Significance analysis of processing parameters effect on springback in high strength TA18 tube NC bending

The significant springback occurring after unloading in numerically controlled (NC) bending of high strength (HS) titanium alloy tube will affect the geometric and shape accuracy severely. A 3D elastic-plastic FEM containing NC bending, mandrel retracting and springback process of HS TA18 tube was established based on ABAQUS platform, and reliability assessment has been carried out. The influence significance and rules of processing parameters on springback of HS TA18 tube have been investigated by means of virtual orthogonal tests. It is shown that mandrel protrusion length, friction coefficient between bending die and tube, clearance between pressure die and tube, relative boosting velocity and clearance between mandrel and tube have a significant influence on springback. The mandrel protrusion length has the negative effect on the springback angle. The friction coefficient between bending die and tube, clearance between pressure die and tube, as well as clearance between mandrel and tube have the positive effects. The springback angle increases obviously when relative boosting velocity is lower than 1. Moreover, the prediction model between springback angle and significant processing parameters was established by multi-linear stepwise regression. Compared with virtual tests results, the relative error is less than 5% for φ12 mm×t1 mm×R36 mm HS TA18 tube.