Dynamic response analysis of a train braking system with time-varying coefficient of friction excitations

Coefficient of friction (COF) is a key parameter that reflects the interface tribological behavior and influences the system dynamic response. In this research, the tribological properties of the train braking system friction blocks with different perforation diameters are experimentally explored using a block-on-disc apparatus. And the distribution law of the interface COF is revealed by statistical analysis. It is found that the histogram of the COF approximately follows a normal distribution. Considering the time-varying of the COF, a time-varying COF model is then established based on the normal distribution parameters. Further, the time-varying COF model is integrated into a proposed train braking system numerical model to construct the association between the disc-block friction properties and the braking system dynamic response. Based on this, the dynamic behavior of the braking system subject to interface time-varying COF excitations and block perforation structure is analyzed. The results show the time-varying COF excitations should be considered to accurately reveal the dynamic response of the braking system. Moreover, the friction block processed a perforation diameter of 2 mm obviously reduces dis-c-block friction vibration and improves the stability of the train braking system.