Fundamental Studies on the Spray Drying and Semi-dry Press of Ceramics, (VI):On the Hardness Distribution and Powder Movement in Green Body

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In the dry process of powder pressing, as described in several previous reports, physical and chemical properties of green body after pressing, have been observed to be affected by molding conditions and powder characteristics. In this report, we have further considered the changes of internal states of pressed green body on the hardness distributions and powder movements.Flow of powder under pressing was investigated by photographs of the layer by layer method. Then the locus of individual powder translations was recognized to be accomplished as parabolic (surface) flow whose principal curvature increases with applied pressures and frictions between powder and the die wall. On representation of hardness applied in this experiment, degree of hardness (R-1) would be proportional to the elastic deformation (δ) of body at the position of measuring and has been formulated as the following equation, R-1=2kt/p(δ)where, p is the applied pressure on drilled edge, k the constant of elastic deformation of green body and t the width of drill teeth.In hardness distribution, we pointed out existence of "Equi-flow of Hardness" along which the tendency of hardness distribution becomes contrary and that most of the defects of body, such as lamination and peel-off, would occur in general at the positions along this flow surface.6 Figs, 2 Tables, 6 References.
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