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Volume 30, Issue 8
Displaying 1-6 of 6 articles from this issue
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[in Japanese]1983 Volume 30 Issue 8 Pages 297-305
Published: November 25, 1983
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (4601K) -
Basic algorithm and analysis of early fractureKanji Ueda, Tadaaki Sugita1983 Volume 30 Issue 8 Pages 306-310
Published: November 25, 1983
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe subject of this study is to determine the strength reliability of ceramic cutting tools on the basis of the fracture mechanics concept. An algorithm for the application of the linear fracture mechanics theory is proposed to analyze the brittle failure of the ceramic tools. According to the algorithm, the boundary curve between safe and dangerous zones is determined in terms of critical cutting force and the critical crack length above which the early fracture of the cutting tool is caused by unstable crack propagation for given cutting conditions and the mechanical properties of the tool material. It was found that the critical cutting force increases as the fracture toughness KIC of Al2O3 ceramic tool increases and as the angle of resultant cutting force increases. The cutting edge encounteres a more dangerous situation in the state of concentrated force at the tip of the cutting edge than that of distributed force along the rake face of the tool. The safe zone of Al2O3 tool was also found to be reduced to about one third of that of WC-Co tool.View full abstractDownload PDF (355K) -
Tadatoshi Honda1983 Volume 30 Issue 8 Pages 311-315
Published: November 25, 1983
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSEffects of the lubricant content and the heating rate during dewaxing on the dimensional change, the density and the fatigue strength of sintered irons containing Zn-and Mg-stearates were investigated.
The results obtained were as follows:
(1) Irrespective of heating rates during dewaxing, all as-dewaxed specimens showed a shrinkage in the longitudinal direction except those of 1.5wt% Mg-stearate.
Density of as-dewaxed specimens was lower than that of green compacts, but density of as-sintered specimens after dewaxing was nearly same as that of green compacts.
(2) The fatigue strength of specimens decreased with increasing lubricant content and heating rate during dewaxing. The drop in strength was attributed to phenomena such as nonuniform distribution of porosity in Fe compacts and poor sintering caused by the decomposition of segregated lubricants at rapid heating rate during dewaxing.
(3) In specimens dewaxed at high heaitng rate, there were a few void and larger interparticle spaces remaining after dewaxing. In contrast, smooth facet and ductile fracture mode were observed in specimens dewaxed at low heating rate.View full abstractDownload PDF (3107K) -
Sachio Oki, Toshihiko Akiyama, Keiichiro Shoji1983 Volume 30 Issue 8 Pages 316-320
Published: November 25, 1983
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA Study has been made on the fracture behaviour of sintered carbon steels under static tensile stress. The specimens containing 0.2, 0.4, and 0.8 mass% carbon were made from atomized iron powders of different particle size (+145, -145+250, and -250 mesh).
The microscopic fracture appearance of sintered carbon steel was ductile fracture in necks between particles, and depended on the microstructure of matrices. The apparent porosity in projected fracture surface was much higher than the value predicted by the porosity of specimen.
Scanning electron microscopic examination of fracture surfaces showed an evidence of six distinct modes of fracture; i.e. (a) tear ridge, (b) dimple, (c) lamellar dimple or midrib dimple, (d) tearing off of cementite plate, (e) cleavage with inter phase separation, and (f) cleavage.
The apparent porosity in projected fracture surface reflects these fracture modes, therefore gives an information on the fracture behaviour of sintered steels.View full abstractDownload PDF (3981K) -
Naoichi Yamamoto, Shin-nosuke Higashi1983 Volume 30 Issue 8 Pages 321-326
Published: November 25, 1983
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe formation conditions of various kinds of oxides of manganese, such as Mn (OH)2, Mn3O4, γ-MnOOH, α-Mn2O3, Mn5O8, α-MnO2, β-MnO2 are studied in Mn7+-Mn2+-OH- system with hydrothermal method in a temperature range of 95°C to 270°C. Combination of neutralization, oxidation-reduction and disproportionation reactions gives a reasonable interpretation on the formation mechanism of these compounds.View full abstractDownload PDF (1593K) -
Eiichi Sentoku, Shinichi Nakabayashi, Hiroshi Kawbata, Yoshio Fujimura1983 Volume 30 Issue 8 Pages 327-330
Published: November 25, 1983
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe sintered cermet tools are to vary in pore density, hardness, specific gravity, and transverse rupture strength with the sintering condition.
This paper presents new results of continuous and intermittent turning tests of two kinds of cermet tools under cutting speeds ranged from 1.25 m/sec to 5.0 m/sec. The two tools have the same composition, but are of different pore density. In the continuous cutting, the noticeable results were not obtained as expected. In the intermittent tests, one tool with high porosity is found to wear faster than the other when cutting speed is low. At higher speeds, there was no remarkable difference in the tool life of both specimens. From these experiments, the fracture-causing cracks are thought to stop advancing at these pores.View full abstractDownload PDF (1393K)
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