Design process to minimize roof surface defects by flexural function computed by Finite Element method

초록

Appearance and exterior precision of the vehicle has become important factor as well as the performance. However curvature of the roof changes after oven process. In this study, Finite Element Analysis (FEA) is used to establish a method to predict the curvature change on the roof. Critical factor of curvature change on the roof is the thermal behavior of mastic sealer. Mastic sealer is a blowing agent which is applied between roof exterior panel and rails. Therefore the mechanism of the mastic sealer is considered to predict the curvature change accurately. Validation of the simulation model is performed by comparing the location and amount of the curvature change on the roof. In order to minimize the curvature change, Taguchi method is used. Total of eight factors are chosen for sensitivity analysis. In order to exclude the deformation due to residual stress after the oven process, it is selected as noise factor. Response is the maximum curvature change calculated by flexural function. Flexural function is introduced to distinguish absolute curvature that is not affected by the horizontal or vertical movement of roof panel. Flexural function calculates slope of plane normal vector for each nodes before and after the oven process. Total 18 cases are performed and as a result, length of each sealer, pitch of sealer, and location of rail are the most influential factors on the curvature change. Based on the result, optimized values are investigated. Using the optimum values, curvature change is reduced 12 percent.

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