Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Volume 21 , Issue 226
Showing 1-11 articles out of 11 articles from the selected issue
  • Kazuo KOBAYASHI, Akira KITAMURA
    1972 Volume 21 Issue 226 Pages 629-635
    Published: July 15, 1972
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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  • Akiyoshi CHATANI, Susumu UCHIYAMA
    1972 Volume 21 Issue 226 Pages 636-640
    Published: July 15, 1972
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The dynamic stress concentration due to circular or semi-circular notches of mild steel strips under longitudinal impact was studied by resistance wire strain gages. The shape of the stress wave incidental to the notched portion was regarded almost as a pulse of which the duration was about 150μsec, though small fluctuations caused by the lateral inertia were observed in the measured stress.
    Under such a pulse stress wave, the maximum stress of notched portion was measured, and its ratio to the nominal mean stress determined by one dimensional theory was defined as a dynamic stress concentration factor. As a result, it has been clarified that the dynamic stress concentration factors in the case of long duration (150μsec), of the stress compared with the dimensions of notches, agree with those in the static cases. And with assumption of plane stress, the stress produced in the strip subjected to the longitudinal impact, will be obtained with high accuracy.
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  • Tsuneshichi TANAKA, Shinpei DENOH
    1972 Volume 21 Issue 226 Pages 641-645
    Published: July 15, 1972
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Temperature is one of the most important factors which affect the fatigue strength, and many researches have hitherto been conducted on the fatigue strength at various temperatures, but little is known about the fatigue strength under fluctuating stress amplitude at high temperature. In this research, notched and unnotched specimens made of aluminum alloy 7075-T6 were tested at room temperature, 200°C and 300°C. Constant stress fatigue test and Low-High and High-Low type two-stress fluctuating fatigue tests were conducted for each test condition. Discussion was made on the cumulative cycle ratio at high temperature. It has been claryfied that the cumulative cycle ratio is less than 1.0 in the High-Low test and it is greater than 1.0 in the Low-High test at room temperature and 200°C. But, at 300°C, the cumulative cycle ratio is greater than 1.0 in the High-Low test and it is less than 1.0 in the Low-High test. The test result can be explained by the variation of the metallurgical structure of the used material caused during the experiment. An additional experiment was conducted to show the appropriateness of the explanation.
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  • Yukihiro KADOGAWA, Tamotsu YAMATE
    1972 Volume 21 Issue 226 Pages 646-651
    Published: July 15, 1972
    Released: June 03, 2009
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    The viscosity of melts in the system R2O (R=Na, K, Li+Na, Na+K, K+Li, and Li+Na+K)-PbO-SiO2 was measured by the platinum ball pulling-up method at temperatures ranging from 1000° to 1400°C.
    The results obtained are summarized as follows:
    (1) In connection with the fact that the glass contains a small amount of alkali it is found that, on the molar basis. the potash glass is more viscous than the soda glass.
    (2) The effect on the material that is charged with alkali is observable in the Li-K glass containing two different kinds of alkalis i.e., Li2O and K2O.
    (3) In the Li-Na-K glass containing constant quantity of 2.5mol. %Li2O or K2O, the minimum of viscosity is observable at the molar concentration ratio (βk and βNa) of about 0.33. But, in the glass containing constant quantity of 2.5mol. %Na2O, it is observable at molar concentration ratio (βLi) of about 0.5.
    (4) The same tendency of composition and the correlation between the viscosity and the apparent activation energy of viscous flow is also observable.
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  • Koichi HANASAKI, Ichiro ITO
    1972 Volume 21 Issue 226 Pages 652-659
    Published: July 15, 1972
    Released: June 03, 2009
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    The formulas for the numerical determination of stresses in an infinite elastic medium having two circular holes of different diameters subjected to different hydrostatic pressures on their walls, have been deduced from the well-known Airy's stress function represented by the bipolar coordinate system.
    Modifying the above formulas, we can also determine the stresses in a semi-infinite elastic medium having a circular hole closed to the straight boundary, under the cases of loading on both the walls of the hole and the straight boundary, and of loading on either of them.
    In the present study, we calculated the stresses in an infinite or a semi-infinite medium under the above mentioned conditions using the formulas, and discussed the results of the stress analysis. Some examples of the results obtained are as follows:
    (1) In the case of the infinite medium having one hole subjected to hydrostatic pressure and another hole with free surface, unless the interval of their holes is extremely small, the maximum tensile stress on the wall of the hole subjected to pressure does not occur at the intersection (A) of the wall and the line through the center of their holes, but occurs at the point having the value of θ=30°∼60° (Fig. 2, ∼4).
    (2) In the case of the infinite medium having two holes subjected to equal pressure, the maximum tensile stress occurs at the inner intersection of the wall of the smameter diameter hole and the line through the center of two holes (Fig. 8, 9).
    (3) In the case of the semi-infinite medium having a hole subjected to pressure, the maximum tensile stress on the wall of the hole occurs at the point having the value of θ=80°∼90° (Fig. 11).
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  • Koichi AKIZONO, Ken ATAGI
    1972 Volume 21 Issue 226 Pages 660-664
    Published: July 15, 1972
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    It is very important that the behavior of structurals will be studied under repeated impact loads, but there have been few papers hitherto published about impact fatigue since few efficient impact fatigue testing machines have been made available.
    So, we devised a new rotating disk type impact fatigue testing machine, of which the impact velocity and the number of impacts per minute were 5.5m/sec and 600 respectively, and studied the effects of microstructure on the impact fatigue lives.
    The 0.24% carbon steels, and 0.85% carbon steels with lamellar and spheroidal pearlite structure were used, of which some were annealed while others were left as they were when obtained.
    The results obtained are as follows.
    (1) The impact fatigue lives of 0.24% carbon steels were longer than those of 0.85% carbon steels, and the slopes of S-N curves of the former were steeper than those of the latter.
    (2) The impact fatigue life of the annealed 0.24% carbon steel was longer than that of the 0.24% carbon steel that was left as it was.
    (3) The impact fatigue life of 0.85% carbon steel with lamellar pearlite structure was almost the same as that of 0.85% carbon steel with spheroidal pearlite structure.
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  • Miyaziro OMORI, Kikuziro TANABE, Koshiro KUROKI
    1972 Volume 21 Issue 226 Pages 665-670
    Published: July 15, 1972
    Released: June 03, 2009
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    It is well known that the martensite processed by ausforming increases in its power of resistance to degeneration due to tempering. In this report, the tempering behaviors of Mn-Cr-B spring steel ausforming at comparatively lower temperatures in the stable phase of austenite were investigated by hardness test, tension test and electron microscopy. Comparing these properties with those of the conventionally quenched specimens, the following results have been obtained.
    (1) The tempered hardness of the ausforming steel is higher by one to three Rockwell C units than that of the conventionally treated steel throughout the range of tempering temperatures in consequence of the increase in its power of resistance to degeneration due to tempering. Moreover, the effect of ausforming persists throughout the long holding time in tempering.
    (2) The yield strength, the ultimate tensile strength and the yield ratio of the ausforming steel are always higher than those of the conventionally quenched specimens, and the ausforming steel has a slightly higher ductility at higher strength level.
    (3) The carbides in the ausforming steel are very fine and dispersed densely in comparison with the conventionally heat-treated specimens, and these carbides grow slowly during the tempering process.
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  • Minoru NAKASHIMA, Seiki WATANABE
    1972 Volume 21 Issue 226 Pages 671-678
    Published: July 15, 1972
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The clarification of the plastic strain distributions in the notched portions of annealed aluminium bars containing the circumferential semicircular notch was made using the specimen bars which were cut into halves along the longitudinal axis and joined closely to each other before the test. The plastic strains were measured by the photograting method. And, using the experimental results, the stress distributions in the minimum cross section and the strength of the notched specimen under both the uniaxial tension and compression were analysed.
    The results obtained are as follows:
    (1) The plastic strains, radial, circumferential and axial, occur not uniformly in the minimum cross section, but are maximum at the notch root. The strain concentration factor becomes higher as the notch sharpens. The radial and circumferential strains in the minimum cross section are equal on the axis, and various at the other points. The tendency of the plastic strain distributions approximately agrees with that of the elastic strain distributions calculated by using Neuber's theory (Poisson's ratio is 0.5).
    (2) The curvature 1/ρ of the principal strain lines at the minimum cross section is approximately represented in the following equations. If aa≤1, 1/ρ=r/(aρa). If aa>1, 1/ρ=0 for 0≤r≤(a-nρa) and 1/ρ={nρa-(a-r)}/(nρa2) for (a-nρa)≤ra, where r is the distance from the axis, a the radius of the minimum cross section, ρa the radius of curvature at the notch root, and the factor n is dependent on the notch configuration.
    (3) The radial stress is different from the circumferential stress at each point, except on the axis. In the region of the mean axial strain over 2∼5%, the maxima of the hydrostatic tension and compression are on the axis in the dull notched specimens and shift in the direction of the notch root as the notch becomes sharper. In the compressive deformation and the tensile deformation with a mean axial strain below ten-odd percent, the results of the calculated notch strength approximately agree with experimental ones, in case that the change in notch configuration is taken into consideration. In the calculation value of n=1 was taken in the above equation.
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  • Shigeaki YOMODA
    1972 Volume 21 Issue 226 Pages 679-684
    Published: July 15, 1972
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Complex dynamic moduli of Al/resin/Al sandwich bars were measured by the vibrating lead method and the forced vibrating method.
    The influence of adhesive on the vibrational properties of the sandwich bars were studied in terms of temperature dependence of complex dynamic moduli.
    PVAc, PVC, PSt, PVAc/PVC, PVAc/PSt blend and cyanoacrylate adhesive were used for the material core of sandwich bars. The observed loss maximum of E" of Al/PVAc/Al, Al/PVAc-PVC/Al and Al/PVAc-PSt/Al sandwich bars at 50°C corresponded with the flow dispersion of PVAc.
    The observed loss peak of E" of Al/PVAc-PSt/Al and Al/PSt/Al sandwich bars at 114°C corresponded with the flow dispersion of PSt. The influence of flow dispersion of resin on the vibrational properties of the sandwich bars were larger than the dispersion of glass transition of resin.
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  • Matsuo MAEDA, Sadao HIBI, Hirokazu SHIMIZU, Hajime YAMANAKA
    1972 Volume 21 Issue 226 Pages 685-691
    Published: July 15, 1972
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In this paper is presented a report of the studies made of the specimens which were made up of polyethylene resin filled with randomly oriented short glass fibers, the effect of the fibers of finitely short length and embedded in the random orientation on the stress-strain curve of FRTP, and the S-s curve which was analyzed by using the law of mixture. As the result the following conclusions have been obtained.
    (1) The stress-strain curve of FRTP is separable into two parts, i. e., the part A, which gives rise to the elastic deformation of the glass, and the other the part B, in which alone the plastic deformation of the specimen takes place.
    (2) The strain ε separating the part A from the part B, can be theoretically evaluated from Eq.(10) in this paper.
    (3) The convert of the part A to the part B does not discontinuously occur at the strain ε, but continuously appears in the vicinity of ε.
    (4) The strain ε signifies onset of the fracture process with FRP with little ductility in contrast.
    (5) As compared with the glass volume fraction, the bearing load fraction of the total glass embedded in FRTP is very small. The reason for this is that there are two facts that the glass fiber is very short and that it is embedded in a state of random orientation.
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  • K. Hayashi
    1972 Volume 21 Issue 226 Pages 692-701
    Published: July 15, 1972
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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