THE LOAD CHARACTERISTICS OF THE BOGIEFRAME OF HIGH-SPEED EMUS

The bogieframe of the bogie of a high-speed electric multi-unit (EMU) carries not only forces from the primary and secondary suspensions, but also loads caused by the vibrations of the components of the vehicle. The components include the motors, gear boxes, traction devices, brake equipment and so on. Consequently, the structural strength of the bogieframe is important to the operation safety and reliability of the high-speed EMU. However, there are few studies related to the load characteristics of the bogieframe of EMUs. The decoupling and dimension reduction method for load identification is presented. The identification loads of the bogieframe include the axlebox spring force, lateral force of the trailing arm knot, motor vertical and lateral forces, gearbox force and anti-roll bar force. The bogieframe of a Chinese standard high-speed EMU was manufactured and calibrated for the force measurement. All forces were measured in a field experiment on a high-speed railway in China. The measured peak speed of the high-speed EMU was 368 km/h. After dealing with the sampled data, the time history of the forces was obtained. The dynamic characteristics of the forces were analyzed in the time and the frequency domains. The rain flow count method was implemented to count the loads. The maximum loads and load spectra were presented with different operation speeds of the train. The equivalent loads of the measured forces of the bogieframe for two-million-time fatigue tests were presented according to the load spectrum and the service life of the high-speed train. The results show that the operation speed of the train and track excitations had a great effect on the axlebox spring forces, trailing arm knot forces, motor forces and gearbox forces. The operation speed of the train and curve radius of the track had great influences on the forces of the anti-roll bar devices. Large impact loads of the bogieframe occurred because of the field welding joints of the rails. The frequency of the impact loads of the axlebox springs ranged from 49 Hz to 51 Hz. The maximum dynamic load factor of the axlebox force was 0.23. When the train operated on the main section of the railway, the maximum vertical and roll load coefficients of the bogieframe were 0.14 and 0.1, respectively. The peak loads of the motor and gearbox were close to the dynamic values presented by JIS E4028. The amplitude ratio is helpful to reveal the changing characteristics of the amplitude in the frequency domain. The investigation is useful to disclose the dynamic characteristics of the loads and to study the structural damages and fatigue test of the bogieframes of high-speed EMUs.