Engagement behavior of degrading wet friction clutches

This paper presents modeling, simulation and experimental validation of the friction material degradation effects on the dynamic engagement behavior of a wet friction clutch system. The clutch system is modeled as a 3 DOF lumped-mass-spring-damper incorporating an extension of the Generalized Maxwell Slip (GMS) friction model. The effects of the dynamic sliding velocity (relative velocity between the input and output shafts) and changing normal load are taken into account in the friction model. As the degradation progresses, the Stribeck-function parameters and the tangential contact stiffness change, so affecting the friction characteristics. These parameters are then used in the simulations to investigate their effects on the engagement behavior of the clutch. The simulation results show that the sliding velocity profile and the post-lockup torsional vibration response change. Furthermore, in order to verify and validate the simulation results, the experimental data obtained from accelerated lifetime tests, carried out on two different paper-based wet friction clutches using a fully instrumented SAE#2 test setup, are analyzed and discussed. The experimental results show qualitative agreement with the simulation results.