Springback Prediction of 6Xxx-Series Aluminum: Effect of Hardening Model, Friction and Binder Loading

Predicting the final shape of automotive structural components after springback is a challenge to the inclusion of high strength aluminum alloys into the vehicle body-in-white. Complex deformation paths and reverse loading of sheet material during forming operations can induce significant Bauschinger effects and kinematic hardening behaviour. Capturing the through-thickness stress gradient is critical when predicting springback, which is governed by tooling dynamics, frictional forces, and material plasticity. In this study, the anisotropic behaviour of a AA6xxx-T4 aluminum alloy was characterized to calibrate a BBC2005 yield function, kinematic hardening effects were characterized through a novel uniaxial compression-tension technique, and a technology demonstrator U-shaped rail component was formed and scanned to assess the final shape after springback. Multiple model variations were analyzed in AutoForm R12, modifying simulation control parameters, binder loading condition (uniform vs. column), friction model (Coulomb vs. TriboForm), and hardening model (isotropic vs. kinematic). The use of column binder loading paired with TriboForm friction model provided the most significant improvement for thinning and springback prediction accuracy with kinematic hardening being a second order effect compared to accounting for friction and binder force.