拉延筋对拉深成形及回弹影响的关键技术研究

发布时间：2018-04-02 00:17

本文选题：拉延筋　切入点：成形质量　出处：《合肥工业大学》2017年硕士论文

【摘要】：在汽车覆盖件成形过程中,会出现起皱、拉裂、回弹等现象,工程师往往通过设置拉延筋来改善板料的成形缺陷。传统拉延筋的形式较单一,使得板料成形质量不够理想。针对以上实际问题,该文以板料塑性成形理论为基础,通过设计五种不同组合形式拉延筋,运用有限元数值模拟方法,对HSLA350与AL6061两种材料进行U形件拉延有限元分析,分别得出两种材料六种模型的成形极限图及减薄率。结果表明:外推40mm拉延筋确实能够改变板料的应力分布,改善板料的成形质量。在六种模型中,外推拉延筋模型中流过拉延筋后板料主应力最小,减薄率最小。在回弹数值模拟中,预测了所有U型件模型的回弹位移及侧壁角度。结果表明:拉延筋能有效抑制侧壁回弹,其中外推拉延筋的回弹位移与侧壁角度最小。从理论上揭示U型件侧壁角度与板料应力梯度之间的关系,得出外推40mm拉延筋能够改变材料应力梯度,且梯度值最小。证明其强化后的材料不再流入模腔内部,达到改善U形件侧壁翘曲的目的。本文自主设计U型件冲压实验模具,完成两种材料六种模型的冲压实验。实验结果表明,外推40mm拉延筋模型中的板料成形效果最好,无起皱、开裂等现象。在侧壁减薄率结果中,HSLA350材料外推40mm拉延筋的板料减薄率最小;AL6061材料所有模型减薄率较为接近。在侧壁翘曲程度结果中,两种材料中外推40mm拉延筋模型中板料的侧壁角度小于其他组别,验证了模拟仿真结果的准确性。
[Abstract]:In the forming process of automobile panel, wrinkle, crack, springback and so on will appear. Engineers often use drawing bars to improve the forming defects of sheet metal.The traditional form of drawing bar is single, which makes the forming quality of sheet metal not ideal.In view of the above practical problems, based on the theory of sheet metal plastic forming, this paper designs five kinds of drawing bars with different combination forms, and applies the finite element numerical simulation method to the finite element analysis of HSLA350 and AL6061 for U-shaped drawing.The forming limit diagram and thinning rate of six models of two kinds of materials were obtained respectively.The results show that extrapolated 40mm drawbars can change the stress distribution of sheet metal and improve the forming quality of sheet metal.Among the six models, the main stress and the thinning rate of the sheet metal after flowing through the drawing bars are the minimum in the extrapolation drawing bar model.In the numerical simulation of springback, the springback displacement and lateral wall angle of all U-shaped models are predicted.The results show that the springback of the side wall can be effectively inhibited by the drawing bar, and the springback displacement and the lateral wall angle of the extrapolation drawbar are the least.The relationship between the lateral wall angle of U-shaped workpiece and the stress gradient of sheet metal is revealed theoretically. It is concluded that extrapolated 40mm drawbars can change the stress gradient of the material and the gradient value is the minimum.It is proved that the reinforced material will no longer flow into the cavity, which can improve the warpage of the U-shaped side wall.In this paper, U-shaped stamping test die is designed, and six models of two kinds of materials are completed.The experimental results show that the sheet metal forming effect is the best in the extrapolated 40mm drawing bar model without wrinkling and cracking.In the results of side wall thinning rate, the sheet metal thinning rate of HSLA350 material extrapolated with 40mm drawing bar is the lowest and the thinning rate of all models of AL6061 material is close to each other.In the results of side wall warping degree, the lateral wall angle of sheet metal in 40mm drawing bar model is smaller than that in other groups, which verifies the accuracy of simulation results.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG386

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