CHARACTERIZATION OF ROAD PROFILES BASED ON FRACTAL PROPERTIES AND CONTACT MECHANICS

Abstract

ABSTRACT A major challenge in tire and road engineering is to understand the intricate mechanisms of friction. Pavement texture is a feature of the road surface that determines most tire–road interactions, and it can be grouped into two classes of macro-texture and micro-texture. Since the effects of micro-texture and macro-texture dominate the friction measurements at low and high slip speeds, they can help provide sufficient resistance to skidding, if maintained at high levels. A non-contact profilometer is used to measure the macro- and micro-texture of several different road surfaces. The friction number for each surface is measured using the Michigan Department of Transportation's (MDOT) single axle friction trailer. Some fractal parameters of the measured profiles are estimated, and it is proved that all measured profiles display strong fractal behavior. The correlation between texture and fractal parameters and friction is investigated. It is shown that while global fractal quantities fail to classify pavement profiles, the pointwise Hölder exponent as a local fractal parameter, and also the mean square roughness, can discriminate profiles that have different frictional properties. For five road surfaces, two-dimensional (2D) characterization is done using one-dimensional (1D) profile measurements. The hysteretic coefficient of friction is estimated using the contact theory developed by B.N.J. Persson. Good correlation is observed between the wet friction measurements and friction prediction results.