Theoretical and Numerical Investigation of the Limit Strain of a 5754-O Aluminum Alloy Sheet Considering the Influence of the Hardening Law

This work focuses on the limit strains of 5754-O aluminum alloy sheets with consideration of the hardening law effect. Based on uniaxial tension test data, the hardening laws of Swift, Voce, LSV and Hockett–Sherby were applied to determine the mechanical properties. The fitted parameters and the Yld2000-2d yield function were introduced into the Marciniak–Kuczynski (M–K) theory to predict the forming limit curve (FLC). This prediction was not consistent with the Nakajima test results. Assessment of the effect of the hardening law on the predicted FLC indicated that the hardening law affected the yield surface evolution through the hardening rate. Afterward, an improved LSV hardening law was proposed to depict the plastic stress–strain relationship, and both the theoretical prediction and the numerical simulation verified the validity of the improved model. The results were compared with the test data, and good agreement was shown.