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

This work describes experimental and theoretical studies on frictional characteristics of tires at low slip velocities and low slip ratios, which are important in antilock braking systems. 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 the asperity peak density of abrasive papers. The contact area between rubber and the rough surfaces of the abrasive papers was analyzed under vertical load and tangential force using the two-dimensional explicit finite element analysis (FEM). FEM results show that both the sum of length of the real contact area and partial slip are larger with finer surfaces under the same vertical load and tangential force. We conclude that rolling/sliding friction at a low slip ratio is affected by ploughing and hysteresis rather than by adhesion.