| The highest goal of forging production is to make the best with the lowest cost.To reduce the cost of forging production, energy consumption and materials waste should be reduced. To improve the quality of the forging, the shape of the final forging, the deformation uniformity and the microstructure of the forging have been taken into consideration. The preform die and the preform shape have direct relation with the quality of the forging, which would directly affect the deforming force and the forming quality. So the optimal design for preform in forging process is the most direct and effective way to reduce the cost and improve the quality of the forging.The development and present situation of the research on optimal design for preform in forging process is reviewed, lots of optimization methods have been applied to optimal design for preform, and almost each objective function have been studied, but no one optimization method could be applied to all objective functions. Ant Colony Algorithm(ACA) is a new evolutionary optimization algorithm, which has strong robustness, excellent distributed computing mechanism and can be incorporated with other optimization algorithm easily. Besides, ACA has been widely applied to other engineering community. This paper is based on the basic ACA, combining the ACA with finite element numerical simulation method. The shape of the preform die has been taken as optimization object, and a systematic study of several evaluated objects in forging process has been made in order to lay the foundation for further study on establishing a universal system of preform design which is suitable for the practical production.Firstly, the basic theory of the visco-rigid plastic finite element method is presented in this dissertation. The basic assumption of the visco-rigid plastic finite element method and the basic equations of the plastic mechanics are given. The essential principles and the solution procedures of the visco-rigid plastic finite element are introduced. According to the main contents and principles of optimization design, a study on the model of evaluated objects optimization in forging process has been made. Three objective functions which were based on the shape of the final forging, the deforming force and deformation uniformity have been established respectively. This paper expounds the mechanism principle and the mathematical model of the ACA in detail.Secondly, based on the basic ACA, a modified ACA model which is fit for multivariate continuous function optimization has been built. The modified ACA program has been developed using C language. The validity of the model and the program has been verified by two simulation examples. This paper shows the procedures of preform optimization design using the modified ACA model in forging process. And a basic system used for preform optimization design is established by combining the ACA with FEM. In addition, this paper introduces the function of each module.Finally, preform optimization design of typical H-Section axisymmetric forging is studied using the system established in this paper, and three single objective functions and a multi-objective function are considered. After optimization, the forging with small-flash is obtained in the optimization design based on the shape of the final forging. The deforming force is decreased in the optimization design based on deforming force. Deformation uniformity is significantly increased in the optimization design based on deformation uniformity, and forging with good deformation uniformity as well as small deforming force is obtained in the multi-optimization design based on the deforming force and deformation uniformity. These optimization results are all verified by DEFORM-a commercial finite element software. Through contrasting with the results of simulation, it is indicated that the optimization method and the preform optimization design system are reasonable and reliable. |
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