The stiffness and buckling behavior of panels with stamping-induced imperfections

Abstract

With the decrease of sheet thickness, the stiffness and buckling behavior of automobile body panel are more and more concerned. In this paper, the stiffness and buckling behavior of panels with stamping‐induced imperfection is studied. Imperfections caused in drawing and springback are obtained by finite element analysis and introduced to define the initial state of the panel before indenting. The indenting procedure is simulated in ABAQUS Standard. In order to solve the buckling problem, a viscous pressure that is proportional to the relative velocity between surfaces is added artificially. For comparison, a simplified model in which imperfections are not considered is also established. Comparing the simulation results with the reference experiment, we find that the stamping‐induced imperfections lead to a more severe oil canning phenomena under a buckling load, although they increase panel’s initial stiffness a bit. Moreover, among all stamping‐induced imperfections, the geometrical imperfection (surface deflection) is beneficial to increase panel’s buckling load, and the material imperfections (residual stress and uneven thickness) help to decrease panel’s buckling load and can make oil canning more severe during post‐buckling. Influences of blank holder force, sheet thickness and material property on panel stiffness and buckling behavior are also studied. The work of this paper is beneficial to processing optimization, material selection, and reinforcement design for automotive exterior panels.