ABSTRACT
The present  study investigates the effect of holes and leakage grooves introduced in cylindrical protrusion of the rubber flooring on the static friction coefficient displayed by rubber footwear under dry, water, water + 5.0 vol. % soap, oil and water + 5.0 vol. % oil lubricated sliding conditions. Rubber test specimens were prepared in the form of cylindrical protrusion of 28 mm diameter and 10 mm thickness. Holes with different diameter and numbers (0, 1, 2, 3 and 4) were introduced in rubber protrusions. The holes were punched to produce holes of 1.5, 3, 4 and 4.5 mm diameter. Then the rubber protrusions were adhered to flat rubber of 6 mm thickness fitted with leakage grooves then the arrangement were adhered to the wood blocks.
 
At dry sliding, friction coefficient increased with increasing number of holes and grooves. Besides, friction coefficient decreased with increasing applied load. At water lubricated sliding, increasing diameter of holes was insignificant on friction coefficient. As the number of holes and grooves increased friction coefficient increased. This behaviour related to the easy escape of water through the holes and grooves out of the contact area. Maximum friction value (0.65) was observed for four holes of 1.5 mm diameter. At water and detergent lubricated sliding, friction coefficient drastically decreased with increasing normal load.  At oil lubricated sliding, friction coefficient increased with increasing number of holes and grooves. The maximum friction values were noticed at four holes of 3 mm diameter. At emulsion of water and oil lubricated sliding, smooth rubber surface displayed higher values of friction coefficient compared to surfaces lubricated by oil only. As the applied normal load increased friction coefficient decreased.