THE EFFECT OF STRAIN RATE ON POSITION OF FORMING LIMIT CURVE

To evaluate formability in sheet metal forming, experimentally determined Forming Limit Curves (FLC) are often used. These conventional curves represent the forming limits of a material. The most widely used approach to experimentally determine the onset of necking of sheet metals is formulated in EN ISO 12004-2. The first goal of this work is to investigate limit strains for dual phase steel HCT490X with nominal thickness 0.6 mm. The second goal is to evaluate influence of strain rate on position of forming limit curve also for material HCT490X. The FLC curve has been measured through Nakajima test on universal testing machine. The test set-up and the shape of samples result from EN ISO 12004-2. Unrepeatable, isotropic and highly contrast pattern was applied on samples and was measured using 3D photogrammetric system ARAMIS by GOM. The punch movement velocity was gradually changed and experimentally measured forming limit curves are compared in this paper.