Sep
26
11:45 AM11:45

Stiff and soft active control of friction by vibrations and their energy efficiency, 59th German Tribology Conference, Göttingen

Presentation at the 59th German Tribology Conference, an event of the German Society of Tribology.

The conference informs about the newest advances in science and technology in the area of tribology. The reduction of friction and wear in manufacturing and in practical applications is an extraordinarily important objective for both industry and research. 

Title:
Stiff and soft active control of friction by vibrations and their energy efficiency

Authors:
J. Benad (1), M. Popov (1,2,3), K. Nakano (4), V. L. Popov (1,2)
1 Technische Universität Berlin, Berlin 10623, Germany
2 National Research Tomsk Polytechnic University, Tomsk 634050, Russia
3 National Research Tomsk State University, Tomsk 634050, Russia
4 Yokohama National University, Yokohama 240-8501, Japan

Abstract:
This work builds upon the results of two recent theoretical studies on the influence of friction by normal and sideways oscillations. The findings are in part rewritten to a more compact and dimensionless form so as to present the results for both oscillation modes side by side in a consistent manner. Thereby, it is shown that for the considered system the macroscopic coefficient of friction is only a function of a dimensionless sliding velocity and a dimensionless oscillation amplitude. Furthermore, the energy efficiency is characterized for both modes for the first time by comparing the total energy needed for a sliding motion which includes the superimposed oscillations with the energy needed for the same sliding motion without the additional oscillations. It is shown that this ratio is also only a function of the two dimensionless system parameters. We consider a simple one-spring model in a displacement-controlled setting. Any system-dynamical feedback is neglected. The lower end of the spring either slides, sticks or jumps on a rigid plane. In the case of normal oscillations, the macroscopic coefficient of friction can be reduced only when the contact point undergoes a stick-slip motion (“stiff control of friction”) whereas with sideways oscillations the macroscopic coefficient of friction can be reduced also when the contact point is continuously sliding (“soft control of friction”). It is found that the motion with superimposed sideways oscillations requires more energy for any combination of system parameters, than the corresponding motion without the oscillations. For the case of normal oscillations however, there are combinations of system parameters for which the motion with the superimposed oscillations requires less, the same, or more energy than for the reference case without the oscillations.

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Sep
17
1:30 PM13:30

Numerical methods for the simulation of deformations and stresses in turbine blade fir-tree connections, International Workshop Science of Wear, Beijing

  • Lee Shau Kee Sci. & Tech Building, Tsinghua University, Beijing (map)
  • Google Calendar ICS

Presentation at the International Workshop Science of Wear held at the Tsinghua University, Beijing, China. The workshop serves to survey the state-of-the-art in the field of wear research and to map out likely developments in the near future.

Title:
Numerical methods for the simulation of deformations and stresses in turbine blade fir-tree connections

Abstract:
The rotating components in a gas turbine are a challenge for both design and manufacturing. Especially turbine blades lead the way in terms of future technology. Improvements of these components may result in a lower weight, an increased turbine performance, a longer life, and lower operating costs. For aero engines, such improvements have a positive impact on the entire aircraft. Among the most critical parts of the turbine are the fir-tree connections of turbine blade and turbine disk. The loads in these connections strongly influence the living of blade and disk. In this work, different numerical methods for the simulation of deformations and stresses in turbine blade fir-tree connections are examined. The main focus is on the Method of Dimensionality Reduction (MDR), the Boundary Element Method (BEM) and the Finite Element Method (FEM). Generally, fir-tree connections require a computationally expensive finite element setup. Their complex geometry exceeds the limitations of the faster numerical techniques which are used with great success within the framework of the half-space approximation. Ways to extend the range of application of the MDR and the BEM to the particular problem of the highly undulating surfaces of the fir-tree connection will be shown and discussed.

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May
9
11:20 AM11:20

The influence of sideways oscillations on friction, 2nd YTRS, Berlin

  • Technische Universität Berlin, H 1035 (map)
  • Google Calendar ICS

Presentation at the 2nd Young Tribological Researcher Symposium (YTRS) at the Technical University of Berlin.

Title:
The influence of sideways oscillations on friction

Authors:
J. Benad (1), K. Nakano (2), V. L. Popov (1,3), M. Popov (1,3,4)

1 Technische Universität Berlin, 10623 Berlin, Germany
2 Yokohama National University, Yokohama 240-8501, Japan
3 National Research Tomsk Polytechnic University, 634050 Tomsk, Russia
4 National Research Tomsk State University, Tomsk 634050, Russia

Abstract: 
This study is devoted to a theoretical analysis of sliding friction under the influence of in- plane oscillations perpendicular to the sliding direction. Contrary to previous studies of this mode of active control of friction, we consider the influence of the stiffness of the tribological contact in detail and show that the contact stiffness plays a central role for small oscillation amplitudes. We consider the case of a displacement-controlled system, where the contact stiffness is small compared to the stiffness of the measuring system. It is shown that in this case the macroscopic coefficient of friction is a function of two dimensionless parameters – a dimensionless sliding velocity and dimensionless oscillation amplitude. In the limit of very large oscillation amplitudes, known solutions previously reported in the literature are reproduced. The region of small amplitudes is described for the first time.

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Oct
20
4:15 PM16:15

Presentation of the Flying V at the Aerodays 2015 in London

Short presentation of the Flying V aircraft configuration as part of a student competition at the Aerodays 2015.

The Aerodays are the European flagship event in aviation research and innovation and take place once, during each EU Research Framework Programme.

Title:

The Flying V - A new aircraft configuration for commercial passenger transport

Abstract:

In this work an idea on how to efficiently use the volume inside a pure flying wing for commercial passenger transport was derived and a configuration proposal was made with this idea. This configuration was then compared with a reference aircraft.

The idea is to arrange two cylindrical pressurized sections for the payload swept back in the shape of a V and place them inside the front section of a wing with the same sweep angle.

The streamwise cut through the oblique pressurized section is flat and elliptical and thus, it fits efficiently into conventional airfoils. The cut of the pressurized section orthogonal to the leading edge however, is circular. This leads to an efficient structural solution as pressure can be preserved well in a cylindrical shape.

The proposed configuration is called the Flying V. For this configuration transition and outer wings extend the span of the highly swept middle wing at a lower sweep angle to 65m. The Flying V was designed in this work with a capacity of 315 passengers in a two class layout for a cruise speed of Ma=0.85.

The Airbus A350-900 has the same capacity and cruise speed and was chosen as a reference aircraft. Preliminary estimations made in this work indicate that the Flying V might have a benefit over the reference in terms of aerodynamics (10% higher L/D) and mass (2% lower empty weight). More qualitative arguments in favor of the Flying V which could be derived are the compactness and simplicity of the configuration (less parts, no high-lift devices, no fairings, straight lines) and the shielding of the engines from the ground (low noise). Remarkable is also the elliptical lift distribution of the naturally stable design using only a moderate wing twist and no reflexed camber lines. A radio controlled model of the Flying V will be presented in this work to demonstrate these aerodynamic characteristics and support the estimations and simulations which were made.

So far, the Flying V is an idea and everything which is presented in this work can be regarded as the first step of a long iteration which will be necessary to develop the concept further.

More information:

Read more about the Flying V aircraft configuration on this website.

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Sep
23
2:15 PM14:15

Presentation of the Flying V at the German Aerospace Congress 2015 in Rostock

  • Stadthalle Rostock, Saal 2 (A) L2 0094 (map)
  • Google Calendar ICS

Presentation of the Flying V aircraft configuration at the German Aerospace Congress 2015, an event of the German Society for Aeronautics and Astronautics (DGLR).

Title:

The Flying V - A new aircraft configuration for commercial passenger transport

Abstract:

In this work an idea on how to efficiently use the volume inside a pure flying wing for commercial passenger transport was derived and a configuration proposal was made with this idea. This configuration was then compared with a reference aircraft.

The idea is to arrange two cylindrical pressurized sections for the payload swept back in the shape of a V and place them inside the front section of a wing with the same sweep angle.

The streamwise cut through the oblique pressurized section is flat and elliptical and thus, it fits efficiently into conventional airfoils. The cut of the pressurized section orthogonal to the leading edge however, is circular. This leads to an efficient structural solution as pressure can be preserved well in a cylindrical shape.

The proposed configuration is called the Flying V. For this configuration transition and outer wings extend the span of the highly swept middle wing at a lower sweep angle to 65m. The Flying V was designed in this work with a capacity of 315 passengers in a two class layout for a cruise speed of Ma=0.85.

The Airbus A350-900 has the same capacity and cruise speed and was chosen as a reference aircraft. Preliminary estimations made in this work indicate that the Flying V might have a benefit over the reference in terms of aerodynamics (10% higher L/D) and mass (2% lower empty weight). More qualitative arguments in favor of the Flying V which could be derived are the compactness and simplicity of the configuration (less parts, no high-lift devices, no fairings, straight lines) and the shielding of the engines from the ground (low noise). Remarkable is also the elliptical lift distribution of the naturally stable design using only a moderate wing twist and no reflexed camber lines. A radio controlled model of the Flying V will be presented in this work to demonstrate these aerodynamic characteristics and support the estimations and simulations which were made.

So far, the Flying V is an idea and everything which is presented in this work can be regarded as the first step of a long iteration which will be necessary to develop the concept further.

More information:

Read more about the Flying V aircraft configuration on this website.

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Feb
4
4:00 PM16:00

Presentation of the Flying V at the Seminar of Mechanics at the Technical University of Berlin

  • Technical University Berlin, M123, S. f. Mechanik (map)
  • Google Calendar ICS

First public presentation of the Flying V aircraft configuration.

Title:

The Flying V - An entirely new aircraft configuration - First public presentation

Abstract:

Outwardly, commercial passenger aircraft have changed little since the 1960s. The conventional configuration made up of wing, fuselage and tail assembly is the state of the art.

Recent preliminary calculations show, that a new configuration called the Flying V might have a potential benefit over the conventional configuration in terms of mass and aerodynamic efficiency.

This unconventional configuration will be introduced in the talk. Also, the first successful flights of a demonstrator model will be shown.

More information:

Watch a the trailer for the presentation here.
See the University's announcement here.
Read more about the Flying V aircraft configuration on this website.

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