This study aims to comprehend the bistable and multi-stable behaviour of flexible straws with the intention of utilising it for future engineering applications. This behaviour is achieved by the multiple inversions of conical frustum shells within the corrugation of a flexible straw. This study examined the effects of various material models, geometry variables and loading methods on the inversion of close-top and open-top conical frustum shells via experiments and FEM simulations. This thesis consists of three main parts, and the second and the third parts are complementary to each other: First, we investigated the effects of applying a uniform vertical load to the upper rim of open-top frustum shells via FEM simulations. A reference model was simulated based on the measurements of an ordinary polypropylene flexible straw specimen, using two material models - linear elastic and elastically perfectly plastic. The effects of the interactions between frusta of the corrugated segment of a flexible straw were also studied by evaluating the difference in responses between an individual frustum and conjugated models of two or three frusta. It was found that by constraining the rotation of its bottom rim, an individual frustum can fairly reproduce the complex bistable behaviour of the shorter frustum within the corrugated part of a flexible straw. Furthermore, detailed parametric studies that focused on the effects of various geometric parameters were conducted and generalised formulas that predicted the critical force were derived. A comparison between the simulated results and the analytical model in predicting progressive inversion was made to distinguish the geometric boundaries that separate the one-off snap-through to the progressive inversion of frustum shells. Next, the behaviour of close-top frustum shells in response to vertical point loading at various locations on the top surface was evaluated. A hyperelastic material was used to fabricate the physical specimens. During the experiments, the corresponding deformed shapes were recorded by 3D scanning in addition to measurements of the displacement and reaction force. We observed a close resemblance between the experimental and FEM simulated results, which validated the FEM models. Two local peaks were observed before the structure was fully inverted into its secondary stable state and the overall critical force of the structure was defined by the higher one of the two. The relationship between their magnitudes and the loading locations was analysed and an optimal loading location which gave the minimum critical force was proposed and verified by additional simulations. Furthermore, generalised formulas in predicting critical force were also acquired based on parametric studies. The optimal loading location was found to be constant in spite of variations in height and thickness. The third part of this thesis discussed the effects of lateral point loading on both close-top and open-top frustum shells at various locations on the side surface and supplemented the second part. It is found that the removal of the top surface could cause the critical force to decrease if a point load was applied laterally. Moreover, we were able to fully invert the structure with a lower critical force through lateral loading in comparison to vertical loading.

This master thesis deals with the estimation of magnet losses in a Permanent Magnet(PM) motor inserted in a nut-runner. This type of machine has interesting featuressuch as being slot-less and running at a very high speed (30000 rpm). An extensiveliterature review was performed in order to investigate the state of the art in estimationof the losses in magnets of a PM machine. Analytical models to calculate the no-loadback-emf and the magnetic ux density in the air-gap due to the currents in the statorare presented rst. Furthermore, several of the analytical models for calculating lossesin magnets described in the literature were tested and adapted to the case of a slotlessmachine with a parallel-magnetized ring. Then, a numerical estimation of thelosses with nite element method (FEM) 2D was carried out. In addition, a detailedinvestigation of the eect of simulation settings (e.g., mesh size, time-step, remanentmagnetic ux density in the magnet, superposition of the losses, etc.) was performed.Finally, calculation of losses with 3D FEM are also included in order to compare thecalculated losses with both analytical and FEM 2D results. The estimation of thelosses includes the variation of these with frequency for a range of frequencies between10 and 100 kHz. / Detta examensarbete handlar om uppskattningen av magnetforluster i en permanentmagnetmotor (PM) inford i en mutterdragare. Denna typ av maskin har intressantafunktioner, som att den ar slot-less och att den kors i en hog hastighet (30000rpm). En omfattande litteraturstudie utfordes for att kunna uppskatta forluster imagneterna pa basta satt. Forst presenteras analytiska modeller for att berakna denelektromotoriska kraften (EMK) och den magnetiska odestatheten i luftgapet somuppkommer pa grund av strommarna i statorn. Dessutom har era av de analytiskamodellerna for berakning av forlusterna som beskrivits i litteraturen testats och anpassatstill en slot-less maskin med en parallelmagnetiserad ring. En numerisk uppskattningav forlusterna har sedan utforts med hjalp av nita elementmetoden (FEM) 2D.Dartill har en detaljerad undersokning genomforts hur olika parameterinstallningarpaverka utfallet. De FEM parametrar som har undersokts har bland annat bestattav berakningsnatets storlek, tidssteg, remanens odestatheten i magneten och om superpositionav forlusterna galler. Till sist har berakningar for forluster med 3D FEMutforts och jamforts med resultaten for bade de analytiska och FEM 2D resultaten.Uppskattning av forluster innefattar variationen av dessa med ett frekvensomrade mellan10 och 100 kHz.

Master’s thesis deals with computational modeling of 3D printing process done by FDM method made from PETG material using finite element method. Research section contains a brief description of 3D printing process modeling possibilities using finite element method and summarizes fundamental mechanical properties of thermoplastics. In practical section there is an evaluation of specimens printed of PETG material tensile tests. Further there is performed a sensitivity analysis of various influences on vertical imperfection of printed part Idler and is done its design modification, which is based on results of this analysis.

This master thesis deals with the design of the internal wing structure of 3D printed flying wing VUT 714. As a part of this work was performed a load calculation, static strenght test, comparative FEM analysis and subsequently topology optimization was performed. The outcome of this master thesis is a rational design of the wing internal structure based on the load calculation and knowledge of effect of this load on the structure.

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.

This thesis is aimed on three-dimensional finite element time domain analysis. Vector finite elements are used for analysis of cavity resonator made from PEC and filled with vacuum. Results are compared with classical “nodal” finite elements and with published literature.