On testing of the stiffness and the dent resistance of autobody panels

Abstract

The purpose of this study has been to establish a platform which can be used in future attempts to set up at least a reasonable (scientifically based) company standard for stiffness and dent resistance tests. Stiffness and dent testing equipment was developed and used in this investigation. This equipment, which is mounted in a mechanical testing machine, consists chiefly of three parts: a table, on which the panel is placed; a fixture, which is used to restrain the panel; and a punch, with which the panel centre is loaded. Two different punches are used: a flat-headed punch of diameter 100 mm in the stiffness tests and a hemispherical punch of diameter 25 mm in the dent resistance tests. The boundary conditions play a significant role in the stiffness and the dent resistance measurements. The largest stiffness is obtained with the boundary configuration case I, whilst the boundary configuration case IV yields the smallest stiffness. The attained experimental results show that the thicker the sheet thickness at the panel centre, the greater will be the panel stiffness. The greater the panel radii (the more severe the springback), the smaller the stiffness. The experimental results show too that the larger the initial yield strength, the higher is the dent resistance. The thicker the sheet, the higher is the dent resistance.