Abstract
The effects of vibration on the emergency braking tribological behaviors of the brake shoe of a deep coal mine hoist were investigated in this study. The thermal, frictional and mechanical parameters of the brake shoe were obtained. The vibration characteristics of the brake shoe during emergency braking were investigated, employing multibody dynamics analysis. The effect of vibration on the emergency braking tribological behaviors (temperature and stress distributions) of brake interfaces was explored using the finite element method. The self-made tribo-brake test rig of a brake shoe was employed to reveal the friction deterioration behaviors of the brake shoe during emergency braking. The results show obvious vibrations of all brake shoes along the direction of positive braking pressure during emergency braking. The vibration causes increases in the equivalent Von Mises stress and temperature at the contact interfaces between the brake disc and the brake shoe as compared to the case of ignoring the vibration. Along the rotation direction of the brake disc, the equivalent stress and temperature of the brake disc surface present three overall rapid increases, as well as two slight decreases during emergency braking. As compared to cyclic emergency braking, continuous emergency braking exhibits more obvious tribological degradation of the brake shoe, attributed to enhanced vibration. The wear loss of the brake shoe increases with increasing emergency braking cycles and continuous emergency braking time.
Highlights
F + m· a (t) where P(t) is the specific braking pressure, F is the braking force provided by the braking system, m is the mass of the brake shoe, a (t) is the vibration acceleration and S is the frictional area of the brake shoe
The maximum equivalent stress and maximum temperature at the contact interfaces increase by 19.1% and 11.3% respectively, which indicates that the vibration effect intensifies the thermal stress fields at the contact interfaces during emergency braking
The vibration was obvious along the direction of braking pressure between the brake disc and the brake shoe, as compared to unobvious vibrations in other directions, during emergency braking in the case of all the brake shoes evaluated
Summary
In China, kilometer-deep coal reserves account for 47% of proven coal resources [1]. Mining deep coal resources with a buried depth greater than 1500 m is a major development strategy in China. It is of great significance to investigate the emergency braking tribological behaviors of a brake shoe under the effects of vibration in order to improve the braking safety and reliability of a 1.5-km-deep coal mine hoist. Olesiak et al [9] analyzed the effect of the temperature field distribution on the coefficient of friction and the wear rate of the brake shoe. Wang et al [3] studied the effects of hoisting on the equivalent von Mises stress and temperature fields of a brake shoe. Emergency braking tribological behaviors (uneven distributions of thermal stress and friction deterioration) of brake shoes under the vibration effect for 1.5-km-deep coal mine hoists have not yet been reported.
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