A Comparative Study on the Formability Prediction of Steel Sheets by Anisotropic Models Based on Associated Flow Rule and Non-Associated Flow Rule

A comparative study on the formability prediction of a ferritic steel sheet by anisotropic models based on associated flow rule and non-associated rule is carried out. The uniaxial tensile tests along seven directions of the sheet from rolling direction to transverse direction with an interval of 15° are performed for the anisotropic yield stress and r-value. For the biaxial stress state, both bulge test and punch test are performed. The BBC2003 based on the associated flow rule is employed and its anisotropic parameters are calibrated to the yield stresses and r-values from the tensile tests along rolling direction, transverse direction and diagonal direction and the biaxial test. The non-associated quadratic Hill48 model is also calibrated to the same set of experimental data. Similar level of the predicative capability on the yield and plastic deformation directionality by the associated and non-associated based models is observed. With the common basis on the anisotropic plasticity characteristics, they are combined with the Marciniak–Kuczynski (MK) model to predict the formability of the steel sheet and distinct difference in the prediction is observed between the two models.