【作者】 邱宁佳；

【导师】 李明哲；

【作者基本信息】 吉林大学 ， 材料加工工程， 2014， 博士

【摘要】 柔性轧制成形是结合多点调形工艺与轧制成形工艺，用上下柔性工作辊形成的不均匀辊缝完成三维曲面成形件的快速、连续、高效轧制成形技术。具有材料利用率高，成形范围广，成形效果好等优点。柔性轧制成形可以实现凸曲面件、鞍形件、盘形件、扭曲形件等多种三维曲面件的简单易控、高效连续成形。因此，研究柔性轧制成形的工艺特性，开发新型柔性轧制成形设备具有较广阔的市场应用空间和较高的科研开发价值。本文建立了柔性轧制成形的有限元模型，并对模型设置不同的工艺参数后分别进行数值模拟，分析了成形结果中的应力应变特征和工艺参数对成形件成形效果的影响，并对成形情况进行了相关实验验证，探讨了柔性轧制成形缺陷问题，提出了一些改进成形实验的设想。主要研究内容和结论归纳如下：(1)柔性轧制的原理和特点对柔性轧制技术的原理和成形设备进行了介绍，对比分析柔性轧制技术与传统轧制技术的根本区别。介绍了柔性轧制成形装置的整体结构和使用不均匀辊缝方式完成板料成形的特点，其优势在于简单易控，出形快速高效。阐述了板形控制理论，提出了使用调形控制以一次调形工艺方式柔性轧制的方法。使用几何关系推导了板形函数、成形件厚度和双向主曲率半径三者之间关系的算法，以此作为成形件板形研究的理论依据。(2)柔性轧制成形有限元模型的建立从弹塑性有限元求解着手，使用显式动力学的有限元方法对板料成形过程进行力学分析。介绍了柔性轧制成形的数值模拟基本理论，并给出了有限元方程。建立了柔性轧制成形有限元模型，并处理了建模求解时的相关问题。对凸曲面件和鞍形件进行轧制实验与数值模拟，得到与实验结果一致的模拟结果，证明了柔性轧制成形技术的可行性。(3)柔性轧制成形的数值模拟从塑性变形理论入手，剖析了柔性轧制成形技术能够加工三维曲面件的原因。分析了与轧制参数有关的弹塑性曲线的变化情况，讨论了板料最小可轧厚度问题。对柔性轧制模型进行力学分析，从理论上解析应力应变状态，通过计算轧制力矩给出纵向曲率的计算方法。结合柔性轧制建模的模拟结果，分析了凸曲面件和鞍形件在轧制过程中的应力应变分布特征，说明了出现双向弯曲现象的原因，并对理论分析和计算方法的正确性进行了验证。(4)柔性轧制成形的应力应变特征针对柔性轧制成形的特征和工艺参数做了数值模拟分析。根据成形件的几何特征和双向弯曲变形机理，找出了影响变形的辊弯曲半径、压下量、板厚等工艺参数。结合调形技术与纵横双向的几何关系，分析工艺参数对成形效果的影响，计算出模拟轧制实验时柔性辊轮廓的排布情况。分别对凸曲面件与鞍形件进行有限元数值模拟，对得到的不同成形件进行应力应变分析，找出各成形件应力应变分布情况的区别，进而分析了出现不同形状的原因。(5)柔性轧制成形的板形分析给出了使用柔性轧制装置进行板料成形实验时某些重要问题的解决方案。对实际的调形工作进行深化分析，并针对柔性辊调形工艺精度问题提出了靠模检验方法。介绍了三维光学扫描仪对实际成形件的处理方法，为成形件的测量提供前提。从横纵双向成形两个方面入手，对模拟成形件进行了板形分析：横向成形分析时，找出了横向的成形规律以及板料厚度变化规律；纵向成形分析时，计算了纵向不同位置的弯曲半径变化趋势，并分析其变化规律。使用上述方法对实际成形件进行了板形分析，并与模拟结果做对比，得出成形规律一致的结论，验证了柔性轧制成形技术的正确性与可行性。(6)柔性轧制成形缺陷的数值模拟分析了柔性轧制成形过程中出现的起皱和压痕缺陷。针对起皱问题，主要通过对成形件失稳变形的理论分析，总结出起皱时的临界失稳条件，以鞍形件的起皱作为研究对象，通过对柔性辊弯曲半径、最大压下量以及板料厚度等工艺参数的分析，说明各参数对成形件起皱的影响。针对压痕问题，提出了柔性辊调形改进方案，给出柔性辊局部调形方法，以凸曲面件的压痕作为研究对象，说明使用权因子对柔性辊辊形做局部微调能够较好地抑制压痕。介绍了柔性轧制成形的小挠度成形特性，利用曲面光顺性判定准则对成形件成形效果进行分析验证，说明了通过该方法能得到质量较好的成形件。更多还原

【Abstract】 Flexible roll forming (FRF) is a new process of forming method. Combined withmulti-point forming and roll forming, the basic principle is forming three-dimensionalcurves fast, continuously and efficiently by using flexible rolls, which are composed bythe uneven roll gap. The advantages are to reform the materials utilization rate, to widenthe forming range, to improve the forming effect. FRF can be easy to form thethree-dimensional curves parts, such as convex surface parts, saddle parts, disc parts andtwisted shape parts, etc. Studying the characteristics of FRF and developing the newequipment of FRF have a wider application space market and higher research anddevelopment value.In this paper, the finite element model of the flexible roll forming was established,and the model parameters are set for numerical simulation. The stress-straincharacteristics in the forming results have been analyzed. The influence of processparameters on the forming effect has been discussed. Some experiments have beencarried out to verify the plate forming conditions. Defects problem in the process offorming has been studied. Some ideas have been proposed to improve the formingexperiment.The main contents and conclusions are summarized as follows:(1) The principle and characteristics of FRFThe principle of FRF and forming equipment were described, and it shows thedifference between FRF and traditional rolling fundamental through the comparativeanalysis. The device and structural characteristics of FRF were introduced. Theadvantage is simple and easy to control, and fast and efficient to form. The shape controltheory was described, and using method of the sole tune-shaped process was proposed.As the theory basis of plate-shaped study, plate-shaped function, forming part thicknessand bidirectional primary curvature radius were deduced by using the geometricrelationship. (2) The establishment of the finite element model for FRFProceed from the elastic-plastic finite element solution, mechanical analysis wasperformed by using explicit dynamic finite element method for forming process. Thebasic theory of FRF numerical simulation was introduced, and finite element equationwas given. The finite element model of FRF was established, the related problems in theprocess of solving Model were processed. Experiment and numerical simulation wereperformed to form the convex curved part and the saddle part, and the simulated resultsand experimental results were consistent. It is proved the feasibility of FRF.(3) Numerical simulation for the process of FRFAccording to plastic deformation theory, it was explained the reason forthree-dimensional surface parts processing can be completed by F RF. The changes ofelastic-plastic curve were analyzed, and the minimum rolling thickness of the sheet wasdiscussed. The model of FRF was studied with mechanical analysis of stress and strainstate in theory, and longitudinal curvature calculation method was given by calculatingthe relationship of the rolling moment. Combined with the simulation result of FRF，stress and strain distribution characteristics were analyzed in the process of rollingforming parts. It illustrated the reasons for a two-way bending phenomenon and formingthe three-dimensional curves parts, and the correctness of the theoretical analysis andcalculation method was verified.(4) The stress and strain characteristics of FRFThe characteristics and process parameters of FRF were analysis in the numericalsimulation. According to the geometric characteristics of FRF, two-way bendingdeformation mechanism of the forming parts was analyzed, and process parametersaffecting the bending deformation were identified. According to the geometri calrelationship of the adjustment technology and two-way bending, the flexible roll contourwas calculated. Different process parameters were compared as the known conditions tocomplete the simulation experiments. The finite element numerical simulation ofConvex Curves parts and saddle parts were completed, and the results obtained wereanalyzed for stress and strain. Parameter conditions were different, and the results ofstress and strain distribution are also different. It can be able to analyze the c auses ofdifferent shapes sheet.(5) The shape analysis of FRFHere were some solutions to some important issues when forming experiment byusing the FRF experimental apparatus. Actual adjustment work was calculated detailed,and the inspection method was introduced for the flexible roller adjustment precision of experiment device. The processing method of three-dimensional optical scanner wasintroduced to measure the forming parts. Shape analysis was considered from theforming of transverse and longitudinal bidirectional. The regular was found out for thetransverse forming and the thickness changes, and radius of curvature change trend wascalculated and analyzed for the longitudinal forming. The shape analysis was carried outon the experimental results, which was compared with simulation and obtained similarconclusion. It verified the correctness and feasibility of FRF.(6) Numerical simulation of defects for FRFThe wrinkle defects and indentation defects were analyzed, which were oftenencountered in the process of FRF. The critical condition of wrinkling was summarizedthrough the analysis of forming a buckling deformation theory for wrinkle defects.Through the analysis of process parameters, the influences of the wrinkle on formingparts were interpreted for saddle parts as research subjects. The flexible rollerimprovement program of FRF was put forward to indentation defects, which is themethod of Local adjustment to the shape of flexible roller. Using weight factors tofine-tune flexible roll, indentation defects were able to suppress better for convex curvesparts as research subjects. The characteristics of the small deflection for FRF wereintroduced, and the criteria of surface fairing were used to verify the effect of formingparts. It is proved that the better quality of forming parts can be obtained by using thismethod.更多还原