On twist springback prediction of asymmetric tube in rotary draw bending with different constitutive models

Springback and twist deformation of asymmetric AA6060-T4 aluminum tube in rotary draw bending process are studied experimentally and numerically. Of particular interest is the influence of constitutive model on the twist springback prediction results. The whole forming and springback process of this aluminum tube is performed using the finite element code ABAQUS. Several material models are analyzed, all considering isotropic and kinematic hardening combined with one of the following plasticity criterion: von Mises, Hill׳48 and Yld2000-2d. The material parameters of these constitutive models are determined from the tensile and forward-reversal shear tests of the tube. The material tests show that transient Bauschinger effect and curve crossing phenomena are observed for this tube subjected to reversal loading. The capability of two hardening model, naming isotropic and combined isotropic/ kinematic hardening model, to capture these behaviors are discussed. Comparison between the wist springback prediction results by different constitutive models shows that the springback angle is more sensitive to the hardening model while the twist deformation is more sensitive to the yield criterion. The stress distributions of the tube during different forming stages are analyzed and some explanations concerning their influence on springback mechanism are given. A detailed study on the tangent and hoop stress distributions of the tube also explains some source of the twist deformation for this asymmetric tube.