Abstract
Abstract
The effect of ‘off-contact’ electric potentials on the frictional behaviour of an agate-brass rubbing couple was investigated using a commercial pin-on-disc wear machine. The electric field was set to cover a large portion of the disc surface area but excluding the agate ball and brass contact. This is referred to as the ‘off-contact’ potential. A suspension of 1 wt % zinc stearate powder dispersed in de-ionized water was adopted as a lubricant in the experiments. Experimental results show that the coefficient of friction can be increased markedly by imposing a positive biased potential (disc with negative charge) when it exceeds a threshold value. For applying negative biased potentials, there are no obvious effects recorded. Furthermore, the amount of increase in the coefficient of friction by imposing a fixed potential decreases with an increase in the applied load and the sliding speed, but the decreasing rate gradually becomes smaller. Experimental results under a. c. potentials in the frequency range from 0.1 to 100000 Hz were also presented and no obvious changes in the coefficient of friction for an agate-brass rubbing couple were observed.
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