This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.

Resource Abstract

Automotive drivetrain component design requires clearance for vehicle assembly. The metal to metal gear lash impacts from a drivetrain torque reversal excitation, such as throttle tip in or tip out event, may cause a clunk noise and vibration issue that could degrade the vehicle quality and customer satisfaction.
This paper presents an innovated CAE method for a driveshaft clunk sound prediction. A hybrid elastic multi body and acoustics approach is used to simulate the radiated clunk sound from the driveshaft. The elastic multi body model consist detail chassis, steering, suspension and powertrain systems with flexible driveshafts by means of the Craig Bampton method. The three dimensional gear contact forces are calculated using analytical equations for each different gear designs in the drivetrain. The Hertzian contact theory is used to calculate the drivetrain gear impact forces due to their contact geometry design effects. The driveshaft elastic deformation during a throttle tip in maneuver is used to excite an acoustic model to predict the radiated sound along the driveshaft surface. The acoustic model consist of acoustic meshes for the driveshaft and its surface vibration excitations from the elastic multi body model and for the driveshaft surrounding boundaries to predict the acoustic cavity effect of the vehicle under body. Analytical microphones are placed consistence with the vehicle measurement conditions. It allows the time and frequency domain analyses of the driveshaft radiated sound from vehicle tip-in or tip-out events at any exterior location of the vehicle. The elastic multi body model was correlated for the pinion nose vibration and the driveshaft radiated sound using three vehicle test data. Critical driveshaft elastic modes contributing the sound radiation are identified. Different drivetrain designs, such as 4x4, 4x2 and driveshaft configuration with different wheel bases, are investigated for their clunk sound characteristics. This new method is now being used for drivetrain clunk noise and vibration assessments during early development stages.