational behavior and functionality of the bearing including the sensor system. With this knowledge, a wear model was created, which determines the wear condition of the bearing independently of the direction of force based on the sensor values. Furthermore, with the determined data, a precisely fitting signal amplifier can be efficiently developed.

The focus of interest in this study is the RHex robot, which is a hexapod robot that is capable of locomotion over rugged, fractured terrain through statically and dynamically stable gaits while stability of locomotion is preserved. RHex is primarily a research platform that is based on over five years of previous research. The purpose of the study is to build a virtual prototype of RHex robot in order to simulate different behavior without manufacturing expensive prototypes. The virtual prototype is modeled in MSC ADAMS software which is a very useful program to simulate flexible multibody dynamical systems. The flexible half circular legs are modeled in a finite element program (MSC NASTRAN) and are embedded in the main model. Finally a closed loop control mechanism is built in MATLAB to be able to simulate real autonomous RHex robot. The interaction of MATLAB and MSC ADAMS softwares is studied.

Cette thèse présente une étude expérimentale et numérique d'essais de chute libre et de vibrations aléatoires d'emballages en carton ondulé contenant différents calages en mousse. Un modèle d'homogénéisation efficace pour le carton ondulé a été développé. Dans ce modèle homogénéisé, le carton ondulé est représenté par une plaque 2D. Au lieu d'utiliser une loi de comportement locale (reliant les déformations aux contraintes) à chaque point d'intégration, l'homogénéisation conduit aux rigidités globales (reliant les déformations généralisées aux forces résultantes) pour la plaque équivalente homogène. Ce modèle a été implémenté dans le logiciel Abaqus. Le comportement de la mousse a été déterminé expérimentalement et modélisé avec un modèle de mousse déformable d'Abaqus. Les emballages sont soumis à des tests de chute libre d'une hauteur donnée sur un sol rigide et des essais de vibrations aléatoires type bruit blanc sur table vibrante. Les résultats numériques obtenus en utilisant la simulation avec le modèle homogénéisé concordent bien avec les résultats expérimentaux. Nous avons également montré que la contribution de la caisse en carton ondulé à la réponse au choc et à la vibration aléatoire ne pouvait pas être négligée dans la conception des calages. / This thesis presents experimental and numerical studies of drop tests random vibrations of corrugated cardboard packaging containing different foam cushions. An efficient homogenization model for the corrugated cardboard has been developed. In this homogenized model, the corrugated cardboard is represented by a 2D plate. Instead of using a local constitutive law (relating the strains to the stresses) at each material point, the homogenization leads to global rigidities (relating the generalized strains to the resultant forces) for the equivalent homogeneous plate. This model was implemented into the FE software Abaqus. The foam behaviour was experimentally determined and modelled using a crushable foam model of Abaqus. The packages are tested in free fall from a given height on a rigid floor and submitted to white noise random vibrations. The numerical results obtained using the FE simulation with the homogenized model agree well with the experimental results. We have also shown that the contribution of the corrugated cardboard box to the shock and random vibration responses could not be neglected in the design of cushioning package.

Gegenstand dieser Arbeit ist es, Simulationsergebnisse von Pro/MECHANICA und ANSYS zu vergleichen, um somit einen Hinweis auf die Qualität der Berechnungsergebnisse von integrierten FEM-Systemen zu bekommen. Als Beispiele dienen verschiedene Bauteile aus dem Gebiet der Strukturmechanik (linear-elastischer Bereich), welche mit Pro/MECHANICA und ANSYS modelliert und berechnet werden. Abschließend erfolgt eine Gegenüberstellung der Daten aus FEM und analytischer Rechnung, sowie eine Bewertung der Ergebnisse.

Stimuli-sensitive hydrogels are polymeric materials, which are able to reversibly swell in water in response to evironmental changes. Relevant stimuli include variations of pH, temperature, concentration of specific ions etc. Stacked layers composed of multiple thin hydrogels - also referred to as hydrogel-layer composites - combine the distinct sensing properties of different hydrogels. This approach enables the development of sophisticated micro uidic devices such as bisensitive valves or uid-sensitive de ectors. In order to numerically simulate the swelling of a polyelectrolyte hydrogel in response to an ion concentration change the multifield theory is adopted. The set of partial differential equations - including the description of the chemical, the electrical and the mechanical field - are solved using the Finite Element Method. Simulations are carried out on a twodimensional domain in order to capture interactions between the different fields. In the present work, the ion transport is governed by diffusive and migrative uxes. The distribution of ions in the gel and the solution bath result in an osmotic pressure difference, which is responsible for the mechanical deformation of the hydrogel-layer composite. The realized numerical investigation gives an insight into the evolution of the displacement field, the distribution of ions and the electric potential within the bulk material and the interface between gel and solution bath. The predicted behavior of the relevant field variables is in excellent agreement with results available in the literature.

Nafion membranes, are polymeric thin films widely employed in micro-batteries and fuel cells. These devices are expected to play a key role in the next generation energy systems for use in vehicles as a replacement to combustion engines. In fact, a minimum environmental impact is guaranteed by reduced carbon dioxide emissions. It is usually complicated to investigate the behavior of thin membranes through experiments. Therefore, numerical simulations are carried out in order to enable a better understanding of the phenomena and of the multi-field couplings occurring in polymeric membranes. A continuum-based, three-dimensional and electro-chemo-mechanical (ECM) model for a hydrated polymer membrane is presented. Different effects are taken into account: (i) mechanics, (ii) water uptake, (iii) ion transport, and (iv) electrostatics. The dissipation inequality drives the choice of the suitable constitutive equations of the multi-physics theory. In the mechanical field, an additive decomposition of the deformation gradient in (i) a distortion part, related to the ion motion, and (ii) an elastic part, is assumed. The multi-field model is numerically solved within the finite element framework. Time-dependent simulations are performed by using the commercial tool COMSOL Multiphysics. Furthermore, two closed form solutions are obtained by using (i) a one-dimensional reduced model and (ii) an approach based on the bar theory with an electro-chemical distortion field.

Die Dynamik von elastischen Membranen, Kapseln und Schalen hat sich zu einem aktiven Forschungsgebiet in der simulationsgestützten Physik und Biologie entwickelt. Die dünne Oberfläche dieser elastischen Materialien ermöglicht es, sie effizient als Hyperfläche zu approximieren. Solche Oberflächen reagieren auf Dehnungen in Oberflächenrichtung und Verformungen in Normalenrichtung mit einer elastischen Kraft. Zusätzlich können Oberflächenspannungskräfte auftreten. In dieser Arbeit präsentieren wir eine neuartige Arbitrary Lagrangian-Eulerian (ALE) Methode um solche in (Navier-Stokes) Fluiden eingebetteten elastischen Schalen zu simulieren. Dadurch, dass das Gitter an die elastische Oberfläche angepasst ist, kombiniert die vorgeschlagene Methode hohe Genauigkeit mit Effizienz in der Berechnung der Lösungen. Folglich kann man die Simulationen mit einer verhältnismäßig geringen Gitterauflösung durchführen. Der Fokus dieser Arbeit liegt bei achsensymmetrischen Formen und Strömungen, wie sie bei vielen biophysikalischen Anwendungen zu finden sind. Neben einer allgemeinen dreidimensionalen Beschreibung formulieren wir achsensymmetrische Kräfte auf der Oberfläche, für welche wir eine Diskretisierung mit der Finite Differenzen Methode vorschlagen, welche an eine Finite-Elemente Methode für die umgebenden Fluide gekoppelt ist. Weiterhin entwickeln wir eine Strategie zur impliziten Kopplung der Kräfte, um Zeitschrittrestriktionen zu reduzieren. In verschiedenen numerischen Tests werden wir zeigen, dass akkurate Ergebnisse schon in einer Größenordnung von Minuten auf einer Single-Core CPU erreicht werden können. Die Methode wurde in drei aktuellen Anwendungen verwendet, wobei mindestens zwei davon nach unserer Kenntnis im Moment mit keiner anderen numerischen Methode simuliert werden können: Zunächst präsentieren wir Simulationen von biologischen Zellen, die im Zuge eines RT-DC (Real-Time Deformability Cytometry) Experiments durch einen schmalen mikrofluidischen Kanal advektiert und dabei verformt werden. Danach zeigen wir die Ergebnisse erster Simulationen der uniaxialen Kompression biologischer Zellen zwischen zwei parallelen Platten im Zuge eines AFM Experiments. Schließlich präsentieren wir Resultate erster Simulationen von neuartigen mikroschwimmenden Schalen, welche lediglich durch äußere Einflüsse (wie z.B. Ultraschall), zum Schwimmen angeregt werden können. / The dynamics of membranes, shells, and capsules in fluid flow has become an active research area in computational physics and computational biology. The small thickness of these elastic materials enables their efficient approximation as a hypersurface, which exhibits an elastic response to in-plane stretching and out-of-plane bending, possibly accompanied by a surface tension force. In this work, we present a novel arbitrary Lagrangian-Eulerian (ALE) method to simulate such elastic surfaces immersed in Navier-Stokes fluids. The method combines high accuracy with computational efficiency, since the grid is matched to the elastic surface and can therefore be resolved with relatively few grid points. The focus of this work is on axisymmetric shapes and flow conditions, which are present in a wide range of biophysical problems. Next to a general three-dimensional description, we formulate axisymmetric elastic surface forces and propose a discretization with surface finite-differences coupled to evolving finite elements. We further develop an implicit coupling strategy to reduce time step restrictions. Several numerical test cases show that accurate results can be achieved at computational times on the order of minutes on a single core CPU. Three state-of-the-art applications are demonstrated, where to our knowledge at least two of them cannot be simulated with any other numerical method so far. First, simulations of biological cells being advected through a microfluidic channel and therefore being deformed during an RT-DC (Real-Time Deformability Cytometry) experiment are presented. Then, the uniaxial compression of the cortex of a biological cell during an AFM experiment is investigated. Finally, we present the results of first simulations of the observed shape oscillations of novel microswimming shells which can be locomoted by exterior influences (e.g. ultrasound waves) only.

Main goals of this master thesis are following: to perform the state of the art research of overpressure constructions (especially space habitats, plane fuselages); to create an own concept of the functional inside ending (hole) in the sandwich panel for a door; to perform stress-strain analysis of this concept; to perform the design optimalization of this concept in order to minimise the weight. To solve the problems above software Ansys 17.2 is chosen, because it allows to: model the material of the honeycomb core of sandwich panel as homogenous linear orthotropic material; evaluate reserve factors of all critical limit states; perform the design optimalization; perform Monte Carlo simulation. First and second design optimalizations discover, that with defined parameters: 0,635 mm width of aluminium sandwich face sheets and inner overpressure 0,1 MPa, a creation of the model, that would be safe by changing the values of design variables is not possible. Specifically, the maximum value of shear stress on the glued areas between aluminium face sheets and honeycomb core is higher than the shear strength of the glue. Therefore, two new concepts are created. First for inner pressure 0,03 MPa and bigger width of aluminium face sheets 3,175 mm, second for inner pressure 0,02 MPa and same width of aluminium face sheets 0,635 mm. For both these concepts, an overall reserve factor is calculated. First, the value of an overall reserve factor is calculated deterministically. Secondly, the value of an overall reserve factor is calculated stochastically considering the variance of material properties of the honeycomb core ± 10 % by Monte Carlo simulation. An overall reserve factor of the concept with inner pressure 0,02 MPa is determined as 1,21. An overall reserve factor of the concept with inner pressure 0,03 MPa is determined as 1,20. The weight of the concept for inner pressure 0,03 MPa is though 4 times bigger than the weight of the concept for inner pressure 0,02 MPa. In the concept for inner pressure 0,02 MPa the maximum value of HMH stress in aluminium components is critical, stochastically considered material properties of the honeycomb core don’t have a significant influence on this value. In the concept for inner pressure 0,03 MPa the value of maximum shear stress on the glued areas between aluminium face sheets and the honeycomb core is critical, stochastically considered material properties of the honeycomb core have a significant influence on this value. In the concept for inner pressure 0,03 MPa an absolute error of overall reserve factor is 8 % (overall reserve factor calculated deterministically was 1,28) which is significant. Monte Carlo simulation is also used to find that the value of Poisson ratio XY of the honeycomb core doesn’t have statistically significant influence on all limit states. Value of the reserve factor of the honeycomb core is higher than 2 in both concepts. Monte Carlo simulation discovers that this value can be significantly lower. Using Tsai-Wu failure criteria the reserve factor in the concept for inner pressure 0,02 MPa is determined as 2,72 deterministically x 2,41 stochastically (absolute error 31 %), in the concept for inner pressure 0,03 MPa the reserve factor is determined as 6,85 deterministically x 6,17 stochastically (absolute error 68 %).

In der vorliegenden Arbeit werden verschiedene Randwertprobleme zur Beschreibung der Ausbreitung magnetotellurischer Felder mit Hilfe der Finite-Elemente-Methode numerisch gelöst. Die zwei- und dreidimensionalen Randwertprobleme zur Simulation des elektrischen oder des magnetischen Feldes, des magnetischen Vektorpotentials und des elektrischen Skalarpotentials, des magnetischen Vektorpotentials allein oder des anomalen magnetischen Vektorpotentials werden aus den Maxwell-Gleichungen hergeleitet. Auf Grundlage von Anwendung der Konvergenztheorie auf die Finite-Elemente-Lösung werden Konvergenzstudien für zweidimensionale Modelle des homogenen und des geschichteten Halbraums sowie für das dreidimensionale COMMEMI 3-D-2-Modell durchgeführt. Diese werden genutzt, um die Randwertprobleme hinsichtlich ihrer Effizienz zu bewerten. Außerdem liefern Konvergenzstudien eine Abschätzung des lokalen Fehlers der numerischen Lösung für ein realitätsnahes Modell des Vulkans Stromboli und seiner Umgebung, welches digitale Geländedaten enthält. / This thesis presents the numerical finite-element solution of different formulations of the magnetotelluric boundary value problem. Based on Maxwell\'s equations, the two-dimensional and three-dimensional boundary value problems are derived in terms of the electric or the magnetic field, the magnetic vector and the electric scalar potential, the magnetic vector potential only, or the anomalous magnetic vector potential. To evaluate their efficiency, convergence studies are performed for the two-dimensional models of the homogeneous and the layered halfspace as well as for the COMMEMI-3-D-2 model. Moreover, convergence studies yield estimates of the local error of the numerical solution for a close-to-reality model of Stromboli volcano incorporating digital terrain data.