Determination of mapping relation between wheel flat and wheel/rail contact force for railway freight wagon using dynamic simulation

In order to comprehensively consider the dynamic behavior of vehicle system and the contact forces between wheel and rail, the vehicle-track coupling model is established considering the flexible wheelset and rail modal characteristics. Guyan reduction theory is introduced to reduce the degrees of freedom of wheelset and rail and to improve the calculation speed. Due to small axle load variation of freight wagon operating on the special line for the coal transportation, the vehicles with different speeds and wheel flat lengths, whether in empty or loaded conditions, are simulated and then the mapping relations between the flat lengths and wheel/rail impact force are obtained. Subsequently, the fitting functions for the empty and loaded vehicles are fitted to quantitatively detect the wheel flat by trackside equipment. The results indicate that the fitting function of empty vehicle has a better effect on predicting the flat length within 6% error since wheel/rail contact force of empty vehicle induced by wheel flat increases with the increase of flat length, while that of loaded vehicle presents a parabola variation trend at low speed and increasing trend at higher speed.

Estimation of Wheelset Natural Vibration Characteristics Based on Transfer Matrix Method with Various Elastic Beam Models

The elastic vibration of the wheelset is a potential factor inducing wheel-rail defects. It is important to understand the natural vibration characteristics of the flexible wheelset for slowing down the defect growth. To estimate the elastic free vibration of the railway wheelset with the multidiameter axle, the transfer matrix method (TMM) is applied. The transfer matrices of four types of elastic beam models are derived including the Euler–Bernoulli beam, Timoshenko beam, elastic beam without mass and shearing stiffness, and massless elastic beam with shearing stiffness. For each type, the simplified model and detailed models of the flexible wheelset are developed. Both bending and torsional modes are compared with that of the finite element (FE) model. For the wheelset bending modes, if the wheel axle is modelled as the Euler–Bernoulli beam and Timoshenko beam, the natural frequencies can be reflected accurately, especially for the latter one. Due to the lower solving accuracy, the massless beam models are not applicable for the analysis of natural characteristics of the wheelset. The increase of the dividing segment number of the flexible axle is helpful to improve the modal solving accuracy, while the computation effort is almost kept in the same level. For the torsional vibration mode, it mainly depends on the axle torsional stiffness and wheel inertia rather than axle torsional inertia.

Parameter Studies for Wheel Wear Using a Flexible Wheelset

In order to reduce wheel profile wear of high-speed train and extend the service life of wheels, a high-speed vehicle multi-body dynamic model and wheel profile wear model are established, in which the wheelset is considered as flexible. The influence of wheel profile, track gauge, and rail cant is extensively studied. The simulation results show that the type XP55 wheel has smallest cumulative wear depth, and type LM wheel has largest wear depth. It is known that the equivalent conicity of the wheel should not be too large or too small. The track gauge with 1435-1438mm and rail cant with 1:35-1:40 can have better wheel wear performance.