Three Dimension Rigid-plastic Finite Element Simulation for Two-Roll Cross-wedge Rolling Process

Cross-wedge rolling (CWR) is a metal process of ro ta ry forming. To produce a part, one cylindrical billet should be placed between t wo counterrotating and wedge-shape dies, which move tangentially relative each other. The billet suffers plastic deformation (essentially, localized compressio n) during its rotation between the rotating dies. Compared to other numerical si mulation methods, the finite element method (FEM) has advantages in solving gene ral problems with complex shapes of the formed parts. In cross-wedge rolling, t here are four stages in the workpiece deformation process, namely knifing, guidi ng, stretching and sizing stage. It is time-consuming and expensive to design t he CWR process by trial and error method. The application of numerical simul ation for the CWR process will help engineers to efficiently improve the process development. Tselikov, Hayama, Jain and Kobayashi, and Higashimo applied the sl ip-line theory in study of CWR process analysis. Zb.pater studied CWR process i ncluding upsetting by upper-bound method. The above numerical simulation were b ased on the two-dimensional plain-strain assumption ignored the metal flow in workpiece axial direction. Therefore, the complex three-dimensional stress and deformation involved in CWR processes were not presented. Compared to other nume rical simulation methods, the finite element method (FEM) has advantages in solv ing general problems with complex shapes of the formed parts. As yet, a few 3-D finite element simulation studies on CWR process have been reported in literatu res. In this paper, the process of cross wedge rolling (CWR) has been simulated and analyzed by 3D rigid-plastic finite element method. Considering the charact eristic of CWR, the static implicit FEM program is selected. The models proposed in this study uses the commercial code DEFORM 3D to simulate the CWR process. T his is an implicit Lagrangian finite element code, which includes many new enhan cements functions. A new method of utilizing multiple processors using the MPI s tandard has been implemented. Automatic switching between the two different defo rmation solvers (Sparse Solver and Conjugate Gradient Solver) has also been impl emented in order to increase the speed of simulations. In this paper, all stages in CWR process are simulated to be able to closely understand and analyze the a ctual CWR process. For simulating all forming stages in CWR process, the dynam ic adaptive remeshing technology for tetrahedral solid elements was applied. T he stress distributions in cross section of forming workpiece are analyzed to in terpret fracture or rarefaction in the center of workpiece. Authors also analyze d the time-torque curve and the laws of load changing.

Cross-Wedge Rolling of Shafts With an Eccentric Step

A new concept for forming eccentric shafts on the basis of the cross-wedge rolling （CWR） process was presented. This concept was based on the application of special guides, which, by acting on a billet, lead to its controlled movement in the vertical direction. This movement made possible eccentric cutting of tools into the billet. FEM calculations and experimental rolling tests clearly confirmed the effectiveness of the proposed forming method.

Forming and uniformity of shaft parts without a stub bar by axial closed-open-type cross-wedge rolling

To realize cross-wedge rolling of shaft parts without a stub bar in a short process,an axial closed-open-type cross-wedge rolling technique was proposed.Based on the strain characteristics in the rolling,evaluation indices of deformation uniformity were provided,and the DEFORM-3D software was adopted to conduct numerical simulations of the rolling process.The metal flow and strain distribution in all stages of the rolling process were analyzed.It is shown that the strain value of the rolled piece close to the end is relatively high while the overall strain distribution is uniform in the rolling process.When the percentage reduction in area is smaller,the fluctuation range of the equivalent strain will be lower and the overall uniformity of the rolled piece will be better.A variable angle wedge was implemented to make metal flow inward and eliminate concavity.Finally,rolling experiment was performed,which indicate that the shape of the rolled piece obtained is consistent with the simulation results.Concavity value in the rolling is decreased by 92%as compared to conventional open rolling.The research results lay a theoretical basis for realizing closed-open-type cross-wedge rolling without a stub bar.

Cavity formation in cross-wedge rolling processes

The problem of end-face cavity formation in parts produced by cross-wedge rolling was studied in order to reduce material consumption.The cavity depth was measured by the displacemern method.Twenty-one different cases of rolling were analysed by finile element method to determine the effects of process parameters such as the wedge tool angle,the temperature of material,the tool velocity and the reduction ratio on the depth of end-face cavities.Relationships between these parameters are examined in order to establish depe ndencies enabling quick and simple selection of a con cavity allowance in order to remove the cavities.The equations for calculating the con cavity allowance were verified in an experimental process for manufacturing ball pins with the use of flat tools.Rolling tests were performed using a billet with its length selected in compliance with the established dependencies.The experimental results demonstrate that the proposed solution is a viable method for end-face cavity removal.

楔横轧轧制螺旋齿形件力能参数的影响因素

针对楔横轧轧制螺旋齿形轴类件的成形过程复杂、轧制力与轧制力矩等力能参数受轧制条件以及工艺参数的影响规律复杂等问题,采用DEFORM-3D有限元软件模拟楔横轧轧制螺旋齿形件的成形过程,分析不同工艺参数对轧制力和轧制力矩的影响规律。在H630楔横轧机上进行轧制实验,分别采用AD7202压力传感器和TorqueTrak9000扭矩仪测试轧制过程中轧制力和轧制力矩,进而验证各工艺参数对力能参数的影响规律。研究结果表明:轧制力和轧制力矩随轧制温度的升高而减小,随齿高变化率、轧制速度以及轧辊直径的增加而增加,其中,轧制温度对力能参数的影响最明显,齿高变化率和轧制速度的影响次之,轧辊直径的影响最小;进行轧机设计时,为了确保轧机承受足够大载荷,一般选取较低的轧制温度、较大的齿高变化率和较大的轧制速度。

4Cr9Si2马氏体钢气门楔横轧工艺研究

通过热模拟等温压缩实验,获得4Cr9Si2马氏体耐热钢的本构关系。借助DEFORM-3D有限元软件针对4Cr9Si2马氏体耐热钢楔横轧成形过程进行数值模拟,得到工艺参数对轧件缩颈和心部疏松的影响规律。通过轧制实验验证有限元模拟的正确性,对轧制后的轧件进行金相组织分析。研究结果表明:随着成形角增大,楔入段轴向金属流动速度大于横向金属流动速度,减小横向应力最大值和横向应力持续时间,使轧件心部缺陷产生可能性减小;随着展宽角增大,同样可以减小横向应力数值和横向应力持续时间,使轧件心部缺陷产生可能性减小;随着成形角减小和展宽角增大,减小轴向力Fz,改善缩颈现象;其横截面中心原奥氏体晶粒尺寸为11μm,气门杆部微观组织得到改善。

楔横轧非对称轴类件轴向窜动量影响研究

建立了非对称楔横轧有限元模型,采用二次正交旋转组合法设计模拟工况,回归出轴向窜动量公式,经检验轴向窜动量回归公式高度显著,实验验证了部分模拟工况,表明回归公式具有良好的预报性;依据回归方程,研究了成形角差、展宽角差、断面收缩率差等工艺参数对轴向窜动量的影响,获得了轴向窜动量的影响主次因素以及减小轴向窜动量的工艺参数选取原则。

齿顶斜率对楔横轧螺旋齿形件成形质量的影响

针对车削、铣削等机加工方法加工大直径螺旋齿形件时加工效率低、材料浪费率高、工件齿形承载强度低等问题,提出楔横轧轧制螺旋齿形轴类件的工艺方法。文章采用DEFORM-3D有限元分析软件模拟和轧制实验验证相结合的方法,详细分析了模具齿顶斜率对梯形螺旋齿形件外形尺寸(齿高、螺距)的影响规律,以及不同齿顶斜率对轧件中心产生破坏的影响规律,得出齿顶斜率的优化区间。研究结果对楔横轧轧制螺旋齿形件的模具设计及成形规律的深入研究提供了重要的参考依据。

多楔楔横轧复杂铝合金轴类件堆料缺陷的影响因素研究

在楔横轧多楔复杂轴类件成形过程中,堆料缺陷影响坯料的外部尺寸,对后续的成形质量产生很大的影响。本文通过三维有限元数值模拟分析了楔横轧工艺参数对铝合金轴类件堆料缺陷的影响。结果表明:轧制速度对堆料的影响最大,轧件成形轧制速度控制在8 r/min时堆料程度最小;断面分配系数对堆料的影响次之,堆料缺陷程度随断面分配系数的增大而增加;成形角对堆料影响最小,堆料缺陷程度随多楔成形角的增大而增加。

坯料端部形状对楔横轧轧件凹心影响的研究

运用DEFORM软件,对不同端部形状的坯料进行楔横轧轧制过程的数值模拟,并将坯料端部形状角λ对轧件端部凹心的影响规律进行较系统分析。结果表明,轧件端部凹心随着形状角λ的减小而减少,通过合理设计坯料形状角λ可以有效减小轧件端部凹心。该研究结果为楔横轧实际生产节材,实现无料头楔横轧生产提供理论依据。

基于有限变形理论的齿轮楔横轧制坯热力耦合模拟

楔横轧齿轮轧制成形是一个全新的课题,在轧制过程中轧件的变形、温度场及力能参数都有待研究。将楔横轧技术与齿轮范成加工原理相结合,设计了楔横轧齿轮轧制的模具,给出了楔横轧齿轮轧制成形热力耦合本构模型,并在SuperForm平台对轧制成形过程进行了有限元模拟,获得了轧件在成形过程中的变形规律、温度场分布及力能参数变化等数据,详细分析了数值模拟结果,为进一步研究齿轮楔横轧制坯提供参考。

楔横轧无料头辊剪制坯成形机理研究

为了解决楔横轧生产工艺中的料头缺陷,运用DEFORM-3D软件建立了无料头辊剪制坯的有限元模型,并通过网格法阐明了辊剪制坯工艺的成形机理。通过改变轧辊的旋转速度改善了堆料情况,提高了坯料端面的成形质量。在工艺参数允许的情况下,堆料值随着旋转速度的减小而减小。此外,提高辊剪过程的稳定性,防止坯料轴向窜动,也是解决堆料问题的方法之一。研究结果能为无料头楔横轧生产提供理论依据。

楔横轧辊剪制坯力的研究

为了阐明无料头楔横轧辊剪制坯工艺的变形机理,基于DEFORM-3D软件建立了它的刚塑性有限元模型,分析了辊剪制坯过程中应力应变变化情况以及工艺参数对力的影响规律,得到了辊剪制坯的应力应变场以及辊剪制坯展宽段变形规律。结果表明,随着旋转速度增大,径向力和切向力降低;随着进给速度增大,径向力和切向力也增大。结果能为完善辊剪制坯工艺、实现无料头楔横轧提供技术支持和理论依据。

轧制过程中楔横轧模具表面力学行为研究

楔横轧过程中模具的表面力学行为对其磨损有非常重要的影响,是决定模具寿命的重要因素之一。建立了楔横轧的热—力耦合弹塑性有限元模型,研究了模具表面的力学行为。结果表明,在楔面交界的棱线处应力较高,在楔入段尾端及展宽段与精整段的过渡处存在两个峰值。在轧制的前段和后段,径向应力和剪切应力分别占主导地位。研究结果为提高楔横轧模具的寿命提供了参考依据。

圆弧角对楔横轧轧件端部凹心的影响研究

为了解决轧件头部质量从而提高材料利用率,提出将坯料端部设计成圆弧形的方法来实现对轧件端部凹心的控制。首先,通过DEFORM软件建立了楔横轧的有限元模型;然后,通过位移法分析了轧制过程中轧件端部金属的流动规律,得到了不同圆弧角对轧件端部凹心的影响规律;最后,通过实验验证了有限元分析的结论。结果表明,轧件端部凹心随着圆弧角的增大而减小,当圆弧角为90°时,轧件的端部凹心长度减少69.04%,证明将坯料端部设计成圆弧形的方法可以有效控制轧件端部凹心。结果能为实现楔横轧无料头轧制,提高材料利用率,降低生产成本奠定理论基础。

轧制参数对楔横轧变截面等内径空心轴晶粒粒径的影响

为了得到楔横轧变截面等内径空心轴的微观组织演变规律,借助刚塑性有限元软件DEFORM-3D,建立楔横轧热力微观组织耦合的有限元模型,对轧制过程的微观组织演变过程进行数值模拟,研究原始相对壁厚、成形角和展宽角对轧件平均晶粒粒径的影响规律。研究结果表明:轧件平均晶粒粒径随坯料原始相对壁厚Q的减小而减小,随着成形角α的减小而减小,随着展宽角β的增大先减小后增大。综合楔横轧空心轴内孔椭圆度和平均晶粒粒径的影响,原始相对壁厚Q=0.625、成形角α=40°、展宽角β=3°为最优的轧制参数,建立的有限元模型具有可靠性。

面向难变形材料精密成形的板式楔横轧机研究

为满足楔横轧工艺研究的需要,推动板式楔横轧机在我国的应用与发展,中国科学院金属研究所与白俄罗斯科学院物理技术研究所共同开展了高精度板式楔横轧机(IM500)的研制工作。IM500轧机采用卧式水平结构和液压驱动的单板可动设计方案,由主体机械结构、液压站、电控柜三部分组成。在主体机械结构方案设计过程中,采用有限元模拟方法进行同步校核优化。在IM500轧机上,分别采用45钢、GH4169、TC11三种材料进行楔横轧实验。结果表明该轧机具有轧件尺寸精度高、维护和更换零部件方便、自动化程度高等突出优点。

Novel evaluation method for metal workability during cross wedge rolling process

This study presents a novel method using a disk-like sample to assess the workability of metal during the cross wedge rolling(CWR)process.Using this method,we can quantitatively evaluate the moment destruction which occurs at the center of the sample during CWR.In this study,45 steel was selected to demonstrate the proposed method.Firstly,we designed a model for the tools and sample,conducted finite element simulations to analyze the distribution regulations of metal flow,stress,and strain,and evaluated the relationship between the damage and moving distance of the tool during the forming process.Then,we obtained the optimal deformation temperature range,rolling speed,and geometry parameters for the tool.Finally,experiments were conducted from 20℃ to 1200℃ to verify the accuracy of the developed model.It was demonstrated that the model was significantly accurate in accessing the workability of 45 steel in the CWR process.The proposed method could be generalized to investigate the CWR process for other materials,such as aluminum alloys,superalloys,titanium alloys,etc.

Influence of process parameters on interracial tensile strength of crosswedge rolling of 42CrMo/Q235 laminated shafts

Through rolling experiments and interfacial tensile strength tests of cross-wedge rolled laminated shafts of 42CrMo/Q235 composites, the influence of process parameters, including forming angle, spreading angle, area reduction, rolling temperature and core material diameter on the interfacial shear strength was analyzed. The results show that the sequence of process parameters in order of greatest influence on interfacial tensile strength was rolling temperature, area reduction, core material diameter, forming angle and spreading angle. At the interface of the combined materials, tensile strength decreased as forming angle and spreading angle increased, whereas the tensile strength first increased and then decreased as area reduction, rolling temperature and core material diameter increased.

楔横轧蜗杆轴毛坯成形技术研究

针对蜗杆轴应用范围广、需求量大,目前加工效率低的难题,提出了楔横轧蜗杆轴轧制方法。介绍了楔横轧蜗杆轴设计思想及成形基本原理,采用有限元模拟蜗杆轴轧制过程并在楔横轧机上对相同工况进行实验验证,得到轧件质量较好,与模拟结果基本相同。研究结果表明,楔横轧轧制蜗杆轴毛坯技术是一种高效、可行的轧制技术,它对于楔横轧技术的研究、推广以及蜗杆轴工业生产自动化发展具有重要的现实意义。