SEA Model Building of Automotive Vehicle Body in White Using Experiment and FEM

Many papers have published techniques for estimating SEA parameters using Finite Element Methods (FEM). We have also developed a technique for virtual prototyping of an automotive vehicle body using FEM. In our technique, FEM models are used to derive parameters for an SEA model. The technique does not require a FEM model of the whole system, but uses extracted FEM models that include subsystems sharing a single junction. The subsystem energies and power inputs are calculated by frequency response analysis in FEM. The determination of loss factors is based on the Power Injection Method (PIM). The objective of this work is the construction of an SEA model of a passenger car body-in-white. The model has only structural subsystems.

In order to develop a model with high accuracy, the subdivision of the tested body-in-white is first evaluated using the Initial Slope Ratio (ISR) indicator that shows the coupling strength between subsystems. Based on the ISR indicators, the body-in-white is divided into 38 structural subsystems. The calculations of extracted FEM models for damping and coupling loss factors construct an SEA model of the test car body-in-white.

The constructed model is used to predict the subsystem energy levels. It is shown that the results are in good agreement with the measured levels from shaker tests and the full FEM analysis results of the whole car body-in-white for every SEA subsystem. And, the technique using FEM is applied to predict the subsystem energy change due to structural change in order to test the effectiveness of the constructed models. It is shown that we can predict the energy changes with high accuracy.