A typical driveline Noise, Vibration and Harshness (NVH) spectrum contains the contribution of a significant number of vibration components, ranging from a few Hz to several kHz. This is due to different NVH phenomena that have their causes in the contact behaviour of discrete driveline components. A short duration, audible, high frequency, elastoacoustic phenomenon, which occurs as a load reversal in the presence of lashes in the driveline, is onomatopoeically known in industry as clonk (300–5,000 Hz). Its short duration acts as an impulse that excites a large number of structural modes of the lightly damped driveline system. The above phenomenon has become a major concern to automobile manufacturers in recent years with the modern trend of reducing inertial effects in powertrain systems by use of materials of lower elastic moduli and thinner sections. The most common approach in industry to reduce the radiated clonk noise is by using palliatives, such as metallic wires, foam-filled driveshafts, the Dual Mass Flywheel (DMF) and cardboard liners. However, the mechanisms of vibration and noise reduction that the above palliatives introduce have not been fully understood yet, as these are rather used in an empirical manner. This paper investigates the effect of cardboard liners on the high frequency driveline response, by a combined study of FEA analysis at component level and experimental measurements in a drivetrain rig. The results reveal that cardboard liners reduce the severity of the driveline high frequency vibrations, as well as the number of the driveshafts’ structural modes that are excited by remote impacting of the drivetrain components through their lash zones. The predicted and observed effect of the cardboard liners shows good conformance with the existing literature.
Electric vehicles diffusion: changing pavement acoustic design?
