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Volume 21, Issue 1
Displaying 1-4 of 4 articles from this issue
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Theoretical Analysis of Compaction ProcessYukio Sano1974 Volume 21 Issue 1 Pages 1-8
Published: April 25, 1974
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThis paper deals with a high velocity compaction process of metal powder. The powder is assumed to be homogeneous continuum which can be treated as an ideal fluid, and jump conditions at a shock known as the Rankine-Hugoniot equations are employed for the basic equations.
As an example, copper powder is used here. This powder is uniformly packed in a die with a constant cross-section, and then its free surface is struck by a rigid body. An equation of state of the powder assumed by a static pressure-density relation, and the conservations of mass and momentum specify a motion of an element of the powder. Furthermore it is assumed that the elastic recovery of the powder can be neglected and that the pressure increases only at a shock front, and thereby the powder between the front and a fixed plate is always at rest and a particle velocity of the powder between the body and the front is always the same as that of the body. Then, the conservation of total momentum including the body is added to the above equations. These four equations determine the pressure p, the density q, the particle velocity of the powder v and the velocity of the front
Numerical results obtained showed that the assumptions used in this theory were satisfactory and copper powder compacted at high velocity impacts had uniform density if the friction of the powder at side plates can be neglected.View full abstractDownload PDF (512K) -
Experimental Analysis of Compaction ProcessYukio Sano, Tetsuo Hagiwara, Kiyohiro Miyagi1974 Volume 21 Issue 1 Pages 9-15
Published: April 25, 1974
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper is concerned with an experimental study on high velocity compaction process of metal powder. As well as in the preceding paper, copper powder is uniformly packed in a die and one end is struck by a rigid body. The results obtained are as follows.
1) A shock wave propagating through the powder is observed by a high speed camera. Namely, particles of the powder show the same behavior as in the case of a theory that any particle moves at the same velocity as the body after a shock front arrives at the particle, and stops when the front comes back to it again.
2) As frictional force of the powder at side plates increases with travels of the front when a length of the powder is infinitely long, deviations from theoretical results become large with time.
3) When the length is short, the theory and experiment agrees well. This may be due to the fact that one dimensional flow is almost realized when transverses of the front increase and that influences of the friction decrease.
4) The powder is uniformly compacted at this high velocity impact for the reason above mentioned.View full abstractDownload PDF (3564K) -
Akira Okamoto, Tetsuro Yoshida1974 Volume 21 Issue 1 Pages 16-20
Published: April 25, 1974
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe present study is devoted to investigate the anisotropy of the surface energy obtained by observing shapes of intragranular pores in sintered Cu 0.75Fe 2.25O 4. In the sintered samples which were annealed at the temperatures between 1050°Cand 1200°Cafter fired at 1150°Cfor 3h, the pore configuration consisting mainly of eight (111) planes and some curved surfaces was observed.
In order to confirm whether or not the observed pore configuration attained the equilibrium with the surface free energy and to determine quantitatively the configuration of a given pore, the change of pore shape and pore size at various annealing conditions were examined by using R parameter. Here, R is the pore aspect ratio and it indicates a ratio of distance from the center of pore to (111) plane and to curved surface orientated to near (001) plane.
From the experimental results it was recognized that the pore was in equilibrium with the surface free energy only at 1100°C. On the other hand, the pore shapes largely depended on their growing and shrinking at 1150°Cand 1200°Cand it seems that they are not in equilibrium even after the prolonged annealing. By applying Wulff's theorem to those measuring results, the ratio of surface free energy of (111) plane to that of the curved surface at 1100°Cwere calculated, being about 1.29.View full abstractDownload PDF (2787K) -
Yasumasa Goto, Michitake Higashimoto, Katsuaki Takahashi1974 Volume 21 Issue 1 Pages 21-25
Published: April 25, 1974
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSEquilibrium partial oxygen pressure of SrFe 18O 27 ferrite phase was determined between 1250° and 1460°C by flowing CO2-O2 mixed gas or in air. In air this phase is stable in the temperature between 1400° and 1460°C. At 1350°C the partial oxygen pressure ranges from 6×10-2 to 3×10-2 atm, and at 1300°C from 4 × 10-2 to 2 × 10-2 atm. The polycrystalline ferrites prepared by firing at different temperatures and oxygen pressures contained various amount of ferrous ions. Chemical analysis revealed that the nonstoichiometric parameter x in molar expression SrFe2+2xFe3+18-2xO28-x varied from 1.0 to 0.4. Partial molar free energy of solution of oxygen into the ferrite lattice was calculated as ΔG=6.2×10 3 +6.7T-12xT cal/mole O 2 and standard free energy change of the oxidation of ferrite phase was ΔG°=-8.3×104+46.2T cal/mole O 2. From D. C. resistivity measurement the activation energy of the conduction was calculated to be 0.05 eV. Ferromagnetic Curie temperature was 520°C and the values of coercive force were 6-17 oersteds.View full abstractDownload PDF (335K)
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