Rapid tyre/road separation: An experimental study of adherence forces and noise generation

Adhesion forces in the tyre/road contact interface significantly influence the contact dynamics and resulting noise generation for certain tyre/road combinations. Hence, an experimental setup was built where tyre tread samples are loaded and rapidly unloaded in the direction normal to a wearing course sample from an ISO10844-road. Time records of contact forces and sound pressures are acquired during the separation. The separation process in terms of the contact forces and noise generation is described and interpreted. There is good repeatability in the general character of the time signals for a given geometry, but variations occur requiring statistical analysis, as the initial conditions (on smaller length scales) are only approximately repeated. The measured adherence force depends strongly on load, load duration, and unloading rate, in a way supported by theories for contact of rough surfaces. The total sound pressure level of the noise generated during separation is directly related to the level of the adherence force, but the distribution of energy in 1/3-octave bands cannot be estimated from the adherence force record alone, as they also depend on the exact contact geometry. The details of the contact geometry are also very decisive for the magnitude of the adherence force.