Cross-section distortion and springback characteristics of double-cavity aluminum profile in force controlled stretch-bending
(1. School of Mechanical Engineering, University of South China, Hengyang 421001, China;
2. State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle, Hunan University, Changsha 410082, China)
2. State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle, Hunan University, Changsha 410082, China)
Abstract: A 3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit-implicit solvent method. Considering the computational accuracy and efficiency, the optimal choices of numerical parameters and algorithms in FE modelling were determined. The formation mechanisms of cross-section distortion and springback were revealed. The effects of pre-stretching, post-stretching, friction, and the addition of internal fillers on forming quality were investigated. The results show that the stress state of profile in stretch-bending is uniaxial with only a circumferential stress. The stress distribution along the length direction of profile is non-uniform and the maximum tensile stress is located at a certain distance away from the center of profile. As aluminum profile is gradually attached to bending die, the distribution characteristic of cross-section distortion along the length direction of profile changes from V-shape to W-shape. After unloading the forming tools, cross-section distortion decreases obviously due to the stress relaxation, with a maximum distortion difference of 13% before and after unloading. As pre-stretching and post-stretching forces increase, cross-section distortion increases gradually, while springback first decreases and then remains unchanged. With increasing friction between bending die and profile, cross-section distortion slightly decreases, while springback increases. Cross-section distortion decreases by 83% with adding PVC fillers into the cavities of profile, while springback increases by 192.2%.
Key words: hollow aluminum profile; force controlled stretch-bending; numerical parameters; springback analysis approach; cross-section distortion; springback; process parameters