Design, Construction, and Evaluation of Rubber Friction Tester

Coefficient of friction (COF) for rubber parts is one of the key parametersin their interaction with solid rough surfaces (micrometer to millimeterscales), such as tire-road interactions. COF of rubber depends on viscoelasticproperties of rubber, roughness characteristics of the counter-part surface, andprocess variables such as contact nominal pressure and sliding speed. Due to the needfor measuring COF for rubber, a new friction tester, with continuous variation ofnominal pressure and sliding speed, was designed and constructed in order to assessthe effect of above mentioned parameters. Tire tread compounds, as the most commonrubber part in the field of rubber tribology, was used for this purpose. Viscoelasticproperties of compounds were varied by changing composition of styrene-butadienerubber (SBR) and butadiene rubber (BR) in the blend. Effect of surface roughness wasevaluated by using silicon-carbide papers with different roughness parameters. Bystatistical analysis it was shown that the designed friction tester has high accuracy inmeasuring the coefficient of friction of rubber and differentiating the effective parameters.Increasing the nominal pressure led to reduction of COF and increase in slidingspeed forced it through a maximum. In conclusion, the loss factor of the compoundand asymmetry in roughness distribution of the counter-surface are considered as themost effective parameters on COF of rubber.