NVH Optimization Of Truck Cab Floor Panel Embossing Pattern

Improved sound comfort is a part of Volvo's continued development for improved driver environment. As a part of work in this area, a method for panel embossing optimization with respect to NVH is outlined and exemplified for a truck cab floor. The selection of shapes that build up the end-form is made such that the embossing pattern is guaranteed not to generate hidden corners that cause production problems.

Initial tests on a simply supported plate show that the natural frequency of the fundamental mode can be increased about ten times. The example shows a cab floor for which the process was used to minimize sound transmission. The optimization process was shown to be able to generate plate segments that were stiffer than the main beam structure. In other words, the main beam structure was found to limit how stiff the plates could be made while maintaining an acceptable end result for the NVH analysis.

The results show that the optimization enable noise transmission peaks to be shifted into acceptable RPM ranges (of short duration) and that the noise transmission is significantly reduced at idle and for most of the common RPM range. The optimized floor weight will be reduced compared to the reference floor since the optimized embossing pattern replaces the reinforcing cross beams. A remaining unwanted peak within the common RPM range is difficult to remove with embossing as it is affected by an acoustic cab resonance that is best counteracted through acoustic means.