Study On Preform Design In Forging Process Base On Electric Field

Preform design is a important content in the forging processes design. One or morepreform designs are required for complicated forgings before final forging,The shape ofpreform is also directly correspond with the final forging,it limits the flow of metal andeffects on the final shape and the quality of final forging.For a certain shape of forging，the shape region of preform is infinite, and thepurpose of per-forging design is to obtain the best one.In addition, different processparameters combined with different preform shapes will obtain different qualityforgings. How to choose the best combination between different preform shapes andprocess parameters is the key to produce high quality products and also one of thedifficulties of die design. At present, national and overseas works about preform designmost focus on the method of trial and error which utilizes numerical simulationtechnology to validate results, the validate method which is adopted is different fromthe traditional method of trial and error,but its essential idea is the same.Aim for the problems above, the paper further discusses the electric field methodof the preform design with the existing research findings. Electric field method meansthe equi-potential lines generated between two conductors of different voltages showsimilar trend for the minimum work paths between the undeformed shape and deformedshape. In this paper, electric field method, mathematic model, optimization algorithmand numerical simulation were proposed and have been extended to actual formingprocess. Finally, the best combination of per-forging shape and process parameters wereobtained. The main research findings as follows:①The possibility that simulating the metal forming process based on the similaritytheory has been proved by electric field method，the method of modeling andoptimizing based on MATLAB tool MBC（Model-Based Calibration）was given and ageneral method of per-forging design of gear-section axi-symmetric part base on electricfield method was developed.②Preform design in three stage, pre-treatment, preform and final forging based onelectric field method was conducted by the example of gear-section axi-symmetric part.First，the suitable distribution of equi-potential lines between the blank shape and finalforging shape was obtained by electric field method, The equi-potential values werechosen as a local variable while speed of pressing machine, friction coefficient,temperature were chosen as the global variables, forming load and filling ratio were chosen as optimization goals. The DEFORM-3D software was used to simulate theforging process, the MBC (model-based calibration) toolbox was used to establishmathematic model, and multi-objective optimization for gear—section axi-symmetricpart was performed by using optimization tool CAGE（Calibration Generation）. A gearwith filling completely, uniform deformation and low deforming force was obtained.③Research on the forging of three dimensional complex forging based on electricfield method was conducted by the example of large aircraft of7050aluminum alloyforging. Similar with gear-section axi-symmetric part, the distribution of3-Dequi-potential lines between the blank shape and final forging shape was obtained byelectric field simulation method. The material flow characteristics in the formingprocess were analyzed by the distribution of3-D equi-potential surfaces so that thepossible defects could be predicted. The equi-potential surfaces in3-D electric fieldwere extracted as preform shapes by materiaise’s interactive medical image controlsystem. According to the characteristics of the forging, the equi-potential linesdistribution of different segmentations was extracted to establish3-D model. Finally, thebest pre-forming shape was obtained. Then, the equi-potential values were chosen as alocal variable while speed of pressing machine, friction coefficient， temperature werechosen as the global variables，forming load, grain size and filling ratio were chosen asoptimization goals. The MBC toolbox was used to establish mathematic model.Multi-objective optimization for7050aluminum forging was performed by usingoptimization tool CAGE. Then, the7050aluminum alloy forging with fillingcompletely, uniform deformation and low deforming force was obtained.④The per-forging shape after optimized was simulated, the related field variablesdistribution of final forging were analyzed by the result of simulation, the resultsindicate that, compared with the traditional design, the maximal equivalent stress andequivalent strain of the forging with per-forging minish, the transition region is moreobvious and broader, the forming of materials is more even, the grain sizes are moresmaller, the distribution and flow of materials are more reasonable, The performance offilling die is enhanced, forming load is lower, so the possibility of preform design basedon electric field is proved, and the reliability of their results also is proved.