Updated Approaches to Criteria of Assessment of Dynamics in Wheel–Rail Contact Area

According to the Transport Strategy of the Russian Federation, unprecedented volumes of transportation along BAM and Trans-Siberian Mainline are planned thanks to an increase in train weight standards, traffic speed along the sections, efficiency of traction capacity of diesel locomotives. Similar tasks were already set in the 1970s. Their solution was complicated by insufficient experience (in light of the present state of knowledge) in development and use of frame support and combined traction drives on cargo diesel locomotives, and the lack of an objective idea of operating conditions in which the designed diesel locomotives would have to work. In this regard, the design of wheel-motor units (WMU) of diesel locomotive bogies with axial-supported suspension of traction drives was carried out based on generalised results of empirical studies of the dynamics of various types and series of locomotives.

The objective of the work is to develop a model of mathematical analysis and an algorithm for calculating the categories of dynamic forces and the speed of interaction of wheels of a cargo diesel locomotive in contact with rails at the design stage of development of traction drives to ensure their high technical and economic performance indicators under operating conditions.

Long-term monitoring of dependability of diesel locomotives on the Eastern section of BAM has allowed to identify system failures of the equipment of the locomotive’s underframe, which confirm the bias of the calculated design solutions for traction drives of diesel locomotives of modern TE25A, 2TE25KM and 3TE25K2M series, created in 21st century. System failures of WMU equipment of modern series (TE25KM) are a consequence of direct «mechanistic» borrowing of unsuccessful design solutions of universal diesel locomotive underframes (TE10 and TE116).

The article proposes a clarification of theoretical provisions for modelling qualitative criteria for dynamics in the contact areas of wheels with rails of traction drives of diesel locomotives at the design stage. The mechanism of interaction «wheel – rail» is supported by the mathematical theory of cycloid, a circle motion. The algorithm for estimating forces in the contact areas of wheels with rails is built on the theorems of classical theoretical mechanics of non-free movement of a wheelset and the laws of dynamics as an unchangeable holonomic system.

Clarifications were obtained for kinematics characteristics (angular velocity, angular acceleration); real centres of speed and acceleration of wheels; moments of inertia of rotating unsprung mass of wheel-motor units with axial-supported suspension of traction drives. The new approach makes it possible to quantify the criteria for dynamics in wheel-rail contact areas at the design stage, which were previously not amenable to calculation.

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