Accurate prediction of the profile of thick-walled titanium alloy tube in rotary-draw bending considering strength-differential effect

In rotary-draw bending of thick-walled titanium alloy tube, the tube material exhibits a strength-differential effect (S-D effect) due to the compressive stress state at the inside region but the tensile stress state at the outside region. Neglecting the S-D effect will lead to a significant decrease in the prediction accuracy of the profile of the bent tube, such as wall thickening/thinning degree, cross-section distortion degree and springback angle. Therefore, a new FE model considering the S-D effect is established in this work. In modeling, the material properties obtained from uniaxial tension and compression tests are applied to the outside region and inside region, respectively. Combined with the experiments, the present model is compared with the previous one with only applying tensile material properties to evaluate their prediction accuracies on the tube profile. The results show that, compared with the previous FE model, the present one is more reliable to accurately predict the wall thickening degree, cross-section distortion degree and springback angle for bending specifications φ14 × 1.35 × 42 and φ20 × 1.9 × 60 (tube outer diameter × wall thickness × bending radius, mm) with precisions improved even by 21%, 25% and 17%, respectively.