Prediction of springback for ultra high strength steel sheets

The prediction of springback is of great importance to broaden the application of ultra high strength steel sheets, which always exhibit large of amount of geometric deviation after removal from the tools due to the high elastic strain and the small thickness. In the current work the Lemaitre-Chaboche type isotropic-kinematic model is applied to describe the strain hardening during forming and springback, which takes into consideration both the size extension and the centre movement of the yield locus. The parameters of the kinematic component are calibrated by tensile test as well as hydraulic bulge test, which is essential in the way that a much higher strain level is achievable than in tensile test. The isotropic component is characterised by cyclic uniaxial tension-compression test. Two simple representative tests including top hat drawing and bending under tension tests are performed and simulated with ABAQUS code. Sensitivity study is carried out to investigate the influence of different tooling and processing parameters on the springback amount. The simulation results of the two tests with Lemaitre-Chaboche model correlate well with the experiments. The application of the methodology to industrial parts proves that it is capable to guide the more complicated industrial forming processes