Investigation on strain dependent elastic behavior for accurate springback analysis

In the field of metal forming the effect of springback is of great importance and is one of the research areas. The amount of springback depends substantially on the materials' elastic behavior and the degree of strain hardening. Former studies showed that Young's modulus is influenced by strain hardening and thus detailed knowledge about this correlation is necessary. For an accurate description of strain dependent Young's modulus, a generally valid and consistent formulation in terms of continuum mechanics is required. To reconsider existing formulations, a close examination of the additive decomposition of elastic and plastic strains is necessary that is revealed within this study. Cyclic tensile tests with mild steel DX56 are performed to investigate the strain dependency of Young's modulus experimentally. The theoretically derived formulation is applied to the experimental results. On this basis different determination methods for identifying Young's modulus are utilized and finally analyzed in terms of springback prediction. Finally a new strategy to predict springback is proposed.