挤压型材压制成形回弹预测与补偿研究

航空挤压型材的压制成形工艺是一种重要的飞机钣金成形工艺方法,由于压制成形过程存在回弹现象,科学准确地预测回弹补偿值对于提高产品质量具有重要的意义.为了有效预测航空挤压型材压制成形工艺过程产生的回弹,利用ABAQUS软件建立了一种挤压型材零件压制成形工艺过程的有限元仿真建模方法,利用预定义场模型研究了成形过程的回弹仿真技术并通过工艺试验进行了验证.该方法对于其他种类的航空钣金零件的成形仿真及回弹预测研究也具有积极的参考意义.     

型材挤压过程工艺参数优化模型

提出了一种集数值仿真、人工神经网络和遗传算法为一体的工艺参数优化模型,用于型材挤压成形过程工艺参数优化,合理配置了非对称角铝型材模模孔位置。通过现场试验,验证了提出的工艺参数优化模型是行之有效和正确的。并在模孔位置优化配置结果基础上对其挤压成形过程进行数值仿真,分析了挤压成形过程中各阶段网格畸变情况,给出了挤压变形时应力和应变分布,对指导型材挤压工艺和模具优化设计具有重要意义。     

模孔偏置位置参数对型材挤压成形影响的数值研究

通过引进流速均方差作为评价塑形变形时金属流动速度不均衡性指标，来有效地控制型材挤压成形时金属流动的不均匀性。通过采用有限变形弹塑性有限元方法，对不同模孔偏置位置参数下型材挤压过程进行了数值模拟研究，获得了挤压力、流速均方差和型材件内部应力应变场随其变化的规律，为进一步实现型材挤压工艺参数优化提供了理论参考。     

复合挤压变形规律的研究

利用光塑性方法模拟研究复合挤压变形,获得变形区的全场应变分布曲线;分析材料的流动规律,将变形体分为挤压型变形区,镦粗型变形区和刚性区３个特性区域。建立上限模型,分析模具几何参数对复合挤压变形的影响,证明凸模直径与正挤出口直径对复合挤压变形的影响最大。     

长轴类花键挤压成形极限研究

建立了长轴类花键无约束正挤压的力学条件，采用等挤压比流动模型对矩形花键挤压进行了上限分析，讨论了变形程度、凹模型腔尺寸、齿形参数、摩擦因子等对无约束正挤压挤压相对应力及成形极限的影响，给出了花键挤压相对应力的经验公式，为正确制定挤压工艺提供了理论依据。     

空心型材挤压模具工作带优化设计

目前企业中空心铝材的生产质量和生产效率很大程度上取决于平面分流组合模的结构设计是否合理。本文构建某方管型材成型挤压模具,以其下模模孔工作带的设计为研究对象,采用拉格朗日有限元法数值模拟热挤压过程。结合模拟结果中的金属流速情况,优化工作带尺寸,最终使得金属流速均满足流速判据,保证了型材质量,可有效减少模具开发周期和成本,达到试模修模的快速响应,实现了空心型材热挤压模具的准确快速有效的设计。     

铝合金型材等温挤压参数优化及数据管理

先介绍铝合金型材等温挤压工艺参数的确定方法,即先通过模具尺寸优化,实现型材挤出流度相等,再通过工艺参数优化,实现型材挤出温度相等;将得出的数据及曲线录入挤压工艺数据库管理系统以提高挤压生产线的自动化水平,进而提高产品质量。     

铝合金挤压型材试样加工工艺及疲劳性能研究

车体枕梁是由铝合金挤压型材和板材组焊的箱体结构,是车体上同时承受拉伸和压力载荷的关键部件。本文研究枕梁挤压型材母材疲劳性能测试相关技术问题,探讨了线切割-抛光和铣-磨-抛光两种工艺条件、型材不同厚度壁板疲劳性能的差异,获得了疲劳性能数据。试验结果表明,用铣-磨-抛光工艺加工的试样的疲劳性能优于线切割-抛光工艺加工的试样的疲劳性能;不同厚度壁板中值条件疲劳极限差别不大,但10mm壁板数据分散性明显大于15mm壁板。     

用上限基元技术确定反挤杯形件的挤压力

本文利用上限基元技术对杯形件反挤压进行了上限分析，提出了一种优化的流动模型。对各对参数进行优化分析，得到了各种挤压比下的挤压力的最佳上限解，同时也给出了反挤稳定变形区的高度的最佳取值Ｔ与挤压比Ｇ的关系。计算结果通过实验得到验证，为反挤压杯形件的工艺制定，提供了有价值的依据。     

大宽厚比薄壁异型材挤压多工艺参数优化研究

型材挤压多种工艺参数的优化设计是一个组合优化问题,难以用传统数学优化方法解决。在应用型材挤压CAD/CAE技术建立型材挤压CAD模型,并对其成形过程及其参数变化规律进行CAE仿真的基础上,采用基于正交试验、人工神经网络和遗传算法的型材挤压多工艺参数计算机辅助优化技术建立型材挤压多工艺参数与挤压质量间的关系映射模型,并预测不同参数值搭配对挤压质量的影响,进而确定多工艺参数最优解。试验证明取得了良好的效果。     

采用混合推理方式的挤压工步分析专家系统的研究

采用正向推理与反向推理相结合的方法，开发了用于挤压工步分析专家系统的混合控制策略。运行情况表明，该混合推理方法能增加挤压工步初始方案选择的可靠性，　并能有效地提高系统推理效率。系统实现了工艺分析—参数优化—图形绘制一体化。知识库管理模块采用开放式设计，并使基规则库与各特征规则库相结合。使用Ｖｉｓｕａｌ　Ｃ＋＋作为程序开发环境，系统具有良好的人机界面。     

基于数值分析的塑料挤出模优化设计方法研究

以比例间隔法和射线法相结合的办法建立面向CAE的挤出口模的参数化模型,在对其进行三维数值分析得出流道内压力和速度分布的基础上,以口模出口处型材截面上各子区域平均流速相等为优化目标,基于有限元分析结果和参数化流道模型建立目标函数的数学模型,对模具的一些重要结构参数进行设计优化,优化结果可以直接映射到参数化模型,实现了CAE/CAD的直接集成。通过一个算例的分析,验证了该方法的正确性和有效性。     

Axisymmetric extrusion through adaptable dies—Part 2: Comparison of velocity fields

In Part 1 of this series of papers, six kinematically admissible velocity fields, along with the power terms, were developed for use in upper bound models for arbitrarily shaped dies for axisymmetric extrusion. The three base velocity fields in the deformation zone were derived:

(1) assuming proportional angles in the deformation zone,

(2) assuming proportional areas in the deformation zone, or

(3) assuming proportional distances from the centerline in the deformation zone.

In each case the base velocity was modified by an additional term comprised of two functions, each function containing pseudo-independent parameters. One function allows extra flexibility in the radial direction, and the second function allows extra flexibility in the angular direction. In Part 2, the results obtained in upper bound models for the six velocity fields for extrusion through a spherical die are compared to one another. The velocity fields are compared based upon: (a) the base velocity field, (b) the number and distribution of pseudo-independent parameters in the flexible functions, and (c) the form of the angular flexible function. A spherical extrusion die shape is used to evaluate and compare the three velocity fields. The results demonstrate that the sine-based velocity field is the best. Furthermore, a natural boundary condition exists which allows the shear surface associated with the streamlined portion of a die to energetically disappear. Part 3 uses the best velocity field to determine an adaptable die shape, which minimizes the extrusion pressure and compares the shape to the arbitrarily curved and streamlined die shape of Yang and Han.     

NUMERICAL DESIGN OF DIE LAND FOR SHAPE EXTRUSION

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横向挤压过程的模拟及应用

采用实验和刚塑性有限元法对枝类零件的机警向挤压过程进行了实验研究与理论分析计算,将所得结果进行了比较并介绍了实际应用。     

Axisymmetric extrusion through adaptable dies—Part 3: Minimum pressure streamlined die shapes

In Part 1 of this series of papers, six kinematically admissible velocity fields, as well as the power terms, were developed for use in upper bound models for arbitrarily shaped dies for axisymmetric extrusion. Part 2 compared the results obtained in upper bound models for the six velocity fields through a spherical die shape and demonstrated that the sine-based velocity field was the best. In this final part, the application of the sine-1 field to extrusion through streamlined dies is developed. By fixing the values of two additional constants in the radial flow flexibility function, the two surfaces of velocity discontinuity, which separate the deformation zone from the incoming and outgoing material, will have no shear. In effect, the analysis for streamlined dies can be modeled without the surface of velocity discontinuity power terms. The results for an arbitrarily curved streamlined die, as proposed by Yang and Han, using the sine-1 velocity field and the cylindrical velocity field from the work by Yang and Han are compared. It is found that the upper bound model using the sine-1 velocity field predicts lower values for the extrusion pressure. A method to determine a streamlined die shape is proposed. The method allows flexibility between the entrance and exit by the use of a Legendre polynomial series for representation of the die surface. The method is termed an adaptable die design. The adaptable die design method is used to determine streamlined die shapes, which will minimize the pressure required for the extrusion process.     

Axisymmetric extrusion through adaptable dies—Part 1: Flexible velocity fields and power terms

An adaptable die is one that not only produces the correct geometrical shape, but also is designed through an adaptable method to impart other desirable properties to the product or process. In this first part of a series of papers, six kinematically admissible velocity fields are developed for use in upper bound models for axisymmetric extrusion through various dies, including extrusion through adaptable dies. Three base velocity fields are presented:

(1) assuming proportional angles in the deformation zone,

(2) assuming proportional areas in the deformation zone, or

(3) assuming proportional distances from the centerline in the deformation zone.

The base velocity is modified by an additional term comprised of two functions. One function allows extra flexibility in the radial direction, and the second function allows extra flexibility in the angular direction. There are two forms of the second function, which meet the required boundary conditions. The flexibility function in the radial direction is represented by a series of Legendre polynomials, which are orthogonal over the deformation region. The power terms derived for these velocity fields for use in upper bound models are also presented.Part 2 of this series compares the results obtained in upper bound models for the six velocity fields for a spherical extrusion die. In Part 3, the use of the best velocity field for extrusion through streamlined dies is developed to determine the adaptable die shape, which minimizes the required extrusion pressure. Additionally, the adaptable die shape is compared with results from Yang and Han for arbitrarily curved and streamlined dies.     

STUDY ON THE OPTICAL FLAT PROFILE HIGH PRECISION MEASURING TECHNOLOGY IN THE METHOD OF LASER DATUM

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