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On the Critical Speed of Wheel/Rail Systems

Meinke P., Knothe K.

Machine Dynamics Problems

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2009

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Vol. 33, No. 3

56-69

EN

The presentation considers the term "critical speed of wheel/rail-systems". The equations of motion are written down and its solutions are compared with the experimental findings. Great attention is given to stable limit cycles and to nonlinear and linearized behaviour. Finally a more complex vehicle like a steam locomotive is studied for investigation of its critical speed.

2

On the History of Wheel/Rail Contact Mechanics

Knothe K.

Machine Dynamics Problems

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2005

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Vol. 29, No. 4

69-87

EN

Wheel/rail contact is the most important component of railway vehicle dynamics, especially concerning stability analysis and analysis of damages on the treads. History of contact mechanics to the author's belief is integrated part of contact mechanics. Contributions to the theory of contact mechanics which have been developed in the last 150 years are the "shoulders on which we stand". It is generally assumed that normal contact mechanics goes back to Heinrich Hertz, who published his famous paper in 1881 (Hertz, 1881). To most people it is not known that already Ferdinand Redtenbacher at the Polytechnical School of Karlsruhe tried to solve the wheel/rail normal contact problem 27 years earlier (Redtenbacher, 1855). The starting point of his motivation were practical problems on wheel treads. At present real profiles have to be taken into account. In this case numerical solutions are unavoidable. The results are non-elliptical contact patches. Today the most challenging question is to find a reliable explanation for damage phenomena on the rail tread. The most relevant of these damage phenomena is called rolling contact fatigue (RCF). Already in the 19th century fractures of wheel-set axles (and not damages on the wheel or rail tread) have been investigated by Wöhler (1870). Wöhler's results cannot be used to explain damage phenomena on the rail tread. Probably the first one who tried to explain rolling contact fatigue was Johnson (see Johnson, 1962). He used Melan's shake-down theorem which has been proved in 1938 (Melan, 1938) but may also go back to the nineteenth century. For his analysis, though Tresca's yield criterion has been used, no elasto-plastic computation was necessary. At present additional effects are introduced into the shake-down analysis like temperature or material laws for cyclically loaded steel to get more realistic results.

3

Tangential Rolling Contact and Shakedown Limit Past - Present - Future

Böhmer A., Knothe K.

Machine Dynamics Problems

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2004

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Vol. 28, No. 1

17-40

EN

The following paper gives a survey of two topics, which are of interest in rolling contact in railroad dynamics, firstly the creepforce-creep characteristic, which provides an important value in tractive rolling contact, and secondly the shakedown analysis, which is an important tool for the evaluation of bearable contact stresses in repeated dynamical rolling contact.