Increased Accuracy in Squeak & Rattle Simulations by Enhanced Material Properties, Damping Values and Aligned Evaluation Directions
Paper in proceedings, 2015
Squeak and rattle (S&R) are two undesired phenomena that can affect the quality perception of cars. The main reason of S&R is the relative displacement between parts . One mean to identify the critical area for S&R at Volvo Cars during the virtual phase is the E-line method. This method, which was presented in a SAE paper  2012, calculates the relative displacement along a line/gap. The application of the method at Volvo Cars was shown in a Beta paper 2013 .
Relative displacement calculation along the closure gaps such as tailgate closure gap is shown high sensitivity to damping value and sealing stiffness. Therefore, a correlation work in time domain has been performed to update the damping value and sealing stiffness. The test object is a body in white (BIW) including some assembly parts. The relative displacement along the closure gap of tailgate is measured and simulated in different setups which results in updating the unknown parameters. The updated sealing stiffness value takes into account all three directions and the damping value is only valid for the BIW.
Moreover, in order to increase the precision of the E-line method, a new principle to align measurement directions of the dynamic displacement with measurement directions of calculated geometrical variation has been developed. Geometrical variation or static displacement must be considered when assessing rattle because the minimum size of a gap is one of the essential parameters. Definition of measurement direction is based on a surface strip that is generated in the CAT (Computer Aided Tolerancing) tool RD&T. The combination of E-line with the surface strip shows a higher accuracy in the simulation method, which is presented in an industrial case-study.
These enhancements improve the capability of relative displacement simulation significantly.
dimensioning and tolerancing
3D Laser Vibrometer