Finite element analysis and optimization design of

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Finite element analysis and optimization design of cold forging die for a long time, the design of forming process, die and process analysis are mainly based on accumulated practical experience, industry standards and traditional theories. However, due to the uncertainty of practical experience, the effectiveness of industry standards, and the simplification of deformation conditions and deformation process in traditional theories, it is often not easy to obtain satisfactory results for complex mold design, resulting in a long time and many times of debugging molds, and even the scrapping of molds. Usually, in order to ensure the reliability and safety of the process and mold, conservative design schemes are adopted, resulting in the increase of processes and the increase of mold structure size. Modern forming process and die are developing towards high efficiency, high speed, high precision, high performance, low cost and resource saving, so the traditional design method is far from meeting the requirements. With the emergence and development of computer technology and the increasing requirements for numerical analysis in engineering practice, the finite element analysis method has been developed. The finite element method has been developed rapidly since cloud first proposed it in 1960. Next, we discuss the finite element numerical simulation analysis technology

1. Finite element numerical simulation analysis technology

the traditional experience based and experimental methods have been used in the process design and die design of plastic forming. This design method is difficult to meet the requirements of manufacturing process. With the rapid development of computer technology and the development of plastic finite element theory in the 1970s, many difficult problems in plastic forming process can be solved by finite element method

the rationality of finite element numerical simulation technology used to test the process and die design has been fully reflected in the field of cold forging process. By modeling and determining appropriate boundary conditions, the finite element numerical simulation technology can intuitively obtain the stress, strain, die stress, die failure and possible defects of forgings in the metal flow process. The acquisition of these important information has important guiding significance for the rational die structure, die material selection, heat treatment and the final determination of the forming process

in view of the fact that the finite element numerical simulation technology can be used to test the rationality of the process and die design, a new process for forming spur gear from hollow billet is proposed: pre forging split flow zone split flow final forging. The finite element analysis is carried out by three-dimensional finite element numerical simulation, and the forging load stroke curve and the stress, strain, velocity distribution in the whole forming process are obtained, The simulation results are compared with those of the traditional closed upsetting extrusion process. The analysis shows that the traditional closed upsetting extrusion should select halogen-free flame-retardant materials to reduce the odor of the air in the car. The forming load is large, which is not conducive to the filling of the tooth shape. By adopting the new technology of pre forging split flow zone split flow final forging, the forming load can be greatly reduced, the filling property of the material can be obviously improved, and the gear with full tooth shape angle can be obtained. The forming process of gear cold precision forging is numerically simulated by three-dimensional large deformation elastic-plastic finite element method. The deformation flow of the two-step forming mode with closed die forging as pre forging and closed die forging, hole splitting and constrained splitting as final forging is numerically simulated and analyzed by finite element method. The results of analysis and process experiments show that it is very effective to reduce the working load and improve the corner filling capacity by taking the measures of diversion, especially the diversion of restricted hole in the final forging

it can be seen that the use of finite element analysis method for die design and analysis greatly saves development time, improves design quality, improves efficiency for us, and increases the accuracy and safety of die process in plastic forming. Thus, the whole design mode is changed from empirical design to scientific design

2. Introduction of optimization technology

from the perspective of practical application, the most representative optimization methods based on finite element analysis include the optimization method based on sensitivity analysis and the fitting optimization method based on the value of objective function

the optimization design method based on sensitivity analysis belongs to gradient optimization design method. During the implementation of this method, first determine the objective function and design variables, then find out the relationship between them, deduce the sensitivity derivative common formula of the objective function to the design variables. In the past, it was generally a sample preparation detection formula, solve these sensitivity information according to the existing values of the design variables, then use the optimization algorithm to determine the optimal search direction of the design variables, get the better design variables, and then solve the sensitivity information. Repeat this process, Until the optimization iteration converges

the fitting optimization method based on the value of the objective function is derived from the extrapolation method. In this method, a simple interpolation function is used to approximate the functional relationship between the objective function and the design variable, and the extreme point of the approximate function is solved to approximate the extreme point of the real function. When this method is applied to the optimization of forging process parameters, the objective function value is realized by finite element program

at present, some general finite element analysis software (deform, MARC) have been widely used in the numerical simulation of the forging process, which can easily calculate the stress, strain and other information. Therefore, the fitting optimization method based on the objective function value can separate the finite element program from the optimization algorithm, which is suitable for different forging processes, and is convenient for the parameter optimization of the forging process

although many achievements have been made in the research and application of forging process optimization technology based on finite element analysis, it is still in its infancy. It can be seen that there are still some problems in the research of this field from the construction of the number of objective functions that must be stopped immediately, the selection of optimization design variables to the specific application of optimization methods

(1) many achievements have been made in the research and application of optimization method based on sensitivity analysis. Because this method belongs to gradient optimization method, its convergence speed is relatively fast. However, it still has some shortcomings in practical application: in the process of optimal design, it is necessary to solve the sensitivity information (i.e. derivative) of the objective function relative to the optimal design variables, and it is difficult to deduce the sensitivity information of the complex metal plastic forming process. This method requires that the program code for solving sensitivity information should be embedded into the numerical analysis program code, and the finite element analysis code and optimization algorithm code need to be written, so the programming workload is large. At the same time, the optimization program of this method is not universal

(2) the advantage of the fitting optimization method based on the value of the objective function is that the optimization algorithm is separated from the finite element program, which can make full use of the advantages of the powerful commercial finite element analysis software. This method has strong universality. Its main disadvantage is that the convergence speed is relatively slow. At the same time, in the easy wear fitting problem, but when more design variables are obtained, there will be many complex problems, such as well posed problem, which makes the fitting process fail

(3) forging forming is a complex process. The ideal forging should not only have accurate shape that meets the design requirements, but also have uniform deformation, reasonably distributed deformation force and ideal quality (no macro and micro defects). All the above aspects are the goals of forging production, so it is necessary to carry out multi-objective optimization for the optimal design of forging process. At present, there are few studies in this field

3. Conclusion

with the increasing competition, low cost, high quality and high efficiency are the goals pursued by the manufacturing industry. In the forging industry, in order to improve design efficiency, reduce manufacturing costs and improve product quality, it is necessary to optimize the process parameters that affect the quality of forgings in the forging process. As forging deformation is a very complex problem, it is difficult to achieve the desired effect by using the traditional design method for the optimization of its process parameters. With the continuous development and improvement of computer technology and plastic finite element theory and technology, the numerical simulation method represented by finite element method has been widely used in the solution and analysis of various metal forming problems. Therefore, the application of optimization design method based on finite element analysis in cold forging process/die design is not only possible, but also an inevitable trend. (end)

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