The present research investigates the effect of grooves introduced in the rubber surface on the static friction coefficient when sliding against ceramic surface. Rubber test specimens were prepared from two types of rubber of 2 and 8 MPa modulus of elasticity and 27 and 53 hardness Shore-A. The specimens have a cylindrical shape of 36 mm diameter and 10 mm high. Test specimens were prepared by introducing different grooves with different dimensions. The ceramic surface roughness was 0.14 µm Ra. Friction tests were carried out at 150 N normal load. Tests were carried out at dry sliding conditions as well as lubricated surfaces were lubricated by water, sand, water contaminated by sand, water and detergent, water and detergent contaminated by sand, oil, oil contaminated by sand, oil mixed by water, oil mixed by water and contaminated by sand. Based on the experimental results, it was found that at dry sliding test specimens of triple grooves showed the highest friction coefficient for soft rubber. In the presence of water friction coefficient of hard rubber of double grooves displayed significant friction increase. In presence of water contaminated by sand friction coefficient showed significant increase for soft rubber of triple and quadruple grooves. Friction coefficient of soft and hard rubber of quadruple grooves sliding against ceramic surfaces wetted by water and detergent showed relatively high friction. Introducing quadruple grooves in hard rubber increased friction coefficient generated from the sliding against oil lubricated ceramics. For surfaces lubricated by oil/water dilution friction coefficient showed remarkable increase.
Samy et al. (Tue,) studied this question.