Simon Keller

M.Sc. Simon Keller

  • Postanschrift:
    Karlsruher Institut für Technologie
    Institut für Technische Mechanik
    Teilinstitut Dynamik/Mechatronik
    Postfach 6980
    76049 Karlsruhe

    Haus- und Lieferanschrift:
    KIT-Campus Süd
    Institut für Technische Mechanik
    Teilinstitut Dynamik/Mechatronik
    Geb. 10.23, 2.OG
    Kaiserstraße 10
    76131 Karlsruhe

Dynamics of Systems with Multiple Friction Contacts

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Two-Masses-Oscillator on a moving belt
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Effective Friction Characteristic for Longitudinal Excitation
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Stability Map
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Revolutional Joint with Axial Excitation

Quenching friction-induced oscillations by the use of high-frequency excitation

Dry friction is present in many technical systems and is the reason for a variety of undesired phenomena. The property of non-smoothness and a negative slope at low relative velocities of the friction force may cause friction induced oscillations or stick-slip motion. One attempt to quench these oscillations are superposed high-frequency vibrations. Thus, the effective friction characteristic is smoothed and undesired friction induced oscillations can be quenched. For systems with one degree of freedom, this method is investigated by simulations and experiments, which show good accordance. Systems with multiple degrees of freedom and multiple friction contacts however show a largely richer dynamic behavior. Also, the influence of high-frequency excitation is not investigated yet. To improve the comprehension of such systems, numerical and analytical approaches are inquired. Applied procedures are the excitation of single masses and investigating the effect on the whole system. Furthermore, the influence of the direction of the excitation and the importance of which masses are excited is examined.

 

Superposed oscillations in revolutional joints with dry friction

Along with roller bearings, plain bearings are the type of bearings that are used most in technical systems. By the use of different lubricants and pairing materials, the bearings can be adapted to many different requirements. When lubricants are not deployable because of environmental restrictions, dry bearings have to be used. In such systems, undesired effects like stick-slip-motion or break-away can occur due to dry friction. Especially in positioning facilities, where small tolerances and high precision are required, this can be problematic. There are several approaches to compensate effects caused by dry friction and research still goes on. Especially in control technology, many sophisticated concepts are developed to obtain the desired system dynamics.

Another approach to influence the dynamical behavior of the system is the superposition of high-frequency oscillations. These vibrations can be in plane of the contact surface or normal to it. In-plane oscillations can be divided into transversal and longitudinal motion. The superposed oscillations have a smoothing effect on the system dynamics, which can yield a damping effect that can even suppress friction-induced oscillations. This topic has been subject of research in recent years and many papers were published, where theoretical and experimental results are discussed.

To contribute to the understanding and application of this effect, a novel revolution joint with dry friction and axial excitation is built and investigated. A bolt is clamped between two piezo-actuators, who excite continuum vibrations in axial direction. In the middle of the bolt, there is a plain bearing with a leverage, which can rotate about the bolt. Due to the axial motion of the bolt, there is permanent sliding at the contact area of the plain bearing and no such effects like stick-slip-motion or break-away occur. Additionally, the mean friction torque is reduced. Due to the heat generation of the piezos and the sliding friction contact, the temperature increases, which again influences the mechanical properties of the system.

To investigate the system dynamics, a discretized model is built and the equations of motion are derived and solved to identify characteristic parameters. To consider thermal effects and their influence on the dynamics, the heat equation for the cross section of the plain bearing is formulated and solved.

Contact: Prof. A. Fidlin, S. Keller

Publikationsliste


Thermo-mechanische Betrachtung eines Drehgelenks mit trockener Reibung unter axialer Anregung
Keller, S.; Seemann, W.
2022. I. D-A-CH (Hrsg.), Achte IFToMM D-A-CH Konferenz 2022: 24./25. Februar 2022, Online-Konferenz, Universität Duisburg-Essen. doi:10.17185/duepublico/75424
Quenching friction‐induced oscillations in multibody‐systems by the use of high‐frequency excitation
Keller, S.; Seemann, W.
2021. Proceedings in applied mathematics and mechanics, 20 (1), Art.-Nr.: e202000185. doi:10.1002/pamm.202000185

Betreute Lehrveranstaltungen

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