Analysis of the permanent deformation of automobile hoods

Abstract

One factor that determines the quality of an automobile’s appearance is its appearance integrity, which means that the degree to which an automobile’s physical appearance coincides with its mechanical quality. The painting process of an automobile can cause the permanent deformation of its hood, which lowers its appearace integrity. The painting process is comprised of the dipping process and the oven process. In the dipping process, pressure caused by the flow of fluid can cause the deformation of the automobile hood; in the oven process, the thermal deformation of sealers can cause the deformation of the hood. In an effort to increase automobiles᾿appearance integrity, this study identifies the major causes of deformation and predicts the types of deformation occurring in each process. The numerical model of a hood is established using the stiffness scanning method and analysis, and deformation in the dipping process is confirmed using Finite Elements Method (FEM). Sealers are hypothesized as the main reason for deformation in the oven process, so a study of the sealers is conducted to predict the deformation occurring after the oven process. Further, through a thermal property experiment and viscosity test, we are able to deduce the properties of sealers that cause deformation. This study also examines the effects of hood deformation in the oven process using numerical analysis and compares the degree of deformation caused by pressure and heat. The results show that the absolute value of deformation in the dipping process is greater than that in the oven process. Moreover, it is shown that deformation can occur bi-directionally in the oven process, and the quantity of mastic sealer does affect the degree of deformation.