Effects of microscopic surface roughness on rolling/sliding frictional characteristics of tire tread rubber - Characteristics of friction at low slip ratios

This paper describes experimental and theoretical studies on frictional characteristics of tires at low slip velocities and low slip ratios, which are important in ABS braking. Rolling/sliding friction of tire tread rubber against abrasive papers, which are assumed to represent microscopic surface roughness of pavement surfaces, is measured at low slip velocities. The experimental results show that rolling/sliding frictional characteristics depend on the surface roughness, particularly on asperity peak density of the abrasive papers. Contact area between rubber and the rough surfaces of the abrasive papers was analyzed under vertical load and tangential force by the two dimensional explicit finite element analysis. The results of FEM show that both the sum of length of real contact area and partial slip are larger with finer surfaces under the same vertical load and tangential force. It is concluded that rolling/sliding friction at low slip ratio is affected by ploughing and hysteresis rather than by adhesion.