Tribologic Analysis, Wear Evolution and Torque Trend Estimation of an LSD Clutch Pack

The wear phenomenon in friction clutches involves a variation in the contact pairs characteristics, defining a decay of transmissible torque properties. For multidisk clutch packs installed in electro- actuated differentials, the friction torque evolution allows to define how wear decay can influence the dynamic of the vehicle where the differential is installed in. A tribological analysis of a molybdenum- coated clutch pack was made under typical working conditions in terms of temperature, normal load and sliding speed. Friction coefficient and wear rate trends were outlined to define material characteristics through block-on-ring tests. Metallurgic studies on the specimens used in tribologic tests validated the base material used in the samples. Results from experimental analyses were used as input for a numerical study regarding wear and pressure evolutions during clutch engagement. The application of Reye’s theory and Archard’s law on a FE model of the clutch led to the definition of an algorithm to estimate the friction torque generated by the clutch system and the its lifetime.