-
Mitsuharu KAWASAKI, Setsuhisa TANABE, Katsuhisa TANAKA, Jianrong QIU, ...
1999 Volume 48 Issue 6 Pages
531-534
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Long lasting phosphorescence has been observed in CaO-Al
2O
3-SiO
2 glasses doped with Eu
2+ and Nd
3+ after irradiation with an Hg lamp. The emission is due to the 4f-5d transition of Eu
2+. The phosphorescence wavelength varies from 500 to 600nm, depending on the glass composition. The variation of phosphorescence wavelength is caused by the change of environment around Eu
2+ ions with glass composition. Analyses of thermoluminescence glow curves reveal that the depth of electron or hole trap level which contributes to the phosphorescence process ranges from 0.50 to 0.81eV. It is thought that these are suitable values for the occurrence of thermoluminescence at around room temperature which results in the long lasting phosphorescence.
View full abstract
-
Takashi WAKASUGI, Michael C. WEINBERG, Rikuo OTA
1999 Volume 48 Issue 6 Pages
535-540
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
The crystallization behavior of Na
2O-SiO
2 glasses was studied by Differential Thermal Analysis(DTA). The crystallization peak temperature (
TC) increased with an increase of SiO
2 content. For the quenched glasses, homogeneous nucleation was dominant in the low SiO
2 composition, while surface nucleation was dominant in the composition higher than 55mol%SiO
2. The heat treatment at the temperatures between 653 and 773K reduced
TC due to the nucleation during heat treatment. The decrease of
TC corresponds to the increase of the number of nuclei in the glass sample for DTA measurement. The ratio of crystallization peak temperature to liquidus temperature was used to evaluate the thermal stability of glasses. It was found that this parameter was a good linear relationship with the critical cooling rate for glass formation.
View full abstract
-
Koji HIGUCHI, Junshan LIN, Yoshinari MIYAMOTO, Ken HIROTA, Osamu YAMAG ...
1999 Volume 48 Issue 6 Pages
541-545
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Symmetrically graded materials of the Al
2O
3-BN/TiC/Ni were fabricated by SHS/HIP. High residual compressive stresses were produced in the outer layer due to the thermal expansion mismatch between the outer Al
2O
3-BN ceramic and the inner TiC/Ni cermet layer. The dispersion of BN in the Al
2O
3 layer increased the residual stress to higher levels than that induced in the Al
2O
3/TiC/Ni system. The BN has the layer structure with cleavage faces. The tribological properties of the outer Al
2O
3-BN layer were investigated at room temperature and 500°C in air. The friction coefficient of the outer layer was lower than that of monolithic Al
2O
3, especially at 500°C. The residual compressive stress was found to improve wear resistance of the surface layer.
View full abstract
-
Atsushi NAKAHIRA, Hiroshi AKAMIZU, Kazunori KIJIMA
1999 Volume 48 Issue 6 Pages
546-549
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
CrSi
2 based composites were fabricated by the pulse electric current sintering (PECS) technique and normal sintering technique. The sintering behaviors for these CrSi
2 based composites were mainly investigated. The dense CrSi
2 based composites with the addition of 5-50mol%NbSi
2 were obtained at 1100°C by PECS technique, although not by the normal sintering technique even at 1400°C. Furthermore the relative densities of CrSi
2/NbSi
2 composites prepared by the PECS decreased with the sintering temperature. Young's modulus for these CrSi
2/NbSi
2 composites was evaluated. The microstructure of these CrSi
2/NbSi
2 composites was observed mainly by scanning electron microscopy. NbSi
2 particles were homogeneously dispersed in the CrSi
2 matrix.
View full abstract
-
Masahiro KATO, Hidero UNUMA, Suguru SUZUKI, Minoru TAKAHASI
1999 Volume 48 Issue 6 Pages
550-553
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Addition of Mg into (Al, Cr)
2O
3 pigments significantly varied their colors. The Mg-added pigments consisted of (Al, Cr)
2O
3 corundum phase (C-phase) and Mg(Al, Cr)
2O
4 spinel phase (S-phase). In order to obtain data for the evaluation of the Cr contents in the C-and S-phases, (Al
1-xCr
x)
2O
3 corundum and Mg (Al
1-xCr
x)
2O
4 spinel both with x ranging from 0 to 1 were synthesized, and their lattice constants were measured by the XRD method. Lattice constants of the C-phase in the pigments prepared from (0.9
-x)mol Al
2O
3, 0.1mol Cr
2O
3 and x mol MgCO
3 were independent of the Mg content, and the Cr concentration of the C-phase in each pigment was determined to be 10mol%. On the other hand, a lattice constant of the S-phase decreased with the increase in the Mg content. Using the lattice constant data of the synthesized spinel and corundum, it was shown that the Cr content of the S-phase decreased with the increase in the Mg content. It was concluded that the color variations caused by the Mg addition into (Al, Cr)
2O
3 pigments were attributable to changes of the Cr content of the S-phase.
View full abstract
-
Effects of Milling Precursors on Its Crystallization and Reactivity
Takeshi SHIONO, Ryoji SATO, Haruhisa SHIOMI, Takushi MINAGI, Toshihiko ...
1999 Volume 48 Issue 6 Pages
554-558
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Forsterite, Mg
2SiO
4, precursor was synthesized from alkoxide solution containing MgO powder with average particle sizes of 0.1, 0.05 or 0.01μm. Effects of the particle size of MgO and milling of the precursor on the crystalline phase of precursors and calcined powders were examined. The obtained slurry was very stable. The precursor prepared with 0.01μm MgO was identified as amorphous. Calcining temperature of 1000°C was enough to make monolithic forsterite powder. With increase in particle size of MgO, however, MgO was distinctly identified in the precursor. Calcination of this precursor at 1200°C did not yield monolithic forsterite powder. MgO remained in the calcined powder. In order to eliminate the remaining MgO, the precursor was ball-milled with the planetary milling equipment. It was recognized that such milling was effective to eliminate the MgO and lower the crystallization temperature to forsterite.
View full abstract
-
Masao TAKAHASHI, Iwao WATANABE, Makoto HARADA, Yasuhiko MIZOGUCHI, Tak ...
1999 Volume 48 Issue 6 Pages
559-565
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
The conversion electron yield (CEY)-XAFS spectra have been compared with those measured by the transmission method for ceramics powders and metal alloys. It has been pointed out from the comparison of Ti
K-XAFS spectra of Ti metal foil and sheet that simple cleaning of specimen and elimination of surface oxides are necessary before the CEY-measurement to obtain the bulk information because the CEY method is surface sensitive. The amplitude of the CEY-EXAFS oscillation was somewhat smaller than that of the transmission-EXAFS oscillation for powder and foil samples, suggesting that one should take care of the evaluation of the EXAFS parameters such as the coordination numbers and the Debye-Waller factor on analyzing the local structure using the CEY-XAFS. It has been found from the analysis of both Ni
K-XANES and
K-EXAFS of NiO powder that the non-stoichiometry δ in NiO
1+δ increases in the vicinity of the surface. At such higher energy region as In and Eu
K-edge, the CEY method appears to have potential to the XAFS measurements, especially for either samples which cannot be pulverized or the situation where one cannot prepare the samples with adequate concentration. The signal-to-background ratio S
B for the CEY-XAFS is also discussed; S
B seems to be affected by at least two factors, ie, the Auger electron emission probability and the surface condition of specimen for
K-absorption edge, while S
B at L
III-absorption edge is mostly small in spite of quite large Auger electron emission probability.
View full abstract
-
Hiromu OHUCHI, Shintaro TSUKAMOTO, Yosuke YAMANOBE, Toshinori MORISHIT ...
1999 Volume 48 Issue 6 Pages
566-570
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Solid solution ceramics of the system
xPb(Sc
1/2Nb
1/2)O
3-
yPbTiO
3-
zPbZrO
3, where
x=0-0.4,
y=0.3-0.6,
z=0-0.7,
x+
y+
z=1, were prepared by the solid state reaction of powder materials. The density, dielectric and piezoelectric properties and crystal structures of sintered body were studied. The system was composed of three crystal phases at room temperature: the tetragonal, rhombohedral and orthorhombic. Sintering of the system
xPb(Sc
1/2Nb
1/2)O
3-
yPbTiO
3-
zPbZrO
3 was much easier than that of each terminal compositions, and well sintered ceramics were obtained for the composition near the morphotropic transformation.Piezoelectric ceramics with high dielectric constants and high radial coupling coefficient, kr, and low mechanical quality factor were obtained for the compositions near the morphotropic transformation. Pb(Sc
1/2Nb
1/2)
0.3Ti
0.44Zr
0.26O
3 ceramics showed the high kr of 0.67.
View full abstract
-
Kiyoko SAKAMOTO, Shunro YAMAGUCHI, Atsushi NAKAHIRA
1999 Volume 48 Issue 6 Pages
571-574
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Crystalline aluminium orthophosphate AlPO
4 has various polymorphic forms. However, it is difficult to prepare a pure single phase AlPO
4. In order to synthesize a single phase of AlPO
4, we have undertaken the dehydration of aluminium orthophosphate dihydrate AlPO
4·2H
2O (metavariscite) in organic solvent. The crystalline phases of obtained products were identified by X-ray diffraction method and measurement of MAS-NMR
31P and
27Al. A crystalline AlPO
4 (berlinite, tridymite-form, cristobalite-form, or A-form) was selectively synthesized by controlling the amount of H
3PO
4 and sort of organic solvent (1-butanol and isobutyl methyl ketone).
View full abstract
-
Shiro SAKA
1999 Volume 48 Issue 6 Pages
575-584
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
-
Hisakazu TOMINO, Yoshihito KONDO, Tetsuro TOJYO
1999 Volume 48 Issue 6 Pages
585-591
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
The porous cast-iron bonded diamond grinding wheel showed the high grinding performance for the hard-to-grind ceramics. Hence, it is considered that the grinding performance of the said diamond grinding wheel depends on the porosity, which is the major properties for porous material.
In this paper, to control the porosity of the porous cast-iron bonded diamond grinding wheel, we studied pulse electric current sintering behavior of atomized cast-iron-diamond composite powder. The results were as follows:
(1) The cast-iron powder was deformed plastically at the contact between the diamond grain.
(2) The porosity control of the atomized cast-iron-diamond composite sintered body could be performed independently of the volume fraction and the size of the diamond grain by the pulse electric current sintering method.
(3) Both the volume fraction of diamond grain and the diamond grain size affected significantly the apparent density of the green body, because the extra pores were generated at the contacts between the atomized cast-iron powders and the diamond grains.
(4) The densification of the atomized cast-iron powders in the composite sintered body was affected by the volume fraction of diamond grain, and was not influenced by the diamond grain size.
View full abstract
-
Masayoshi KITAGAWA, Dexin ZHOU, Kiyonori SHIMADA, Hideyuki UMEOKA
1999 Volume 48 Issue 6 Pages
592-597
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Much efforts have been done to understand a constitutive equation of solid polymers. But much attention has not been paid to stress-strain behavior after un-loading. The stress-strain behavior were investigated at uniaxial and biaxial stresses for some paths with strain or stress reversal using polyethylene. The followings are interesting for studying the constitutive laws obtained from the present study: at a stress relaxation (or creep) test after unloading, the stress rate (or the strain rate) changes its sign during the test depending on the test condition (anomalous behavior after unloading; ABU), and 2) under biaxial tension creep test after unloading, only the strain in the direction along which the applied stress was unloaded showed ABU.
View full abstract
-
Yoshinori YAMADA, Toshiji KUROBE, Yoshinori ANDO, Mitsuhiro HORI
1999 Volume 48 Issue 6 Pages
598-603
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Stiffness reduction of poly (methyl methacrylate) (PMMA) subjected to alternating bending deformation is measured as a function of the number of loading cycle, and effects of temperature on the stiffness reduction process are investigated in the present study. Reduced method is found to be applicable between temperature and the number of loading cycle. Apparent activation energy estimated from reduced method is 23±5kcal/mol, which is comparable to that of viscoelastic β-relaxation process for PMMA. The activation energy estimated from the temperature dependence of craze density, 9±4kcal/mol is lower than that estimated on the basis of the reduced method, and this fact suggests the stiffness reduction may be attributed to the characteristics of PMMA rather than craze formation. Effects of subjecting the specimens to cyclic bending on viscoelastic properties and tensile strength are also examined.
View full abstract
-
Hiroyuki HAYAKAWA, Mituo MIYAHARA, Akihiro KANAYA, Kazuo OKAMURA
1999 Volume 48 Issue 6 Pages
604-609
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Strain range partitioning method was applied to creep-fatigue life prediction for ligaments of high temperature boiler headers. Typical operating transient data was used to conduct thermal transient analysis and elastic-plastic-creep stress analysis with three dimensional FEM models simulating ligament parts of headers. Creep-fatigue life was predicted by strain range partitioning method based on the analytical results and creep-fatigue properties of a header material. The results obtained were as follows.
(1) Cracking was expected in ligament parts with inelastic strain produced by thermal transient during start-up and shut-down operation.
(2) The points where ligament crack was predicted to initiate coincided with ones reported in actual plants failure cases.
(3) The effects of operational condition and size of header on ligament crack initiation life were evaluated by this analysis. It was found that the ligament crack initiation life tends to be shorter in the case of the faster ramp rate and the larger header diameter.
View full abstract
-
Seiichi NISHINO, Kazuaki SHIOZAWA, Akihiro KOJIMA, Shoitsu SEO, Yuichi ...
1999 Volume 48 Issue 6 Pages
610-615
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
In this study, the influence of thermal aging and notch on low-cycle fatigue strength of forged mod. 9Cr-1Mo steel was investigated at elevated temperature. Total strain-controlled low-cycle fatigue tests using the smooth specimen and load-controlled low-cycle fatigue tests using the notched specimen were carried out at 873K in air. The triangular, tension-hold and compression-hold trapezoidal waveforms were applied to the specimens in a series of the tests. From the experimental results, there is no effect of the thermal aging on strain-controlled low-cycle fatigue life using the smooth specimen with each strain waveform. However, low-cycle fatigue life of the notched specimen decreased by thermal aging under load-controlled condition with triangular and tension-hold trapezoidal waveform.
View full abstract
-
Seong-Dae CHOI, Hiroshi MISAWA, Koichi AKITA, Shotaro KODAMA
1999 Volume 48 Issue 6 Pages
616-622
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Fatigue tests were carried out with Ti-6Al-4V alloy CT specimens after three kinds of the heat treatments, namely, 1) solution at 1223K, aging at 813K(STA), 2) annealing at 1123K(AN850) and 3) annealing at 1373K(±β-AN). X-ray fractography, which is a technique to estimate applied stress conditions when a fracture occurs and to be used for analysing a mechanism of fracture, was applied on the fatigue fractured surface. Distributions of residual stress and half-value breadth were measured on the fractured surface along the crack propagation direction as a function of a stress intensity factor. It was found that the residual stress on the fatigue fractured surface had a peak value when maximum stress intensity factor was nearly equal to 25MPa√m. The strain induced transformation was confirmed on the fatigue fractured surface from X-ray diffraction profile pattern. Depth of monotonous plastic zone size was estimated from the distribution of the residual stress beneath fractured surface. Depth of monotonous plastic zone size ω
y was expressed by following equation; ω
y=α(
Kmax/σ
y)
2, where the values of α were 0.17 for STA and 0.13 for AN850. By using X-ray fractography technique on fatigue fractured surfaces of Ti-6Al-4V alloy, a value of maximum stress intensity factor
Kmax where the residual stress reach maximum value can be predicted.
View full abstract
-
Hiroshi NAKAI, Toshiyuki KITADA, Masayuki AKIYAMA, Takeshi MITAMURA, T ...
1999 Volume 48 Issue 6 Pages
623-628
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
Investigated in this paper is a new hybrid cable-wire consisting of outer new Fiber Reinforced Plastic (FRP) and a steel wire as a core. First of all, a design method of cross section of the new hybrid cable-wire is proposed on the basis of the safety factors of 1.7, 3.0 and 1.1 against the yield limit state of the core steel wire, the ultimate limit state of the hybrid wire and the hazard state corresponding to the breaking of the outer FRP by accidents from standpoint of fail safe, respectively. Next, the mechanical properties of carbon-steel hybrid wires are dealt with, which consist of outer CFRP containing parallel carbon fibers and a core steel wire, and are dimensioned by the design method and produced by a method called the pultrusion method for trial. Results of a static tensile test, bending test, lateral pressure test and fatigue test prove the possibility of their application to structural cables and the necessity of further study for developing reliable anchorage systems of hybrid cables. A corrosion test emphasizes the importance of investigation on countermeasures against galvanic corrosion of carbon-steel hybrid wires.
View full abstract
-
Masahiko KATO, Dongkun ZHANG, Keijiro NAKASA
1999 Volume 48 Issue 6 Pages
629-635
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
n order to analyze the cracking and delamination processes of hard coating on ductile substrate under bending load, four-point bending tests were carried out for tool steel specimens with WC-Co cermet coating. The coating was divided by cracks repeatedly with increase in the bending load, and finally the delamination of coating occurred. The interval of cracks at the same nominal stress and those at the delamination ware large when the coating thickness was large. The stress distribution in the coating was analyzed by two-dimensional elastic-plastic finite element method. In addition, the stress distribution in the coating was calculated also by an elastic-plastic stress analysis, which introduced the tensile stress in the coating σ
x1(
x) as follows:
σ
x1(
x)=β{1-cosh(α
px)/cosh(α
pL/2)}
where, L is the crack interval, x is distance from the center of divided coating, and α
p and β are constants which contain thickness, material's constant of coating and substrate, and nominal bending stress. The cracking process calculated both by the finite element method and the analytical method agree relatively well with the experimental results.
View full abstract
-
Dongkun ZHANG, Masahiko KATO, Keijiro NAKASA
1999 Volume 48 Issue 6 Pages
636-642
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
In order to evaluate the delamination strength of brittle coating on ductile substrate, the four-point bending test method was proposed by expanding the tensile test method. The delamination energy was derived as a function of bending moment, curvature of specimen at delamination of coating and material's constants by theoretical analysis where the change of strain energy both in coating and substrate at delamination were considered. The method was applied to the specimen with WC-Co coating on an annealed tool steel prepared by high-velocity flame spraying. With increasing bending moment, the coating is divided repeatedly by cracks with almost the same interval. The crack interval at the delamination increases and the delamination energy of coating decreases with an increase in coating thickness. The four-point bending method is also effective to evaluate the delamination strength of brittle coating.
View full abstract
-
Hiroki NIUCHI, Chiaki SATO, Kozo IKEGAMI
1999 Volume 48 Issue 6 Pages
643-648
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS
The volume variation of thermosetting resin during curing process was investigated experimentally. Typical epoxy resin of bisphenol A-epichlorohydrin cured with diamine hardener was used for specimens. The volume of the resin was measured during curing process using buoyancy in the condition of variable temperatures. Considering the results of the experiments, new theoretical procedures to predict the volume variations of thermoset resins were proposed. The prediction by the procedure showed good agreement with experimental results under various conditions of different temperature histories.
View full abstract
-
II: Crystal Plasticity and Its Applications
H. Takahashi
1999 Volume 48 Issue 6 Pages
649-655
Published: June 15, 1999
Released on J-STAGE: June 03, 2009
JOURNAL
FREE ACCESS