Complex Eigenvalue Analysis of Railway Wheel/Rail Squeal: Advanced Study

Complex Eigenvalue Analysis of Railway Wheel/Rail Squeal: Advanced Study

Wheel/rail squeal noise of trains is one of the challenging problems to be solved. Several models such as self-excited instable vibration due to negative damping, flutter instability, hammering effect due to local defects, etc. were proposed, but a successful model for the squeal problem has not been presented until now. In this study, experimental and numerical methods were applied. Squeal noise and acceleration of the rail were measured in a depot when a subway train was running back and forth at a speed of 20, 25 and 30 km/h. Squeal frequencies above 80 dB(A) were 480, 1220, 2200, 4340, 5420, 8860, 9640, and 9960 Hz, which were consistent with natural vibration frequencies of the rail or wheel.  A new numerical approach was presented to investigate the basic mechanism of the wheel/rail squeal noise, using complex eigenvalue analysis by the finite element method. The positive real parts of the eigenvalues reflect self-exciting instable vibration, which is closely related to the occurrence of squeal noise. The effect of parameters such as friction coefficient, wheel/rail contact position, axle load, etc. on the instable vibration was examined. The instability of the vibration system was sensitive to the stiffness of rail support. In lateral creepage, when the adhesion coefficient was less than 0.1, instable vibration modes did not occur. In longitudinal creepage, when the friction coefficient was high enough, instable vibration modes were generated. The predicted unstable modal shapes were different from those in lateral creepage. The longitudinal creepage caused the natural vibrations of the axle.  Numerical predictions could explain many of the field test results.

Author(s) Details

B. C. Goo

Korea Railroad Research Institute, Uiwang, Korea.

J. C. Kim
Korea Railroad Research Institute, Uiwang, Korea.

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