Temperature And Vibration Characteristics Analysis Of The Braking System For High-speed Train Considering Wheel-rail Excitation

The braking system,as the last barrier to guarantee the safety of high-speed trains in service,mainly includes brake disc and brake pads(friction blocks,backing plate and brake pad rest)and other components.Vehicle braking is achieved through the interaction of brake disc and brake pad to generate friction and transfer to the wheel-rail interface to form braking force.During service,the braking system is acted upon by both internal disc-pad friction and external wheel-rail excitation.Among them,the wheel-rail excitation mainly includes the forms of track geometry irregularities,wheel polygonal wear and wheel flats.However,the current research on the braking system of high-speed train often ignores the influence of wheel-rail excitation,which cannot accurately reflect the temperature and vibration characteristics of the braking system in the actual service process.In the process of braking system operation and maintenance,theoretical support and effective guidance of relevant research are urgently needed.Therefore,in order to further grasp the service state of the braking system,the temperature and vibration characteristics of the braking system of highspeed trains with the effect of wheel-rail excitation is systematically studied,mainly including the following parts:First,a rigid-flexible coupled vehicle system dynamics model was established based on the dynamics parameters of a domestic high-speed train,and the accuracy of the dynamics model was verified based on line test data.Then,the finite element models of the braking system were established based on the geometric model of the braking system corresponding to the test benches and verified by the corresponding bench tests respectively.Further,based on the vehicle system dynamics model considering wheel-rail excitation,the displacement boundary conditions of the braking system are obtained through simulation and integrated into the braking system finite element model,and the analysis method of the temperature and vibration characteristics of the braking system with wheel-rail excitation is established.Then,the effect of external excitations(simple harmonic excitation and track irregularity excitation)on the temperature and vibration characteristics of the braking system was investigated.The results show that when the simple harmonic excitation frequency is 20 times of the rotational frequency,the root mean square value of the braking system vibration acceleration increases by 304% than that of ignoring the external excitation.When considering the track irregularity excitation,the root mean square value of braking system vibration acceleration increases by 24%.In addition,the external excitation causes complex local contact behavior of the system,resulting in some differences in temperature maximum and temperature distribution at the friction block interface compared to ignoring the external excitation.Therefore,the influence of external excitation needs to be considered when analyzing and evaluating the temperature and vibration characteristics of high-speed train braking systems.Further,the effect of wheel polygonal wear on the temperature and vibration characteristics of the braking system was analysed.The results indicate that wheel polygonal wear directly affects the contact behavior of the brake disc and the friction block,resulting in dramatic changes in contact area and a significant increase in maximum contact pressure.Compared to neglecting wheel failure,the measured wheel polygonal wear leads to significant localised high temperature phenomena at the friction block interface,with higher maximum interface temperatures.At the same time,the root mean square values of the system tangential and normal vibration accelerations increased by 71.3% and 158.9% respectively.In addition,the vibration of the braking system becomes more intense as the wheel polygon order increases.Finally,the effect of wheel flats on the vibration characteristics of the braking system was investigated.The results show that the wheel flats lead to more complex contact behavior at the interface between the brake disc and the friction block,causing significant impact phenomena.As the length of the wheel flats increases,the standard deviation of the friction block contact area increases and the impact phenomenon becomes more pronounced.In addition,the wheel flats cause a significant increase in the vibration intensity of the system,and the system vibration is more intense as the length of the wheel flats increases.Compared with ignoring wheel failure,the root mean square value of the system vibration acceleration increased by 386.2% when the length of the wheel flats was 60 mm.Therefore,the effect of wheel failure should be considered in the design and operation and maintenance of high-speed train braking systems.