High-temperature tribological behavior of high-speed train braking interfaces: A comparison of fixed and floating friction block joint structures

Abstract

In emergency braking and prolonged braking on long downhill slopes, the brake interface of high-speed trains experiences complex high-temperature tribological behaviors (HTTB), which pose a severe challenge to the braking safety of these trains. Therefore, one of the most important considerations in the design of brake pads for trains is enhancing the braking interface's HTTB. At the moment, one of the most efficient ways to control the tribological behavior is through the design of the friction block's joint structure on the brake pad backplate. It is yet unclear, nevertheless, how this joint affects the brake interface's HTTB. To address this, this work conducted high-speed drag braking simulation experiments on a self-developed brake performance experimenting device for trains. The purpose of these studies was to explore the effects of the friction block's fixed and floating joint structures on the HTTB of the braking interface in trains. This work developed a high-temperature wear simulation method for friction blocks using the finite element software ABAQUS and its subroutines Umeshmotion and Dflux to simulate high-temperature wear of friction blocks. Combining finite element simulation and experimental data, the mechanism by which the friction block connection structure affects the high-temperature tribological behavior at the train braking interface was analyzed. The results show that the friction block connection structure significantly influences the frictional heat characteristics of the interface. The floating connection structure exhibits a higher temperature rise rate and peak temperature, which is 0.3 % higher than that of the fixed connection structure. Additionally, the friction block connection structure has an important effect on the friction and wear characteristics of the braking interface. The floating connection structure reduces eccentric wear of the friction blocks, with eccentric wear (EW) 12.8 % lower than that of the fixed connection structure. Furthermore, the wear rate of friction blocks with the floating connection structure is smaller, being 11.9 % lower than that of the fixed connection structure. Under the floating connection mode, the worn surface contact area is smaller; the total contact platform area is 32.9 % less than that of the fixed connection structure, with almost no accumulation of wear debris, and the third-body layer (TBL) formed by compacted debris is reduced. In terms of friction-induced vibration and noise (FIVN), the floating connection structure shows a distinct ‘thermal-vibration effect’ in the early braking stage, but after stable contact is established, FIVN characteristics are significantly improved, with noise reduced by 23.8 % and vibration reduced by 6.9 %. Overall, the high-temperature tribological behavior (HTTB) at the high-speed train braking interface is significantly affected by the friction block connection structure. Compared with the fixed connection structure, the floating connection structure demonstrates superior performance.