Proceeding of the 17th International Colloquium Tribology 2010 Solving Friction and Wear Problems
International Colloquium Tribology 2010 Solving Friction and Wear Problems edition:17 location:Stuttgart/Ostfildern Germany date:19–21 January 2010
After clutch engagement in the post-lockup phase, the contact stiffness of the friction material plays an important role in the dynamic behaviour of a driveline system. The friction material deteriorates progressively during the service-life of a clutch, which affects the contact stiffness. This deterioration therefore changes the dynamic behaviour of the driveline. In order to be able to predict the dynamic behaviour of the latter in the post-lockup phase, the contact stiffness characteristics at different degradation levels must be investigated. Consequently, this change in the dynamic behaviour can be used as a means to monitor clutch degradation. In this paper, both theoretical analysis, based on a simple contact model, and experimental-setup tests are presented. Three identical paper-based friction materials with different degradation levels were used. To simulate the representative post-lockup phase, disk-on-disk experiments were performed on a newly developed rotational tribometer. In the experiments, those identical specimens were immersed in a new Automatic Transmission Fluid (ATF). The experimental results agree qualitatively with the model and show that the contact stiffness of mildly degraded material is higher than that of the new material, and that the contact stiffness of severely degraded material is lower than that of the mildly degraded material. In addition, variability measurements of the contact stiffness at different angular positions were also performed. The results of those measurements show that the contact-stiffness variability of the new materials is higher than of the degraded ones.