Car body vertical vibration analysis under track medium wave irregularity and the influence factors of ballast bed

A vehicle-track rigid flexible coupling-dynamic model is established. The first five vertical vibration natural frequencies of system are solved. The medium wave track irregularities are taken as the excitation. The car body vertical harmonic response vibration characteristics are analyzed. It could be concluded that the second-order natural frequency is the sensitive response frequency. The car body vertical vibration simulation calculation is analyzed under vertical medium-wave track irregularity with influence factors of ballast bed, including the ballast bed vibration mass, ballast-subgrade linear and nonlinear stiffness. Through a large number of simulation analysis and Da Cheng railway test verification, it is observed that when the ballast bed thickness is between 0.35 m and 0.65 m, the amplitude of car body vertical vibration acceleration is maximum, and the stronger the bed thickness suddenly changes, the greater the acceleration of vibration increases. When the ballast bed thickness is not enough, the car body vertical vibration acceleration increases obviously. The physical correlation between two tests is established for the first time through the correctness of car body vertical acceleration data of track inspection that is verified by ground penetrating radar ballast detection.