This study systematically analyzes the theoretical foundations, process characteristics, and forming mechanisms of tube bending and hydroforming. For stainless steel thin-walled shaped tube fittings, a sequential forming process combining CNC roll bending and hydroforming is proposed. A full process chain finite element model integrating bending and hydroforming is established using AutoForm TubeXpert R10 to investigate the influence of process parameters on the deformation behavior of shaped thin-walled tube fittings. Findings indicate optimal forming results occur at a tube diameter of 62 mm and a bending radius of 95 mm. A bending angle of 55° demonstrates superior cross-sectional distortion control. Hydroforming internal pressure improves tube forming conditions, with 40 MPa delivering the best overall performance. An axial feed of 5 mm is the optimal choice. A friction coefficient of 0.15 achieves a favorable balance between wall thickness control and die-following performance. Comprehensive analysis determined the optimal parameter combination for the bending-hydroforming process of thin-walled shaped tubes, achieving the best balance between uniform wall thickness distribution, cross-sectional shape accuracy, and mold-following quality. Experiments employed SUS321 stainless steel tubing to systematically validate the simulated process parameters for bending-hydroforming of thin-walled shaped tubes. Measured wall thickness deviations between bent and hydraulically formed parts remained within 2% of simulated predictions.
Zhang et al. (Wed,) studied this question.