铝型材多点三维拉压复合弯曲成形工艺

轻量化薄壁型材三维弯曲结构件是高端装备制造业中一种难成形加工的关键零部件。针对此类制件的高精度、低成本的成形需求，提出一种拉弯-压弯相结合的铝合金型材三维弯曲成形工艺，设计多点联动的拉压复合成形单元体结构，通过水平方向由夹钳带动拉弯，垂直方向由各单元体上液压执行机构压弯，实现"W"形三维弯曲零件的成形，并研制成形装备样机。建立分析成形过程及回弹预测的数值仿真模型，通过试验对模型的有效性进行验证，仿真结果与试验结果回弹变形一致，回弹预测最大误差小于15%。此外，研究拉力对矩形截面型材拉压复合成形件回弹变形的影响规律，预拉伸力较补拉伸力对成形件的回弹减小趋势更为明显，当预拉伸力从零达到临界塑性应力Aσ_s时，总回弹减少了26.81%，为保证成形件不发生截面畸变和破裂等成形缺陷，确定了预拉伸力为Aσ_s、补拉伸力为0.3Aσ_s的最优工艺参数。所提出的多点三维拉压复合弯曲成形工艺解决了W形一类型材传统三维拉弯无法实现的多向曲率半径复杂弯曲成形的技术难题，为实现镜面对称结构件的成对一次成形提供了一种新方法。

Multi-points 3D Stretch-press Bending Technology for Aluminum Profile

The lightweight thin-walled three-dimensional (3D) curved structure parts are key components in the high-end equipment manufacturing industry, which are difficult to form and process. In order to satisfy the requirements of complex bending and low cost forming, a new type of multi-points 3D stretch-press bending technology for aluminum profile is proposed. The structure of multi-point linked flexible fundamental unit(FFU) for stretch-press bending process is designed. The clamp is used to drive the workpiece to close with the multi-points die (MPD) in the horizontal direction. Once the clamps reach the target position, the hydraulic piston rod of each FFU presses down to shape the workpiece in the vertical direction. According to the forming principle of this new process, a prototype of forming equipment is developed, which realizes the forming of the W-shpae part. Then a numerical simulation model is established to analysis the forming procedure and to predict springback. The forming experiments are conducted to verify the simulation model. It can be seen that the simulation results are in good agreement with the experimental results. The maximum prediction error is less than 15%. In addition, the effect of tensile force on springback deformation in this process is studied. When the pre-stretch force reaches the critical plastic stress Aσ_s from zero, the total springback decreases by 26.81%. The conclusion can been drawn that the pre-stretch force has more obvious effect on springback reduction than post-stretch force. In order to ensure that the forming parts do not have forming defects such as section distortion and fracture, the springback are 6.13 mm and 4.11 mm in the horizontal and vertical directions with the optimum process parameters pre-stretch force Aσ_s and the post-stretch force 0.3 Aσ_s in forming of a W-shape target part. The multi-points 3D stretch-press bending process is proposed to realize complex bending of multi-direction radius of curvature, such as the W-shape part. A new method is provided to achieve the pairwise forming of the mirror symmetrical structural parts which will be applied in high-end equipment manufacturing industry.