连续辊压成形中的曲面成形机制及成形过程设计方法研究

发布时间：2018-06-15 19:28

本文选题：连续成形 + 柔性辊　；参考：《吉林大学》2015年博士论文

【摘要】：三维曲面零件具有质量轻、强度高、造型美观等优点，被广泛的应用于制造业的各个领域。随着制造技术的飞速发展，三维曲面零件的需求也从大批量单一类型产品向小批量多样型产品转化。模具成形精度高、一致性高是加工曲面件的重要方法，但是并不适合加工不同类型的大型曲面件，且每种零件的生产都需要开发相应的模具，制造成本高昂、生产周期长，也不适合生产单件、小批量产品，因此，迫切需要一种新的柔性成形工艺以适应发展的时代需求。曲面连续辊压成形是一种新型的板料柔性成形技术，可以连续、柔性的加工三维曲面件，适用于不同形状大型三维曲面件的成形。由于成形过程中板料的塑性变形较大，回弹较小，又能通过一套设备加工不同形状零件，该技术具有良好的应用前景。目前曲面连续辊压成形的研究还处于起步阶段，在成形原理、过程设计方法、成形件精度等方面还存在许多亟待解决的问题。本文通过对曲面连续辊压成形过程中板料的弯曲变形的理论分析，建立了横向、纵向弯曲变形方程，给出了过程设计方法，并从数值模拟与实验等方面对该成形方法进行研究。本文研究的主要内容和结论如下：（1）根据曲面连续辊压成形的变形特点，分析成形过程中板料横向、纵向弯曲变形机制。连续成形时，板料在进入上、下柔性辊间接触区之前已经产生横向弯曲变形，到达接触区时，横向曲率已接近柔性辊曲率，板料变成柱面；在接触区内，板料厚向不均匀减薄，纵向不均匀伸长，发生弯曲形成双曲率曲面，，随着柔性辊的旋转，板料的变形在进给方向上积累完成曲面件的成形。建立纵向弯曲变形的基本方程，得到成形件纵向曲率与辊缝中线形状及辊缝分布的关系，典型的两种辊缝分布形式为中间宽两边窄及中间窄两边宽形式。弯曲变形分析中引用平面假设，文中通过数值模拟方法从三个方面验证平面假设的合理性。分析板料的纵向伸长变形、厚向减薄变形，得到纵向伸长量及厚向减薄量的分布公式，通过数值模拟结果验证纵向伸长量分布、厚向减薄量分布规律。（2）建立基于成形件目标曲面设计连续辊压成形过程的方法。对于通过目标件的CAD数模不能直接得到其横向截面线方程及纵向曲率情况，给出横向截面线的NURBS描述及纵向曲率的计算公式。上、下柔性辊轮廓基于目标曲面横向截面线设计，上、下柔性辊之间的辊缝基于目标曲面纵向曲率设计，建立由于辊缝设计的通用公式，设计辊缝应使板料减薄量呈线性分布。柔性辊形状通过控制单元调节，讨论控制点数量对调形精度的影响。基于提出的过程设计方法，进行实验，成形出负高斯曲率曲面及正高斯曲率曲面，实验结果表明，成形件的表面光滑、成形效果良好，说明采用以上过程设计方法加工三维曲面零件具有可行性与有效性。（3）研究成形典型件时上、下柔性辊间接触区的形状，讨论曲面连续辊压成形过程压力载荷分布，给出总成形力的计算公式。通过数值模拟方法分析成形过程中应力应变场的分布，给出模拟件横纵向曲率精度及模拟件与目标件的法向误差分布。板料减薄量不满足线性分布时，可能导致成形件失稳起皱，分析失稳起皱原因及典型件的易起皱区域，发现起皱区域应力应变水平远大与其他位置，辊缝宽度分布与设计辊缝的偏移量越大起皱越严重。成形过程中板料与柔性辊之间的相互作用力会使柔性辊轮廓再次变形，使板料减薄量无法满足线性分布，影响成形件形状。通过数值模拟分析以钢丝软轴作为支承辊时工作辊总成的变形，发现柔性工作辊弹性变形量较小，钢丝软轴由于结构原因发生较大的弹性变形，给出补偿方法，经过数次补偿后辊缝分布精度明显提高。介绍一种以光轴作为支承辊的改进方法，采用直线光轴作为支承辊不需要补偿就能达到较高精度。（4）进行曲面连续辊压成形实验，采用以钢丝软轴作为支撑辊及以直线光轴作为支撑辊的两套设备加工负高斯曲率曲面与正高斯曲率曲面。采用钢丝软轴作为支撑辊时，进行多次补偿可提高辊缝宽度精度，采用直线光轴作为支撑辊时，不需要补偿可使辊缝宽度达到较高精度。成形件的成形效果良好，精度较高，厚度分布规律与纵向曲率半径分布规律均与理论一致，证明过程设计的合理性。
[Abstract]:With the rapid development of manufacturing technology , the demand of three - dimensional curved surface parts is transformed from mass single - type products to small - batch - type products .

The continuous roll press forming of curved surface is a new type of flexible forming technology , which can be continuously and flexibly processed three - dimensional curved parts . It is suitable for the forming of large - scale three - dimensional curved parts with different shapes .

The main contents and conclusions of this paper are as follows :

( 1 ) according to the deformation characteristic of the continuous roll forming of the curved surface , the transverse and longitudinal bending deformation mechanism of the plate material in the forming process is analyzed .
In the contact area , the thickness of the plate is not uniform and thin , the longitudinal non - uniform elongation , the bending forming the double curvature curved surface , along with the rotation of the flexible roller , the deformation of the sheet material accumulates the forming of the curved piece in the feeding direction .

( 2 ) To establish a method for designing the continuous roll forming process based on the target curved surface of the forming part . The calculation formula of the NURBS description and the longitudinal curvature of the transverse section line can not be obtained directly by the CAD model of the target piece . The upper and lower flexible roll profiles are designed based on the transverse sectional line of the target curved surface . The design of the roll gap is based on the design of the longitudinal curvature of the target curved surface . The design roller seam should be designed according to the longitudinal curvature of the target curved surface . The design roller seam should be designed according to the longitudinal curvature of the target curved surface . The design roller seam is designed based on the longitudinal curvature of the target curved surface . The experimental results show that the surface of the forming part is smooth and the forming effect is good . The feasibility and effectiveness of the three - dimensional curved surface parts processed by the above process design method are explained .

( 3 ) The shape of the contact zone between upper and lower flexible rollers during forming process is studied , the pressure load distribution in the continuous roll forming process of curved surface is discussed , and the calculation formula of total forming force is given .

( 4 ) A curved surface continuous roll press forming experiment is carried out , and the negative Gaussian curvature curved surface and the normal Gaussian curvature curved surface are processed by using a steel wire flexible shaft as a supporting roller and two sets of equipment with a straight optical axis as a supporting roller .
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG306

【参考文献】