Experimental study on velocity and temperature dependency of rubber-asphalt friction

The sliding friction of rubber differs from that of many other materials as its internal friction is exceptionally high. In addition, the viscoelastic properties of rubber are strongly temperature- and frequency-dependent. In a slider-substrate system formed by a rubber block sliding on a hard rough substrate, the substrate asperities cause time-dependent deformations on the rubber surface, resulting in viscoelastic energy dissipation in the rubber, which contributes to the sliding friction. The perturbation frequency in the rubber block depends on the surface roughness of the substrate and the sliding speed. The surface roughness of many natural surfaces can be described as self-affine fractal. The advantage of a self-affine fractal treatment of a surface for a sliding friction model is the large range of roughness length scales which are incorporated and whose contribution to the sliding friction can thus be considered. This article presents experimental results for a tyre tread rubber block sliding on an asphalt surface. The sliding friction coefficient as a function of the temperature and sliding speed was measured for such a system in a climate chamber. The measured temperature and sliding speed ranges were from −8°C to +32°C and from 1 mm/s to 1 m/s, respectively. The maximum sliding friction was found for ∼0.1 m/s at 21-32°C. The peak friction velocity decreased when the temperature was reduced.