Experimental evaluation of braking pad materials used for high-speed elevator

Abstract

In this paper, an elevator safety gear braking testing rig was developed based on the disc-pad braking model in principles of energy equivalent and speed equivalent to evaluate the braking behavior of short carbon fiber (SCF) reinforced carbon/carbon (C/C) composite and Cu-based powder metallurgy (P/M) material. Note that the braking pressure and the initial braking speed were controlled between 10 MPa to 56 MPa and 3 m/s to 25 m/s respectively in the experiment, which covers the real braking conditions in high-speed elevator. Then friction behaviors of both braking materials were investigated. Especially, the dependence of the coefficient of friction (COF) on the braking pressure and initial braking speed were minutely studied. Interestingly, it was found the COFs increased with the initial braking speed, but decreased with the improved braking pressure. Besides, wear behaviors under different braking conditions for both materials were explored. Results showed the C/C composite pads were crushed at high initial braking speed (V ≧ 14 m/s) in this experiment, but the Cu-based P/M material could suffer higher initial braking speed, which suggested the Cu-based P/M material had more potential to be used as the braking material applied in high-speed elevator or even ultra-high speed elevator compared to C/C composite adopted in this paper.