Dynamic Analysis of Unstable Vibration of KTX

The acceptance test of Korean TGV imported from France has been performed in Korea. During the test, it was found that lateral vibration of car body was over the acceptable value at the tail of the train at low winter temperature. Many researches have been performed to find the cause of the vibration and its counter-measure. One of the differences between Korean TGV and French TGV is the train set formation. French TGV is operated with 10 car train set formation or two 10 car train set linked by a automatic coupler, whereas Korean TGV has 20 car formation, which are linked by articulate bogies. The purpose of this study is to verify the effects of long train set formation on vehicle dynamics as well as the train stability using vehicle model with 16 cars and 20 cars. Firstly, the reliable vehicle model which shows well the tendencies appeared in the tests with a 16 car train set on the high speed test line is required to find the cause of lateral vibration and its countermeasure. The vehicle model was made for the analysis using multibody dynamic software, VAMPIRE. The analysis results show that the secondary air spring lateral stiffness is the most influential factor to car body lateral vibration. The mode analysis results show that the least damped mode shape is similar to the vibration pattern shown in the tests that the amplitude of the motion increases along the train set and decreases in the tail part. Nonlinear transient analysis shows the similar vibration pattern along the train. The lateral vibration appeared at the speed range between 100km/h and 200km/h and disappeared at low and high speed. The mode analysis result showed that when wheel conicity increased, unstable vibration mode disappeared. And it was verified through a test that when XP55 wheels with higher conicity than GV40 that had been applied to TGV were applied to articulated bogies, lateral vibration of the last trailer car showed stable within the recommended value of acceleration regardless of outside temperature.