On the modelling of the friction characteristics of railway vehicle brakes

Abstract

The rules and standards that define the requirements and methods for the layout of friction brake systems for railway vehicles still demand extensive experimental surveys since the general confidence in the theoretical predictability of the brake pad friction behaviour is limited. In fact, a review of numerous measurements from dynamometer test rigs exposes a large variation of the friction characteristics. Nevertheless, these measurements could be exploited to develop an elaborate friction modelling approach that includes deterministic and stochastic influences. The comparison of vehicle measurements from field tests with simulation results reveals that a significant improvement of the theoretical predictability of braking distances is within reach. Consequently, this applies as well for a more virtual layout and acceptance procedure for railway vehicle brake systems in the future.

Adding a brake shoe temperature model into freight train longitudinal braking dynamics simulations

“…Meanwhile, by using a known vehicle velocity and a known brake force, the brake temperature model developed in Section 3 can be used to calculate the temperature at the wheel-shoe interface. Various publications 9–14 have indicated that temperature has influences on brake CoF. An example format of the CoF variation formula can be expressed as 9 :where μb0 is the kinetic CoF (lowest value); nv and mv are two parameters to describe the CoF variation with vehicle velocity v; nt and mt are two parameters to describe the CoF variation with temperature.…”

“…Meanwhile, by using a known vehicle velocity and a known brake force, the brake temperature model developed in Section 3 can be used to calculate the temperature at the wheel-shoe interface. Various publications [9][10][11][12][13][14] have indicated that temperature has influences on brake CoF. An example format of the CoF variation formula can be expressed as 9 :…”

“…[6][7][8] The force conversion model 5 consists of a brake rigging model that is usually simplified as a multiplication factor and a brake friction model to convert normal brake forces into frictional brake forces. Open literature [9][10][11][12][13][14] has indicated that temperature has influences on brake CoF. Understandably, temperature variations should have influences on the results of train brake performance assessments.…”