DRIVELINE for Automotive Applications Vibration Analysis

Massimo Pasta



The Vibrations are the primary cause of the noise associated with a Driveline for automotive applications. It consists of many parts, made of metals and or other materials, bonded together through several couplings with different stiffness and damping. While passing through the links , between the Diveline and the frame of the vehicle , these vibrations reach the car interior , up to the driver, generating ''noise''. The Noise, Vibration and Harshness, also known by the acronym NVH , is a measure of the comfort of a vehicle and is the result of the combination of three parameters: Noise: is the noise level in the car while driving. Vibration: are the vibrations felt by the driver. Harshness: is the smoothness of gait of the vehicle during sudden transitions of motion (eg rough terrain). Vibrations can also generate fatigue stress in the components of the transmission and thus affect the reliability of the transmission itself. Reducing the magnitude of the vibration transmission means improving driving comfort and reliability of the complete vehicle. The direct measurement of the vibrational level of all components of the transmission, while the vehicle/engine is running , it is not always possible for practical reasons. Some of them in fact, being parts of complex assembly, are not accessible to the various transducers without being disassembled. If this happens some of the measures would be insignificant. It therefore recognizes the importance of having numerical simulation tools , to integrate and to support the experimental findings. Especially in those situations where it is not possible to detect vibrations in the single component.