Numerical Simulation of Engagement of a Wet Clutch With Skewed Surface Roughness

Abstract

The engagement of a wet clutch with skewed surface roughness was investigated. A Weibull asperity height distribution rather than a Gaussian one was utilized in the asperity contact pressure model. The combined effects of surface roughness and skewness on the friction coefficient were studied for new, run-in and glazed wet friction materials. The results show that the engagement time predicted by the Weibull distribution is greater than that obtained using the Gaussian distribution. A torque spike at the beginning of engagement occurs using the Weibull distribution by taking the skewness into account. A positively sloped curve of friction coefficient versus velocity can reduce the torque increase near the end of the engagement. The strain value at the end of engagement obtained by including the skewness is lower than that predicted by excluding it. The surface topography and the friction characteristics change with the engagement wear and thermal glazing. The torque response and the phase plane are presented for the run-in and the glazed wet friction materials as a function of surface roughness, skewness, and friction characteristic.