The paper describes a noise, vibration and harshness (NVH) phenomenon caused by impact of meshing gear teeth pairs, resulting in structural wave propagation and elastoacoustic coupling in the driveline system, referred to in industry as clonk. The numerical investigation combines multi-body dynamics analysis with exible body oscillation behaviour predicted by nite element analysis (FEA) techniques. Particular attention is paid to local non-linearities such as the varying stiffness of meshing gear teeth and their normal backlash. The spectrum of vibration of lightly damped hollow driveshaft tubes shows good conformity with experimental results.

DOI: 10.1243/09544070JAUTO55Abstract: The appearance and persistence of impact-induced clonk noise in rear wheel drive light truck drivelines has led to an urgent need for remedial action. The pressure for delivering results within tight schedules and financial constraints has resulted in palliative actions rather than fundamental investigations. It has been speculated that the use of a dual-mass flywheel (DMF) can lead to attenuation of clonk metallic noise, even though its main purpose has been to counter transmission rattle by reducing the input torsional impulse. The present work investigates the effect of DMF on impact-induced clonk noise and its severity through experimentation. Sound measurements in the driveline only reveal a slight reduction in the overall levels of impact-induced noise, but a significant change in its quality -the sharpness associated with the typical metallic content of clonk is absent. The effect is also highlighted by the main frequency content of the response when DMF is employed. The duration of the clonk phenomenon is altered from the case where a traditional single solid-mass flywheel is employed.

The paper investigates the conditions leading to the emergence and persistence of an acute metallic noise in light-truck drivelines. Sudden demands in torque in the presence of lash zones give rise to this phenomenon, which is onomatopoeically referred to as clonk. The study of clonk requires combined rigid multi-body dynamics and flexible body oscillations. The results show high-frequency contributions in the driveline vibrational response of certain structural modes of the driveshaft pieces, which are induced by remote impact of meshing transmission teeth through backlash. The numerically predicted spectrum of vibration shows good correlation with experimental measurements of radiated noise from a dynamic drivetrain rig.

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