Relationship between percolation mechanism and pore characteristics of recycled permeable bricks based on X-ray computed tomography

The relationship between percolation mechanism and pore characteristics for recycled permeable bricks with different porosities is investigated in this study based on X-ray computed tomography (X-CT). Permeability coefficients are measured and some characteristics including size, amount, and distribution of the pore are analysed. The results show that the effective porosity and permeability coefficient of the recycled permeable bricks exhibit a linear relationship first and then a quadratic curve relationship, where the critical effective porosity is 12%. Meanwhile, we discovered that nonlinear channels in permeable bricks are larger and fewer compared with linear percolation channels, regardless of whether the percolation stage is linear or nonlinear. Additionally, when the area and number ratios of the linear and nonlinear percolation channels reached 80% and 10%, respectively, the overall percolation state of the permeable bricks changed from linear to nonlinear percolation. This research is helpful to improve the mechanical and percolation properties of recycled concrete bricks and promote the application of porous permeable material.

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

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.

Permeable ceramics filled with the threefraction electrofused corundum and the porcelain bond

By means of the raw material grading the porous permeable material was prepared with the electrofused corundum with the porcelain PFL-1 bond. The samples with improved properties were obtained when introducing in the mass of 5 weigh percent of porcelain bond (above 100 % of the fller) after the burning at 1450 оC. Their ultimate strength at bending was 14,6 MPa, the open porosity was 44 % and the gas permeability factor was 0,85 micron2. Ref. 10. Tab. 3.

The Assembly Loads and Some Strengthening Methods of the Products from Porous Material with Coiled Wire

The product from porous permeable material based on a wire coil consists of a round, porous, thin-walled tube. The impact of assembly loads of the porous tube has been examined to determine the maximum values of the compressive force and axial elastic strain during the assembly. To improve mechanical properties of the product additional reinforcement has been proposed: larger diameter wire, woven wire cloth or spring.

The Structure Analytical Research of Porous Permeable Wire Material

The details of making technology of porous permeable material with use of wire are allowed to carry out the analytical research of structure and structural characteristics of wire winding body. Its permit for prognostication the final properties of material, that is produced by the following deformation treatment (diameter reduction). Due to the regular organized arrangement of wire, the coil of winding body is considered as a multispan continuous beam, but a contact of coils - as interaction of two cylinders. Possibility of exactly calculation of the contacts between coils is allowed to go over the single fragment displacements into deformation of whole winding body. During research of deformation processes in regards of winding body geometry and used wire mechanical properties, the structural characteristics of porous permeable wire material are expected. The optimal number of winding layers, eliminating the distortion of organized final structure, is established. The material pressure-compactness relation is obtained in order to control the technological conditions of winding and drafting for guarantee the product required properties.