【作者】 薛鹏飞；

【导师】 李明哲；

【作者基本信息】 吉林大学 ， 材料加工工程， 2012， 硕士

【摘要】 柔性轧制成形技术，是一种使板材连续局部塑性成形的技术，由吉林大学无模成形技术中心提出并投入研究。该技术结合当今应用非常普遍的板材轧制技术与新型的多点成形技术，既有轧制成形效率高的优点，又有多点成形技术对成形工具柔性可调控的优点。柔性轧制成形利用形状可调节的成形辊，使成形的板材形状不再局限于普通轧制的平板类产品。包括球形件、鞍形件和其他更多变截面的三维曲面板类件都属于成形的范畴。本文在介绍了柔性轧制成形方法及成形原理之后，利用数值模拟软件建立柔性轧制成形的模型并对其成形过程进行模拟计算。对比不同下压量及辊弯半径下的板材成形效果，最后总结成形规律。研究的主要内容和结论如下：1、柔性轧制成形基本原理柔性轧制成形以一对柔性成形轧辊为工具。通过调节调形机构，轧辊产生弯曲变形，同时造成辊缝沿轧辊轴线方向非均匀分布。板料在此种轧辊作用下在横向方向产生不均匀的变形，导致板料沿轧制方向出现弯曲变形。依靠柔性辊自身的弯曲使板料在横向方向产生挠曲，最终实现板料的三维成形。本文首先分析了柔性轧制成形板料受力与变形的特点，在此基础上给出了用主应力法计算轧制应力的步骤，并给出不均匀变形的弯曲机制与变形抗力相关内容。最后讨论柔性辊调形的工艺和轧制过程中可能出现的偏差与缺陷。2、有限元模型的建立利用有限元模拟软件对板料成形进行数值分析，准确合理地建立有限元模型是取得正确结果的关键因素。柔性轧制成形两个主要参数为轧辊辊缝的宽度与辊缝宽度值的分布规律，体现在建模上就是不同的上辊下压量与辊弯形态。本文从辊弯形态以及柔性辊离散化的角度确定柔性轧制的建模方案，确定方案之后选择单元模型、材料模型、边界条件等建模参数，最终建立几何模型，并对模型各部件合理划分网格。3、柔性轧制成形数值分析柔性轧制成形作为一种新的板类成形方法，对其成形的结果进行检测与分析，关系着对此项技术优势的评估。由于柔性轧制成形的板料是三维曲面件，所以对成形曲面特征的描述以及应力应变分布的分析是两个评估的标准。本文从成形后板料的伸长量、厚度变化量两个方面分析轧制前后的塑性变形量。利用曲线拟合的方法对成形后的纵向曲线整体曲率进行测算，计算得到一个圆弧方程并求得近似的半径值。对横向特征线采用逆向工程的手段分析其曲率半径，得出结论为横向特征曲线整体曲率变化很小，也能近似以圆弧表示。最后对能代表成形特征的变形均匀区域进行高斯曲率统计计算得出变形后板料的曲面形状接近球面。通过对轧制初始阶段、轧制成形中、轧制结束后板料的应力应变分布与变化趋势，总结得到柔性轧制成形的成形特征。4、下压量与辊弯半径对柔性轧制的影响柔性轧制成形最主要的参数为下压量和辊弯曲半径。本文在其他参数保持不变的前提下对这两个因素分别独立对比分析，通过比较塑性变形量、成形后表面的曲面特征以及应力应变分布得出结论。认为下压量是板料产生变形的原因，其影响着板料塑性变形量、曲面特征。辊弯半径的变化对塑性变形量变化影响很小，对板料的横向与纵向曲率分布有影响，对板料的高斯曲率影响很小，即认为下压量一定时，不同的辊弯半径成形出的球形件曲率半径近似一致。另外，辊弯半径的增大导致板料的应力与应变分布更加合理，变形更加均匀。更多还原

【Abstract】 Flexible roll forming technology, as a kind of continuous partial plastic forming，isbeing raised and researched by the Jilin University dieless forming technology center. Thistechnology combines traditional rolling forming and new multi-point forming（MPF）.It notonly has the normal rolling forming technology’s advantage, high efficiency, but also hasthe MPF’ characteristic, flexible and adjustable forming tools. Flexible roll forming uses akind of rollers whose shapes are adjustable. Through these special rollers, the products arenot only limited to flatbed models, but also other complex types such as spericity, saddletype and irregular sections.After introduced the theory of flexible roll forming, this text sets a basic model by thedynamic explicit finite element software and simulates the forming process, After this, wesum the rules by means of comparing the forming result under different press amounts anddifferent radius of rollers. The main contents and results of the research are as follows:1. The basic principles of flexible roll formingFlexible roll forming uses a couple of flexible rollers as forming tool. Throughadjusting regulators, the rollers are bending deflection. At the same time, the space betweenup rollers and down ones is not uniformly distributed. With this model, the sheet will bechanged into non-uniform transformation and the sheet will turn to curve at the direction offorming. The lateral deflection of sheet is come form flexible roller’s itself curve. Finally,the sheet changes into3D-surface.This article analyses the feature of force and deformationat first, and then derived the stress calculation formula by slab method. On this basis, weget the principle of sheet bending forming and the content about resistance of deformation.Finally, the adjustable technology and forming defect are given.2. Finite element model creationIt is a key factor to create a exact and reasonable finite element model when we want acorrect option in the simulation of flexible roll forming. There are two importantparameters in flexible roll forming, one is the space between up and down rollers, another isthe change low of the space along the axis of rollers. In the finite element model, we callthese two parameters press distance and roller radius. In this paper, the model is created at the view of roller bending shape and discretization. After creating the model, we choose theelement types, material models and boundary conditions and so on.3. Flexible roll forming numerical analysisFlexible roll forming is a new technology, the diction and analysis report of formingresult has a direct bearing on the evaluation of this new technology. Since the production offlexible roll forming is3D-surface sheet metal, the evaluation criteria of the surfacemeasure includes two fields as follows: surface feature and stress/strain distribution. Thistext analyses plastic deformation into two ways including elongation and thicknessreduction. Through the ways of coordinate figure fitting, we found the longitudinal curvecan be defined as a circular arc, whose radius can be fixed. Meanwhile, we use reverseengineering to analyze the transverse feature line and get the result that the curve is similarto a circular arc too. Finally, we pick up and calculate the Gaussian Curvature form thehomogeneously deformed local areas which can represent the forming characteristic, theresult is such area has a nearly same value. Therefore, the surface can be attributed tospherical surface. Through the stress/strain distribution and variation tendency of sheet atthe beginning, middle and end of forming process and, it can be summed a formingcharacteristic about flexible roll forming.4. The influence on flexible roll forming by the press distance and roller’s radiusThe two important parameters of flexible roll forming are press distance and roller’sradius. In this paper, these two parameters are relative analyzed dividedly. Through thecomparation of plastic deformation, the character of the formed surface and stress/straindistribution, we can conclude that the press distance is the major parameter of plasticdeformation, which affects the value of deformation and curved character. Meanwhile, thechange of roller radius has little relationship with plastic deformation and the value ofGaussian Curvature. However, the roller’s radius affects the latitude and longitudecurvature distribution. That is to say, as the press distance is a fixed value, the GaussianCurvature of formed spherical surface is foreign to roller’s radius. In addition, the shapedsheet’s stress/strain distribution will be more reasonable and the deformation will be morewell-proportioned.更多还原