复杂截面冷弯成形圆角减薄率工艺优化研究

目的 针对复杂截面车门中导轨冷弯成形过程复杂、道次繁多、Z字筋圆角减薄率过大等问题，基于车门中导轨冷弯成形工艺，优化Z字筋圆角冷弯成形工艺和减薄率。方法 利用COPRA FEA有限元仿真软件对车门中导轨成形过程进行分析，研究轧辊圆角半径、成形速度、成形策略等对圆角减薄率的影响，结合有限元分析手段不断优化工艺参数来实现中导轨Z字筋圆角精确成形，最终提出最优工艺方案并进行实验验证。结果 对于大圆角成形工艺，圆角处弯曲中性层完全位于料厚范围内，在料厚方向上既有压应力又有拉应力，壁厚减薄量较小;对于小圆角成形工艺，圆角处中性层偏出内弧面，在料厚方向上均受拉应力，壁厚只存在减薄的趋势。实验结果表明，Z字筋圆角厚度由1.33 mm变成1.46 mm，减薄率由原来的26.1%降低至18.89%。仿真结果表明，Z字筋圆角厚度由1.29 mm变成1.52 mm，减薄率由原来的28.3%降低至15.6%。对比仿真结果与实验结果可知，仿真分析最大误差为4.1%，仿真结果具有一定的可靠性。结论 最优工艺路线如下:采用大圆角、慢速成形，成形策略为中前期大圆角成形+后期小圆角成形，成形圆角半径分别为4.5、3.5、2.8、1 mm，弯折角度分别为45°、65°、78°、90°，该方案可以有效解决圆角减薄率过大的成形缺陷。

Optimization of Fillet Thinning Rate Process for Cold Bend Forming with Complex Sections

The work aims to optimize the cold bend forming process and thinning rate of the Z-shaped rib fillet based on the cold bend forming process of the guide rail in the complex cross-section car door, so as to solve the problems of complex processes, numerous passes and excessive thinning rate of the Z-shaped rib fillet. COPRA FEA finite element simulation software was used to analyze the forming process of the middle guide rail in the car door, and study the effects of roller fillet radius, forming speed, forming strategy, etc. on the fillet thinning rate. By combining finite element analysis methods, the process parameters were continuously optimized to achieve accurate forming of the Z-shaped rib fillet in the middle guide rail. Finally, the optimal process plan was proposed and verified through experiments. In the forming process of large fillet, the bending neutral layer of fillet was within the range of material thickness, and there were both compressive and tensile stresses in the direction of material thickness, resulting in a smaller reduction in wall thickness. In the forming process of small fillet, the bending neutral layer of the fillet deviated from the inner arc surface, and the material thickness direction was subject to tensile stress, resulting in a trend of only thinning the wall thickness. The experimental results showed that the thickness of the Z-shaped fillet changed from 1.33 mm to 1.46 mm, and the thinning rate decreased from 26.1% to 18.89%. The simulation results showed that the thickness of the Z-shaped fillet changed from 1.29 mm to 1.52 mm, and the thinning rate decreased from 28.3% to 15.6%. The comparison between simulation and experimental results showed that the maximum error of simulation analysis was 4.1%, which verified the reliability of the simulation results. The optimal process route is to use large fillet and slow forming. The forming strategy is to use large fillet in the early stage and small filler in the later stage. The forming radius of the fillet is 4.5, 3.5, 2.8 and 1 mm, and the bending angle is 45°, 65°, 78° and 90°. This process plan can effectively solve the forming defect of excessive fillet thinning rate.