A Finite Element Study On Wheel/Rail Curve Squeal

With the development of high-speed railway and urban transit, the epoch of rail-industry is coming. But at the same time, the problems of operation quality degradation, track quality deterioration and noise increase arise little by little. Especially, wheel/rail noise seriously affects passengers and residents. So, it is significant to decrease or eliminate wheel/rail noise for developing high speed railway transportation.Research on curve squeal mechanisms available to decrease or eliminate curve squeal noise is an active subject for researchers and engineers. In the literature, the technology and method for the study of railway curve squeal is very limited. In the thesis, Chen's method is applied to study curve squeal. The friction motion stability of wheel/rail system were modeled and analyzed using the finite element method. The method and technology for analyzing curve squeal of a wheel/rail system was developed. This is helpful to enhance the understanding of curve squeal.In the thesis, a finite element solid model of the wheel/rail system with rail support springs is established. When a vehicle negotiates a tight curve track, the lateral creep force of the leading wheelset becomes generally saturated, that is, equal to the normal force multiplied by the friction coefficient. The motion equations of the wheel/rail system are established by friction coupling between the wheel and rail. The complex eigenvalues of the motion equations are obtained by solving their characteristic equations. If the real part of an eigenvalue is positive, the corresponding mode is unstable, which may result in squeal. The analysis result shows that when the coefficient of friction between wheel and rail is high, there are positive real parts of eigenvalues. This shows that in the case, there is a propensity of occurrence of curve squeal. In this thesis, the influences of the friction coefficient, stiffness of the rail support spring and load on wheel/rail system are also discussed. Based on the numerical simulation result, the following conclusions can be drawn:(1) Curve squeal when a train negotiates a tight curve is predicted using the finite element software ABAQUS. The simulation result is consistent with the test result in frequency range. So, this method can be used to predict wheel/rail curve squeal.(2) The coefficient of friction has a heavy influence on occurrence of wheel/rail curve squeal. With friction coefficient increasing, the real part values of the complex eigenvalues of coupling modes increase and more modes with positive real parts arise. That shows that the propensity of squeal occurrence will increase.(3) When curve squeal occurs, the modes of the wheel/rail system are characterized by mode coupling. Namely, some neighboring modes with close frequencies may merge with an increase of friction coefficient. In the merging points, the real parts of the corresponding complex eigenvalues are positive. In the case, the wheel/rail system has a propensity of squeal occurrence.(4) The track structural parameters have a distinct influence on occurrence of curve squeal. It is found that a stiffer or a softer stiffness of the rail support spring is not suitable for decreasing or suppressing wheel-rail curve squeal. An appropriate wheel/rail stiffness can be good for suppress or elimination of wheel/rail curve squeal.(5) The axle load has less influence on occurrence of wheel/rail curve squeal. The simulation results show that there small differences between the positive real parts of complex eigenvalues for different axle loads .