Clonk: an onomatopoeic response in torsional impact of automotive drivelines

Vehicular driveline is a lightly damped non-linear dynamic system that is p rone to noise and vibration response when subjected to excitation. There ar e many sources of excitation such as torsional impact caused by the take-up of backlash in the powertrain system. Such sources of excitation exist in transmission backlash, in driveline splines and in pinion-ring gear contact in the differential. Abrupt application or release of the throttle in slow moving traffic or rapid engagement of the clutch can be followed by an ono matopoeic response of the driveshafts, referred to in the industry as clonk . This is a disagreeable, audible and tactile response in some vehicles and can also coincide with every cycle of low-frequency longitudinal vehicle r esponse, commonly referred to as shuffle or shunt. This paper describes the phenomenon of clonk and investigates its occurrence both by an experimenta l technique and by detailed modal analysis of driveshaft pieces. It is show n that finite element predictions agree well with the experimental findings and that the high-frequency structural modes can lead to discernible radia ted noise. The preliminary findings reported here point to a need for a mor e detailed elasto-acoustic analysis.