Scientific publications without theses

Results: 828
Created on: Thu, 20 Jun 2024 23:10:26 +0200 in 0.0673 sec

Chavez, Jhohan; Böhm, Valter; Becker, Tatiana; Gast, Simon; Zeidis, Igor; Zimmermann, Klaus
Actuators based on a controlled particle-matrix interaction in magnetic hybrid materials for applications in locomotion and manipulation systems. - In: Magnetic hybrid-materials, (2022), S. 653-680

The paper deals with the investigation of magneto-sensitive elastomers (MSE) and their application in technical actuator systems. MSE consist of an elastic matrix containing suspended magnetically soft and/or hard particles. Additionally, they can also contain silicone oil, graphite particles, thermoplastic components, etc., in various concentrations in order to tune specific properties such as viscosity, conductivity and thermoelasticity, respectively. The focuses of investigations are the beneficial properties of MSE in prototypes for locomotion and manipulation purposes that possess an integrated sensor function. The research follows the principle of a model-based design, i.e. the working steps are ideation, mathematical modelling, material characterization as well as building first functional models (prototypes). The developed apedal (without legs) and non-wheeled locomotion systems use the interplay between material deformations and the mechanical motion in connection with the issues of control and stability. Non-linear friction phenomena lead to a monotonous forward motion of the systems. The aim of this study is the design of such mechanical structures, which reduce the control costs. The investigations deal with the movement and control of 'intelligent' mechanisms, for which the magnetically field-controlled particle-matrix interactions provide an appropriate approach. The presented grippers enclose partially gripped objects, which is an advantage for handling sensitive objects. Form-fit grippers with adaptable contour at the contact area enable a uniform pressure distribution on the surface of gripped objects. Furthermore, with the possibility of active shape adaptation, objects with significantly differing geometries can be gripped. To realise the desired active shape adaptation, the effect of field-induced plasticity of MSE is used. The first developed prototypes mainly confirm the functional principles as such without direct application. For this, besides the ability of locomotion and manipulation itself, further technological possibilities have to be added to the systems.

Becker, Tatiana; Raikher, Yuriy L.; Stolbov, Oleg V.; Böhm, Valter; Zimmermann, Klaus
Magnetoactive elastomers for magnetically tunable vibrating sensor systems. - In: Magnetic hybrid-materials, (2022), S. 625-652

Magnetoactive elastomers (MAEs) are a special type of smart materials consisting of an elastic matrix with embedded microsized particles that are made of ferromagnetic materials with high or low coercivity. Due to their composition, such elastomers possess unique magnetic field-dependent material properties. The present paper compiles the results of investigations on MAEs towards an approach of their potential application as vibrating sensor elements with adaptable sensitivity. Starting with the model-based and experimental studies of the free vibrational behavior displayed by cantilevers made of MAEs, it is shown that the first bending eigenfrequency of the cantilevers depends strongly on the strength of an applied uniform magnetic field. The investigations of the forced vibration response of MAE beams subjected to inplane kinematic excitation confirm the possibility of active magnetic control of the amplitude-frequency characteristics. With change of the uniform field strength, the MAE beam reveals different steady-state responses for the same excitation, and the resonance may occur at various ranges of the excitation frequency. Nonlinear dependencies of the amplification ratio on the excitation frequency are obtained for different magnitudes of the applied field. Furthermore, it is shown that the steady-state vibrations of MAE beams can be detected based on the magnetic field distortion. The field difference, which is measured simultaneously on the sides of a vibrating MAE beam, provides a signal with the same frequency as the excitation and an amplitude proportional to the amplitude of resulting vibrations. The presented prototype of the MAE-based vibrating unit with the field-controlled "configuration" can be implemented for realization of acceleration sensor systems with adaptable sensitivity. The ongoing research on MAEs is oriented to the use of other geometrical forms along with beams, e.g. two-dimensional structures such as membranes.

Zentner, Lena; Henning, Stefan; Fröhlich, Thomas
Design of compliant mechanisms based on rigid-body mechanisms. - In: Romanian journal of technical sciences, ISSN 2601-5811, Bd. 67 (2022), 1, S. 61-78

The design of compliant mechanisms is a much more complicated task than their analysis. Consequently, there are many more methods available for the analysis of compliant mechanisms than for their synthesis. In this article, a contribution to the synthesis of compliant mechanisms is made by presenting a comparison of two different methods for their design. In both methods rigid-body systems are used as a basis for compliant mechanisms. Depending on the task of the compliant mechanism, one of these methods can be selected and applied. The deviations between the results of the used theory and measurement results as well as FEM results are less than 5.5 % for displacements and acting forces. Selected mechanisms for the realization of a straight-line motion of a point and for given relative motions are presented as examples.

Wittke, Martin; Wolf, Matthias; Weigert, Florian; Darnieder, Maximilian; Gerlach, Erik; Zimmermann, Klaus; Theska, René
Investigations on a torque-compensating adjustment drive for mechanically sensitive devices. - In: Proceedings of the 22nd International Conference of the European Society for Precision Engineering and Nanotechnology, (2022), S. 81-82

Boeck, Thomas; Sanjari, Seyed Loghman; Becker, Tatiana
Parametric instability of a vertically driven magnetic pendulum with eddy-current braking by a flat plate. - In: Nonlinear dynamics, ISSN 1573-269X, Bd. 109 (2022), 2, S. 509-529

The vertically driven pendulum is one of the classical systems where parametric instability occurs. We study its behavior with an additional electromagnetic interaction caused by eddy currents in a nearby thick conducting plate that are induced when the bob is a magnetic dipole. The known analytical expressions of the induced electromagnetic force and torque acting on the dipole are valid in the quasistatic limit, i.e., when magnetic diffusivity of the plate is sufficiently high to ensure an equilibrium between magnetic field advection and diffusion. The equation of motion of the vertically driven pendulum is derived assuming that its magnetic dipole moment is aligned with the axis of rotation and that the conducting plate is horizontal. The vertical position of the pendulum remains an equilibrium with the electromagnetic interaction. Conditions for instability of this equilibrium are derived analytically by the harmonic balance method for the subharmonic and harmonic resonances in the limit of weak electromagnetic interaction. The analytical stability boundaries agree with the results of numerical Floquet analysis for these conditions but differ substantially when the electromagnetic interaction is strong. The numerical analysis demonstrates that the area of harmonic instability can become doubly connected. Bifurcation diagrams obtained numerically show the co-existence of stable periodic orbits in such conditions. For moderately strong driving, chaotic motions can be maintained for the subharmonic instability.
Behn, Carsten; Will, Christoph; Merker, Lukas; Steigenberger, Joachim
Bending vibration systems which are complementary with respect to eigenvalues. - In: Mechatronics and life sciences, (2022), S. 277-286

In developing prototypes, one fundamental activity is to model appropriate systems which mimic fundamental features of (biological) paradigms. In this way, we set up different models for the investigation of natural frequencies. The aim is to detect object contacts of technical sensors in observing their vibration behavior. For this, we compare the range and the shift of natural frequencies determined from the analysis of the arising two-point boundary-value problems. In particular, we found two systems with complementary spectra of eigenvalues. Considering boundary damping we analyzed these eigenvalues in the first octant of the complex plane. The fundamental result is that these two systems offer no common eigenvalue, they are alternative. This is an interesting and unique observation.

Platl, Vivien; Zentner, Lena
An analytical method for calculating the natural frequencies of spatial compliant mechanisms. - In: Mechanism and machine theory, Bd. 175 (2022), 104939, S. 1-17

Compliant mechanisms are becoming increasingly important in both research and industry. The design and the static analysis of such mechanisms has made much progress in recent years, yet comparatively little research has been done on their dynamic behaviour. The aim of this paper is to advance the dynamic analysis of spatial compliant mechanisms by pursuing the calculation of their natural frequencies. So far, their determination is only possible with time-consuming 3D-FEM simulations or via pseudo-rigid-body models and Lagrangian equations. An analytical method is developed to simplify and accelerate the calculation of the natural frequencies of compliant mechanisms. The method is integrated into an algorithm on which a graphical user interface is developed to allow the design and calculation of the system in the most time efficient and intuitive way. The results are verified by 3D-FEM simulations and validated through an experiment. The evaluation shows good agreement with the reference models. The results of this paper allow a reliable and efficient calculation of natural frequencies and serve to facilitate further work regarding the dynamic analysis of compliant mechanisms.
Harfensteller, Felix; Henning, Stefan; Zentner, Lena; Husung, Stephan
Modeling of corner-filleted flexure hinges under various loads. - In: Mechanism and machine theory, Bd. 175 (2022), 104937, S. 1-11

Compliant mechanisms are widely applied in precision engineering, measurement technology and microtechnology, due to their potential for the reduction of mass and assembly effort through the integration of functions into fewer parts and an increasing motion repeatability through less backlash and wear, if designed appropriately. However, a challenge during the design process is the handling of the multitude of geometric parameters and the complex relations between loads, deformations and strains. Furthermore, some tasks such as the dimensioning by means of optimization or the modeling for a controller design require a high number of analysis calculations. From this arises the need for sufficient computational analysis models with low calculation time. Existing studies of analysis models are mostly based on selected load cases, which may limits their general validity. The scope of this article is the comparison of models for the analysis of corner-filleted flexure hinges under various loads, to determine their advantages, disadvantages and application fields. The underlying methods of the study can further be used to evaluate future models based on a broad selection of possible load cases.
Zimmermann, Martin;
Untersuchung des Feuchtetransportes und dessen Einfluss auf Form- und Eigenspannungsänderungen in Furnieren. - Düren : Shaker Verlag, 2022. - XII, 181 Seiten. - (Berichte aus der Mechanik)
Technische Universität Ilmenau, Dissertation 2021

ISBN 978-3-8440-8523-5

Gegenstand der vorliegenden Arbeit ist, die Untersuchung der Feuchteaufnahme und -weiterleitung in Furnieren, wie sie während der industriellen Verarbeitung vorkommt. Es steht damit die Aufnahme von freiem Wasser einschließlich der damit einhergehenden quellungsbedingten Form- und Eigenspannungsänderungen bei Furnieren im Fokus der Betrachtungen. Hierzu werden, nach Vorstellung ausgewählter Grundlagen aus Forschung und Technik, Konzeption und Realisierung experimenteller Untersuchungen erläutert. Die am Beispiel von Rotbuchenfurnier (Fagus Sylvatica L.) durchgeführten Untersuchungen unterscheiden dabei zwischen Versuchsreihen zur Wasseraufnahme und der damit verbundenen Verformungsentwicklung. Die Randbedingungen der verschiedenen Messreihen berücksichtigen für Holz typische anatomische Eigenschaften (z. B. Faserausrichtung), relevante Befeuchtungsszenarien aus der industriellen Furnierverarbeitung (einseitige, zweiseitige und allseitige Feuchtezufuhr) sowie Einflüsse aus der Furnierherstellung (Unterscheidung rissbehaftete/rissfreie Furniersichtseite). Darüber hinaus ist die mathematische Beschreibung der Feuchtebewegung in Furnieren Gegenstand der Arbeit. So werden auf Basis der Fick’schen Diffusionsgesetze, mit Hilfe der Finite-Elemente-Methode, feuchteabhängige Kennwertverläufe (Transportkoeffizienten) für longitudinalen und radialen Feuchtetransport in Rotbuchenfurnier abgeleitet. Im Ergebnis kann festgehalten werden, dass der Feuchtetransport in Furnier sehr gut mit Hilfe der entwickelten Modelle beschrieben werden kann. Ferner werden, basierend auf den durchgeführten Untersuchungen, ein für Furnier typisches und von Vollholzerzeugnissen abweichendes Verformungsverhalten herausgestellt sowie allgemeine Aussagen zur Formstabilität von Furnieren abgeleitet.

Platl, Vivien; Lechner, Leo; Mattheis, Thomas; Zentner, Lena
Development of a calculation tool for the natural frequencies of planar compliant mechanisms :
Entwicklung eines Berechnungstools für die Eigenfrequenzen von planaren nachgiebigen Mechanismen. - In: Achte IFToMM D-A-CH Konferenz 2022, (2022), insges. 2 S.


... until 2022 from the Technical Mechanics Group

Results: 519
Created on: Thu, 20 Jun 2024 23:10:03 +0200 in 0.0611 sec

Zimmermann, Klaus; Gerlach, Erik
Arbeitsbuch Technische Mechanik
Unicopy Campus Edition. - Ilmenau : Technische Universität, Fakultät für Maschinenbau, Fachgebiet Technische Mechanik, 2020. - iv, 241 Seiten. - (Ilmenauer Editionen)
Schorr, Philipp;
Ein Beitrag zur Entwicklung mobiler Roboter basierend auf multistabilen Tensegrity Strukturen. - Ilmenau : Universitätsverlag Ilmenau, 2020. - 1 Online-Ressource (xviii, 135 Seiten)
Technische Universität Ilmenau, Dissertation 2020

In: Universitätsverlag Ilmenau

In dieser Arbeit wird die Anwendung von Tensegrity Strukturen mit mehreren stabilen Gleichgewichtskonfigurationen zur Realisierung von Lokomotionssystemen in der mobilen Robotik untersucht. Diese Strukturen werden unter dem mechanischen Aspekt modelliert und verschiedene Aktuatorstrategien zur Realisierung eines kontrollierten Wechsels zwischen den unterschiedlichen stabilen Gleichgewichtslagen abgeleitet. Zur experimentellen Verifikation der theoretischen Ansätze wird ein Prototyp einer multistabilen Tensegrity Struktur entwickelt. Die experimentellen Ergebnisse bestätigen die vorteilhaften Eigenschaften multistabiler Tensegrity Strukturen sowie die Möglichkeit von kontrollierten Konfigurationswechseln. Infolge von Erweiterungen des mechanischen Modells unter Berücksichtigung von Umwelteinflüssen wird das Bewegungsverhalten von Tensegrity Strukturen simuliert. In dieser Arbeit wird die Fortbewegung durch die Gleichgewichtslagenwechsel der multistabilen Tensegrity Struktur realisiert. Abhängig von der gewählten Aktuierungsstragie kann eine schreitende Lokomotion, eine kriechende Lokomotion sowie eine springende Lokomotion realisiert werden. Experimente mit dem entwickelten Prototyp bestätigen die zuvor untersuchten Lokomotionsformen. Durch Kombination der verschiedenen Bewegungsmodi resultiert ein multimodales Lokomotionssystem. Dieses Lokomotionssystem erlaubt die Anpassung des Lokomotionsprinzips hinsichtlich der gegebenen Umgebungsbedingungen.
Boeck, Thomas; Sanjari, Seyed Loghman; Becker, Tatiana
Parametric instability of a magnetic pendulum in the presence of a vibrating conducting plate. - In: Nonlinear dynamics, ISSN 1573-269X, Bd. 102 (2020), 4, S. 2039-2056

A pendulum with an attached permanent magnet swinging in the vicinity of a conductor is a typical experiment for the demonstration of electromagnetic braking and Lenz law of induction. When the conductor itself moves, it can transfer energy to the pendulum. An exact analytical model of such an electromagnetic interaction is possible for a flat conducting plate. The eddy currents induced in the plate by a moving magnetic dipole and the resulting force and torque are known analytically in the quasistatic limit, i.e., when the magnetic diffusivity is sufficiently high to ensure an equilibrium of magnetic field advection and diffusion. This allows us to study a simple pendulum with a magnetic dipole moment in the presence of a horizontal plate oscillating in vertical direction. Equilibrium of the pendulum in the vertical position can be realized in three cases considered, i.e., when the magnetic moment is parallel to the rotation axis, or otherwise, its projection onto the plane of motion is either horizontal or vertical. The stability problem is described by a differential equation of Mathieu type with a damping term. Instability is only possible when the vibration amplitude and the distance between plate and magnet satisfy certain constraints related to the simultaneous excitation and damping effects of the plate. The nonlinear motion is studied numerically for the case when the magnetic moment and rotation axis are parallel. Chaotic behavior is found when the eigenfrequency is sufficiently small compared to the excitation frequency. The plate oscillation typically has a stabilizing effect on the inverted pendulum.
Böhm, Valter; Schorr, Philipp; Feldmeier, Tanja; Chavez, Jhohan; Henning, Stefan; Zimmermann, Klaus; Zentner, Lena
An approach to robotic end effectors based on multistable tensegrity structures. - In: New trends in mechanism and machine science, (2020), S. 470-478

In this paper compliant multistable tensegrity structures with discrete variable stiffness are investigated. The different stiffness states result from the different prestress states of these structures corresponding to the equilibrium configurations. Three planar tensegrity mechanisms with two stable equilibrium configurations are considered exemplarily. The overall stiffness of these structures is characterized by investigations with regard to their geometric nonlinear static behavior. Dynamical analyses show the possibility of the change between the equilibrium configurations and enable the derivation of suitable actuation strategies.

Schorr, Philipp; Schale, Florian; Otterbach, Jan Marc; Zentner, Lena; Zimmermann, Klaus; Böhm, Valter
Investigation of a multistable tensegrity robot applied as tilting locomotion system. - In: 2020 IEEE International Conference on Robotics and Automation (ICRA), (2020), S. 2932-2938
Gast, Simon; Zimmermann, Klaus
FEM model of a tactile sensor based on inductance measurements and magnetosensitive elastomer. - In: SMSI 2020, (2020), S. 333-334

Otterbach, Jan Marc;
Ein Beitrag zur Entwicklung eines portablen Systems zur bewegungsinduzierten Wirbelstromprüfung. - Ilmenau : Universitätsverlag Ilmenau, 2020. - 1 Online-Ressource (xxvii, 151 Seiten)
Technische Universität Ilmenau, Dissertation 2019

Die zerstörungsfreie Prüfung ist von besonderer Bedeutung im Lebenszyklus technischer Produkte. Insbesondere bei sicherheitsrelevanten Komponenten in Flugzeugen, Zügen, Pipelines oder Kraftwerken helfen Verfahren der zerstörungsfreien Prüfung, Qualitätsmängel bereits während des Herstellungsprozesses oder in regelmäßigen Wartungskontrollen zu erkennen, ohne deren Funktion zu beeinträchtigen. Heute erfordern steigende Qualitäts- und Sicherheitsanforderungen sowie die Entwicklung neuer Materialien für moderne Leichtbaukonstruktionen immer zuverlässigere Prüfverfahren, um den ordnungsgemäßen Betrieb von Bauteilen und technischen Anlagen zu gewährleisten. Für die Untersuchung von Bauteilen aus metallischen Werkstoffen kommen häufig Wirbelstromprüfverfahren zum Einsatz. Im Gegensatz zu klassischen Induktionsverfahren werden die Wirbelströme bei der bewegungsinduzierten Wirbelstromprüfung durch die Relativbewegung zwischen einer Magnetfeldquelle und einem elektrisch leitfähigen Prüfkörper hervorgerufen. Die dabei auftretenden physikalischen Effekte ermöglichen die Detektion von Fehlern im Prüfkörper. Gegenstand dieser Arbeit ist die Entwicklung eines Prinzips für ein portables System zur bewegungsinduzierten Wirbelstromprüfung, welches für den Einsatz als handgeführtes Prüfgerät zur Untersuchung von Bauteilen an ihrem Einsatzort geeignet ist. Nach einer Einführung in die zerstörungsfreie Prüfung und die in der Industrie am häufigsten eingesetzten Prüfverfahren, werden die bekannten Verfahren der bewegungsinduzierten Wirbelstromprüfung vorgestellt. Basierend auf den Erkenntnissen vorangegangener Studien im Bereich der bewegungsinduzierten Wirbelstromprüfung, erfolgt die Präzisierung der Anforderungen an das zu entwickelnde Sensorsystem und die Diskussion möglicher Lösungsvarianten. Im Rahmen dieser Ideenfindung werden zwei favorisierte Lösungsvarianten beschrieben, für die jeweils ein Messsystem zur experimentellen Validierung entwickelt und aufgebaut wird. Außerdem werden die angewendeten Verfahren der Messdatenauswertung erläutert. Das für den Anwendungszweck besser geeignete Prinzip wird anhand eines Variantenvergleichs ermittelt. Weiterführende Experimente mit dem ausgewählten Sensorsystem dienen dazu, Handlungsempfehlungen für dessen Einsatz als handgeführtes Prüfgerät abzuleiten. Darüber hinaus werden verschiedene Möglichkeiten zur Darstellung und Interpretation von Prüfergebnissen aufgezeigt.
Becker, Tatiana; Stolbov, Oleg V.; Borin, Dmitry Yu.; Zimmermann, Klaus; Raikher, Yuriy L.
Basic magnetic properties of magnetoactive elastomers of mixed content. - In: Smart materials and structures, ISSN 1361-665X, Volume 29 (2020), number 7, 075034, Seite 1-15
Merker, Lukas; Fischer Calderon, Sebastian J.; Scharff, Moritz; Alencastre Miranda, Jorge Hernan; Behn, Carsten
Effects of multi-point contacts during object contour scanning using a biologically-inspired tactile sensor. - In: Sensors, ISSN 1424-8220, Bd. 20 (2020), 7, 2077, insges. 18 S.
Schorr, Philipp; Böhm, Valter; Zentner, Lena; Zimmermann, Klaus
Design of a vibration driven motion system based on a multistable tensegrity structure. - In: Informatics in control, automation and robotics, (2020), S. 302-307