Influence of Adhesion on the Tire-Road Friction Process Regarding Asphalt Type and Sliding Speed

In contrast to a quite good understanding of the hysteretic effects in tire-road contact, there is limited knowledge about the adhesive part of the friction, especially concerning its relevance under wet conditions. In this paper the test apparatus of the German Institute of Rubber Technology is used to investigate the friction coefficient in process of sliding, in particular the adhesion. The adhesion is quantified through the difference between the cases with pure water and with soap water as lubricant. The derived curves of friction over the sliding time are characterized by different parameters in the sliding stages. Results reveal that adhesion amounts to 10% of the total friction even in wet conditions, which means that adhesion is not negligible in predicting the friction. The adhesion in the process of the contact shows a decreasing tendency during the sliding process. Its development over the sliding time varies to a certain degree with the sliding speed and the asphalt type.