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1.
Computer aided preform design in forging using the inverse die contact tracking method 总被引:2,自引:0,他引:2
G. Zhao E. Wright R.V. Grandhi 《International Journal of Machine Tools and Manufacture》1996,36(7):755-769
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. 相似文献
2.
Guoqun Zhao Ed Wright Ramana V. Grandhi 《International Journal of Machine Tools and Manufacture》1995,35(9)
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. 相似文献
3.
Guoqun Zhao Ed Wright Ramana V. Grandhi 《International Journal of Machine Tools and Manufacture》1997,37(9):1251-1271
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. 相似文献
4.
A new technique has been developed for the design of die shapes in the plane strain forging process. The objective of this research work is to develop a design procedure to obtain the number of stages and the shape of each die for manufacturing a desired product. Metal flow during the forging is considered in the design of the intermediate die shapes in multistage forgings. The two approaches developed for the preform shapes design are conformal mapping techniques and ideal material flow simulations. The forging process is simulated using a nonlinear rigid visco plastic finite element program ALPID (analysis of large plastic incremental deformation). Staging criteria is developed from the results of the forging simulation and the number of stages are based on the stress ratio parameterg (mean stress/effective stress) and strain rate gradient information. This paper presents two examples of forgings to demonstrate an optimal die shape design methodology. 相似文献
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6.
G. Q. Zhao R. Hufi A. Hutter R. V. Grandhi 《Journal of Materials Engineering and Performance》1997,6(3):303-310
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. 相似文献
7.
微观遗传算法在预锻模优化设计中的应用 总被引:2,自引:0,他引:2
锻造过程实现净形和近净形制造最关键的一点是对无预锻模进行优化设计。本文用微观遗传算法对H型截面锻件进行了预锻模优化设计,以实现此锻件的无飞边锻造。设计结果表明优化效果显著。而且用遗传算法进行预锻模优化设计,可充分利用现有的CAD/CAM软件,既保持软件的独立性,又能实现两者的双向集成。 相似文献
8.
《International Journal of Machine Tool Design and Research》1984,24(2):105-119
This paper describes an interactive computer programme, implemented on a 64K mini-computer, a size which is within the purchasing capability of most drop forges, to aid the process of preparing data for cost estimation and preform die design for forging on hammers.The programme utilises Interactive -MODCON [1], a CAM system developed for machining finish forging dies, as an input facility to describe the geometry of forged shapes.Provided with an input file describing the geometry of the forging, the programme can be executed to obtain data such as the weight, cross sectional areas, plan area, mean thickness, centre of gravity, perimeter of the forged shape. Based upon these data, essential information required for cost estimation and preform die design is provided using the built-in design rules. The information includes amount of flash, flash geometry, mass distribution curve, forging energy and load, hammer size, minimum preform operations and bar size. 相似文献
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10.
Optimum design of forging dies using fuzzy logic in conjunction with the backward deformation method
F.R Biglari N.P O'Dowd R.T Fenner 《International Journal of Machine Tools and Manufacture》1998,38(8):981-1000
A novel shape optimization method is presented for the design of preform die shapes in multistage forging processes using a combination of the backward deformation method and a fuzzy decision making algorithm. In the backward deformation method, the final component shape is taken as the starting point, and the die is moved in the reverse direction with boundary nodes being released as the die is raised. The optimum die shape is thereby determined by taking the optimum reverse path. A fuzzy decision making approach is developed to specify new boundary conditions for each backward time increment based on geometrical features and the plastic deformation of the workpiece. In order to demonstrate this approach, a design analysis for an axisymmetric disk forging is presented in this paper. 相似文献
11.
Magnesium alloys have relatively low workability at room temperatures due to hexagonal crystal structure. In general, the forging process of magnesium alloys is considered to be very difficult because of the poor flowability and the sensitivity to the temperature and strain rate. Taken spur bevel gear as an example, the hot forging process of the complicated shape parts of magnesium alloy AZ31B was investigated by means of finite element (FE) simulations combined with experiments. After the two-stage hot forming process (preforming operation without gear shape and finish forging operation) was determined, the influence of various shapes of preform dies on the hot forging process was discussed by the commercial finite element analysis software Marc, and the optimum preform die shape was obtained. According to the numerical simulation results, the hot forging experiments of magnesium alloy AZ31B spur bevel gear were successfully conducted. By comparison between experimental load–stroke curves and the calculated ones, it shows that the calculated results are consistent with the experimental ones. 相似文献
12.
基于有限元灵敏度分析的锻造成形微观组织优化设计 总被引:2,自引:0,他引:2
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。 相似文献
13.
基于UBET和FEM的模锻件预成形设计 总被引:4,自引:0,他引:4
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。 相似文献
14.
材料塑性成形过程最优化设计—Ⅰ有限元灵敏度分析方法 总被引:16,自引:2,他引:14
本文采用有限元方法建立了一种非稳态材料塑性成形过程的灵敏度分析理论和模具形状优化设计方法。采用三次B样条函数描述预成形模具形状,B样条函数的控制点坐标(系数)作为优化设计变量,通过对控制点坐标的优化设计,使实际终成形件形状与理想终成形件形状之间的差别最小,从而实现预成形模具形状的优化设计,详细建立了目标函数、有限元节点坐标、节点速度对优化设计变量的解析灵敏度方程及其彼此之间的数学关系,并给出了节点速度灵敏度的边界条件 相似文献
15.
Large-sized frame forging of Ti-alloy is an important forced component of aircraft. The frame forging has complicated shape
which leads to great difficulties in deformation. Some defects may be produced during the forming process such as un-filling
or overlapping. Preform design is an effective method for producing qualified forging. In this article, a new method based
on 3-D electrostatic field simulation is proposed to design preform of a large-sized frame forging of Ti-alloy and a geometric
transformation method is introduced to obtain the preform dimension. In order to select more suitable preform of large-sized
frame forging, FEM software Deform-3D is employed to simulate the isothermal forming process of designed preform. Deformation
uniformity index ψ is introduced as a criterion to judge the forging quality and the most appropriate preform is obtained
by virtual orthogonal test design. 相似文献
16.
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. 相似文献
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18.
A. Santangelo P. Blanke T. Hadifi F.-E. Wolter B.-A. Behrens 《Production Engineering》2013,7(4):409-416
In hot die forging processes, the selection of an ideal preform is of great importance with respect to cavity filling and mechanical load. The common procedure in order to define an adequate preform is the usage of Finite-Element-Analysis (FEA), usually as an iterative process in which various preforms are tested with regard to their suitability. An approach that aims at reducing the number of trials by proposing a first estimation of a suitable preform is presented in this paper. It is conjectured that the material flow paths and resistance can be described by the cavity shape using the Medial Axis Transformation. Based on this, a local inverse material flow for time discrete steps is calculated. The result is a first estimation of an adequate preform shape within a few minutes as an input for further FEA. FE-based parametric design optimization procedure is then presented and compared to the inverse approach, which is identified as a useful complement for the forward simulation technique. 相似文献
19.
通过对8MN快锻液压机上采用胎模锻造中心管锻件的工艺方案的分析,研究了锻造制坯、模具设计的特点和要点,提出了液压机胎模锻造变形力的计算方法,指出锻造难点、可能出现的问题及预防纠正措施,还提出了液压机胎模锻造模具材料的选用方法. 相似文献
20.
设计合适的锻压坯料是保证锻压后锻件具有良好综合性能的基础,通过改进锻压坯料的尺寸来改善锻件各部位的变形程度以获得具有良好组织及性能的锻件。运用有限元模拟软件Deform-3D模拟联接轴等温模锻过程,对不同尺寸的坯料模拟等温锻造过程,随着坯料在Z向厚度尺寸的增加,模锻后锻件的等效应变随之逐渐增加。选择成形效果较佳且模锻后锻件变形程度逐渐增加的锻压坯料进行实验。对热处理后的等温模锻件进行室温拉伸、硬度、电导率、疲劳以及金相实验检测。结果显示:对于横截面沿长轴突变的联接轴锻件,锻件各部位间性能差异较大;等温模锻后,变形程度大的锻件能够获得更好的微观组织和力学性能。 相似文献