Research On Numerical Simulation In Forging Process Based On Element Free Galerkin Method

Metal forming plays an important role in metal part manufacturing. Its advantages are not only in its high productivity, stable quality, and low cost of raw and processed materials, but also in its characteristics of improving the microstructure performance dramatically. It is helpful to simulate the forming process, which can not only cut down the experiment cost, but also find the problems ahead of schedule. With the development of computer technology and computational methods, the Finite Element Method (FEM) gained great achievement and was applied widely in many engineering fields. Although FEM achieves great success in the numerical simulation of metal forming process, the mesh distortion will be inevitable with the accumulation during the metal deformation. Then many difficulties occur in FEM analysis for dependence of the approximation precision on the mesh. Compared with FEM, the meshless approximation based on discrete points information has advantages in the simulation of large deformation problems with mesh distortion for getting rid of the reliance on the mesh. Simultaneously, the meshless method is more flexible and simpler than the FEM in data prepare for the problem simulation and post-process of simulation results.The meshless method, a newly developed numerical method, was used to the simulation of metal forming processes after decade's development, and some progresses were obtained. But there are still many key techniques, which need more attention for the complexity of the metal deformation in unsteady metal forming processes. Especially when the deformation is more severe or metal flow is more complex, the approximation precision of the velocity field and integration precision of deformation domain will be deteriorated for the severe un-uniformity of the metal flow and complexity of the deformation zone. Thus simulation error occurs.The metal flow pattern and the distribution of the stress-strain in the upsetting, which is the typical forging process, have been studied. Based on the meshless analysis program, the paper focused on the numerical simulation of the upsetting. The effect of the friction coefficient, influence domain radius of the weighted function and the discrete points number on the precision and efficiency of the Element Free Galerkin Method (EFGM) is studied. It is found that friction is the primary reason for the drum-shape of the upsetting. The load increases with the increase of the friction, and the asymmetry of the distortion also increases.The influence domain radius is an important parameter. The paper researched its influence on the calculation ability and efficiency of the EFGM at the condition that the other simulation parameters keep constant. The EFGM can not continue to calculate if the radius is too small. The EFGM can simulated more distortion with the increase of the radius. But the simulation ability does not change greatly when the radius is over a value. It is important to select the appropriate radius for the EFGM.Another effect factor in the EFGM is the discrete points number. When the number is doubled, the metal flow can be showed better and the simulation precision is enhanced. On the other hand, the simulation efficiency is reduced evidently. The number of the discrete points should be chosen reasonably.The EFGM results are compared with those obtained by the rigid visco-plastic Finite Element Method at the same condition. They are in good agreement. The theory of the EFGM and the precision and the stability of the programme are validated.Changing the die corner angle and the friction coefficient, the influence of these parameters on the Equal Channel Angular Process is simulated numerically. The smaller die corner angular, the better equal strain distribution, but the extrusion load is bigger, which reduces the life of the die. The friction coefficient does not have great influence on the equal strain distribution, while affects the load remarkably. It is necessary to take measures to reduce the friction between work piece and the die to lessen the load.