Friction and wear properties of two types of copper-graphite brush under strong sliding conditions
The high-speed friction test of the steel rotor was carried out with copper graphite brush, the sliding speed reached 230m/s, and the current density reached 526 A/cm². One brush is a commercial powder metallurgy (PM) sample, and the other is a graphite fiber-Cu/Sn matrix composite. The composite brush is prepared by a proprietary process of liquid gold and runs with graphite fibers perpendicular to the surface of the rotor. Set the coefficient of friction as a function of speed, set the rate of wear as a function of speed, and set the voltage drop as a function of speed and current. The no-current wear rate of PM is much higher than the wear rate of the composite brush, but when the current of 600 A is passed, their order is the same. The voltage drop at the brush-rotor interface shows similar changes to the speed for the two brushes, but for the two voltage rankings, the voltage drop changes with current are different. As the current of the PM brush increases, the voltage drop may increase linearly. For the composite brush, it showed an increase of about 50A, and then changed very little until the current was about 600A. For heavy sparks, the damage on the rotor surface is more obvious than with PM brushes. Use a composite brush. It seems that the difference between the high temperature mechanical properties of the two types of brushes is the reason for their different behavior under severe sliding conditions. But the voltage drop of the two samples varies with the current. As the current of the PM brush increases, the voltage drop may increase linearly.
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