Determination of stiffness characteristics and surface deflection by using virtual joining properties

Abstract

Hood stiffness scanning tests were conducted and numerical modeling of hoods was implemented to simulate hoods having the same stiffness as the test results in order to predict the hood surface deflections occurring during the dipping process among automobile manufacturing processes through the finite element analysis (FEA). The flow stress of the mastic sealer and the hemming sealer was measured through viscosity tests to express the material properties of the adhesive and decreases in the thickness of inner panels were reflected in order to accurately calculate surface deflections. The yield stress of the hemming part and the width of the master sealer were selected as virtual joining properties so that joint complexity and singularity could be compensated for. The virtual joining properties were applied to a total of six hood models and tendencies that correspond to individual hood models were analyzed to define tendency functions thereby presenting a method of predicting virtual properties without undergoing stiffness scanning test and analysis processes. When the results of analyses that predicted surface deflections after dipping processes were compared to 3D-scanning results, the results of analyses were found to have accuracy not lower than 85%. In addition, analyses to predict surface deflections after the dipping process were conducted using numerical models that reflected inner panels with reinforced stiffness and decreases in surface deflections were identified according to the results. Therefore, the fact that designs for reducing surface deflections after the dipping process could be made utilizing the technique implemented in the present study to predict permanent deformation of hoods was proved.