The effect of normal load and sliding velocity on the development of friction at a lubricated steel pin on polymer disk interface was investigated. Polyoxymethylene homopolymer disks were lubricated with a lithium soap thickened synthetic hydrocarbon grease and tested against a 6 mm diameter stainless steel pin. The normal load was varied from 3 to 80 N, and the sliding velocity was varied from 0.0004 to 0.2 m/s. The engineering friction coefficient displayed a power law dependence on the external applied load, indicating a significant adhesive effect in the presence of the lubricant. The true friction coefficient was 0.04, and the average adhesion force was calculated to be 29 N. With the soft disk and hard pin configuration, velocity and time effects were found to be negligible in the presence of the dominant dependence on the normal load. However, a velocity effect emerged with steel disks and polymer pins, likely due to a temperature rise at the polymer surface.

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