Optimum design of preform geometry and forming pressure in tube hydroforming using the equi-potential lines method

The quality of a tube-hydroformed component as well as the tooling cost and processing time involved in the process are notably affected by the component’s preform. Hence, it is necessary to produce a proper preform shape for the successful hydroforming from the initial tube to final shape. In this paper, the notion of equi-potential lines (EPLs) is used to find an appropriate preform shape in the tube hydroforming process for the first time. The EPLs generated between two conductors of different voltages show minimum work paths between the initial and final shapes. Based on this similarity, the EPLs method is utilized for preform shape design. Next, the forming pressure of the preform is determined using finite element analysis. Finally, the computationally expensive procedure introduced above is significantly facilitated by employing a multi-layer perceptron neural network which is trained using results from application of the procedure to a set of uniformly distributed random input vectors. Real-world examples are presented to demonstrate the applicability and efficiency of the proposed approach.     

用有限元法设计金刚石砂轮电解修整的阴极

根据电解成形理论设计阴极,用于金属结合剂成形金刚石砂轮的电解修整。应用有限元法求解电场中的拉普拉斯方程几何反问题,计算出阴极曲线形状。假定初始阴极形状,施加阳极边界条件,从砂轮阳极表面开始逐层计算电位分布,求得修整间隙区域的等电位线,从而得到修整阴极工具曲线族。通过设计阴极与砂轮廓形的对比,分析了成形砂轮轮廓形状,修整电压和电解液电导率对设计阴极形状的影响。研究结果表明:设计阴极与成形砂轮的廓形并不一致。随着成形砂轮廓形曲率,修整电压和电导率的增加,设计阴极与砂轮廓形的偏差加大。为了修整出精确的砂轮廓形,成形砂轮的修整参数应保持稳定。     

基于类等势场的粉末高温合金盘件预成形设计及有限元模拟

为了提高产品的质量和工作效率并降低生产成本,需对预制坯进行合理的预成形设计.根据能量最小原理和最小阻力原理,利用塑性变形过程中坯料的流动规律与静电场等势线分布类似这一特性,提出一种能够进行预成形设计的新方法--类等势场法,并采用该方法对粉末高温合金盘件进行预成形设计,从中优选出6组预成形形状,并利用商用有限元软件MSC/SuperForm对上述预制坯的等温成形过程进行数值模拟,得到了6组粉末高温合金盘件终锻结束时各个部分的等效应变分布以及预锻和终锻的变形程度分配.通过对盘件轮毂、辐板和轮缘三部位以及整体盘件最大等效应变和最小等效应变的比较与分析,以及预锻变形量和终锻变形量的比较,并参考模具法向和切向的受载情况,认为选择3号预锻模为最佳方案.结果表明,该方法克服了传统方法精度低、耗时和耗力等缺点,其结果可靠.     

Design of intermediate die shape of multistage profile drawing for linear motion guide

The design of an intermediate die shape is very important in multistage profile drawing. In this study, two design methods for the intermediate die shape of a multistage profile drawing for producing a linear motion guide (LM) guide is proposed. One is the electric field analysis method using the equipotential lines generated by electric field analysis, and the other is the virtual die method using a virtual drawing die constructed from the initial material and the final product shape. In order to design the intermediate die shapes of a multistage profile drawing for producing LM guide, the proposed design methods are applied, and then FE analysis and profile drawing experiment are performed. As a result, based on the measurement of dimensional accuracy, it can be known that the intermediate die shape can be designed effectively.     

Evolutionary forging preform design optimization using strain-based criterion

Preform design plays an important role in forging design especially for parts with complex shapes. In this paper, an attempt was made to develop a topological optimization approach for the preform design in bulk metal forming processes based on the bidirectional evolutionary structural optimization strategy. In this approach, a new strain-based element addition and removal criterion has been proposed for evaluating and optimizing the material flow in the forging process. To obtain a smooth preform boundary, a closed B-spline curve based on the least square algorithm is employed to approximate the uneven surface of the updated preform profile. A C# program has been developed to integrate the FE simulation, shape optimization, and surface approximation processes. Two 2D forging preform design problems are evaluated by using the developed method. The results suggest that the optimized preform with the strain uniformity criterion has shown better performance in improving the material flow and deformation uniformity during the forging process. The results also demonstrate the robustness and efficiency of the developed preform optimization method.     

基于变形均匀性的锻造模具形状优化设计方法

以直接设计预成形模具形状为目标,提出并建立了一种控制变形均匀性的灵敏度分析理论和模具形状优化设计方法。以任意单元的等效应变与所有单元的平均等效应变的差值的平方和作为目标函数,Ｂ样条曲线表示模具形状,Ｂ样条曲线控制点坐标作为优化设计变量,优化设计的目标是通过设计预成形模具形状使目标函数最小,即使整个工件的变形尽可能均匀。给出了目标函数的表达形式,详细推导了目标函数、单元等效应变率和单元各应变率分量对优化设计变量的灵敏度,给出了优化设计的步骤。应用该方法对圆柱体平模镦粗工艺进行预成形优化设计,给出了相应的优化设计结果,并提出了一种检验优化结果的变形均匀因子,优化与未优化结果的比较表明优化取得了良好的效果。     

A new approach of preform design based on 3D electrostatic field simulation and geometric transformation

Preform design is an important aspect of the research and development of the forging processes, which plays a key role in improving product quality, such as improving material filling capacity and reducing forming loads. In industry, preforms are generally designed by the iterative trial-and-error approach. This approach, however, leads not only to the increase of tool cost but also to prolonged production time. On the basis of the minimum energy principle and the minimum resistance law, a new approach by means of 3D electrostatic field simulation and geometric transformation is proposed in this paper to design the preform shape. Two axisymmetric (a disk and a blind-hole) forgings and a long-axis part are used to demonstrate this method, and finite element package DEFORM 3D is used to simulate the forming process for the purpose of verifying the validity and effectiveness of this approach.     

Preform design in forging process of complex parts by using quasi-equipotential field and response surface methods

The International Journal of Advanced Manufacturing Technology - The preform design is the key to bulk metal forming. An approach to optimize 3D preform shape in multi-step die forging based on...     

非等温成形过程中的预锻模具形状优化设计

采用塑性有限元、灵敏度分析和工程优化算法相结合的方法,对非等温成形过程中预锻模具形状进行了优化设计。预锻模具形状采用三次B样条函数表示,B样条函数的控制点作为设计变量,通过优化预锻模具形状,可实现净形锻造,得到无飞边完全充满模腔的合格终锻件。给出了模具形状优化设计步骤,推导了速度灵敏度方程和温度灵敏度方程。最后以一轴对称圆盘锻造过程为例,对预锻模具形状进行了优化设计。     

基于数值模拟的锻造预成形优化设计系统集成

净形和近净形制造要求锻造预成形设计不仅要实现产品的形状,而且要实现材料、能耗、锻件质量等目标优化。仅仅依靠经验已不可能达到优化设计的要求,必须借助于数值模拟结果中包含的丰富的信息来指导设计。本文提出了基于数值模拟的锻造预成形优化设计系统框架,针对现有的设计和分析工具功能强大却相对独立的特点,提出了可实现预成形优化设计的设计和分析工具集成的方法。     

锻造预成形多目标优化设计的研究

采用有限元灵敏度分析方法，首次对锻造过程预成形进行了多目标优化设计研究。多目标包括锻件的形状及其变形均匀性两个方面，优化设计的目标是使锻件的形状和变形均匀性综合性能最好。提出了新的无量纲的锻件形状子目标函数和变形均匀性子目标函数，并给出了总目标函数和各子目标函数的表达形式，并详细推导了各目标函数相对于优化设计变量的灵敏度。应用该方法对截面为H形的轴对称锻件进行了预成形优化设计，取得了良好的效果。     

电沉积技术中象形阳极的形状设计

利用ANSYS有限元软件，通过电场分析和优化设计，对电沉积技术中所用的象形阳极进行了形状设计。以电铸某喷管为例，辅助人工干预的办法，得到了带有屏蔽段的优化象形阳极，使阴极电场强度(电流密度)分布的均匀性得到了改善。该设计方法可替代传统的经验设计方法。     

Preform design for large-scale bulkhead of TA15 titanium alloy based on local loading features

Large-scale TA15 (Ti–6Al–2Zr–1Mo–1V) titanium alloy bulkhead is a key lightweight load-bearing structure part in an aircraft, which has a large plane view and has a complex shape with high ribs and thin webs. In its forging process, the forming defects, such as folding and under-filling are prone to occurrence. The near-net shape forming with saving force of this large-scale complex component can be realized with proper preform design combining local loading condition. By analyzing isothermal local loading process characteristic of large-scale bulkhead, it indicates that the simple unequal-thickness billet is suitable for small lot manufacture of large-scale TA15 titanium alloy bulkhead. Considering the geometry and forming characteristics, such as large dimension, complex shape, mass data, etc., a design method of unequal-thickness billet using analytical analysis and numerical simulation is proposed. The preform for a large-scale TA15 titanium alloy bulkhead is designed by the proposed method. The basic three-dimensional shape of billet is determined by the analytical models based on local loading features, and the basic billet is modified according to numerical simulation result and considering the local loading forming characteristic, and then the preform without resulting in folding and under-filling can be obtained after two modifications.     

控制锻件变形均匀性和变形力的锻造预成形多目标优化设计

以影响锻件质量的重要因素--锻造预成形模具形状为研究对象,对锻造过程展开同时包括锻件变形力和变形均匀性两个方面的优化设计的研究.研究目标是使锻件变形最均匀的同时变形力最小,即获得变形均匀性和变形力综合性能最好的终锻件.基于有限元数值模拟方法,采用有限元灵敏度分析方法,首次对同时控制锻件变形均匀性和变形力的锻造过程预成形进行多目标优化设计研究.给出总目标函数和各子目标函数的表达形式,并详细推导各目标函数相对于优化设计变量的灵敏度.利用自行开发的程序,对断面为H形的轴对称锻件进行预成形多目标优化设计,给出优化过程中总目标函数及各子目标函数、预成形模具形状、预成形件形状及终锻件等效应变和y向应力的分布变化情况.结果表明,通过对预成形模具形状进行优化设计,总目标函数、变形均匀性子目标函数和变形力子目标函数分别下降了13%,33%和6%左右,达到了同时对锻件变形均匀性和变形力进行优化的目的.     

基于有限元逆向模拟技术的预成形模具设计

介绍了基于刚一粘塑性有限元方法的正向和逆向模拟技术,并将该技术应用于链轨节锻件的复杂锻造工艺的预成形设计,实现了从理想形状的终锻件设计预成形件和预成形模具的目标。所设计的预成形件和预成形模具降低了终锻模具的磨损,提高了材料的利用率,保障了预成形件在后续模具中的定位稳定性,井应用于生产实际,取得了较好的经济效益。     

圆盘锻件纯形状锻造模具优化设计

在讨论圆盘锻件模具设计现状的基础上,提出了一种金属成形过程的有限元灵敏度分析方法和以此为基础的模具形状优化设计方法。对圆盘件锻造过程进行了灵敏度分析和模具形状优化设计。结果表明,采用优化设计的预锻模具,可得到侧面无鼓形的纯形状圆盘锻件,并且预锻模具形状光滑、简单、便于加工和锻造生产。为圆盘锻件的纯形状锻造模具设计提供了一种定量分析方法。     

An optimization strategy based on a metamodel applied for the prediction of the initial blank shape in a deep drawing process

The transformation of the sheet into a product without failure and excess of material in a deep drawing operation means that the initial blanks should be correctly designed. Therefore, the initial blank design is a critical step in deep drawing design procedure. Consequently, an easy approach for engineers in predicting the initial blank shape is necessary to reduce wastage in material and to overcome the large time consumed in the classical approaches. Thus, the aim of the present investigation is to propose an automatic procedure for the quick sheet metal forming optimization. In fact, a metamodel will be build based on artificial neural networks which will be coupled then with an optimization procedure in order to predict the initial blank shape in a rectangular cup deep drawing operation. The metamodel is built from the finite element simulations using ABAQUS commercial code. This procedure allows a significant reduce of the CPU time compared to classical optimization one. The results show that the desired shape is in good agreement with the one calculated using the optimized blank shape.     

预锻模形状设计优化的新方法—微观遗传算法

锻造过程实现净形和近净形制造关键是优化预锻模的设计。引入一种可对预锻模形状进行设计优化的新方法－微观遗传算法，并用此方法对平面就方坯锻造进行了预锻模形状设计优化，目标是消除锻件的同鼓形效应。设计结果表明优化效果显著。     

On plastic design of complex machine parts

The technique of statically admissible plastic discontinuous stress fields is used in the plastic design of machine parts of complex shape. If the shape of the part is given the stress field is used to find a lower bound on the bearing capacity. In the case of plastic design an appropriate stress field gives a safe estimate of the shape of the designed part. Complex three-dimensional stress fields are composed of elementary sub-fields, all geometrical and statical parameters of which are tabulated in order to simplify the design procedure. Thus the procedure consists in appropriate arrangement of sub-fields into a complex system of stresses.     

Preform design of hybrid-forming process to make sheet metal IT products with a sharp edge

Existing forging processes have limitations in forming products with sharp edges. Therefore, a new hybrid-forming process that combines drawing and forging processes was designed to form a sharp-edged product. First, a corner radius of a preform design was arranged to be smaller than the minimum bent area corner radius formed in general drawing processes. Then, the shape of the preform was planned to have the exact shape of the final product. Given that forming loads are a limiting condition in forging processes, they were set as an evaluation criterion to determine design requirements for final product shapes and the shapes of preforms. The reliability of finite element analysis results was verified by comparing analysis and experiment results, and a multistage preforming process was implemented to satisfy the determined evaluation criterion. This study demonstrates that IT products with sharp edges can be formed.