基于近似替代模型的多工位高速锻造预锻模具优化

多工位高速锻造是一种节能减耗的先进成形技术,与传统的单工位多工序锻造有较大区别,不合适的预锻工位模具设计在生产中会造成载荷过大、锻件充填质量差、折叠等问题。文章提出了基于近似替代模型的多工位高速锻造预锻模具优化设计方法,采用拉丁超立方抽样方法构造初始样本点集,应用有限元软件获得响应值,并应用Kriging模型和BP神经网络模型建立真实问题的替代模型,来近似拟合预锻工位模具形状与成形载荷、成形质量之间的关系,并结合基于惩罚函数法的遗传算法求得最优解。以3工位高速锻造问题为例,经过优化取得了良好的效果,与初始设计相比,成形质量显著提高,成形载荷下降了40%左右。     

Preform optimization for hot forging processes using an adaptive amount of flash based on the cross section shape complexity

In multistage hot forging processes, the preform shape is the parameter mainly influencing the final forging result. Nevertheless, the design of multistage hot forging processes is still a trial and error process and therefore time consuming. The quality of developed forging sequences strongly depends on the engineer’s experience. To overcome these obstacles this paper presents an algorithm for solving the multi-objective optimization problem in designing preforms. Cross wedge rolled preforms were chosen as subject of investigation. An evolutionary algorithm is introduced to optimize the preform shape taking into account the mass distribution of the final part, the preform volume and the shape complexity. A crucial factor in preform optimization for hot forging processes is the amount of flash. Therefore an equation for improving the amount of flash is derived. The developed algorithm is tested using two connecting rods with different shape complexities as demonstration parts.     

缸头模锻成形过程数值模拟

缸头模锻成形是一个复杂的大变形过程,其成形质量影响因素众多,用解析法难以进行精确分析。采用有限元方法对整个成形过程进行模拟,获得了缸头模锻成形过程金属流动变形规律,对成形过程中出现的充不满、折叠等缺陷进行了分析,指出需修改预成形形状的尺寸参数。试验结果表明,采用改进后的预成形形状的尺寸参数能获得比较合格的终锻件。     

面向微观组织优化的锻造工艺预成形优化设计

以锻件晶粒尺寸细小均匀为目标,以预成形形状设计为对象,提出了锻造成形过程微观组织优化设计方法,构建了锻造成形过程微观组织优化目标函数,并确定锻造成形预成形形状作为优化过程的设计变量,给出了优化设计的具体步骤,采用微观遗传算法和有限元模拟方法开发了锻造过程微观组织优化程序,并对典型的圆柱体镦粗进行了面向微观组织优化的预成形设计,取得了较好的效果.     

Sensitivity analysis based preform die shape design using the finite element method

This paper uses a finite element-based sensitivity analysis method to design the preform die shape for metal forming processes. The sensitivity analysis was developed using the rigid visco-plastic finite element method. The preform die shapes are represented by cubic B-spline curves. The control points or coefficients of the B-spline are used as the design variables. The optimization problem is to minimize the difference between the realized and the desired final forging shapes. The sensitivity analysis includes the sensitivities of the objective function, nodal coordinates, and nodal velocities with respect to the design variables. The remeshing procedure and the interpolation/transfer of the history/dependent parameters are considered. An adjustment of the volume loss resulting from the finite element analysis is used to make the workpiece volume consistent in each optimization iteration and improve the optimization convergence. In addition, a technique for dealing with fold-over defects during the forming simulation is employed in order to continue the optimization procedures of the preform die shape design. The method developed in this paper is used to design the preform die shape for both plane strain and axisymmetric deformations with shaped cavities. The analysis shows that satisfactory final forging shapes are obtained using the optimized preform die shapes.     

基于有限元灵敏度分析的锻造成形微观组织优化设计

采用有限元、灵敏度分析与工程优化算法相结合的方法,以能充满型腔且少无飞边的终锻件的晶粒度分布均匀化为目标,以预成形形状为优化对象,对锻造成形过程的微观组织进行了优化设计。采用三次B样条函数描述预成形模具形状,并以B样条函数的控制点坐标为设计变量,给出了锻造过程微观组织演变的模型,建立了衡量锻件充型性能及微观组织分布均匀化的目标函数,推导了目标函数对设计变量的灵敏度,给出了优化设计步骤。并以一典型H型锻件为例,对锻件的微观组织进行了优化,取得了较好的结果。     

叶片精锻三维有限元反向模拟脱模准则的确定

叶片精锻过程的预成形设计是提高叶片锻件质量和降低产品成本的一个极其重要的方面,基于有限元法的反向模拟技术能够从叶片终锻件形状反演出预成形毛坯形状。为此,本文介绍了有限元反向模拟的基本步骤,综述了确定反向模拟中边界节点脱模准则的方法。针对叶片精锻三维有限元反向模拟过程,提出用跟踪拟合修正的方法来确定边界节点脱模的时间序列,确定了反向模拟的脱模准则。将所确定的脱模准则应用到叶片精锻三维有限元反向模拟程序中,可得到合理的叶片预成形毛坯形状。     

Shape Optimization of Initial Billet for TA15 Ti-Alloy Complex Components Preforming

基于DEFORM-3D有限元平台建立TA15钛合金复杂构件预锻成形过程的有限元模型,并结合实验分析典型预锻成形过程及缺陷产生原因;在此基础上采用一套系统的优化方法,从预锻成形最后时刻展开逆向修正,经过逐步优化得到了合理的初始毛坯形状,有效的避免了填充不满、折叠等缺陷的发生,获得了填充完好、内部晶粒尺寸均匀细小的预锻件;并基于优化结果开展了成形试验,验证了结果的可靠性。     

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。     

基于UBET和FEM的模锻件预成形设计

提出了一种用于锻造过程预成形模拟设计的新方法——基于 U BET和 FEM的混合正 /反向模拟预成形设计技术 ,即先用 UBET进行反向模拟 ,快速找出可能的预锻件或初始坯料 ,再用 FEM进行正向模拟验证 ,必要时可根据正向模拟结果对坯料或预锻件进行修改 ,使之能够达到完全充满型腔且飞边尽可能小的最佳效果。应用 U BET和FEM的混合正 /反向模拟预成形设计技术进行预成形设计 ,并与实验结果进行对比 ,结果与实测值基本吻合。     

体积成形预成形设计及优化方法的研究与应用

文章立足于体积成形预成形设计及优化领域的新发展,侧重介绍了在叶片锻造预成形设计及优化方面的应用。对包括工程实际、物理模拟、数值模拟以及类等势场模拟在内的体积成形预成形的各种设计方法进行了全面阐述;归纳总结了目前研究较为热门的基于数值模拟,并结合一定寻优方法的体积成形预成形优化设计的各种主流及创新方法,而且对这些方法的基本原理、优缺点以及应用前景等做了详细介绍;对未来预成形设计及优化技术的总体发展趋势进行了展望。     

面向微观组织优化的锻造工艺预成形优化设计及实验研究

以锻件晶粒尺寸细小均匀为目标,以预成形形状设计为对象,提出了锻造成形过程微观组织优化设计方法,构建了锻造成形过程微观组织优化目标函数,并确定锻造成形预成形形状作为优化过程的设计变量。采用遗传算法和有限元模拟相结合的方法,开发了锻造过程微观组织优化程序,对典型的H型锻件进行了面向微观组织优化的预成形设计,取得了较好的效果。并根据优化设计的结果进行了实验研究,优化结果的晶粒尺寸及其分布趋势与实验结果比较吻合。     

A new approach to optimal design of multi-stage metal forming processes with micro genetic algorithms

This paper describes a new method for design optimization of process variables in multi-stage metal forming processes. The selected forming processes are multi-pass cold wire drawing, multi-pass cold drawing of a tubular profile and cold forging of an automotive outer race preform. An adaptive micro genetic algorithm (μGA) scheme has been implemented for minimizing a wide variety of objective-cost functions relevant to the respective processes. The chosen design variables are die geometry, area reduction ratios and the total number of forming stages. Significant improvements in the simulated product quality and reduction in the number of passes has been observed as a result of the micro genetic algorithms-based optimization process.     

Computer aided preform design in forging using the inverse die contact tracking method

The inverse die contact tracking method presented in this paper utilizes both the forward and inverse finite element simulations to design the preform shapes in forging processes. The procedure starts with the forward simulation of a candidate preform into the final forging shape. A record of the boundary condition changes is produced by identifying when a particular segment of the die makes contact with the workpiece surfaces in forward simulation. This recorded time sequence is then optimized according to the material flow characteristics and the state of die fill to satisfy the requirement of material utilization and forging quality. The modified boundary conditions are finally used as the boundary condition control criterion for the inverse deformation simulation. Additionally, a procedure to determine process staging points using trial forward simulation is given. As an example, the preform design of a plane strain forging process is performed. The fuller, buster and blocker dies are designed by using the inverse deformation simulation.     

单工序锻造过程预制坯多目标优化设计的研究

针对单工序锻造在终锻之前一般都需要以镦粗进行预制坯的实际情况，以刚粘塑性有限元为工具，以获得形状和变形均匀性都较好的终锻件为优化设计目标，以镦粗的压下量为优化设计变量，采用黄金分割法对其预制坯工艺进行了多目标优化设计的研究。并对一轴对称锻件的镦粗压下量进行了优化设计，优化取得了明显的效果。     

Forging preform design with shape complexity control in simulating backward deformation

This paper presents a preform design method which employs an alternative boundary node release criterion in the finite element simulation of backward deformation of forging processes. The method makes use of the shape complexity factor which provides an effective measure of forging difficulty. The objective is to release die contacting nodes in a sequence which will minimize the geometric complexity throughout the backward deformation simulation. This is done by calculating the effect of releasing each of a select group of boundary element nodes at each finite element solution step. The particular detached node which results in the minimum shape complexity factor will be released for the current step. This process continues for each backward step until the last few nodes remain in contact. This design method is demonstrated through the simulated forging of an integrated blade and rotor turbine disk blank. A preform shape developed by this method is compared with an empirically designed preform. Performance parameters for comparison include die fill, flash volume, effective strain variance, frictional power and die load. Comparing the results of the forward simulations indicates improved performance of the preform design using FEM based backward deformation method over that of the empirical design.     

Effects of Parameters on Inhomogeneous Deformation and Damage in Isothermal Local Loading Forming of Ti-Alloy Component

Isothermal local loading (ILL) forming technology provides a new way to form largescale rib-web (LSRW) components of Ti-alloy, widely used in the aero-space fields as key load-bearing structures. However, the metal undergoes complex plastic inhomogeneous deformation and microstructural evolution, this will lead to macroscopical forming defects and further damage due to multi-process parameters and local loading method, making the process and forming quality hard to control. Using numerical simulation, combined with experiment, influences of various process parameters on forming process, inhomogeneous deformation and damage have been explored for ILL of LSRW components, such as the types of die-forging mode, frictional conditions, and local loading parameters (partitioning of the loading zone, constraint conditions, and loading pass). Then the reasonable forming conditions for LSRW components of Ti-alloy to be studied are proposed. The practical forming experiment of TA15 LSRW component was achieved successfully and the forging with good forming quality, excellent microstructure, and comprehensive mechanical properties was obtained, which indicates the reliability and practical value of results obtained in this article.     

体积成形过程预成形优化设计系统的开发研究

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 ,针对精密成形问题 ,提出了一种对多工序锻造过程预成形模具进行优化设计的方法 ,并在此基础上开发了界面友好、自动化程度高、易于使用的锻造优化设计工具软件DOTFORGE。该软件通过优化设计预成形模具形状 ,可实现对锻造过程中多种目标的优化控制。给出预成形优化设计的目标函数和设计变量以及灵敏度分析方法 ,详细介绍了软件的结构功能、关键技术以及应用实例。     

Sensitivity analysis based preform die shape design for net-shape forging

A sensitivity analysis method for preform die shape design in net-shape forging processes is developed in this paper using the rigid viscoplastic finite element method. The preform die shapes are represented by cubic B-spline curves. The control points or coefficients of B-spline are used as the design variables. The optimization problem is to minimize the zone where the realized and desired final forging shapes do not coincide. The sensitivities of the objective function, nodal coordinates and nodal velocities with respect to the design variables are developed in detail. A procedure for computing the sensitivities of history-dependent functions is presented. The remeshing procedure and the interpolation/transfer of the history-dependent parameters, such as effective strain, are stated. The procedures of sensitivity analysis based preform die design are also described. In addition, a method for the adjustment of the volume loss resulting from the finite element analysis is given in order to make the workpiece volume consistent in each optimization iteration. The method developed in this paper is used to design the preform die shape of H-shaped forging processes, including plane strain and axisymmetric deformations. The results show that a flashless forging with a complete die fill is realized using the optimized preform die shape.     

UBET-based numerical modeling of bulk deformation processes

The paper summarizes the development of numerical procedures for modeling bulk deformation process and preform designing techniques based on the upper bound elemental technique (UBET). UBET has a unique place where an approximate, but faster solution is needed for decision making. In designing and optimizing multistage forging and profile ring-rolling processes, an approximate solution can be used to identify the most influential process parameters. Once an optimum combination of process conditions are determined, computationally intensive, but more accurate finite element analysis can be used to verify and refine results. In this paper, UBET procedures for closed-die forging and profile ring rolling are high-lighted. Experimental investigations are used to validate the model predictions. Also, the UBET-based preform design tool is presented as a process and die design tool for multistage forging processes. Application of these techniques is presented with evidence of effective material usage and extended overall die-life.