Modeling of the compaction of powder filter elements during radial isostatic pressing

Abstract

The method of computer simulation was used to study the process of radially isostatic pressing of filter elements made of steel powder BBS15. Powder compaction occurs under the influence of an elastic ele¬ment made of polyurethane. The volume of the deformable body is considered as a continuous medium. To describe the behavior of this medium, the relations of the theory of plasticity of a porous body and the finite element method are used. The patterns of compaction of products of two types are considered (hollow cylinders, including multilayer ones, and filters of complex shape in the form of a bulb). When pressing multilayer filters, the load was removed after compaction of each layer. A new powder was placed in the cavity between the obtained layer and the elastic element, which took its original shape. Further, the pressing process was continued. The porosity distribution in the case of compaction of a single-layer cylindrical filter is uneven. The value of porosity increases with increasing radius. As the degree of deformation increases, the difference between the porosity of the material at the inner and outer surfaces of the filter decreases. The compaction of the outer layer of the two-layer filter occurs in the same way as the preliminary compaction of the first (inner) layer. The denser inner layer deforms slightly and acts as a mandrel. Further, the outer layer is compacted and both layers are deformed. The compaction of the layers of a three-layer filter is similar. The thickness and porosity of the layers can be controlled by changing the initial porosity of the powder, the inner diameter of the elastic element, as well as the pressing load. Two compaction schemes (radial and axial) were considered in the manufacture of complex-shaped filters in the form of a bulb. The distribution of porosity is uneven and depends on the compaction scheme. The material of the filter wall is compacted more intensively in the case of radial pressing. The porosity is higher at the outer surface of the filter wall and lower at its inner surface.The bottom material of the filter is compacted more intensively in the case of axial pressing.The use of the pressing scheme, in which the powder is first compacted in the radial and then in the axial direction, allows to get a more uniform distribution of porosity. Keywords: radial isostatic pressing, porous permeable material, filter, density distribution, porosity.