Title: Evolution of Trim Modeling with PEM for Structureborne Noise Prediction in Full Vehicle
text: The need in the automotive industry to understand the physical behavior of trims used in a vehicle is high. The PEM (poro-elastic method) was developed to permit an explicit representation of the trims in the FEM full vehicle models and to give tools to diagnose the effect of the trims and test design changes (porous material property, geometry, etc.,). During the last decade, the evolution of software and hardware has allowed the creation of models with highly detailed trim description (porous material using Biot parameters, plastic trims, etc.,). These models can provide good correlation up to 400Hz compared to measurements in contrast to classical NSM (Non Structural Mass) methodology which shows limitations. This paper will first introduce the classical method using non-structural masses, local masses and high values of acoustic damping to represent the trim which shows limitations for predicting the response above 200Hz and does not allow a detailed analysis of the effect of trims on the vibro-acoustic behavior of the vehicle. A review of the literature of the evolution of the modeling techniques for full vehicles with PEM representation of the trims is presented from early models with only some porous trims represented as PEM to the latest ones where most of the trim parts ranging from acoustic porous trim (dash insulator, absorbers, etc.,) to the elastic plastic parts (dashboard, pillar trims, etc.,) are included in the model. The influence of modeling accurately the coupling conditions between the trims and the inner cavity or the structure will be discussed. The different results available to diagnose the problems and the influence of the design improvements and visualize them via methods such as intensity contour plots will be introduced.