In recent decades the development of technologies capable to offer highly localized and precise temperature control has received increasing attention due to their relevance and applicability in numerous engineering fields. Multiple scientific papers have been written that focus on the enhancement of the performance of thermoelectric materials and micro-devices. This Ph.D. thesis in the field of Mechanical Engineering pursues three main research goals regarding electrothermal phenomena: (1) To provide an optimization design strategy for micro-thermoelectric coolers by analyzing the interplay between electrical and thermal fluxes during device operation. (2) To analyze the suitability of a device, based on micro-thermoelectric coolers, for controlling the thermal environment in microbiological systems. (3) To develop an experimental technique, based on optical pump-probe thermal imaging, to extract the thermal conductivity anisotropy of thin films. For this purpose, numerical simulations and experiments were carried out. The results show, that the design of micro-thermoelectric devices must take into account the impact of parameters that are typically neglected in the construction of macro scale devices. Poorly designed parameters, such as the metallic contacts, the distance between thermoelectric elements and their interaction with the substrate, carry severe reductions of the performance of micro-thermoelectric devices. It is demonstrated that the optimal performance is achieved when the thermoelectric legs are properly dimensioned, so that a balance of the Fourier and Joule fluxes is reached. Numerical analyses prove that micro-thermoelectric coolers offer a feasible alternative to overcome the current spatial and temperature limitations of conventional technologies and therefore enable to investigate the thermal environment of biological systems at the micro-scale. Guidelines for the implementation of the experimental platform are provided. The evaluation of the numerical and experimental data proves that optical pump-probe thermal imaging is suitable to characterize both the in-plane and the through-plane thermal conductivity of thin films. The experimental conditions to extract the anisotropy of the sample under study are determined. The outcome of this work yields new insights into electrothermal phenomena at the micro-scale and thus creates new routes in the design, fabrication and characterization of micro- thermoelectric materials and devices.:Acknowledgements IV Erklärung der Urheberschaft VI Summary VII Zusammenfassung VIII Table of content IX List of figures XI List of tables XIV Abbreviations and symbols XV 1 Introduction 1 1.1 Motivation 1 1.2 Outline of the thesis 4 1.2.1 Chapter 2 - Fundamentals 4 1.2.2 Chapter 3 - Design guidelines of micro-thermoelectric coolers 4 1.2.3 Chapter 4 - Development of a platform for biological systems experimentation 4 1.2.4 Chapter 5 - Development of a technique for thermal transport characterization in thin films 5 1.2.5 Chapter 6 - Main conclusion and future research 5 1.3 Main research objectives 5 2 Fundamentals 7 2.1 Thermoelectric phenomena 7 2.2 Performance estimation of micro-thermoelectric coolers 10 2.3 Finite element modelling 12 2.3.1 Introduction to finite element modelling 12 2.3.2 Finite element modelling of thermoelectric phenomena 17 2.4 Thermoreflectance imaging microscopy 19 3 Design guidelines of micro-thermoelectric coolers 26 3.1 Introduction 26 3.2 Micro-thermoelectric coolers: an alternative for thermal management 28 3.3 Analysis approach 29 3.3.1 Input current optimization 31 3.3.2 Metallic contacts 32 3.3.3 Leg pair geometry 35 3.3.4 Fill factor 38 3.3.5 Experimental characterization of µTECs 41 3.4 Summary 44 4 Development of a platform for biological systems experimentation 46 4.1 Introduction 46 4.2 Thermal analysis on biological systems 48 4.3 Platform conceptual proposal 50 4.4 Analysis approach 52 4.4.1 Input current optimization 52 4.4.2 Fill material 54 4.4.3 Thermotaxis 55 4.4.4 Top material 56 4.4.5 Cold spot optimization 58 4.5 Experimental platform construction 59 4.6 Summary 62 5 Development of a technique for thermal transport characterization in thin films 64 5.1 Introduction 64 5.2 Thermal anisotropy characterization in thin films 65 5.3 Experimental apparatus 66 5.4 Experimental measurements 69 5.5 Analysis approach 72 5.5.1 Thermal conductivity anisotropy analysis 76 5.5.2 Effect of the laser power on the temperature distribution 79 5.5.3 Enhancement of the system sensitivity 80 5.6 Summary 83 6 Main conclusion and future research 85 6.1 Main conclusion 85 6.2 Outlook 88 7 References 89 8 Scientific output 97 8.1 Publications in peer review journals 97 8.2 Selected conference abstracts 98 9 Curriculum vitae 99

Considering the unlikely core melt down scenario for a light water reactor (LWR) a possible failure mode of the reactor pressure vessel (RPV) and its failure time has to be investigated for a determination of the loadings on the containment. Worldwide several experiments have been performed accompanied with material properties evaluation, theoretical, and numerical work. At the Institute of Safety Research of the FZR a finite element model has been de-veloped simulating the thermal processes and the viscoplastic behaviour of the ves-sel wall. An advanced model for creep and material damage has been established and has been validated using experimental data. The thermal and the mechanical calculations are sequentially and recursively coupled. The model is capable of evalu-ating fracture time and fracture position of a vessel with an internally heated melt pool. The model was applied to pre- and post test calculations for the FOREVER test se-ries representing the lower head RPV of a PWR in the geometrical scale of 1:10. These experiments were performed at the Royal Institute of Technology in Stock-holm. The results of the calculations can be summarised as follows: # The creeping process is caused by the simultaneous presence of high tem-perature (>600 °C) and pressure (>1 MPa) # The hot focus region is the most endangered zone exhibiting the highest creep strain rates. # The exact level of temperature and pressure has an influence on the vessel failure time but not on the failure position # The failure time can be predicted with an uncertainty of 20 to 25%. This uncer-tainty is caused by the large scatter and the high temperature sensitivity of the viscoplastic properties of the RPV steel. # Contrary to the hot focus region, the lower centre of the vessel head exhibits a higher strength because of the lower temperatures in this zone. The lower part moves down without significant deformation. Therefore it can be assumed, that the vessel failure can be retarded or prevented by supporting this range. # The development of a gap between melt crust and vessel wall could not be proofed. First calculations for a PWR geometry were performed to work out differences and commonalities between prototypic scenarios and scaled experiments. The results of the FOREVER-experiments cannot be transferred directly to PWR geometry. The geometrical, mechanical and thermal relations cannot be scaled in the same way. Because of the significantly higher temperature level, a partial ablation of the vessel wall has to be to expected in the PWR scenario, which is not the case in the FOREVER tests. But nevertheless the FOREVER tests are the only integral in-vessel retention experiments up to now and they led to a number of important insights about the behaviour of a vessel under the loading of a melt pool and pressure.

Die vorliegende Arbeit umfasst die Entwicklung, Implementierung und Anwendung von Verfahren zur Parameteridentifikation schädigungsmechanischer Materialgesetze. Die duktile Schädigung wird auf kontinuumsmechanischer Basis durch Erweiterung der von Mises Fließbedingung mit dem Gurson-Tvergaard-Needleman sowie mit dem Rousselier Modell beschrieben. Das klassische Rousselier Modell wird dabei für beschleunigtes Porenwachstum und Porennukleation ergänzt. Das nichtlineare Rand- und Anfangswertproblem wird mit dem finite Elemente System SPC-PMHP berechnet, welches im Rahmen des Sonderforschungsbereichs (SFB) 393 für Parallelrechner entwickelt wurde. Im Zusammenhang mit der Entfestigung des Materials wird ein Lokalisierungskriterium für die Dehnungen im geometrisch nichtlinearen Fall angegeben. Die Identifikation der Materialparameter erfolgt über gemessene Kraft-Verschiebungskurven, lokale Verschiebungsfelder und über den Zeitpunkt der Lokalisierung. Dazu wird ein nichtlinearer Optimierungsalgorithmus verwendet, der mittels Gradientenverfahren die Zielfunktion in das nächste Minimum überführt. Eine semianalytische Sensitivitätsanalyse liefert die Ableitungen der Verschiebungen und Kräfte nach den Parametern. Verschiedene numerische Untersuchungen geben Aufschluss über die anzuwendende Optimierungsstrategie. Abschließend werden die lokalen Verschiebungsfelder mit dem Objektrasterverfahren sowie die Kraft-Verschiebungskurven an gekerbten Flachzugproben aus StE 690 ermittelt und die Parameter des Materials identifiziert.

Neue elektrische Antriebskonzepte ermöglichen es, eine hohe Funktionalität in einem eingeschränkten Bauraum unterzubringen. Damit steigt auch in der Landwirtschaft das Interesse an elektrischen Antrieben. Die Projektgruppe Elektrische Maschinen und Antriebe der HTW Dresden beteiligt sich mit der TU Dresden an einem Projekt, bei dem beginnend mit der elektrisch angetriebenen Dreschtrommel umfassend an einem Mähdrescher untersucht wird, wie diese Antriebe in einzelne Funktionselemente integriert werden können. Neben der Auslegung der Antriebe werden Verfahren erarbeitet, die Verluste im Motor mit hoher Genauigkeit zu berechnen. So können in Zukunft passgenaue Kühlkonzepte für diese Antriebstechnik entwickelt werden. Anforderungen gerade im Bereich der Elektromobilität fordern den Blick für neue Materialien, deren elektromagnetisches und thermisches Verhalten werden in ihrem Einfluss auf die Erwärmung untersucht. Analytische und kombinierte Berechnungsmethoden in 2D-FEM gestatten die vereinfachte Rechnung unter Berücksichtigung von Grundwelle und entstehenden Harmonischen zu qualifizieren. Verlustberechnungen aus der transienten FEM-Rechnung ermöglichen diese Verbesserung. Die Methode wird am Beispiel der elektrischen Dreschtrommel mit den berechneten Verlustverteilungen beschrieben. Neue Methoden der 3D-FEM, wie sie die Software Ansys bietet, werden für die Nutzung von Einflüssen der Wirbelstromeffekte und in Auswertung für die Segmentierung von Permanentmagneten dargestellt. Die exemplarisch gewonnenen Erkenntnisse liefern einen Beitrag für weitere Schneidwerksantriebe am Mähdrescher, aber auch darüber hinaus in Projekten mit Herstellern elektrischer Maschinen. / New concepts for electrical drives make it possible to put a high functionality into a restricted structural form. Thereby the interest in electrical drives increases also in the farming. The project team Electrical machines and drives of the HTW Dresden participates together with the TU Dresden in a project, where starting with the electrically driven threshing cylinder is comprehensively examined at a combine harvester, how these drives can be integrated into single function elements. Besides the dimensioning of the drives are developed methods to calculate losses in the engine with high precision. So custom-fit cooling concepts can be developed for this drive technology in future. Requirements just in the area of the electric mobility call looking for new materials, whose electromagnetic and thermic behavior are examined in her influence on the warming. Analytical and combined computation methods in 2D-FEM allow the simplified calculation under consideration of the fundamental wave and the arising harmonic ones. Loss calculations by means of the transient FEM calculation make possible this improvement. The method is described at the example of the electrical threshing cylinder with the calculated loss distributions. New methods of the 3D-FEM, as the software of Ansys offers, are presented for the use of influences of the eddy current effects and in evaluation for the segmentation of permanent magnets. The exemplarily got knowledge provides a contribution for further cut header drives at the combine but also furthermore in projects together with manufacturers of electrical machines.

Im Rahmen von FuE-Kooperationen arbeitet die TU Chemnitz, Professur für Strukturleichtbau und Kunststoffverarbeitung zusammen mit der AMB berlungwitz GmbH aktuell an der Entwicklung von langfaserverstärkten Kunststoffseilrollen für Aufzugsanlagen, welche die in diesem Bereich vorhandenen Leichtbauanforderungen erfüllen. Dabei wird die gesamte Entwicklungskette von der Bauteilkonstruktion und -berechnung über die Prozesskettengestaltung und Prozessparameterfindung bis hin zur Prüfung und Validierung von Probekörpem ausgeführt. Der grundsätzliche Technologieansatz zur Fertigung der Seilrollen-Rohteile ist das Fließpressen von glasmattenverstärkten Thermoplasten (GMT). Die vorliegende Arbeit beschäftigt sich schwerpunktmäßig mit der Berechnung und Auslegung der Bauteile.

Gegenstand dieser Arbeit ist die Forschungsdisziplin, welche in der Strukturmechanik als Modellordnungsreduktion bekannt ist. Im Mittelpunkt stehen Kopplungsprozesse von starren und elastischen Mehrkörpersystemen - sowohl in theoretischer Hinsicht als auch bezüglich der praktischen Realisation im Rahmen des Finite-Elemente-Programms ANSYS und des Mehrkörpersimulationsprogramms SIMPACK. Eine Vielfalt von strukturerhaltendenMOR-Methoden wurde zum Zwecke des Überblicks dargestellt. Darüber hinaus findet sich eine Kategorisierungsmethodik in Hinsicht auf den später beschriebenen FEM-MKS-Kopplungsprozess. Die Effizienz der MOR-Methoden wird sowohl hinsichtlich der Qualität der ROM als auch bezogen auf die hierfür benötigte Rechenzeit bemessen. Aus diesem Grunde wurden etliche MOR Schemata dargelegt, mit dem Ziel, den Effizienzfaktor während der Berechnung eines ROMs zu maximieren, das heißt maximale Qualität und minimale Rechenzeit zu erzielen. Die Validierung der dynamischen ROM-Eigenschaften basiert auf der Anwendung der sogenannten Modellkorrelationskriterien. Dies wurde an vier Anwendungsbeispielen aus dem Feld der Strukturmechanik getestet: der 3D-Balkenstruktur, der UIC60-Schiene, dem Pleuel und der Kurbelwelle. Die Anwendung der diagonal perturbation-Methodik verbessert die Kondition der Steifigkeitsmatrix eines Modells, von beiden Arten von Lösungsprozeduren, d.h. direkte und iterative Verfahren, betroffen sind. Die dynamische Bewegung mechanischer MKS wird als ein Index-3-DAE-Systemformuliert und die Information über die elastischen Körper wird in Form der sogenannten Standard Input Datei in einen MKS-Code transferriert. Die Einführung des Back-projection-Ansatzes ermöglicht die weitere Verwendung bestimmter ROM-Typen, derren assoziierten physikalische Eigenschaften unangemessen definiert wurden. Zum Abschluss werden die theoretischen, modellierenden und numerischen Fortschritte der Arbeit resümiert und kombiniert im Sinne der Model Order Reduction Package Toolbox (MORPACK). Die Matlab-basierte MORPACK-Toolbox ermöglicht den FEM-MKS-Kopplungsprozess für die Verwendung von ANSYS und SIMPACK. Hierin sind ein Großteil der zuvor erläuterten Erweiterungen eingeschlossen. Mit Hilfe der zwei integrierten inneren MOR- und SID-Schnittstellen als auch der vier Anwendungsebenen wird der Import von freien oder eingespannten ROM in SIMPACK ermöglicht. / The research discipline referred to as the Model Order Reduction in structural mechanics is the topic of this Thesis. Special emphasis is given to the coupling process of rigid and elastic Multi Body Dynamics in terms of both the theoretical aspects and the practical realization within the environment of the commercial Finite Element and the Multi Body Systems software packages, ANSYS and SIMPACK respectively. In this regard, a variety of structure preserving Model Order Reduction methods is presented and a categorization methodology is provided in view of the later FEM-MBS coupling process. The algorithmic scheme of several of the MOR methods indicates the capability of generating qualitatively better Reduced Order Models than the standardized Guyan and Component Mode Synthesis approaches. The efficiency of a MOR method is measured in terms of both the quality of the ROM and the associated time required for the .computation Based on the application of the, so called, Model Correlation Criteria the efficiency of the MOR schemes is tested on four application examples originating from the area of structural mechanics, i.e. the 3D elastic solid bar structure, the UIC60 elastic rail, the elastic piston rod, and the elastic crankshaft model. Herewith, the superiority of alternative MOR schemes in comparison to Guyan or CMS methods is demonstrated in terms of the ROM?s quality and the computation time by the use of either the one-step or the two-step MOR algorithms. Numerous of the FE discretized structures suffer from the, so called, ill-conditioned properties regarding the associated stiffness matrix. On one hand, the direct solution of a MOR method might produce erroneous ROMs due to the associated truncation phenomenon and on the other hand, any kind of iterative approach suffers from vast computation times. The application of the diagonal perturbation methodology improves the condition properties of the model?s stiffness matrix and thus, both kinds of the aforementioned solution procedures are affected. The back-projection approach is introduced, which projects the ROM belonging to the Non physical subspace reduction-expansion methods category back onto the physical configuration space and thus, enabling its further usage in a MBS code, e.g. SIMPACK. Finally, the theoretical, modelling, and numerical advancements are combined in terms of the Model Order Reduction Package. The Matlab-based MORPACK toolbox enables the FEM-MBS coupling process for the ANSYS-SIMPACK utilization and herewith, several of the aforementioned enhancements are included. With the help of the two integrated inner interfaces, i.e. MOR and SID, as well as four application levels, the import into SIMPACK of alternatively free or fixed ROMs is enabled. The functionality of MORPACK is demonstrated based on two application examples, namely, the 3D elastic solid bar and the UIC60 elastic rail, the dynamic properties of which are validated prior to their import into SIMPACK.

Concrete is a predominant construction material due to several advantages; however, the pure cementitious composites have shown quasi-brittle behavior with undesirable typical large cracks under tensile loading conditions. Thus, the addition of a small volume of short fibers is a well-known strategy to increase the ductility and toughness of cementitious matrices besides optimization of the crack opening. Strain-hardening cement-based composites (SHCCs) is a particular class of fiber-reinforced concretes (FRCC) that can develop controlled multiple cracks while subjected to incremental tensile loading conditions. However, a proper composition design, especially concerning fiber and bond properties, still follows a trial and error approach. This work presents a newly developed model to simulate SHCC at the meso-scale level. This model is based on Finite-Element-Method and allows for nonlinear behavior for cement matrix, fiber material, and bond laws. Concerning three complexities of target FRCC, i.e., crack formation in the cement matrix, a large number of explicit fibers with arbitrary random distribution, and fibers’ interaction with the cement matrix via the bond, extra features are added to standard FE consist of: • Further development of the Strong Discontinuity Approach (SDA) to model discrete cracking of continuum elements on the element level • Discretization of single fibers by truss elements with truss nodes independently placed of continuum nodes • Connecting SDA elements to explicit truss elements by particular bond elements. In this research study, first, theoretical basics and special implementation issues were described. Later, this newly developed model was calibrated with several simple configurations. The bond law utilized in the simulation was derived from single fiber pullout test and calibrated with several analyses. In the next step, 2D SHCC dumbbell specimens under tensile loading condition were simulated, and a series of numerical case studies were performed to assess the quality, credibility, and limitations of the numerical model. It should be noted that cracking patterns could not be directly compared to experimental cracking patterns as the simulation model’s current state is deterministic by random material properties that influence the experimental specimen behavior. Taking the effect of random field and other simplifying assumptions into account, the simulation model seems to describe enumerated SHCC behavior at an acceptable level. In summary, a further base is given for the target-oriented design of FRCC material composition to reach the given objectives of material properties. The concepts and methods presented in this study can simulate short and thin polymer fibers in a random position and steel fibers and structures with long reinforcement in a regular arrangement.

This bachelor's thesis aims to shed light on the professional ethical dilemmas that may arise in public libraries, what tools the librarians use, and what role experience plays in ethical thinking. With a theoretical framework based on Dreyfus and Dreyfus, as well as Säljö, we paint a picture of how ethical learning takes place in accordance with the five-step model, as well as how different tools can be used at the different levels of learning. Our findings suggest that experience is not equal to be an ethical expert, and that the tools that the librarians uses are useful on the lower levels of awareness, but that the librarians tends to act with more intuition when he/she grows more in their experience, although there are some cases where the expert still uses rules.

Med strängare krav på miljöpåverkan och en konstant efterfrågan på högre prestanda är optimering en essentiell del av vår vardag. Genom korrekt arbetsmetodik och optimering kan den växande efterfrågan på både prestanda och minskad miljöpåverkan överträffas. Att utveckla ett optimalt koncept av en länkarm hos en prestandabil är ett konkurrenskraftigt steg med stor betydelse. Genom att i ett tidigt skede i produktutvecklingsprocessen kunna skapa en optimal design minskar risken för stora kostnader på grund av ändringar i de senare faserna och bidrar således till en ökad lönsamhet. Att utnyttja Finita Elementmetoden som en del av en CAE driven produktutvecklingsprocess är således en utmärkt väg att gå och bidrar starkt till ändamålet genom att lösa avancerade problem med en simpel och adaptiv metodik. Bilindustrin präglas av innovativa och effektiva lösningar där både FEM och RE är välkända metoder. Projektet ska upplysa innebörden av en strukturerad arbetsmetodik vid optimering genom implementering av ett flertal produktutvecklingsfilosofier kombinerat med FEM/FEA. Genom att optimera en länkarm från en Audi R8 Coupé V10 quattro tillämpas och utvecklas välfungerade och starkt begrundade metoder. Produktutvecklingsfilosofier såsom Reverse Engineering och ett iterativt arbetssätt resulterade i en förbättrad länkarm med lägre vikt såväl som minskade spänningar och deformation. En viktminskning på 22%, en spänningsminskning på 47% och en minskad teoretisk elastisk deformation på 33% uppnåddes. Utöver dessa förbättringar ökade även robustheten med 25%. / With harsher regulations of environmental impact combined with a consistent demand on increased performance, optimization becomes an essential part of our everyday lives. Through a well-developed methodology and optimization process, the tougher demands of both performance and environmental impact could be exceeded. Developing an optimal concept of a control arm in a high-performance vehicle application is a competitive step of great importance. By creating an optimal design in early development stages of the product development process, the economic impact could be minimized. This therefore leads to an increase in profitability. Involving the Finite Element Method as a part of the product development process is therefore an excellent path toward solving advanced problems through a simple and adaptive work methodology. The automotive industry is characterized by innovative solutions where both the Finite Element Method and Reverse Engineering are well-known methods. The project has a foundation that strongly represents the meaning of a systematical optimization methodology through various product development philosophies combined with FEM/FEA. Through optimization of a control arm from an Audi R8 Coupé V10 quattro proved and well-grounded methods are applied and further developed. Product development philosophies such as Reverse Engineering and an iterative work process resulted in an improved control arm with lower weight as well as decreased stresses and deformation. A weight loss of 22%, stress reduction of 47% and a reduced theoretical elastic deformation of 33% was achieved. Beyond these improvements an increased robustness of 25% was achieved.

In recent time, some of the construction processes of multi-storey timber buildings are achieved by using prefabricated volume modules since this method is very beneficial due to its high prefabrication level and the fast on-site assembly of the modules. The main structural component of these modules is a light-frame shear wall that stabilizes these modules from the effect of horizontal forces. A shear wall typically consists of timber frame with studs and rails and sheathing panels connected by dowel type fasteners to one or both sides of the frame. The structural behavior of shear wall and its racking performance is controlled by adequate design of its mechanical joints where sheathing-to-framing joints is the key issue in evaluating the overall behavior of shear wall. This study mainly deals with modelling of light-frame shear walls based on linear elastic characteristic for sheathing-to-framing joints. The objective of this study is to create two effective computer-based models (beam-spring-shell and beam-spring-shell-solid) to predict linear behavior of light-frame shear walls. In addition, the study deals with an experimental investigation of various types of short light-frame shear walls. Finally, the study compares modelling and experimental results to verify that they are in good agreement and that an efficient FE model is able to predict the structural behavior of shear walls for a short computational time. The study optimizes use of beam-spring-shell model which is as reliable as the beam-spring-shell-solid model, emphasizing its advantages over the resource-consuming solid model. The beam-spring-shell model is efficient and can be implemented and used for design and analysis of modular-based timber buildings.