Analysis of FEM Results Based upon FOA

In FOA (First Order Analysis) any vehicle body structure might be interpreted as a collective simple structure that can be decomposed into 3 fundamental structure types. The first structure is the “BEAM”, whose cross sectional properties as well as its material dominates the mechanical behavior, the second is the “PANEL (shear panel, plate, and shell)”, whose mechanical behavior can be varied by changing its geometrical properties in the thickness direction, i.e. adding beads or flanges. The third structure is the “JOINT”, which connects the proceeding structures, and transfer complex three-dimensional loads with three-dimensional deformation. In the present work, we shall propose a methodology to identify a portion of an arbitrary FE model of an automotive body structure, with a “BEAM” structure in the FOA approach. In the latter chapter of this paper, cross section loads will be related with cross sectional properties in the aspect of the element strain energy concept. Comparing the ratio of contribution of each physical energy component can help us to decide which cross sectional properties are not efficient and need to be improved under a specific loading condition. In order to check the validity of this approach, some examples of validation that use a simple box beam and a practical vehicle body structure will be presented. Finally, sizing optimization which employs the Response Surface Methodology (RSM) will be introduced in order to stiffen a cross sectional property which shows poor capacity relatively.