Contact forces and noise generation during hastily separation of tyre tread blocks from road surfaces
Paper in proceedings, 2005
Adhesive bonds in the passenger car tyre/road surface contact have a large influence on the contact dynamics for certain tyre/road combinations. The effect is most pronounced for road surfaces with low roughness, so-called smooth surfaces. An experimental setup was designed to study time records of contact forces and sound pressures as tyre tread samples are hastily separated from road surfaces samples. The general character of the separation process on a macroscopic length scale is described, interpreted, and related to theories on smaller scales. A single value (dynamic) adherence force is determined out of the records and it is related to the initial conditions; magnitude of preload, preload duration, and unloading rate. It was found that the exact contact geometry, on larger scales, yields the details in the contact force record and distribution of sound pressure levels in 1/3-octave bands. A model aiming at describing the observed behaviour must consider a wide range of length scales; a dynamic contact model is proposed that considers the exact contact geometry on larger scales via discretisation and uses statistical properties of the surfaces at lower scales to determine contact criteria at contact points.