Wagons experience different types of vibrations while moving on the rail, amongst which the
lateral vibration is the most important one. In higher speeds, the lateral vibration causes Hunting,
which is a specific inconstancy. In this article the lateral vibrations were investigated by deriving
nonlinear equations of motion of a high speed passenger wagon while moving in a straight path.
Sources of nonlinearities of the wagon model are wheel profile and creep forces in wheel and rail
contact. The wheel profile has been imported into the equations by using a multi-nonlinear function and in order to extract the mathematical model of wagon, heuristic creep theory was used. In addition, both single and double point wheel-rail contact have been considered in the modeling of wagon. 21 degrees of freedom are used for modeling of the wagon, which are lateral and vertical displacement of each wheelset, the lateral and vertical displacement, roll and yaw angle of each Bogie frame, and the lateral and vertical displacement, roll, pitch and yaw angle of the car body.
The governing equations of motion were solved using MATLAB. Results show the critical speed
of wagon is 83 m/s.
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