The dynamic behavior of HEMU-430X, the Korean next -generat ion high-speed
train, was invest igated through numerical analysis and an on -t rack test . Before
the on-t rack test , VAMPIRE analysis resul ts showed that HEMU-430X was
expected to sway st rongly at the tai l end because of the yaw damper posi t ion.
Some countermeasures such as changing the wheel profi le, damping coeff icient
of the 2nd lateral damper, and damping coeff icient of the yaw damper were taken
into account to solve this problem. By changing the yaw damper posi ton, the
hunt ing mot ion was expected to disappear effect ively. In the on -track test , the
dynamic behavior of HEMU-430X was assessed according to the EN 14363
standard by measuring the carbody, bogie, and axle accelerat ions, and i t sat isf ied
the safety cri teria. From the viewpoint of the running characterist ics, the RMS
value of the carbody lateral accelerat ion occasional ly exceeded the cri teria;
however, this was related to the ride qual i ty and not the safety assessment . Thehunt ing mot ion appeared at speeds of 150, 350, and 387 km/h, and
countermeasures such as the changing the yaw damper posi t ion, instal l ing
carbody to carbody dampers, and increasing the damping coeff icient of th e MC
car yaw damper, respect ively, were taken to reduce these vibrat ions; then, a
highest test speed of 421.4 km/h was achieved. Subsequent ly, the cr i t ical speed
tended to decrease wi th mi leage; this was at t ributed to carbody hunt ing. To
suppress this carbody hunt ing, the relat ion between the cri t ical speed and the
yaw damper proper ty was invest igated in detai l . Carbody hunt ing was at t ributed
to excessive lateral damping ar ising f rom improper design of the yaw damper
instal l angle. To solve this problem, the removal of some yaw dampers was
examined in an on-track test and found to be somewhat effect ive. The revised
design was proposed based on numer ical analysis, and i t wi l l be verified in an
on-track test . Final ly, the parameters of suspension were opt imize d to improve
cri t ical speed.
