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ISSN 1614-3914
This work considers dampers that do not solely focus on a single strategy but instead combine them. The capabilities of conventional dry friction dampers are expanded by taking into account piecewise defined contact geometries. This leads to friction dampers that change their behavior depending on the amplitude of the oscillations. The vibration damping device in this work, introduces damping at high oscillation amplitudes and takes advantage of absorption at low oscillation amplitudes.
Umfang: X, 155 S.
Preis: 45.00 €
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In dieser Arbeit wird der Reibwert für den trockenen Kontakt zweier gleitender metallischer Körper in Abhängigkeit verschiedener physikalischer Parameter berechnet. Dafür wird ein thermomechanisches Modell entwickelt und für verschiedene Kontaktkonfigurationen unter Berücksichtigung der Oberflächenrauigkeit beider Kontaktkörper ausgewertet. Darüber hinausgehende Untersuchungen zu den Auswirkungen des berechneten Reibwerts im Kontext von reibungserregten Schwingungen schließen sich an.
Within this work, the friction coefficient is calculated for the dry contact of two sliding metallic bodies as a function of various physical parameters. For this purpose, a thermomechanical model is developed and evaluated for different contact configurations considering the surface roughness of both contact bodies. Subsequent investigations on the consequences of the calculated friction coefficient in the context of friction-induced vibrations are carried out.
Supplementary data: Matlab-Code zur Dissertation "Thermomechanischer Kontakt und stochastische Dynamik gleitender Körper mit rauen Oberflächen"
Umfang: VI, 171 S.
Preis: 53.00 €
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Für die dynamische Analyse hydraulischer Ventile wird ein Verfahren basierend auf der singulären Störungsrechnung und dem Mittelwertbildungsverfahren entwickelt. Es erfolgt die Berechnung periodischer Lösungen sowie die Analyse der Stabilität unter dem Einfluss nicht-glatter Phänomene. Basierend auf dieser Analyse werden reduzierte Modelle entwickelt, mit denen eine teils signifikante Rechenzeitersparnis in der Simulation instationärer Bewegungen und in der nichtlinearen Regelung erzielt wird.
A method based on the singular perturbation theory and the averaging method is developed for the dynamic analysis of hydraulic valves. Periodic solutions are calculated and stability is analyzed under the influence of non-smooth phenomena. Based on this analysis, reduced models are developed, which exhibit significantly improved computational time efficiency, both in the simulation of non-stationary motions as well as in nonlinear valve control.
Umfang: VIII, 201 S.
Preis: 53.00 €
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The gas foil bearing (GFB) technology is a key factor for the transition to oil-free rotating machinery. Among numerous advantages, GFBs offer the unique ability to be lubricated with working fluids such as refrigerants. However, the computational analysis of refrigerant-lubricated GFB–rotor systems represents an interdisciplinary problem of enormous complexity. This work pushes forward existing limits of feasibility and establishes a new strategy that enables stability and bifurcation analyses.
Umfang: XXXI, 137 S.
Preis: 54.00 €
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The impact of two non-uniform elastic rods is considered and a recursive method was developed that solves the inverse problem: Find the location-dependent impedance function of the impacting rod that generates a prescribed impact force. The developed method delivers exact solutions in closed-form. Moreover, a condition is derived which states if a physically meaningful solution exists. Finally, the underlying 1D model has been validated experimentally.
Umfang: VIII, 124 S.
Preis: 44.00 €
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Die Beeinflussung reibungsbehafteter Systeme mithilfe überlagerter Schwingungen ist seit vielen Jahren Gegenstand der Forschung. Infolge überlagerter Schwingungen können sich geglättete Reibkennlinien ergeben, so dass die ursprünglich nicht-glatten Eigenschaften trockener Reibung unterdrückt werden. Im Rahmen der vorliegenden Arbeit werden die Ergebnisse der in der Literatur etablierten Modellierung ergänzt und im Hinblick auf nachgiebige Kontakte und experimentelle Ergebnisse erweitert.
The impact of superimposed vibrations on systems with dry friction has been subject of many scientific studies. Using an appropriate vibrational excitation can suppress non-smooth properties and yield smooth friction characteristics. Within the present contribution, several aspects are added to established modelling results from literature. Concerning compliant contacts and experimental investigations, the corresponding results are extended significantly.
Umfang: VII, 167 S.
Preis: €55.00 | £50.00 | $97.00
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Der Einfluss der Fußgeometrie auf die Energieeffizienz beim zweibeinigen Gehen wird untersucht. Es wird eine Methode zur Optimierung der Fußgeometrie für einen zweibeinigen Roboter entwickelt. Grundlage ist ein ebenes Modell mit beliebieger, konvexer Fußgeometrie in Kombination mit einer Regelung auf Basis der hybriden Nulldynamik. Es werden optimale Bewegungen und Fußgeometrien ermittelt. Im Vergleich zu einem Modell mit Punktfüßen ergeben sich Energieeinsparungen von über 80%.
The influence of foot geometry on energy efficiency in bipedal walking is investigated. A method for the optimization of the foot geometry of a bipedal robot is developed. It is based on a planar model with arbitrary convex foot geometry in combination with a hybrid zero dynamics based controller. Optimal gaits and foot geometries are determined. The average energy consumption can be reduced by more than 80% compared to a model with point feet.
Umfang: X, 292 S.
Preis: €55.00 | £50.00 | $97.00
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This work presents an efficient solution procedure for the elastohydrodynamic (EHD) contact problem considering structural dynamics. The contact bodies are modeled using reduced finite element models. Singly diagonal implicit Runge-Kutta (SDIRK) methods are used for adaptive time integration. The structural model is coupled with the nonlinear Reynolds Equation using a monolithic coupling approach. Finally, a reduced order model of the complete nonlinear coupled problem is constructed.
Umfang: XV, 131 S.
Preis: €40.00 | £37.00 | $70.00
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A nonparametric identification method for highly nonlinear systems is presented that is able to reconstruct the underlying nonlinearities without a priori knowledge of the describing nonlinear functions. The approach is based on nonlinear Kalman Filter algorithms using the well-known state augmentation technique that turns the filter into a dual state and parameter estimator, of which an extension towards nonparametric identification is proposed in the present work.
Umfang: XXVIII, 194 S.
Preis: €47.00 | £43.00 | $83.00
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To counter lubricant shortage at a frictional contact (starvation), lubrication liquids, e.g. oils, are actively transported from a distant location towards the undersupplied tribocontact. This is done via small channels or generally via structures cut into a flat surface. In this way one can use capillary force as a cheap and reliable driver of the lubricant flow. Numerical modeling and experiments show that this method can be considered a promising new option to enhance tribocontact operation.
Umfang: XVI, 172 S.
Preis: €45.00 | £41.00 | $79.00
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