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.