@inproceedings{9527, author = {{Hemsel, Tobias}}, booktitle = {{Mechatronik 2005 Innovative Produktentwicklung}}, number = {{Band 2}}, pages = {{1013--1032}}, title = {{{Modellgestützte Analyse piezoelektrischer Transformatoren}}}, volume = {{1892}}, year = {{2005}}, } @inproceedings{9528, author = {{Hemsel, Tobias and Mracek, Maik and Twiefel, Jens and Vasiljev, Piotr and Wallaschek, Jörg}}, booktitle = {{Proceedings of the First International Conference on Ultrasonic Motors and Actuators (IWOUMA)}}, pages = {{32--36}}, title = {{{Linear ultrasonic motors based on coupling of longitudinal vibrations}}}, year = {{2005}}, } @article{9529, abstract = {{In dieser Arbeit wird ein analytisches Berechnungsverfahren vorgestellt, mit dem der gesamte Positions- und Orientierungsraum (ErrorWorkspace) ebener Mechanismen mit spielbehafteten Gelenken kinematisch beschrieben bzw. dargestellt werden kann. Für die Berechnung wird der gesamte Positions- und Orientierungsraum im Kinematischen Bildraum dargestellt, wobei auf besondere Merkmale eingegangen wird. Der ErrorWorkspace, der mit Hilfe des Berechnungsverfahren bestimmt wird, wird an einem Koppelgetriebe, an einem Filmgreifergetriebe und an einem Double-rocker four-bar mechanism mit Kurbelantrieb dargestellt und analysiert. ({\copyright} 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)}}, author = {{Hofmeister, Adolf and Sextro, Walter and Röschel, Otto}}, issn = {{1617-7061}}, journal = {{PAMM}}, number = {{1}}, pages = {{201--202}}, publisher = {{WILEY-VCH Verlag}}, title = {{{Unkontrollierbare Bewegungen ebener Mechanismen mit Gelenkspiel}}}, doi = {{10.1002/pamm.200510078}}, volume = {{5}}, year = {{2005}}, } @inproceedings{9530, author = {{Mracek, Maik and Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{Proceedings of the First International Conference on Ultrasonic Motors and Actuators (IWOUMA)}}, pages = {{23--24}}, title = {{{Parallel Operation of Ultrasonic Linear Motors}}}, year = {{2005}}, } @inproceedings{9531, author = {{Twiefel, Jens and Hemsel, Tobias and Kauczor, Christopher and Wallaschek, Jörg}}, booktitle = {{6th International Workshop on Research and Education in Mechatronics}}, pages = {{356--361}}, title = {{{Teaching Mechatronics to a Mixed Audience from Industry and University}}}, year = {{2005}}, } @inproceedings{8951, author = {{Fu, Bo and Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{Proceedings of the 18th International Congress on Acoustics, ICA}}, pages = {{4--9}}, title = {{{Model-based Diagnosis for Sandwiched Ultrasonic Transducers}}}, year = {{2004}}, } @inproceedings{8952, abstract = {{In turbomachinery, friction contacts are widely used to reduce dynamic stresses in turbine blades in order to avoid expensive damages. As a result of energy dissipation in the friction contacts the blade vibration amplitudes are reduced. In case of so-called friction dampers, which are pressed on the platforms of the blades by centrifugal forces, the damping effect can be optimized by varying the damper mass. This optimization can be done by means of a simulation model applying the so-called component mode synthesis and the Harmonic Balance Method to reduce computation time. It is based on the modal description of each substructure. In a real turbine or compressor blading great differences in the magnitude of the individual blade amplitudes occur caused by unavoidable mistuning of all system parameters like contact parameters and natural frequencies of the blades. It may happen that most of the blades experience only small stresses whereas a few blades experience critical stresses. Therefore, it is necessary to consider mistuning for all system parameters to simulate the forced response of bladed disk assemblies with friction contacts. For a mistuned bladed disk the complete system has to be modeled to calculate the dynamic response. In practice, usually the standard deviations instead of the distributions of the system parameters are known. Therefore, Monte-Carlo simulations are necessary to calculate the forced response of the blades for given mean values and standard deviations of the system parameters. To reduce the computational time, an approximate method has been developed and extended for small and moderate standard deviations of the system parameters to calculate the distribution and the envelopes of the frequency response functions for statistically varying system parameters, in the following called statistical mistuning. The approximate method is based on a sensitivity analysis and the assumption of a Weibull distribution of the vibration amplitudes of the blades. Both, the approximate method and the assumption of a Weibull distribution of the vibration amplitudes are validated by Monte-Carlo simulations. By these investigations the influence of different arrangements of the system parameters for given mean values and standard deviations of the vibration amplitudes of the blades can be determined, too. For the present investigations only a small influence of the arrangement of blades with respect to their natural frequencies has been observed. On the other hand, an intentional mistuning of the damper masses and the natural frequencies of the blades in a systematic way, in the following called systematic mistuning, can be investigated to reduce the amplitudes of the system. The simulation results of a systematic mistuning has been validated by a test rig with a rotating bladed disk assembly with friction dampers. The investigations show a good agreement between the simulations and the measurements but only a slight decrease of the maximum amplitudes in case of a systematic mistuning. Copyright {\copyright} 2004 by ASME}}, author = {{Götting, Florian and Sextro, Walter and Panning, Lars and Popp, Karl}}, booktitle = {{Proceedings of ASME TURBO Expo, Power for Land, Sea, and Air}}, keywords = {{Friction, Disks}}, number = {{GT2004-53310}}, pages = {{257--267}}, title = {{{Systematic mistuning of bladed disk assemblies with friction contacts}}}, volume = {{6}}, year = {{2004}}, } @inproceedings{8953, author = {{Hemsel, Tobias}}, booktitle = {{Proceedings of the First International Conference on Ultrasonic Motors and Actuators (IWOUMA)}}, title = {{{Linear piezoelectric motors and their application}}}, year = {{2004}}, } @inproceedings{9519, abstract = {{Several positioning tasks demand translatory drive instead of rotary motion. To achieve drives that are capable e.g. to drive the sunroof of a car or to lift a car's window, multiple miniaturized motors can be combined. But in this case many other questions arise: the electromechanical behavior of the individual motors differs slightly, the motor characteristics are strongly dependent on the driving parameters and the driven load, many applications need some extra power for special cases like overcoming higher forces periodically. Thus, the bundle of motors has to act well organized and controlled to get an optimized drive that is not oversized and costly.}}, author = {{Hemsel, Tobias and Mracek, Maik and Wallaschek, Jörg and Vasiljev, Piotr}}, booktitle = {{Ultrasonics Symposium, 2004 IEEE}}, issn = {{1051-0117}}, keywords = {{drives, electromechanical effects, linear motors, ultrasonic motors, car sunroof, car window, electromechanical behavior, high power ultrasonic linear motors, multiple miniaturized motors, positioning tasks, translatory drive, Costs, Electromagnetic forces, Frequency, Laboratories, Manufacturing, Mechatronics, Micromotors, Ultrasonic imaging, Vibrations, Voltage}}, number = {{Vol.2}}, pages = {{1161--1164}}, title = {{{A novel approach for high power ultrasonic linear motors}}}, doi = {{10.1109/ULTSYM.2004.1417988}}, volume = {{2}}, year = {{2004}}, } @article{9520, abstract = {{Friction, especially friction of elastomers, can cause acoustic problems like noise, squeal and comfort drawbacks like vibrations and wear. Therefore, rubber friction affects the function of many products in technical applications, e.g. seals, belts and tires. It can be classified according to different physical phenomena like adhesion, hysteresis, cohesion and viscous friction, see [3]. The topic of this paper is hysteresis friction of rubber that is caused by the energy dissipation due to internal material damping during the process of deformation. The deformation itself occurs during the sliding of a rubber element across the micro-scaled asperities of a rough surface. In this paper, the sliding process of a rubber element over real surfaces is simulated in time domain and compared to experiments. ({\^A}{\copyright} 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)}}, author = {{Lindner, Markus and Sextro, Walter and Popp, Karl}}, issn = {{1617-7061}}, journal = {{PAMM}}, number = {{1}}, pages = {{101--102}}, publisher = {{WILEY-VCH Verlag}}, title = {{{Hysteretic Friction of a Sliding Rubber Element}}}, doi = {{10.1002/pamm.200410032}}, volume = {{4}}, year = {{2004}}, } @inproceedings{9521, author = {{Littmann, Walter and Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{Proceedings of the 18th International Congress on Acoustics}}, pages = {{2889--2892}}, title = {{{Design criteria for piezoelectric transformers}}}, volume = {{4}}, year = {{2004}}, } @inproceedings{9522, author = {{Mracek, Maik and Wallaschek, Jörg and Hemsel, Tobias}}, booktitle = {{Proceedings of the 18th International Congress on Acoustics}}, pages = {{417--420}}, title = {{{Self configuration of miniature ultrasonic linear motors}}}, year = {{2004}}, } @inproceedings{9523, abstract = {{During operation, the rotating blades of a gas turbine are subjected to centrifugal forces as well as fluctuating gas forces, resulting in blade vibrations. In addition to material damping, aerodynamical and blade root damping, underplatform dampers are widely used to increase the amount of damping and to decrease blade vibration amplitudes. The friction forces generated by the relative displacements between the underplatform damper and the blade platforms provide a significant amount of energy dissipation. In practice, a number of different underplatform damper designs are applied. Basically, these are wedge dampers with flat contact areas, cylindrical dampers with curved surfaces or asymmetrical dampers with both flat contact surfaces on one side and curved contact surfaces on the other. The latter damper type combines the advantages of both the wedge and the cylindrical damper by preventing the damper from pure rolling on the one hand as it has been observed for cylindrical dampers and on the other hand, avoiding a diverged plane area contact in case of a wedge damper, causing a damper lift-off. This paper will focus on the investigation of cylindrical and asymmetrical underplatform dampers. A comparison between measurements of rotating assemblies in Siemens PG gas turbines (V84.2, V64.3A and V94.3A(2)) under test and real operating conditions with cylindrical and asymmetrical underplatform dampers and the predictions of the developed theoretical model are presented. Special attention is paid to the frequency shift due to the application of an underplatform damper, since in particular for stationary gas turbines, in addition to the amplitude reduction, the accurate prediction of the resonance frequency is of major interest. Copyright {\copyright} 2004 by ASME}}, author = {{Panning, Lars and Popp, Karl and Sextro, Walter and Götting, Florian}}, booktitle = {{Proceedings of ASME TURBO Expo, Power for Land, Sea, and Air}}, keywords = {{Dampers, Gas turbines}}, number = {{GT2004-53316}}, pages = {{269--280}}, title = {{{Asymmetrical Underplatform Dampers in Gas Turbine Bladings: Theory and Application}}}, doi = {{10.1115/GT2004-53316}}, volume = {{6}}, year = {{2004}}, } @inproceedings{9524, author = {{Fu, Bo and Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{Proceedings of the 18th International Congress on Acoustics, ICA}}, pages = {{4--9}}, title = {{{Model-based Diagnosis for Sandwiched Ultrasonic Transducers}}}, year = {{2004}}, } @inproceedings{8933, author = {{Götting, Florian and Sextro, Walter and Panning, Lars and Popp, Karl}}, booktitle = {{Schwingungen in rotierenden Maschinen VI SIRM, Referate der Tagung in Darmstadt}}, editor = {{Irretier , H and Nordmann, R and Springer, H}}, pages = {{201--210}}, publisher = {{Vieweg-Verlag}}, title = {{{Schwingungsverhalten von verstimmten Beschaufelungen mit Reibelementen}}}, year = {{2003}}, } @article{8934, abstract = {{Im Folgenden wird eine Berechnungsmethode vorgestellt, die es erlaubt, das räumliche Schwingungsverhalten eines elastischen Mehrkörpersystems (EMKS) mit Reibkontakten in rechenzeit- und speicherplatzsparender Form zu analysieren. Der von trockener Reibung und Mikroschlupf geprägte, nichtlineare Dämpfungsmechanismus in den Reibkontakten eines EMKS wird dabei realitätsnahe abgebildet. Die Plausibilität der mit der Methode gewonnenen Berechnungsergebnisse wird beispielhaft an einem einfachen EMKS, einem in Längsrichtung geteilten, einseitig eingespannten Balken gezeigt. Für den geteilten Balken werden die Frequenzgänge des Torsionswinkels um die Längsachse und der Auslenkung um die biegeweiche Achse berechnet.}}, author = {{Genzo, Alexander and Sextro, Walter and Popp, Karl}}, issn = {{1617-7061}}, journal = {{PAMM}}, number = {{1}}, pages = {{120--121}}, publisher = {{WILEY-VCH Verlag}}, title = {{{Erzwungene Schwingungen von elastischen Mehrkörpersystemen mit Reibkontakten}}}, doi = {{10.1002/pamm.200310046}}, volume = {{2}}, year = {{2003}}, } @inproceedings{8935, author = {{Hemsel, Tobias and Wallaschek, Jörg}}, booktitle = {{Proceedings of the 5th International Congress of Intelligent Materials (ICIM)}}, title = {{{Modelling and Analysis of Piezoelectric Transformers}}}, year = {{2003}}, } @inproceedings{8936, author = {{Littmann, Walter and Hemsel, Tobias and Kauczor, Christopher and Wallaschek, Jörg and Sinha, W}}, booktitle = {{Proceedings of World Congress Ultrasonics}}, pages = {{547--550}}, title = {{{Load-adaptive phase-controller for resonant driven piezoelectric devices}}}, year = {{2003}}, } @article{8937, abstract = {{Friction damping devices such as underplatform dampers are widely used in turbomachinery applications to reduce blade vibration amplitudes. In this paper, a model is presented briefly to calculate the forced response of mistuned bladed systems with friction dampers. Some results will give an insight in the vibrational behavior of frictionally damped bladed disks and how the damping gain is affected by the damper properties.}}, author = {{Panning, Lars and Sextro, Walter and Popp, Karl}}, issn = {{1617-7061}}, journal = {{PAMM}}, number = {{1}}, pages = {{118--119}}, publisher = {{WILEY-VCH Verlag}}, title = {{{Design of Friction Dampers for Mistuned Bladed Disks}}}, doi = {{10.1002/pamm.200310336}}, volume = {{3}}, year = {{2003}}, } @article{8938, author = {{Panning, Lars and Sextro, Walter and Popp, Karl}}, journal = {{International Journal of Rotating Machinery}}, number = {{3}}, pages = {{219--228}}, publisher = {{Hindawi Publishing Corporation}}, title = {{{Spatial dynamics of tuned and mistuned bladed disks with cylindrical and wedge-shaped friction dampers}}}, volume = {{9}}, year = {{2003}}, }