Optimal Shape Design of an Extrusion–Forging Die Using a Polynomial Network and a Genetic Algorithm

The objective of this paper is to obtain an optimal die shape in consideration of the influence of metal flow deformation in the extrusion–forging processes. The finite-element method was used to analyse comprehensively the effects of different die shapes on extrusion–forging deformation. A polynomial network was used to construct the relationship model and a genetic algorithm was used to obtain the optimal shape of the extrusion–forging die. Through repeated cross-verifications of modelling and experiment, the errors between the results of the finite-element analysis and the prediction of the polynomial network are very small. The result of the deformation analysis and the optimal design approach to die shape in this study could be extended to the design of a more complicated forging die. This would be beneficial to forging industries.     

液压机组合板机架的整体工作性能分析

本文用有限元混合法和专用计算程序对大型模锻液压机的组合板机架进行了弹性接触分析,求出接触内力及其分布,还应用SAP5结构分析程序做为空间问题对机架的工作载荷和预紧力分布的不均匀性及其对机架的整体工作性能的影响进行了分析计算,合理地确定了预紧力和螺栓的预紧量,保证了机架整体工作的充分条件。文中以大型多向模锻液压机的工作样机-650吨多向模锻液压机为例进行了计算验证,得出了具有实用价值和准确的结果,解决了研制模锻液压机的关键技术。     

大型座舱骨架整体成形有限元模拟及实验研究

为研究飞机大型座舱骨架的整体成形,在DEFORM一3D软件中对该铝合金锻件的整体锻造过程进行了有限元模拟,并优化了模具结构及坯料。在模拟结果的基础上生产了坯料和模具,并在万吨水压机上对坯料进行了整体锻造,实际生产的锻件质量良好。研究表明,模拟结果与实际生产基本一致,通过大型座舱骨架整体成形的有限元模拟实现了模具结构和坯料的优化,减少了试模次数,提高了锻件的质量。     

房车转向节整体模锻关键技术与模具装置研发

房车转向节轮廊尺寸大、结构极其复杂,目前采用的分体制造技术存在材料利用率和生产效率低、产品性能差的问题。为此,提出了转向节整体模锻成形的工艺方案,着重研究了其关键工序弯曲成形的工艺优化并进行了专用模具装置开发。采用经典塑性成形理论、有限元数值模拟和试验相结合的方法,分析了弯曲过程的应力应变状态、金属流动和损伤分布。工艺试验结果表明,所提出方案合理,实现了以整体模锻取代分体制造,材料利用率由约45%提高至70%以上,生产效率提高4~5倍。     

细胞操作用锻针器的设计

提出了利用单片机对锻针器进行计算机程序控制的方法，实现了锻针器工作过程数字化控制及屏幕可视化操作，提高了锻造精确度和稳定性，为我国锻针器的制造提供技了术基础。     

Preform and forging process designs based on geometrical features using 2D and 3D FEM simulations

The requirements of compact and integrated industrial products make it more difficult to produce these complicated parts. The aim of this paper attempts to propose methods of finish forging die and preform designs to produce a product consisting of a solid spur gear and cylindrical cup features. One- and two-step forming processes were proposed and evaluated using computer-aided engineering simulations. For one-step extrusion or upsetting processes, diameters and heights of billet were calculated using the product volume and the corresponding cup or gear features, respectively. For two-step forming process, Tee-shaped preform designs were proposed based on the product volume and the feature volume ratio of cup to gear; corner and fillet arcs were adopted to modify the profile of Tee and control the material flow in the finisher die. The forming processes of preform and finisher were analyzed using the two- and three-dimensional finite-element method models to predict the detail characteristics of sectional material flow and the completely three-dimensional deformation results, respectively. Experimental tests were also carried out to validate the proposed simulation models and design methods. The forming loads, the stress and strain distributions of forged part, and the occurrences of defects were studied and a suitable preform and corresponding die designs were obtained. The proposed preform designs were verified via the numerical analyses for the feasibility study. Finally, a sound gear product had been made successfully using the proposed suitable design of preform.     

Simulation of chevron crack formation and evolution in drawing

The objective of the present work is to clarify ductile fracture phenomena in bulk metal forming, by means of finite-element analyses and experiments. We have developed a computer program, based on a conventional computer program of the finite-element method, by which the behavior of crack propagation after ductile fracture can be analyzed. The phenomenon that inner fracture defects occur periodically in the axial direction in drawing has been simulated using the computer program. The following results were obtained. First, to analyze multipass drawing we have proposed a method of calculating residual stress after drawing and a method of considering initial stress before drawing. Second, to perform accurate simulation, we have developed a method of fracturing one element in each step and a method of separating nodes at the fracture. Finally, we have proposed a method for evaluating ductile fracture in terms of void volume fraction and axial stress, and we have shown the validity of the method by comparing the analytical results with experimental ones.     

An Automated Process Planning and Die Design System for Quasi-Axisymmetric Cold Forging Products

This paper deals with an automated computer-aided process planning and die design system with which a designer can determine operation sequences even after only a little experience in process planning and die design of quasi-axisymmetric cold forging products by multistage former working. The approach is based on knowledge-based rules, and a process knowledge base consisting of design rules is built. Knowledge for the system is formulated from plasticity theories, empirical results and empirical knowledge of field experts. Programs for the system have been written in AutoLISP for AutoCAD with a personal computer. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM software, DEFORM and ANSYS, to form a useful package. The system is composed of three main modules and five submodules. The process planning and die design module considers several factors, such as the complexities of preform geometry, punch and die profiles, specifications of available multiformers, and the availability of standard parts. The system uses 2D geometry recognition and is integrated with the technology of process planning, die design, and CAE analysis. The standardisation of die parts for wheel bolts requiring a cold forging process is described. The system developed makes it possible to design and manufacture quasi-axisymmetric cold forging products more efficiently.     

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.     

An Analysis of Draw-Wall Wrinkling in a Stamping Die Design

Wrinkling that occurs in the stamping of tapered square cups and stepped rectangular cups is investigated. A common characteristic of these two types of wrinkling is that the wrinkles are found at the draw wall that is relatively unsup-ported. In the stamping of a tapered square cup, the effect of process parameters, such as the die gap and blank-holder force, on the occurrence of wrinkling is examined using finite-element simulations. The simulation results show that the larger the die gap, the more severe is the wrinkling, and such wrinkling cannot be suppressed by increasing the blank-holder force. In the analysis of wrinkling that occurred in the stamping of a stepped rectangular cup, an actual production part that has a similar type of geometry was examined. The wrinkles found at the draw wall are attributed to the unbalanced stretching of the sheet metal between the punch head and the step edge. An optimum die design for the purpose of eliminating the wrinkles is determined using finite-element analysis. The good agreement between the simulation results and those observed in the wrinkle-free production part validates the accuracy of the finite-element analysis, and demonstrates the advantage of using finite-element analysis for stamping die design.     

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.     

混合多目标遗传算法及其在热挤压模具型腔形状优化设计中的应用

将复合形法引入遗传算法来反映决策者对多目标问题中各目标函数的偏好信息，提出一种新的结合复合形法的混合多目标遗传算法。针对热挤压模具型腔轮廓形状优化问题，结合刚-粘塑性有限元模拟和神经网络技术，利用三次样条函数插值来表达凹模型腔轮廓形状，以表面载荷沿凹模型腔轮廓表面均匀分布和挤压力最小为目标，建立了多目标优化的数学模型，对挤压模具型腔轮廓形状进行多目标优化设计，得到了最优的凹模形状。对几种不同模具凹模型腔采用MARC／AutoForge有限元软件进行数值模拟对比研究，结果表明，结合复合形法的多目标遗传优化算法是一种较好的模具型腔形状多目标优化设计方法，其优化结果是有效的和显著的。研究结果说明，通过优化型腔形状来提高模具寿命的效果十分显著。     

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.     

巨型模锻液压机同步控制系统建模及仿真

为了提高巨型模锻液压机同步控制系统的快速响应性,在300MN模锻液压机的基础上,针对800MN模锻液压机的特点重新设计了同步控制系统,并基于液压基础理论和动力学理论,联合建立了活动横梁运行时同步控制系统的整体数学模型。将原方案和现有方案进行了对比仿真,结果表明:新设计的800MN同步控制系统的响应特性较原方案的响应特性有较大幅度的改善,响应速度和动静态精度均有较大提高。     

Specimen geometries predicted by computer model of high deformation forging

This paper presents the specimen geometries predicted by a finite element model of isothermal forging. In isothermal forging the specimens are subjected to very high deformations and considerable flow of material results. The geometries are shown by a number of computer produced plots of finite element meshes which represent the flow of the material at various stages during the forging process. The predicted geometries are found to conform well with experiments for a variety of specimen and die configurations.     

Effect of ductile fracture criteria on chevron crack formation and evolution in drawing

The purpose of this study is to clarify the mechanics of ductile fracture in bulk metal forming processes by finite-element analysis and experiments. The author has developed a computer program, based on a conventional computer program involving the finite-element method, by which the behavior of crack propagation after ductile fracture can be analyzed. The phenomenon in which a ‘chevron crack’ appears periodically in the axial direction during drawing has been simulated using the developed computer program. Special attention is focused on the effect of various kinds of ductile fracture criteria on chevron crack formation and evolution during drawing. Results obtained are summarized as follows. First, the analytical results obtained using Gurson's fracture criterion and using Oyane's fracture criterion agree well with the experimental result. Second, the analytical results using Cockcroft and Latham's fracture criterion and using Brozzo et al.'s fracture criterion agree somewhat with the experimental result. Finally, the analytical result obtained using Freudenthal's fracture criterion does not agree with the experimental result.     

汽车前轴精密辊锻成形过程的数值模拟

汽车前轴的精辊-模锻工艺是一种用小成形力锻造设备成形较大型前轴锻件的塑性加工技术,其工艺关键在于精密辊锻。前轴的精密辊锻分4个道次,是典型的局部成形工艺。辊锻工艺由于旋转的模具与辊锻件之间的接触区域在不断变化,一直以来成为数值模拟的难点。对4个道次的模具建立了模型,采用三维刚塑性有限元程序DEFORM-3D模拟了前轴精密辊锻工艺,分析了辊锻过程中金属变形的规律,研究了模具参数对成形质量的影响以及辊锻力矩的变化规律。模拟结果对于改进辊锻工艺设计、提高模具设计水平具有指导作用。     

Wear analysis of hot forging dies

In hot forging, die wear is the main cause of failure. In this paper, the wear analysis of a closed hot forging die used at the final stage of a component has been realized. The simulation of forging process was carried out by commercially available software based on finite volume method and the depth of wear was evaluated with a constant wear coefficient. By comparing the numerical results with the measurement taken from the worn die, the wear coefficient has been evaluated for different points of the die surface and finally a value of wear coefficient is suggested.     

The forging of helical gears (I): Experiments and upper-bound analysis

In this paper, the forging of helical gears has been investigated. A punch and a die are tooth-shaped for the guiding type forging of helical gears. The punch compresses a cylindrical billet placed in a die insert. As a consequence the material of a billet flows into the tooth region. The forging has been analysed by using the upper-bound method. Kinematically admissible velocity fields have been developed, where an involute curve has been introduced to represent tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters, such as modules, numbers of teeth, helix angles and friction factors on the forging of helical gears. Some forging experiments were carried out with commercial aluminium 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.     

计算机辅助辊锻模具设计通用系统的研究

本文研究了制坯辊锻模具的计算机辅助设计通用软件系统,实现了辊锻过程的全部设计计算与绘制图纸的自动化。对于欲用辊锻工艺制坯的任意形状与尺寸的模锻件,只要输入相应的描述锻件几何形状用原始数据及某些必要的参数,电子计算机就可以快速、精确地完成从工步方案选择到模具尺寸计算的全部设计任务,并自动绘制出可供生产用的辊锻工步图与模具图。本文在描述锻件几何状形时采用了等截面体、变截面体、旋转体等三种形状体的组合法,使得能够用较少的原始数据描述各种不同形状的锻件。在简化锻件截面图时,本文提出了自动简化数学模型,明显地提高了设计效率。