ABSTRACT
The effect of applied load on the static friction coefficient displayed by rubber disc fitted by single groove sliding against ceramics is investigated. 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 had a cylindrical shape of 36 mm diameter and 10 mm height. Test specimens were prepared by introducing single groove with different dimensions. The ceramic surface roughness was 0.14 µm Ra.
Friction tests were carried out at 50, 100, 150 and 200 N loads. 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.
It was found that for dry sliding against ceramics, friction coefficient slightly increased with increasing load. For soft rubber friction coefficient slightly decreased with increasing normal load. In the presence of sand friction coefficient slightly decreased with increasing applied load. For soft rubber load had no effect on the values of friction coefficient. Load has no effect on the friction coefficient displayed by hard rubber specimens sliding against ceramic surface lubricated by water contaminated by sand.
In the presence of detergent friction coefficient decreased with increasing normal load. For hard and soft rubber specimens sliding against ceramics wetted by water and detergent contaminated by sand friction coefficient increased with increasing applied load. Friction coefficient generated from sliding of rubber against oil lubricated ceramic surfaces decreased with increasing normal load. Friction coefficient for rubber test specimens sliding against ceramic surface lubricated by oil and contaminated by sand decreased with increasing normal load. For rubber specimens sliding against ceramic surface lubricated by oil/water dilution and contaminated by sand load showed insignificant effect on friction coefficient.