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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. • An safety gear braking testing rig that can simulate the real braking conditions for high-speed elevator is developed. • The short carbon fiber reinforced carbon/carbon and Cu-based powder metallurgy braking materials are applied. • The dependence of the coefficient of friction on the braking pressure, initial braking speed and initial braking power intensity are investigated. • Wear behaviors under different braking conditions for both braking materials are explored. [ABSTRACT FROM AUTHOR]

The transient non-Newtonian thermal micro-elastohydrodynamic lubrication point contact model and the adhesive wear model in mixed lubrication point contact are applied to a heavy-loaded modified herringbone gear drive respectively in steady running phase and start-stop phase. The fundamental parameters of both elastohydrodynamic point contact and wear model are derived from the meshing characteristic and kinematics analysis of herringbone gears. The effects of pinion torque, rotational speed and surface roughness on the maximum pressure and temperature rise and the minimum film thickness are discussed in gear steady running condition for full film lubrication contact. Meantime, the asperity load ratio, contact flash temperature and tooth wear depth are investigated in gear start-stop phase for mixed lubrication point contact. The results show that the lubrication performance of herringbone gear is deteriorated by substantially increased pressure and temperature rise resulting from a larger tooth surface roughness and rotational speed. The tooth wear depth of herringbone gear in start-stop phase is likely greatly reduced with a larger start-stop acceleration. Moreover, the lubrication and wear performances for the complete running cycle of herringbone gear drive from start-up to stop indicate that large tooth surface roughness rather than high load are more prone to herringbone gear thermo-mechanical and wear failures. • A Non-Newtonian thermal transient point contact EHL model is applied to modified herringbone gears. • A mixed EHL point contact wear model is developed for herringbone gears. • Gear thermo-mechanical failure can occur at pitch point due to large tooth roughness. • Tooth wear in start-stop phase can be greatly reduced with large start-stop acceleration. [ABSTRACT FROM AUTHOR]