The prediction of maximum forging load and effective stress for different material of bevel gear forging

The manufacture of gears by applying hot or cold bulk forming processes is a quite widespread production method due to its well-known basic advantages such as material and time cost reduction and the increased strength of the teeth. However, the associated process planning and tool design are more complicated. In the precision forging of gears, the workpiece volume, the die design, the power requirement and careful processing are more critical than traditional forging technology. For complete filling up, predicting the power requirement is an important feature of the near net-shape forging process. In this paper, a finite element analysis is utilized to investigate the material properties such as yielding stress, strength coefficient and strain hardening exponent effects on forming load and maximum effective stress. The adductive network was then applied to synthesize the data set obtained from the numerical simulation. The predicted results of the maximum forging load and maximum equivalent stress of bevel gear forging from the prediction model are consistent with the results obtained from FEM simulation quite well. After employing the prediction model one can provide valuable references in prediction of the maximum forging load and maximum equivalent stress of bevel gear forging under a suitable range of material parameters.     

齿轮冷精锻工艺预锻模具齿形优化设计

在直齿圆柱齿轮两步成形冷精锻工艺中 ,预锻模具齿形设计对改善材料填充性能 ,降低成形载荷具有重要意义。本文采用正交试验法与数值模拟技术相结合的方法 ,来解决预锻模具型腔优化设计问题。选取了描述预锻模具几何形状的 3个参数作为影响因素 ,以预锻终锻总载荷值为指标 ,通过有限元模拟分析来获得虚拟试验结果 ,最终确定预锻模具型腔几何形状参数的最佳值 ,为提高齿轮精锻成形质量提供有效依据。     

A Study on the Extrusion by a two-step process for manufacturing helical gear

Much research has been carried out in the manufacturing of helical gears by cold forging or by extrusion. Although cold forging is applied to some bevel, spur, and helical gears, problems in connection with the reduction forming load and tool life still make it difficult for these methods to be commercialized. In this study, focusing on reducing a load in forming helical gears, the extrusion of helical gears by two-step process is proposed. This process is composed primarily of extruding a billet to a spur gear and then twisting the previous spur gear extruded to a helical gear. Cylindrical billets of Cr-Mo steel(SCM 415) and aluminium alloy(Al60 series) were used as specimen materials for the experiments. The maximum loads obtained by upper-bound analysis and FEM are compared with the results of experiments. The loads of the analysis have good agreements with those of the experiment. The newly proposed method can be used as an advanced technique that remarkably reduces the forming load and replaces the conventional forming.     

直齿圆柱齿轮精锻成形过程数值模拟及参数分析

采用三维有限元数值模拟方法分析了直齿圆柱齿轮的精锻成形过程，选择模拟表面单元数、加载步长、模数、齿数、齿轮高度等参数进行了多次模拟分析，根据模拟结果对比分析了以上诸参数对成形工艺的影响。确定了适宜的表面单元数目和加载步长值，较好地满足了模拟的需要。从数值模拟结果分析可知，在齿轮其他参数不变的情况下，锻造载荷随模数和齿数的增加而增加，模数的变化对载荷的影响显著；在对高度不同的齿轮成形过程的模拟分析中发现，在成形的初始阶段，高度越小载荷越大，在填充终了阶段，随高度增加载荷稍有增加。     

Impedance analysis of forging process and strategy study on compliance for forging manipulator

In the field of heavy forging, there are numerous researches on deformation rule in forging process by FEM simulation, however, not many scholars take the equipment constraint and the mutual reaction load between the forging manipulator clamp and the forging blank into account, which will impact on safety of manipulator body and quality of forging blank. This paper presents an impedance model to describe the load and formulates compliance strategies correspondingly to reduce the mutual reaction load for forging manipulator. Firstly, an FEM model of forging process is built. Meanwhile, the clamp of forging manipulator is added to the model as movement constraint and interaction part between the manipulator and the forming process. Secondly, a typical forging process is simulated by changing the movement constraint, and then an impedance model is established to describe the relationship between the load and movement constraint. Finally, two kinds of compliance strategies are formulated according to the impedance model, one is called free compliance, and the other is initiative/passive compliance. The simulation results show that compliance strategies reduce the load amounting to 5 000 kN in z direction between the manipulator clamp and the forging blank obviously, which may lead to serious accidents, such as the capsizing of forging manipulator, the fracture of manipulator clamp, and so on. The proposed research simulates the more real forging process, gets the initiative/passive compliance strategy which is more simple and suitable to the real producing and better for forming a forging process planning and control system in the modern production, and improves the quality and efficiency of heavy forging.     

高直臂小间距等厚板材零件步进式冲锻工艺

针对高直臂小间距、不能展平的等厚板材零件,提出了步进式冲锻成形工艺。该工艺先通过冲压成形零件的大间距两直臂,然后通过若干次弯曲工步来缩小两直臂间距直至达到目标值。每次弯曲成形后对工件弯曲变形部位需进行冷锻平整,选择合理的工步数是保证冷锻过程中不出现材料重叠、起皱或破裂等现象的关键。建立了流线型弯曲的数学模型,通过该模型得到每个弯曲工步极限图。采用数值模拟结合试验的方法获得了无工艺缺陷的产品,产品性能优良,生产效率高。该步进式冲锻工艺为成形高直臂小间距等厚金属板材零件提供了新途径。     

叶轮半固态挤压锻造过程数值模拟

采用DEFORM3D软件对叶轮的半固态挤压锻造过程进行了数值模拟,获得了叶轮成形的主要参数变化规律.结果表明:半固态挤压锻造法可以完成叶轮的成形;叶轮的成形可分为三个阶段,叶片主要是依靠材料的挤压完成成形的,在叶片成形的中期,坯料内部尤其是叶片根部存在着变形不均匀现象,而在叶片成形后期,挤压力急剧增大,最终挤压力为2 780 kN.     

基于刚粘塑性有限元模拟的汽轮机叶轮模锻的预成形优化

针对汽轮机叶轮模锻的预成形设计,本文建立了以打击能耗最低和模具作用载荷最小为目标函数,以完全填充为约束条件,以坯料初始高径比为优化变量的预成形坯料优化方案。利用刚粘塑性有限元方法模拟汽轮机叶轮等温模锻成形过程,具体分析了不同坯料初始高径比对成形载荷、塑性应变能以及分流面的影响。数值模拟结果表明获得的预成形H/D最佳尺寸可明显减少模锻锤击次数和模具磨损。所提出的有限元模拟预成形优化方法十分有效,克服了以往凭经验设计的弊端。     

锻造模具的随机疲劳损伤分析

塑性应变控制的低周疲劳失效是锻造模具的主要失效形式，由于受到多种因素的影响，其损伤过程呈现随机性。应用有限元与BP神经网络，建立了一种基于损伤累积理论的锻造模具的随机疲劳损伤分析模型。首先用有限元对锻造过程中模具内的场变量进行分析，由计算结果找到模具的危险部位，认为危险部位失效时的寿命即为模具寿命，并计算出确定性损伤；再考虑模具材料及实际工况的随机性，应用BP神经网络对模具的损伤进行模拟；根据损伤的累积效应，得出考虑随机因素作用下的模具疲劳寿命。以锻造齿轮模作为分析对象，得到不同工况下模具疲劳寿命的频数分布，其分布规律基本服从Weiubull分布。另外，还分析了打击速度对模具寿命的均值和离差的影响及可靠性随使用次数的变化。该 模型可用来对模具进行寿命预测和可靠性分析。     

A new sheet metal forming system based on the incremental punching, part 1: modeling and simulation

In heavy forging, a manipulator is indispensable to assist and help the precision of the forming process. This paper presents a multi-system simulation methodology combining the forging finite element method (FEM) simulation and the kinematics analysis to evaluate the mutual reaction loads between the forging process and the assisting manipulator. The forging is realized by the thermal–mechanical FEM simulation and the kinematics movements are analyzed based on the statics and dynamics modeling of the manipulator. The reaction load generating from the forging process to the manipulator clamps is treated as an input parameter for the kinematics analysis system, which will then calculate the movement of the manipulator. And this movement is regarded as the passive compliant movement constraint and applied on the forging process through the manipulator clamps. Using this coupled system, the study compares the reaction loads with and without the active vertical compliant movement and/or the passive horizontal compliant movement and reveals the effect of these compliant movements on the reaction loads.     

An analysis of external spline gear forming by an upper bound energy method

Closed-die forging of external spline gear forms is analysed using an upper bound elemental energy method. The kinematically admissible velocity field for the three-dimensional deformation was obtained on the assumption that the profiled surface of the tooth was straight but tapered. The upper bound to the deforming load necessary and the deformed configurations are predicted using integration of the formulation of energy expressions which were obtained from the presented velocity fields. Two different forging methods denoted here as A, viz. a side extrusion method and B, an upset forging method, the details of which are given in the text, were considered in the present analysis and the theoretical results compared with experimental ones. Experiments were carried out on plasticine as model material at room temperature where talcum powder was used as a lubricant. The present investigation revealed that the analytical method B predicts a reduced forging load and improved configuration better than method A for the forged products.     

Spring back phenomenon exhibited in the process of hollow cylinder upsetting

Spring back of the end surfaces of the billet and the elastic deflection of the dies in the process of hollow cylinder upsetting between elastic platens is investigated using a thermo-elastic-plastic coupling model. The finite-element method and the finite-difference method are adopted to simulate the forming process, and the unloading process is performed on the elements of the workpiece in response to the spring back phenomenon accounted for in this study. Therefore, the effect of die elasticity on the variation of the inner surface profile of the hollow cylinder, predictions of forging load, and the distributions of temperature and strain components may be examined. The surface asperity of the billet and the forging load obtained by simulation agree quite well with the results of the upsetting experiment.     

A new upper bound solution for analysis of the radial forging process

Radial forging is an open die forging process used for reducing diameter of shafts, tubes, stepped shafts and axels, and creating the internal profiles for tubes such as rifling the gun barrels. In the present research, a new model based on calculating the deformation work was developed to find an upper bound limit for the deformation load in the case of radial forging of rods and tubes. Also, the model was used to assess the effects of the process parameters. The accuracy of the model was tested by comparing the predicted results with those achieved from the experiment at work of Uhlig [Investigation of the motions and the forces in radial swaging. Doctoral Dissertation, Technical University Hannover, 1964]. A good agreement was found between the two sets of results.     

直齿轮精锻成形新工艺及试验研究

与精锻成形工艺相比,传统的切削加工方法加工直齿轮具有诸多弊端。而当前提出的闭式镦挤成形工艺载 荷过大,严重制约着精密成形直齿轮工艺的实用化。提出采用预锻分流区一分流终锻新工艺精密成形直齿圆柱齿 轮,设计了能够进行多种组合的精锻成形试验模具,并对空心管坯和实心圆柱坯进行了传统的闭式镦挤和新的分 流成形工艺试验,试验结果表明:与传统的闭式镦挤和现有的圆柱直齿轮成形工艺对比,提出的成形工艺工序简 单,终锻后齿形充填饱满,端面平整,而且成形载荷降低了37％以上,具有生产实用化的前景。     

汽车曲轴终锻模阻力墙新型结构参数试验

提出曲轴锻模阻力墙新型结构,分析阻力墙结构中三个重要参数(高度、间隙、斜度)对终锻成形载荷的影响,运用有限元分析软件Deform3D对曲轴终锻过程进行数值模拟仿真,并采用最小二乘法拟合得到了它们之间的影响规律曲线,为阻力墙的优化设计和提高曲轴终锻模具寿命提供了理论参考。分析影响规律曲线发现：终锻最大成形载荷随终锻模阻力墙高度的增加而升高,在同时考虑曲轴锻件成形质量和模具寿命的情况下,终锻模阻力墙高度的合理取值范围为[10, 30] mm;终锻最大成形载荷随终锻模阻力墙间隙值的增加而降低,合理取值范围为[2.0, 3.5] mm;随着终锻模阻力墙斜度增加,终锻最大成形载荷随之升高,而终锻模阻力墙根部的磨损能得到有效控制,合理取值范围为[0°, 20°]。通过试验对上述结论的合理性与可行性进行了验证。     

轴径零件温-冷精锻综合成形工艺及有限元仿真

温 -冷精锻综合成形是一种先进的金属塑性加工工艺 ,近年来在汽车工业中得到了广泛应用 ,并有取代传统的热锻成形的趋势。汽车后轴径是汽车工业中的典型锻件。本文分析了该零件的精锻加工特性 ,建立了其温 -冷精锻成形的有限元模型 ,根据有限元仿真结果确定了该零件的温 -冷精锻综合成形工艺的参数     

An integrated computer-aided decision support system for die stresses and dimensional accuracy of precision forging dies

Precision forging is a field in which decision support systems can be effectively and widely applied and depends on knowledge and rules derived from the past experience of forging die design engineers. Precise components are becoming quite important in attempts to reduce cost and improve reliability. There are thus many application areas in which the rules themselves become inherent to the parts or the processes. In forging die design, dimensional accuracy is one of the main goals. The load carrying capacity and life of any forged product is greatly affected by its dimensional accuracy. To predict the precise dimension of the part and determine the die dimension for precision forging, it is necessary to analyze the factors which affect dimensional accuracy. Dimensional evolution of die and product should be analyzed at each stage of forging. In this study, both radial and tangential stresses are encountered in the determination of die stresses since cylindrical workpieces were used. In order to sustain dimensional accuracy of the forging die, differences between the forging product and the die insert such as elastic die expansion and product contraction are presented.     

Hot shape forging of gas turbine disk using microstructure prediction and finite element analysis

The Waspaloy, a Ni-based superalloy, has been widely used for forging material of gas turbine disk since it requires the high tensile strength at high temperature and good resistance to low cycle fatigue. The purpose of this study is to develop a forging process of turbine disk that satisfies the hot deformation characteristics of Waspaloy. Generally, the hot forging of superalloy has been subjected to isothermal forging since the available temperature range of forging is narrow. However, the non-isothermal forging was used to make a turbine disk in this study. Therefore, the analyses of temperature variation and deformation behavior of the material were important to obtain the sound forging products. The hot compression test was carried out to know formability at high temperature and microstructure evolution during hot deformation. In order to define the optimum forging conditions including material temperature, strain rate, strain, microstructure evolution and forging load, the commercial finite element analysis code was used to simulate the forging procedure of turbine disk. The hot forged turbine disk was heat-treated for obtaining the high temperature properties. The cut-off tests on the heat-treated forged disks were carried out. Experimental results were compared with the simulation results by FE analysis. Test results were in good agreement with the simulations. This study shows that the superalloy turbine disk can be manufactured by the semi-closed die forging.     

自由锻造油压机常锻工况能耗特性

为分析大功率自由锻造油压机电液比例控制系统能量分布规律,以常锻工况为例,综合考虑操作工操作影响,研究了操作手柄控制方式及系统控制流程,建立了油压机电液比例控制系统的能耗计算模型和仿真模型,并通过20MN快锻油压机实测数据验证了仿真模型的正确性。基于仿真模型,对20MN自由锻造油压机电液比例控制系统的能耗分布规律进行了仿真,重点研究了油压机不同载荷和操作工操作速度对系统能耗的影响。锻造油压机常锻过程存在较大的速度变化,恒定的流量源不能匹配负载变化,导致20MN自由锻造油压机满载时能量利用率仅为14.3%。研究结果还表明,载荷越大、操作工操作越熟练,系统的能量利用率越高。     

Contribution in the evaluation of a performance index of hot forging dies

The present paper focuses on a new concept of evaluation of a performance index of hot forging dies through the combination of a process behaviour model and a reliability approach analysis of the forging process. The process behaviour is modelled and simulated using the computer-aided engineering FORGE® tool that allowed optimizing the forging parameters and determining the stresses and strains together with temperatures during the forging process and also identifying the factors affecting the die life. The respective reliability mechanical model is developed and reliability simulations have been conducted using PHIMECASoft tool in order to evaluate the reliability index β and determine the sensitivity of the variations in the random values of the input parameters of the forging process. The concept of this contribution has been applied to real industrial dies used to forge automotive steering levers produced in the forging workshop of the Ferrovial Company of Annaba in Algeria. The performance index is given by the number of forged parts corresponding to the reliability index of the dies before failure occurs.