Mesoscopic Simulation On The Compression Deformation Process Of Powder Particles

The powder compression is the second step of powder molding processes and the green compact of this step is not the final product, but its performance has a great impact on the performance of the final products. Traditional experimental methods can’t show the change of the particles in the compacting process on real time. The finite element method based on the continuum and the discrete element method based on discrete body used in powder compacting research has made some achievements. But the former ignores powder granularity. The latter ignores the variability of particles, while considered the granularity. Therefore, the two methods mentioned above can’t investigate the deformation of compacting process accurately. This paper uses the finite element method of discrete body to simulate powder compacting process. Analysis the particle strain and the density influence by interfacial friction, pressing force, compacting way etc.This paper analysis the development of powder metallurgy technology and the research status of the powder pressing process simulation at home and abroad systematically. Combined with the main technology of powder metallurgy production and raised the main content of this paper. Combined the theories of powder compression and the finite element theory of Marc, successfully solved the numerical problems of the powder compaction process. In order to provided the friction parameters and the standards of density changes to the simulation, developing a device of measuring friction coefficient. Experiment for the friction coefficient of the different powder materials in the different pressing forces, obtained the friction coefficient relation to the different materials and the coefficient and density relation to the different force.Established three finite element models:two-dimensional orderly model, three-dimensional spherical particle model and the two-dimensional random mode. Defined the material properties, the contact model and boundary conditions of the model according to Marc, and set the key parameters. Successfully resolved the problem of the convergence in numerical solution and achieved the good results. Investigated the rules of the flow of particles, strain, and compacts density effected by the die wall friction, way of compression and pressing. The results showed that the deformation process of the pressed powder particles consists of three stages:the initial stage of small deformation, the major stage of the sharply changes of strain and the stabilized stage. The die wall friction is the mainly reason to the density difference of inside and outside and the deformation and density of particles close to die wall. Effective lubrication and double action compaction can effectively improve the density distribution. The density can’t be increased with the increased of compacting pressure of compaction infinitely. The compacting pressure should be based on the different types of the powder, so that the production efficiency and production quality of powder metallurgy can be improved effectively.