18. Improvement of Denting Behavior of Aluminum Sheet by Pre-stretching

In order to evaluate the resistivity of flat parts in the outer car body skin to mechanical loads denting experiments are performed. During a denting experiment the aluminum sheet is continuously loaded normal to its surface up to a maximal force with a punch. The characteristic denting resistance and denting stiffness are calculated from the experimental data. In general an increase of the flow strength has positive effects on the resistance to denting. The mechanical resistivity of aluminum sheet metal against plastic deformations which is the flow strength is being improved by pre-stretching as the material strain hardens during stretch-forming. In this work two different 6xxx aluminum alloys are pre-stretched in uniaxial direction up to major strains of 0.02, 0.05, 0.08 and 0.1 with a device for segmented stretch-forming. Subsequently quasi-static denting tests have been performed. Characteristic values of the denting tests have been evaluated and compared with the mechanical properties of the respective pre-stretched sample.