A new upper-bound elemental technique approach to axisymmetric metal forming processes

A new upper-bound elemental technique (UBET) is proposed to improve the ineffectiveness of UBET for solving forging problems that are geometrically complex or need a forming simulation for predicting the profile of free boundary. This method combines the advantages of the stream function and the finite element method (FEM); specifically, the curve fitting property of FEM and the fluid incompressibility of the stream function. The formulated optimal design problems with constrained conditions are solved by the flexible tolerance method. Three forming problems (ring upsetting, closed-die, and backward-extrusion forging) are used to illustrate this method: the results of ring upsetting show a good ability of simulating for predicting the forming profile of a free boundary; the closed-die forging produces a lower upper-bound solution than UBET; and backward-extrusion forging demonstrates the flexible curve fitting property for a complex geometric boundary.     

小型车轮模锻一次成形工艺与模具设计

在对小型车轮结构特点分析的基础上,提出了轮类锻件模锻一次成形工艺;确定了模锻一次成形工艺方案,设计了成形、冲孔模具;并分析了影响金属流动充填模腔的有关因素,提出了改进措施.实践表明,采用该工艺成形的轮坯具有良好的内外在质量,这是一种适合多种结构轮型零件的成形工艺.     

直齿圆柱齿轮开放成形数值模拟

为了降低齿轮精密成形力,在对闭式镦挤成形齿轮分析的基础上,提出了直齿圆柱齿轮开放成形新方法,即开放式温镦挤-冷推挤复合成形工艺。用三维刚塑性有限元对闭式镦挤和开放成形两种直齿圆柱齿轮成形方法进行了数值模拟分析。结果表明,开放成形与闭式成形相比,可明显降低成形力,改善模具受力条件,提高成形工件的质量。并根据模拟所得载荷-行程曲线,计算出开放镦挤齿形变位系数为0.2时,成形力所作功最小,为“开放镦挤”齿轮凹模的设计提供了依据。     

齿轮温挤精密成形工艺数值模拟

为了降低齿轮的成形力,在研究闭式镦挤成形齿轮法的基础上,提出了一种新的直齿圆柱齿轮温挤径向导流——约束分流两步成形工艺方案,采用三维大变形弹塑性有限元法对以闭式镦挤和以温挤径向导流——约束分流两步成形方式的成形情况进行了数值模拟分析。得到了新工艺成形过程的应力分布图以及载荷——形成曲线。数值分析结果表明：约束分流成形与闭式成形相比可明显降低成形力,有利于金属的流动,保证了齿形充填良好,改善模具受力条件,提高成形工件的质量。     

半轴锥齿轮温精锻工艺的数值模拟和实验研究

针对半轴锥齿轮的齿形难以成形的特点,提出了一套基于闭塞式锻造成形的工艺方案.利用数值模拟软件DEFORM-3D,分析了始锻温度对最大成形载荷的影响规律,连皮厚度、连皮位置对齿轮成形时的最大应力、最大损伤因子、最大成形载荷的影响规律.通过数值分析得到了有效确保应力最小、损伤因子最小、成形载荷适当的工艺参数,并将成形力控制在7.6MN以内.研究内容最终得到了实验验证.     

Analysis of three-dimensional upset forging of arbitrarily-shaped prismatic blocks

The present study is concerned with upset forging of arbitrarily-shaped prismatic blocks which is characterized by three-dimensional deformation with sidewise spread and bulging along thickness. A kinematically admissible velocity field to incorporate the three-dimensional deformation is proposed. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to some chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets and commercially pure copper billets at room temperature for different frictional conditions and geometrical shapes such as clover and rounded rectangles. The theoretical predictions both in the forging load and the deformed configuration are shown to be in good agreement with the experimental results. Therefore, the proposed method of analysis in this work can be used for the prediction of forging load and deformation in upset forging of arbitrarily-shaped prismatic blocks.     

轿车行星锥齿轮冷闭式锻造数值模拟分析

以轿车差速器行星齿轮为例,对冷闭式锻造成形过程进行了数值模拟,揭示了轿车行星锥齿轮冷闭式锻造成形规律,数值模拟结果为轿车行星锥齿轮冷闭式锻造工艺与模具设计提供了有效参考.     

Analysis of upset forging of cylindrical billets considering the dissimilar frictional conditions at two flat die surfaces

An upper-bound method is applied to the determination of forging load and deformed bulge profile during upset forging of cylindrical billets. A simple kinematically admissible velocity field which takes into account the dissimilar frictional conditions as well as the same frictional conditions at the top and bottom die surfaces is proposed for upset forging of cylindrical billets. From the proposed velocity field the upper-bound load and the deformed profile are determined by minimizing the total power consumption with respect to two chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets at room temperature for several frictional conditions. The theoretical predictions both in the forging load and the deformed profile are in good agreement with the experimental results.     

An analysis for three-dimensional upset forging of elliptical disks

An upper-bound method is applied to determine the forging load and the deformed configurations during upset forging of elliptical disks. A simple kinematically admissible velocity field for three-dimensional deformation is presented which takes into account the lateral sidewise spread as well as the bulging along thickness. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to two chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets at room temperature for different elliptical shapes and lubrication conditions. The theoretical predictions both in the forging load and the deformed configurations are in good agreement with the experimental results.     

十字轴小飞边精密成形工艺

针对十字轴热模锻成形过程中飞边大、成形力大的问题,根据十字轴形状尺寸及锻造成形工艺特点,提出十字轴小飞边精密成形工艺。采用Deform-3D对十字轴小飞边精密成形工艺过程进行数值模拟,对模拟成形的十字轴锻件及其金属速度场、等效应变、模具载荷-时间曲线进行分析。模拟结果显示,十字轴锻件成形完整,金属流动均匀,模具载荷减小。结合模拟结果,设计制造模具进行十字轴成形工艺试验。试验得到的十字轴锻件,填充饱满,无折叠、表面裂纹等缺陷,飞边明显减小,与模拟结果一致。结果表明:改变十字轴热模锻成形工艺,采用十字轴小飞边精密成形工艺,使锻件飞边减小,锻造过程成形载荷降低。     

圆柱直齿轮冷精锻模拟及试验研究

针对大模数圆柱直齿轮冷锻的困难性,提出了开放式分流和齿顶分流等2种分流工艺。结合浮动凹模技术,通过数值模拟与物理试验相结合,对2种工艺进行了分析研究,并与一般轴向分流工艺方案进行了对比。结果表明：这2种工艺方案能大大地降低载荷及单位压强,提高充填性能。锻件只需车削外圆或端面即可得到合格零件,不影响齿面纤维分布。     

An upper-bound approach to plane-strain problems using a general triangular element

This paper investigates an upper-bound elemental approach to plane-strain deformation of rigid, perfectly plastic material. A kinematically admissible velocity field based on nodal velocities is derived from a proposed arbitrarily triangular element. From the derived velocity field, the upper-bound forming load and deformation configuration are determined by optimizing independent parameters related to the velocity field. This new element formulation can be applied to diversified plane-strain metal-forming problems, even though only the application to strip forging is discussed in this paper.     

精密锻造成形技术在我国的应用

简要介绍了精密锻造成形技术的发展概况及主要应用领域,列举了大量的工程应用实例来阐明冷锻成形、温锻成形、闭塞锻造成形、精密热模锻成形、复合成形、等温锻造成形等精密锻造成形工艺在我国的应用情况。     

Forging of helical gears: Upper bound analyses and experiments

In this paper, forging of helical gears has been investigated. The forging process of helical gears has been classified into two types of operations: guiding and clamping. The two types of forging of helical gears have been analyzed by using the upper-bound method. Kinematically admissible velocity fields have been developed in which an involute curve has been introduced to represent the tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters such as module, number of teeth, helix angle and friction factors on the forging of helical gears. Some forging experiments were carried out with commercial aluminum alloy to show the validity of the analysis. Good agreements were found between the predicted values of the forging load and those obtained from the experimental results.     

冲孔连皮对伞齿轮冷闭塞锻造成形的影响研究

采用冷闭塞锻造技术生产伞齿轮具有节材、高效、低成本的特点,而且能得到机械性能好的高精度齿轮。利用Deform有限元分析软件对伞齿轮冷闭塞锻造成形过程进行了数值模拟,研究了锻件上的冲孔连皮对其成形过程的影响。基于正交试验设计,以降低凸模成形载荷为目标对冲孔连皮结构进行了优化,得到一组合理的冲孔连皮结构参数,为伞齿轮的闭塞锻造工艺及模具设计提供了依据。     

有限元模拟在后轴支架锻造设计中的应用

针对汽车后轴支架,进行锻造过程三维有限元模拟和工艺、模具设计。采用刚粘塑性有限元模拟技术,得到锻件内部应力场、应变场等参数,分析了这些参数对锻件塑性变形的影响。在此基础上,对此类锻件传统的锻造工艺进行了改进,将预锻工序由开式模锻改进为封闭飞边闭式模锻。同时,模具设计重点从预成形设计考虑,给出了合理的制坯模具设计。在40MN热模锻压力机上进行了试验,试验表明,模拟结果和实际成形过程吻合良好。     

轮毂轴承套圈闭式锻造成形数值模拟分析

根据轮毂轴承套圈的产品特点,设计了闭武精锻成形工艺方案.并通过Deform-3D对成形过程进行了数值模拟,分析了闭式锻造过程中金属的变形规律.数值模拟结果为轴承套圈闭式锻造工艺与模具设计提供了有效参考.     

Finite element simulation and experimental study of hot closed-die upsetting

Close-die upsetting often forms part of the sequence of producing a finished part from a billet in closed-die precision forging. Experiments have been performed to obtain the geometry of the deformed workpiece, and also the forging load as a function of punch movement during the closed-die upsetting. An elastic-plastic finite element program has also been used to simulate the process. In order to obtain realistic results from the simulation, preliminary experiments were carried out to ensure that the thermal parameters were properly introduced. The results obtained from the simulation are in good agreement with those from the experiments. As the FE simulation has been validated by experiment it may be used alone with confidence to generate data for an intelligent knowledge-based system (IKBS) for forging die design which includes similar processes.     

半轴套管锻造折迭问题的有限元模拟研究

采用商用有限元软件DEFORM3D对半轴套管胎模锻成形过程进行了计算机模拟。再现了半轴套管锻造成形中折迭产生的全过程，分析半轴套管成形过程的应力场和速度场分布，模拟结果表明，半轴套管在成形过程中首先产生失稳弯曲，随后在芯轴的作用下两股金属汇合而形成折迭。为解决该问题，采用带有凸起的凸模，并适当加大圆角，利用模具形状的限制，来避免坯料产生失稳弯曲，从而可以有效的防止半轴套管成形过程中折迭的形成。     

皮带轮温精辗压近净成形工艺模拟分析

为了克服当今皮带轮生产中材料浪费、生产率低、精度低等缺点,提出了皮带轮两步温精辗压近净成形新工艺。通过数值模拟的方法,分析了其成形过程和载荷,以及影响锻件成形质量的几个关键因素。数值模拟结果表明：工艺方案合理可行。锻件外围部分变形量大,变形均匀,质量高,所需成形力小。模具形状和运动参数匹配对成形质量和载荷影响很大,模具运动方式可以自由选择。