Finite Element Analysis of Rail Stresses and Wheel-Rail Displacements under the Effect of Track Stiffness Irregularities and Rolling Wheel Speeds
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Date
2021-03
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Addis Ababa University
Abstract
The world of today has the transportation sector growing and railway transportation system is contending all transportation modes by this time. This fact is because railway transportation system is able to carry a large number of passengers at low cost and reduced time while also being environmental friendly.
Even if the railway is booming, there are things that are still challenging and need more attention, and among those challenge, there is the track irregularities. The irregularities have many causes and in this project the main cause of irregularities is the variation of track stiffness.
Track irregularities including stiffness variation are known to accelerate the track deterioration and to affect the rail vehicle; but a little is known how this effect is correlated with train speeds, under dynamic loading conditions.
This study aims to investigate the combined effect of rail vehicle speeds and track irregularities caused by railway spatial stiffness variation on the wheel and rail stresses, deformations and vertical displacements.
Explicit dynamic finite element analysis using ABAQUS software package is used in this study. The model is composed of a train wheel rotating on a rail across several sleepers, which are fixed at their base. The equivalent average of the sleeper moduli is chosen to resemble the total average track modulus under the rail, in real situation.
The variation of track stiffness in the model is achieved by changing the statistics of the randomly distributed sleeper moduli. It is found that increase in speeds and the longitudinal variation in track stiffness for a given track stiffness mean results in increased amplitude of oscillations of rail deflections, and reduction of a corresponding oscillation frequency, and in increased level of von Mises stresses at much higher level of stiffness variations.
For the deflection of the rail as the speed changes the deflection varies as well. In this project considering the speed variation for example at standard deviation of 60 MPa, at speed of 10, 15, 20 m/s the deflection is 2.208017, 2.271236, and 2.271308 mm respectively.
As the standard deviation is changing also it causes the rail maximum deflection to vary. Taking example at speed of 10 m/s the increase of standard deviation magnitude caused the increase in maximum rail deflection magnitude as for standard deviation of 20, 40, and 60 MPa the deflections are 2.084149, 2.108914, and 2.208017 mm respectively.
For stresses as the model was considered to be perfect plastic the maximum stress was found not to exceed the maximum yield stress which is 475 MPa. To better understand the rail stress behavior, the non-linear plasticity model must be considered.
This study significance is to help railway engineers make better rail maintenance strategies.
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Keywords
track irregularities, sleeper modulus, track stiffness variation, rail deflection, rail stress