Analysis of the densification of powder materials subjected to uniform omnidirectional loading
| Autor: | V. E. Perel'man |
|---|---|
| Rok vydání: | 1977 |
| Předmět: |
Pressing
Materials science business.industry Metals and Alloys Shell (structure) Structural engineering Deformation (meteorology) Condensed Matter Physics law.invention Stress (mechanics) Cross section (physics) Brittleness Mechanics of Materials law Materials Chemistry Ceramics and Composites Composite material Hydrostatic equilibrium business Porosity |
| Zdroj: | Soviet Powder Metallurgy and Metal Ceramics. 16:668-672 |
| ISSN: | 0038-5735 |
| Popis: | 1. In the pressing of parts from powders in hydrostatic and isostatic pressure vessels the processes occurring in the material being densified are identical with those characterizing pressing in dies: An indispensible element of pressing is the destruction of the porous structure of the material (through plastic and brittle deformation), as a result of which the density of the structure grows. 2. Uniform omnidirectional loading of a porous compact, even one of spherical shape, does not set up a uniform stress state in the material, so that σr ≠ σϕ ≠ σs, nor does it bring about a uniform stress distribution along the coordinate axis, which means that σr=f(r) ≠ const. 3. To determine the character of the stress, strain, and density distributions in parts undergoing pressing in hydrostatic and isostatic pressure vessels, it is necessary to employ standard methods for the mathematical analysis of the deformation and densification of porous (powder) media. 4. The greatest distortion of compact geometry is experienced with materials having large angles of internal friction, i.e., materials of high porosity. 5. To assess the change in compact geometry occurring during the densification process, particularly in its early stages, it is permissible to employ methods of calculation and modeling of the deformation of shells under identical loading conditions. The accuracy of such an analysis can be increased by calculating shell deformation in successive stages, the initial shell geometry and wall thickness in each stage being the result of the calculation of the preceding stage. 6. The distortion of parts during pressing can be minimized by using shells of variable cross section and decreasing the angle of internal friction of the starting material; one may also employ shell shapes calculated by the methods recommended in Paragraphs 3 and 5. |
| Databáze: | OpenAIRE |
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