992 research outputs found
Modelling of railway curve squeal including effects of wheel rotation
No full textRailway vehicles negotiating tight curves may emit an intense high-pitch noise. The underlying mechanisms of this squeal noise are still a subject of research. Simulation models are complex since they have to consider the non-linear, transient and high-frequency interaction between wheel and rail. Often simplified models are used for wheel and rail to reduce computational effort, which involves the risk of oversimplifications. This paper focuses on the importance to include a rotating wheel instead of a stationary wheel in the simulation models. Two formulations for a rotating wheel are implemented in a previously published wheel/rail interaction model: a realistic model based on an Eulerian modal coordinate approach and a simplified model based on a rotating load and moving Green's functions. The simulation results for different friction coefficients and values of lateral creepage are compared with results obtained for the stationary wheel. Both approaches for the rotating wheel give almost identical results for the rolling speed considered. Furthermore, it can be concluded that a model of a stationary flexible wheel is sufficient to simulate curve squeal
Towards a model for prediction of railway tread brake noise
No full textA model for complex linear stability analysis of railway tread brakes has been developed. It accounts for
inertial effects due to wheel rotation as well as damping provided by tangential wheel–rail contact forces.
Kinematic constraint equations are used to model the normal brake–wheel contact. For a brake–wheel
friction coefficient higher than 0.2, unstable vibrations develop for several system eigenmodes in the
frequency range above 6 kHz. The required level of brake–wheel friction at onset of instability is
influenced by the wheel profile and the tangential wheel–rail contact damping. The present work
constitutes the first step in the development of a prediction model for railway tread brake noise
Astrid Lindgren and the Archives
No full textThe author Astrid Lindgren (1907-2002) is for many Swedes a genuine national icon. On several occasions, when the most popular and influential Swede is to be announced, Astrid Lindgren’s name is always one of the top names. Astrid Lindgren is for the Swedes known not only as a famous author, but also as a person who spoke out on things she found wrong in the Swedish society. In the history of Swedish literature 1945 is usually regarded as a milestone and Astrid Lindgren’s book Pippi Longstocking was published and revolutionised both children’s literature and the attitude to children and their upbringing. Astrid Lindgren also worked as editor-in-chief for the publishing house Rabén & Sjögren from 1946 to 1970 and for almost a quarter of a century she was responsible for the children’s literature while at the same time she was in practise her own editor. Today, ten years after she passed away 94 years old, her remaining papers, letters and manuscripts are kept in different archives where interesting research can be carried out. There is a substantial amount of material from her rich and prolific life and in this article I wish to illustrate how this material can be used to provide a deeper knowledge of Astrid Lindgren as a person and as an editor.</p
Astrid Lindgren : Author and Publishing Editor
No full textI den tryckt boken felaktigt ISBN 978-91-89460-13-3 (print), 978-91-89460-14-0 (pdf)</p
Astrid Lindgren : Author and Publishing Editor
No full textI den tryckt boken felaktigt ISBN 978-91-89460-13-3 (print), 978-91-89460-14-0 (pdf)</p
Astrid Lindgren : Author and Publishing Editor
No full textI den tryckt boken felaktigt ISBN 978-91-89460-13-3 (print), 978-91-89460-14-0 (pdf)</p
Business Model Innovation and the Impact of Globalization
No full textAuthor Astrid LechnerMasterarbeit Universität Linz 201
Astrid Lindgrens tänder
No full textArtikeln visar hur författaren skapar komiska situationer kring tänder och tandvård. Artikeln behandlar också allmänt temat Att gå till tandläkaren inom barnlitteraturen.The article shows how the author creates comical situations around teeth and dental care. The article also generally deals with the theme Going to the dentist, in children's literature.</p
A numerical investigation of curve squeal in the case of constant wheel/rail friction
No full textCurve squeal is commonly attributed to self-excited vibrations of the railway wheel, which arise due to a large lateral creepage of the wheel tyre on the top of the rail during curving. The phenomenon involves stick/slip oscillations in the wheel/rail contact and is therefore strongly dependent on the prevailing friction conditions. The mechanism causing the instability is, however, still a subject of controversial discussion. Most authors introduce the negative slope of the friction characteristic as a source of the instability, while others have found that squeal can also occur in the case of constant friction due to the coupling between normal and tangential dynamics. As a contribution to this discussion, a detailed model for high-frequency wheel/rail interaction during curving is presented in this paper and evaluated in the case of constant friction. The interaction model is formulated in the time domain and includes the coupling between normal and tangential directions. Track and wheel are described as linear systems using pre-calculated impulse response functions that are derived from detailed finite element models. The nonlinear, non-steady state contact model is based on an influence function method for the elastic half-space. Real measured wheel and rail profiles are used. Numerical results from the interaction model confirm that stick/slip oscillations occur also in the case of constant friction. The choice of the lateral creepage, the value of the friction coefficient and the lateral contact position on the wheel tread are seen to have a strong influence on the occurrence and amplitude of the stick/slip oscillations. The results from the interaction model are in good qualitative agreement with previously published findings on curve squeal
Astrid Lindgren oggi. Spunti per una riflessione
No full textThe Author does a study in deep about the charming work of Astrid Lindgren. Her books rapresent a widening of social childhood, and we can find some marks of fantastic mind and unconventional behaviour in them. The Author underlines the actuality of Lindgren’s literature
- …
