Dynamic Analysis of the Interaction Between Vehicle Floor Panels and Interior Carpets - Simulations and Measurements

Abstract: Floor panels of vehicles are known to radiate structure-borne sound into the vehicle compartment. To reduce the structure-borne sound, numerical models are used in the development of vehicles to evaluate different design options of the vehicle body. The panels are covered with carpets composed of foam and heavy layer of rubber, which causes challenges and complications when predicting interior sound. In the current models used to predict sound, the carpets are modelled as non-structural mass added to the panels. It is believed that the heavy layer setup of the carpets leads to a sprung-mass resonance in the frequency of interest for structure-borne sound. This affects the dynamic behaviour and sound radiation of the floor panels. Further, the panels and carpets are believed to not be in full contact with each other, and the contact condition is assumed to vary among vehicles and over time. Therefore it is assumed that the current modelling strategy used to model floor panels is not able to predict the dynamic behaviour of the panels and carpets with sufficient accuracy. This leads to erroneous results and conclusions in the development of cars. A step towards a modelling strategy capable of predicting interior noise levels with higher accuracy, is to understand the dynamic behaviour of panels and carpets. In this Master's dissertation, an example structure of a floor panel with carpet is studied experimentally and numerically. The effect of the carpet on the dynamic response in the panel, and the response in the panel compared to that in the heavy layer is investigated. It was found that a model with a simple linear-elastic solid representation of the carpet is able to represent the basic phenomena that govern the dynamic behaviour of panels and carpets. Although, further investigation is needed to achieve adequate correlation of the vibration levels and resonance frequencies. A sprung-mass resonance of the carpet was clearly observed in both measurements and numerical analyses. A significant effect of contact condition between panel and carpet was also found.