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For analysis of the obtained results, suppose that ratio L/V = 1.3, i.e., criterion (27) is satisfied and derailment is not possible. However, it is seen from the table that for variant (a) neither criteria (30) nor (31) are satisfied and both predict derailment. For variant (b), criterion (30) is not satisfied, or it predicts derailment, and criterion (31) is satisfied, i.e., by this criterion, derailment is not possible. This means that the wheel starts to roll on the contact point A and two-point (O, A) contact passes into one-point contact at A. Then, this contact point slides down the

Thus, it is expedient to estimate possibility of derailment by criterion (30), since it provides both, the wheel flange contact point sliding down the rail lateral surface and impossibility of the wheel rolling on the same point, and ensures less value (more conservative) of the allowable ratio of the lateral and vertical forces L/V than

Prediction and avoiding of derailment are the most important problems of which many scientific works are devoted for their solution but the desirable results are not obtained yet. The survey of the literature and our experience show that the derailment is especially influenced by the friction coefficient that is not predictable, and

It is shown that for prediction of the friction coefficient and providing its stability, it is necessary to provide the contact zone with the continuous and restor-

• A friction factor as well as other tribological properties of interacting surfaces depends on the properties and degree of destruction of the third body.

• The sharp increase of the friction factor in the contact zone of steering surfaces indicates a beginning of the irreversible (progressive) destruction of the third

• For avoidance of derailment, decreasing the wear rate and ensuring sufficient durability of the rails, wheelsets, and brake shoes, a continuous or reversible

determine by the flash of the friction moment or criterion of destruction of the

• A criterion of impossibility of derailment providing additionally impossibility of the wheel rolling on the wheel flange contact point is offered, which ensures

• Destruction of the third body in the laboratory conditions is proposed to

rail lateral surface, the two-point contact restores, and so on, this process is repeated. However, at passing from two-point (O, A) contact into one-point contact at A, the lateral and vertical forces on the steering surfaces increase. Typical for these surfaces, increased relative sliding increases the power and thermal loads in the contact of these surfaces, generating the convenient conditions for destruction of the third body. This results in sharp increase of the cohesion forces, scuffing, and friction coefficient that promotes climbing of the wheel flange on the rail lateral surface. This is confirmed by the numerous laboratory researches carried out by us as well as the trace of the wheel climbing on the railhead lateral surface (Figure 1)

that has a form of scuffing.

Transportation Systems Analysis and Assessment

criteria (31) and (27).

5. Conclusion remarks and future works

able third body of due properties.

third body.

218

in contrast to other parameters, it varies in a wide range.

The main results of the paper can be formed as follows:

body that contributes to the wheel climbing on the rail.

third body must be provided in the contact zone.

George Tumanishvili\*, Tengiz Nadiradze and Giorgi Tumanishvili Institute of Machine Mechanics, Tbilisi, Georgia

\*Address all correspondence to: ge.tumanishvili@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
