# Basic theory of numerical simulation of forging process

The process of loading metal raw materials with mold and other equipment to produce plastic flow to produce products that meet the established requirements is called metal plastic forming process. In the process of plastic forming, many complex changes in the internal structure, material flow, stress-strain distribution and so on need to be observed by some related auxiliary equipment. Such a complex testing procedure undoubtedly increases the initial cost investment and R & D time of the part forming process exploration. In order to improve this situation, the numerical simulation technology of metal plastic forming came into being. In order to improve this situation, the numerical simulation technology of metal plastic forming came into being.

#### Theory of metal plastic forming

All solid metals are crystals in which the metal atoms are arranged in a certain order. The metal atoms in the crystal are in equilibrium state without external force. The external force forces the crystal interior to produce the stress, the metal atom maintains the equilibrium state to be broken and causes the crystal interior atom to arrange the order and the relative position change, macroscopic will cause the metal size and the shape change to cause the metal size and the shape change.

On the micro level: the internal stress of metal crystal caused by external force drives the position of the equilibrium atom to move, and the atom tends to return to its original position; if the external force increases continuously and exceeds a certain limit value, the atom will completely break away from the original equilibrium state and enter the next equilibrium position, even if the external force is completely cancelled at this time, because the atom is in a new equilibrium state, it will not Return to the original location. This process is macroscopically reflected in the irreversible deformation of metal, that is, plastic deformation.

Crystal level: polycrystal is a certain number of aggregates with different grains. The metal materials we come into contact with are polycrystalline. The plastic deformation of polycrystals can be divided into:

1.Intergranular deformation: the relative movement between grains in polycrystalline;

2.Intragranular deformation: the change of relative position between different regions in the crystal.

In polycrystals, the deformation of a grain must be the result of the interaction between a grain and its neighboring grains. If there are atoms with irregular array in the grain boundary, the lattice will be distorted, which will hinder the development of deformation.

#### Numerical simulation technology of metal plastic forming

Forging process is a kind of plastic forming process. The numerical simulation of forging process needs to consider the physical properties of materials, the shape and size of billets, the load of dies and the processing temperature to determine the appropriate process parameters, so as to achieve the purpose of improving the efficiency and reducing the cost of numerical simulation of metal plastic forming, so as to achieve metal plastic forming The purpose of numerical simulation is to improve efficiency and reduce cost.

The numerical simulation technology of metal plastic forming can be divided into two categories: numerical simulation and physical simulation. Physical simulation is to simplify the actual product parts into general simple shape parts by reference to the physical properties of the material, which has great limitations. Numerical simulation technology is to simulate the forming process of the workpiece by numerical method and make the calculation results continuously approach the real forming situation and show it directly.

Compared with the traditional experimental trial production method, numerical simulation technology can greatly save the research cycle and development cost of new product manufacturing process, and guide the improvement and optimization of the process by intuitively displaying the change process of internal organization structure and forming effect in the process of workpiece forming. Based on the above advantages, the numerical simulation technology is very suitable for the analysis of the casting forging compound forming process of the driven spiral bevel gear in this paper.

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