Center for Railway Engineering

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Browsing Center for Railway Engineering by Subject "(lateral and vertical) Track irregularity"

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    The Effect of Track Irregularities on Wheel-Rail Contact Relationship
    (Addis Ababa University, 2016-06) Tadios, Sisay; Mequanent, Mulugeta (Mr.)
    Track irregularity is an inevitable problem in any rail network and it is the source of track deterioration and degradation. This becomes evident in railway projects spanning cities. Hence, the effect of track irregularities on wheel-rail contact relationship is studied with the aim to solve the contact geometry and contact pressure problems induced by these track irregularities. In this regard, independent analysis and parametrization of the rail head surface geometry and the wheel thread geometry is conducted first and the wheel and rail contact point is determined, with the help of the predefined simplified coordinate system. After the identification of the wheel-rail contact point, mathematically, Hertzian contact theory is applied to calculate the contact area. Accordingly, for an applied normal wheel load of 125kN, the contact area was found to be 118.3 mm2. Finite element models were also used to simulate the lateral and vertical irregularities, with the help of computer software, ABAQUS. Eight finite element models were analyzed for the study: four for lateral irregularity, three for vertical irregularity, and one model for the tracks without irregularity. When lateral irregularity is applied on the model the contact pressure on the rail was found to be increasing as compared to the model simulating tracks without irregularity, with a maximum increment of 33.34% for +30mm lateral irregularity. However, contact area and normal contact force induced on the rail decreases by 15.47%, for -8mm and +10mm lateral irregularity, and 15.17%, for +20mm lateral irregularity, respectively. Similarly, for the applied +30mm vertical irregularity the contact pressure increases by 54.14%, however for +10mm vertical irregularity the contact pressure decreases by 9.15%. Moreover, the +30mm vertical irregularity gives the maximum contact area with a magnitude of 67.66 mm2.