A New Equivalent Static Load (ESL) Creation Procedure for Complete Vehicle

When dealing with the structural behavior of a car body, analyzing the dynamic distortion in all body closure openings in a complete vehicle, provides a better understanding of the body characteristics compared to traditional static load cases such as static torsional body stiffness. This is particularly relevant for non-traditional vehicle layouts and electric vehicle architectures where mass distribution and in particular battery mass and stiffness play a completely different effect with respect to the internal combustion engine vehicles. A methodology typically adopted to measure the body response, e.g. when driving a vehicle on a rough pavé road, is the so-called Multi Stethoscope (MSS). The MSS is measuring the distortion in each body closure opening in two diagonals. During the virtual development, the distortion is described by the relative displacement in diagonal direction in time domain using a modal transient analysis. The results are shown as Opening Distortion Fingerprint ODF and used as assessment criteria within Solidity and Perceived Quality. By applying the Principal Component Analysis (PCA) on the time history of the distortion, a Dominant Distortion Pattern (DDP) can be identified. The DDP means that, for a given pavé time history, more than 50 % of the body deformation states are similar to each other. This paper presents a deeper analysis about the forces which are associated with this Dominant Distortion Pattern (DDP). The new aspect of this analysis is that all forces (54 in total) between the wheel suspension and the trimmed body are considered. Based on the results of this force analysis, a new procedure for creating an Equivalent Static Load (ESL) was developed. Finally, by automating this creation procedure it is shown how the new ESL can be integrated in the virtual vehicle development.