Research On Braking Friction Characteristics And Chatter Of Railway Vehicles

The safety of railway trains in operation has become a key question with the increase of their running speeds and the loads. Braking safety is an important part of the safety of railway trains. Therefore, it is significant to study friction characteristics of vehicle braking systems.A series of braking friction tests using different braking shoe and pad materials were carried out on a MM-1000 dry sliding friction test machine. The braking friction and rotation speed were measured with a data acquiring system. Various examinations on worn scars were performed by means of an Optical Microscopy (OM), a Hardness Tester, a Confocal Laser Scanning Microscopy (CLSM). The effects of braking normal pressures and initial speeds on baking friction characteristics and braking chatters were studied in detail. Main conclusions can be drawn as follows:1. Initial braking speed has a clearer influence on a distance-average friction coefficient and an instantaneous friction coefficient. As initial braking speeds are increased, distance-average friction coefficients and instantaneous friction coefficients are decreased. Braking pressures have also a distinct influence on friction coefficient. The increase in the braking pressure can result in the decrease in the distance-average friction coefficient.2. Initial braking speeds have a greater influence on the temperature increment, but braking pressure only has a little influence. The increase in initial braking speeds can lead to the increase in the temperature increment.3. For the friction of disc braking materials, both initial braking speeds and pressures have a distinct influence on wear mass loss. As the initial braking speeds and pressures are increased, the wear mass loss is increased obviously.4. The higher initial braking speeds, the larger braking chatter accelerations are. It is found that the domain frequencies of braking chatters in the x and z directionsare focused on a region of 60 to 160 Hz and the domain frequencies of braking chatters in the y direction is concentrated in a regime of 60 to 300 Hz. Furthermore, the negative slope in friction force-speed is found not to be the main cause of braking chatter generation.