Thermoelastic Instability in an Automatic Transmission Clutch With a “Finger” Piston

An important practical case of frictionally excited thermoelastic instability (TEI) in a wet multidisk friction clutch of an automotive transmission that includes so-called finger piston is investigated. Advanced finite element model of thermoelastic multi-surface contact problem is used. Theoretical results are verified experimentally. The study shows that the finger piston used in transmission clutches can trigger unstable thermo elastic behavior which leads to severe hot spots.