Mechanical Design

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Browsing Mechanical Design by Author "Addisu, Negash"

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    Analysis of Wheel/Rail Contact Geometry and Applied Load Conditions on the Rail Head Surface
    (Addis Ababa University, 2012-10) Addisu, Negash; Daniel, Tilahun (PhD)
    Now a day the railway transport infrastructure in Ethiopia is the major issues in relation to the development of the country. To strengthen this infrastructure, related researches must be conducted at the beginning of the construction of the sector. This paper which mainly concerned about the analysis of wheel/rail contact is done to predict and minimize failures caused by improper wheel/rail contact. The objective of this research is to determine the optimum wheel/rail contact and to identify the position of contact, which is basic to justify the way of load distribution on the contacting interface. In this paper the analysis of wheel/rail contact is based on the X, Y, and Z coordinate systems. With the help of these coordinates the type and place of contact on the wheel/rail interface and the way of stress distribution on the rail head surface is identified. Throughout the whole wheel/rail contact analysis, the Hertz contact theory assumptions are basically considered. Therefore based on Hertz contact theory and analytical results (mathematical models developed), the type of contact between wheel and rail is identified as point contact. The positions of the contact point is on the center of rail head where the rail lateral surface parameter ��2��=0 and varies across the wheel lateral surface depending on the position and arrangement of the wheelset. During the analysis of wheel/rail contact the parameters considered are axle load, wheel and rail profiles. By using these parameters the maximum pressure applied throughout the contact point is calculated to be 794.9 MPa. From MATLAB (7.6) and ANSYS (13) simulation results the main failure causes due to maximum pressure applied are principal and shear stresses having their own direction of application on the rail head surface under axle load applied. The shape of the contact patch on the rail head surface is elliptical. The shape identified is practically matched with the assumptions taken from Hertz contact theory. However the size of elliptical patch depends on the size of load applied. The stress distribution throughout the area of contact patch and the neighboring surfaces depends also on the size and direction of applied load.