Journal of the Japan Society of Powder and Powder Metallurgy

[title in Japanese]

[in Japanese]

1975 Volume 22 Issue 2 Pages 41-46
Published: April 25, 1975
Released on J-STAGE: May 22, 2009

DOIhttps://doi.org/10.2497/jjspm.22.41

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High Velocity Compaction of Powder, 3rd Report

Theoretical Anslysis of Compaction Process by Pseudo-Viscosity Method

Yukio Sano, Tadaaki Sugita

1975 Volume 22 Issue 2 Pages 47-54
Published: April 25, 1975
Released on J-STAGE: December 04, 2009

DOIhttps://doi.org/10.2497/jjspm.22.47

JOURNAL FREE ACCESS

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This paper is concerned with a theoretical study on high velocity compaction process of metal powder by the pseudo-viscosity method. As well as in the first paper, the powder uniformly packed in a die is struck by a rigid body. The pseudo-viscous pressure used here is such that running wave solutions vary smoothly through the shock region. Comparing with the results obtained in the first paper, the following ones were obtained.
1) The results by this method agree well with those by the jump conditions, though there are oscillations of pressure behind the shock.
2) The effects of the elastic recovery of the powder are negligible.
3) When the initial kinetic energy of the striking body is constant, the assumptions used in the first paper become less satisfactory as the impact velocity of the body is larger.
4) The powder is more uniformly and highly compacted as the mass of the body is larger.

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A Unified Theoretical Treatment of Sieving and Screening

H.E. Rose

1975 Volume 22 Issue 2 Pages 55-70
Published: April 25, 1975
Released on J-STAGE: May 22, 2009

DOIhttps://doi.org/10.2497/jjspm.22.55

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On the basis of the hypothesis that it is the blinding process which is the controlling factor in the mechanics of sieving operations, a mathematical treatment of sieving has been developed; the validity of this treatment being confirmed by the results of experiment.
It is shown that logically, this treatment is applicable to the screening process and so provides a new and unified approach to the theory of both these processes.
In order to reduce the results to a form suitable for direct practical application, a semi-empirical expression for the performance of a screen has been developed.

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On the Nonlinear Negative Resistance of Polycrystalline Ferrites

Hideji Igarashi, Shinjiro Tashiro, Kiyoshi Okazaki

1975 Volume 22 Issue 2 Pages 71-76
Published: April 25, 1975
Released on J-STAGE: July 12, 2010

DOIhttps://doi.org/10.2497/jjspm.22.71

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Using the polycrystalline disk of NiZn and CuZn ferrites with a resistivity of 10 ²-10 ⁴Ω⋅m, the local current path was formed by applying an electric field up to the extent of the breakdown voltage between the plate electrode on one face of the disk and the needle electrode on the other face. We named this procedure as “Conduction Treatment”. It was found that after me conduction treatment, this specimen shows the nonlinear negative resistance such as so-called switching phenomena of amorphous semiconductor.
From the optical microscopic observations, it was clarified that 1) the current path was separated by the thin gap from the surrounding bulk of ferrite, 2) the current path phase has larger grain size than those of the surrounding materials, 3) the current path has many crevices along it, 4) when the current flows, all the parts of crevices is bright as if it discharges.
The voltage-current characteristics were examined in details on the samples with a small amount of additives of various metal oxides.

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