Friction Coefficient of Rough Indoor Flooring Materials

The present study investigates the effect of the surfaceroughness of polymeric indoors floorings on the static friction of barefoot as well as foot wearing cotton and polymeric socks under dry,water, water + 5.0 vol. % soap, oil and water + 5.0 vol. % oillubricated sliding conditions. Polymeric floor sheets of differentroughness ranging from 0.05 and 11.0 (mu)m were tested. The testedmaterial is commonly used in entrance areas or corridors and in thesport halls. Cotton and polymeric socks as well as bare foot werefrictionally tested. The results were compared to the friction caused byshoes as simulated by rubber test specimens of vee shape treads wereprepared in the form of square sheets of 100 x100 mm, 10.0 mmthickness. Experiments were carried out using a test rig designed andmanufactured to measure the friction coefficient between the foot andthe tested polymeric flooring materials.The experimental results showed that, at dry sliding, frictioncoefficient of rubber decreased with increasing surface roughness,while for bare foot and polymeric socks, friction coefficient decreaseddown to minimum then increased with increasing the surfaceroughness. Besides, friction coefficient decreased with increasingapplied load. Minimum friction was observed at surface roughnessranging between 6-9 (mu)m. In water lubricated sliding, frictioncoefficient of rubber increased up to maximum then decreased withincreasing surface roughness. Maximum friction values were observedat surface roughness values ranging from 1.5 to 2.0 (mu)m Ra. Cottonsocks showed the highest friction coefficient followed by rubber, barefoot then polymeric socks at 11 (mu)m Ra. Friction coefficient drasticallydecreased with increasing surface roughness at water and detergentlubricated sliding. For the tested flooring materials lubricated by oil,friction coefficient of rubber increased up to maximum values thendecreased with increasing the surface roughness of the flooring materials. The maximum friction values were noticed at 4.0 ìm Ra.Bare foot displayed drastic reduction in friction coefficient, whilecotton socks showed the highest values. When water was diluted by5.0 wt. % oil, rubber smooth flooring surface displayed values offriction coefficient close to that observed for hydrodynamiclubrication where the two sliding surfaces are separated by the fluidfilm. As the roughness increased the fluid film was broken and frictionincreased. Cotton socks showed the highest friction compared to barefoot and polymeric socks.