Formability and Instability Evaluation of Friction Stir Processed AA6063-T6 Tubes During End Forming and Numerical Prediction

Abstract

In the present work, formability of friction stir processed (FSPed) AA6063-T6 tubes during end forming has been evaluated by monitoring load evolution and instability. FSP has been done at different tool plunge depths to study its effect. End expansion, reduction and beading of tubes are performed. Energy absorption capacity of the FSPed tubes is also evaluated. Both experiments and finite element (FE) simulations of end forming are carried out. During FE simulations in ABAQUS v6.17, the processed zone properties including plastic strain ratio and actual thickness are incorporated, along with raw material properties. Out of all the plunge depths, FSP zone made at 2.95 mm shows larger flow strength, ductility, strain hardening exponent and lower dislocation density. However, at 2.95 mm plunge depth, the tube encountered larger thinning due to larger ductility. Moreover, FSP zone having lower flow strength show larger thickening. The results also reveal that the FSP tubes have potential to replace raw tubes as it needs lower forming load and perform equally in specific energy absorption during end reduction and beading. Numerical predictions and experimental data agree well in terms of load requirement during expansion and reduction, while in beading, significant difference is observed after bead initiation. Though FSP tubes have potential applications, instabilities during end forming may restrict their applications at certain situations, which can be improved by FSP parameter optimization.