【作者】 高健；

【导师】 李明哲； 刘卫国；

【作者基本信息】 吉林大学 ， 材料工程（专业学位）， 2015， 硕士

【摘要】 曲面柔性轧制是一种新型的板类件连续柔性成形技术，依靠柔性辊间特殊形态的辊缝，板材在成形过程中能够发生双向弯曲，结合传统板材纵轧技术，可以实现三维曲面零件的连续、高效成形。相比其他曲面板类件的成形方法，曲面柔性轧制成形方法具有加工成本低、成形范围广、成形过程连续性好等优点，通过改变工作辊的弯曲状态和辊缝宽度的分布状态，可以成形出不同形状的曲面零件，能满足市场对曲面板材的个性化需求。因此，展开有关柔性轧制成形技术的理论、实验研究，具有重要的工程研究价值。本文的主要研究内容与结论如下：1)研究传统板材冷轧成形和柔性轧制成形中工作辊的特点，指出两种典型的辊缝形态，结合塑性成形原理分析柔性轧制成形过程中两种辊缝的成形效果，得知板料受挠曲工作辊的弯曲作用与辊缝的不均匀减薄作用是柔性轧制成形件双向弯曲的成因。对比传统板材轧制与柔性轧制中的工作辊与板料的接触状态，分析柔性轧制过程中的摩擦条件及接触力分布情况。探讨柔性轧制成形过程的几何原理，指出根据目标曲面零件逆向推导辊缝形态的可行性，根据柔性轧制成形的辊缝中线函数及厚度分布函数，用极坐标转换法推导了上、下辊辊形函数，并结合有限元数值模拟方法验证了辊形函数的有效性。2)说明柔性轧制成形设备的关键结构及功能，论述实验操作方案。以实验过程中观察到的现象为依据，总结调形机构的机械间隙对设备调形精度的影响程度，提出能够补偿机械间隙的调形操作方法，并对工作辊转动中的振动现象进行了分析。同时，依据实际工作辊的特性对理论辊形函数进行了简化计算，得出更适合于实验操作的简易辊形函数表达式。3)对柔性轧制实验得到的典型成形件凸曲面件和鞍形件进行型面分析，借助逆向工程方法和计算机建模软件，获取多条成形件横、纵向截线，通过拟合方法对比各截线的线型，证实成形件的形状均匀性良好，从实验角度验证了柔性轧制成形方法的有效性。分析实验中出现的起皱缺陷，结合实验现象发现辊形的调形误差会直接导致成形件的起皱，提出使用厚度控制法修正辊形以消除成形件起皱的方案，并通过多次实验验证了控制方法的有效性。4)设计实验方案，研究工艺参数在柔性轧制成形过程中的影响，分析实验成形件的横、纵向曲率半径随工艺参数的改变时的变化趋势。根据转速实验的结果，在一定的速度范围内，成形速度对成形件的纵向曲率有一定的影响，通过对影响效果的分析，总结柔性轧制实验的最适成形速度。在关于板厚的实验中，结果显示，在等最大减薄量和等最大减薄率两种情况下板厚的增大均对成形件的变形产生抑制作用，使板料横、纵向弯曲半径增大，根据分析这于厚板的大变形抗力有关。另外，在实验结果表明，板厚会影响成形件的起皱，结合起皱现象的形成理论，形成失稳现象的临界应力值随板厚的增大而增大，故板料越厚，成形件越不容易起皱。更多还原

【Abstract】 Flexible rolling is a new continuous flexible forming technology for curved surface sheet parts. relied onthe characteristics of rolls’ bending shape and width of the roll gap can be flexible controlled, enables two-way bending of sheet parts, combined with traditional vertical plate rolling technology, can achievecontinuous and efficient forming of three-dimensional surface parts. Compared to other curved surfaceforming methods, flexible rolling method has an advantages with lower cost, wider range of shaping, betterforming continuity etc. Through adapting rolls’ bending shape and roll gap distribution, flexible rollingmethod can process different curved surface parts, meets the individual needs of surface sheet parts marketbetter. Thus, expanding the theory and experiment study about the flexible rolling, summarizing the forminglaw in flexible rolling experiment, have a great value in engineering research. The main contents andconclusions of this paper are as follows:1) Comparative analyze the rolls’ characteristics of traditional cold-rolled sheet metal forming and flexiblerolling, discuss the shapes of two typical roll gaps, analyze the forming results of which with metal plasticforming principle, obtain the reason of flexible rolling parts’ two-way bending which is the work rolls’transverse bending and the longitudinal residual compressive stress caused by uneven plate thinning.Investigate the geometric principles of flexible rolling process, point out the feasibility of the target curvedsurface parts derived the roll gaps’shape reversely, and compare the contact states of rolls and sheet metal intraditional plate rolling and flexible rolling, obtain the friction conditions and the distribution of contact forcein flexible rolling process. According to the centerline distribution function and the width function of theflexible rolling gap, derive the roll shape function of upper and lower rollers by polar coordinate conversionmethod, combined with the finite element method verify the effectiveness of roll shape function in numericalsimulation.2) Point out the key mechanical structures of the flexible rolling equipment according to its functions,and propose the experiment operation program. Summarize the mechanical clearance’ impact on adjustingshape mechanism’s precision, proposed an operation method to compensate the mechanical clearance, andanaslyze the vibration of working rolls, propose adjusting the working rolls’curvature justifiable to control the vibration. Meanwhile, simplify the roll-shape function and calculate the simpler roll-shape function whichis more convenient for experiment operation.3) Analyze the surface characteristics of convex part and saddle part formed by flexible rolling, obtainhorizontal and vertical cut lines of forming parts at different locations with reverse engineering methods andcomputer modeling software, verify the good uniformities of every five cut lines by fitting method, thenverify the feasibility of flexible rolling. As for the winkle defect, the error of adjusting will directly lead towrinkles on forming parts from the conclusion of experiment, propose a thickness control method to eliminatethe winkles and verified valid in the forming experiment.4) Experiment designed to study the effects of the forming speeds and the plate thickness values on flexiblerolling process, analyze the horizontal and vertical curvature trends when changing the process parameters.According to the experimental results, forming speeds has some influence on the curvature of the formingparts. Through the analysis of forming effects, summarize the range of best suitable forming speeds. In theplate thickness experiment, results shows that the thickness increasing causes inhibitory effect on thetranverse bending and longitudinal bending, related to the large deformation resistance according to theanalysis. Besides, there is a phenomenon in the forming experiment that plate thickness has some effect onflexible rolling parts’ winkles, combine the wrinkles forming theory in plastic deformation, the thicker thesheet, the greater the critical stress values of the instability which causes winkles, thus verify the accuracy ofthe experimental results.更多还原