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ISSN 1614-3914
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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Ein Ansatz zur Reproduktion reibungserregter Schwingungen in Schaltgetrieben im hörbaren Frequenzbereich wird präsentiert. Im Vordergrund stehen Folgelasten, die aus den Kontaktreaktionen in der Verzahnung und Reibung zwischen den Kupplungsscheiben resultieren. Zunächst wird ein MKS-Modell mit wenigen Freiheitsgraden vorgestellt, welches sukzessive erweitert wird. Neben der Stabilitätsuntersuchung des stationären Verhaltens werden dynamische Lösungen präsentiert und analysiert.
An approach for the reproduction of friction induced vibrations in shift gearboxes in audible frequency range is presented. The research's core is given by follower forces, which arise out of the sliding clutch and gear contact. Firstly, a multi-body dynamic system with few degrees of freedom is presented, which is extended step-by-step. Besides the pure analysis of the stationary solution's stability, dynamic solutions are presented and discussed.
Umfang: IX, 189 S.
Preis: €52.00 | £48.00 | $91.00
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Basierend auf einem Formalismus zur Simulation von mechanischen Starrkörpersystemen mit flächigen Reibkontakten wird eine Erweiterung auf Systeme mit Rollkontakten vorgenommen. Dabei wird der Fokus insbesondere auf die tangentiale Nachgiebigkeiten im Kontakt gelegt. Ein mathematischer Beweis der Konvergenz der Lösung der tangential elastischen Formulierung gegen die der starren wird dargelegt.
Based on a formalism to simulate mechanical rigid body systems with plane frictional contacts, an extension to systems with rolling contacts is proposed. A special focus is put on tagential contact compliance. A mathematical convergency proof of the solution of the tangential elastic formulation to the rigid one is proposed.
Umfang: XVIII, 216 S.
Preis: €57.00 | £52.00 | $100.00
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This work has studied the crosswind stability of vehicles under nonstationary wind excitation in various scenarios. Railway vehicles running on curved and straight track with varying vehicle speed are studied. Road vehicles are classified into different categories. For each vehicle class, a corresponding worst-case vehicle model has been built. As the wind excitation on the vehicle is a stochastic process, a risk analysis has to be carried out and failure probabilities are computed and analyzed.
Umfang: XXI, 178 S.
Preis: €43.00 | £40.00 | $76.00
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