材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
29 巻 , 317 号
選択された号の論文の16件中1~16を表示しています
  • 中 重治, 平野 真一
    1980 年 29 巻 317 号 p. 107-112
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 藤野 宗昭, 石川 文紀, 大谷 隆一
    1980 年 29 巻 317 号 p. 113-119
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Realistic constitutive equations of deformation under reversed cyclic stresses at elevated temperatures are necessary both for strain analysis of structural members and for fracture analysis of cracked materials. As the first step to obtain such equations, reversed cyclic creep tests were carried out on a carbon steel and an austenitic stainless steel under various conditions by changing stress amplitude, period (τ), the ratio of stresses in compressive and tensile periods (σminmax), and the ratio of compression hold time to tension hold time (τcomten). The following findings were obtained in the study.
    The strain rates in the tensile and compressive periods under a perfectly reversed cyclic stress (σmax=|σmin| and τtencom) are nearly equal to the primary creep rates in static creep tests at stresses equal to the maximum and the minimum stresses of the cyclic creep test, respectively. The strain rate in the tensile period under an imperfectly reversed cyclic stress (σmax>|σmin|, or τtencom) is smaller than the primary creep rate, but larger than secondary creep rate in a static creep test at a stress equal to the maximum stress. Strain hardening seems to be fully eliminated during creep deformation in the former case but partially in the latter case. Although these trends qualitatively support the auxiliary rule of strain hardening proposed by C. E. Pugh et al., the observed strain rates are frequently larger than those estimated by using the auxiliary rule.
  • 早川 雄三
    1980 年 29 巻 317 号 p. 120-124
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fracture behaviors under axial compression or bending were studied for macroscopically isotropic FRP cylindrical shells having R/t<100. The results obtained are as follows.
    (1) In both cases of axial compression and bending of the cylindrical shells, there are two types of fracture behaviors depending upon the R/t ratio of cylindrical shells; buckling and compressive fracture types.
    (2) When both compressive and flexural strength are expressed by use of the buckling coefficient, the coefficient changes considerably because the fracture behaviors vary with the ratios of R/t and L/R of a cylindrical shell.
  • 貞広 嘉和
    1980 年 29 巻 317 号 p. 125-129
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effects of dry grinding on the electron spin resonance spectra and catalytic activity of zinc oxide powder have been studied. The grinding was carried out in a vibration mill or in a ball mill, and the particle size and lattice strains of the products were determined from the X-ray diffraction pattern by applying the Stokes collected Fourier analysis. The catalytic activity was obtained by measuring the activation energy for the catalytic decomposition of hydrogen peroxide. The results obtained are as follows:
    (1) The activation energy decreased when the powder showed an increase of the sharp C peak and A peak in the ESR spectra, but it increased with increasing B peak. This suggests that the sharp C peak and the A peak originate from the donor center, while the B peak from the acceptor.
    (2) The broad C peak disappeared and a new peak appeared when tetracyanoethylene vapour was introduced. Thus, the broad C peak seems to represent the surface broken bonds.
    (3) The sharp C peak increased with decreasing the volume of ZnO crystallites. This fact shows that the sharp C peak would originate from the compressional strain
    (4) The A peak increased when ZnO crystallites were deformed, but it decreased by heating without accompanying weight change. These facts show that the A peak would originate from edge dislocations caused by shear stress.
  • 間島 保, 宮川 松男
    1980 年 29 巻 317 号 p. 130-136
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Longitudinal and transverse strain distributions at the notch root were examined up to the maximum tensile load for three types of aluminum specimens, i. e., two rectangular ones notched on either two or four sides and a circumferentially notched cylindrical one. All of them possess the biaxial state of stress at the notch root.
    For the rectangular specimen notched on two sides the maximum longitudinal strain occurred at the center of the notch root and the longitudinal strain distribution was a convex one, whereas for the retangular specimen notched on four sides the maximum longitudinal strain occurred at the end of the notch root and the distribution was a concave one. These patterns of strain distribution hold from the elastic range up to the maximum load. In the same way as in the elastic range, a high strain concentration existed up to maximum load and the state of stress in the vicinity of the notch root was biaxial tension at least near the maximum load.
    The longitudinal strain at the notch root at the maximum load, which corresponds to the beginning of unstable deformation of the notched specimen, was remarkably greater than the uniform elongation of the unnotched specimen. It is considered that this phenomenon is closely related to the notch strengthening.
  • 谷村 眞治, 井垣 久
    1980 年 29 巻 317 号 p. 137-142
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    A proposed constitutive equation of a single form combining stress, strain, strain rate and temperature effects was examined by applying it to various materials. It was found that the proposed equation is applicable to all the experimental results convering a wide range of strain rate, especially at high strain rates. The parameters of the constitutive equation were presented for fcc and bcc metals in practical forms. A new method to represent the strain rate dependence was also presented. By using the present method, the dynamic and static stress-strain curves can be described fairly well.
  • 西谷 弘信, 田中 哲志, 戸高 健
    1980 年 29 巻 317 号 p. 143-149
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to clarify the coaxing process of aged materials, rotating bending fatigue tests were carried out on the 0.15%C steel aged after quenching at low temperature under various aging conditions and optical microscopic observations were made successively during the coaxing process by using the plastic replica method.
    The main results obtained are as follows:
    (1) The knee-point in the S-N curve coincides nearly with the point where a micro-crack stops propagating.
    (2) As the aging power gets greater, the knee-point on the S-N curve moves toward the lower number of stress cycles and the length of non-propagating cracks becomes longer.
    (3) When the fatigue limit is raised by coaxing effect, the non-propagating micro-crack formed under the first stress level propagate in some degree and then stops by each stepping-up of stress level.
    (4) As the aging power gets greater, both the rate of increase in fatigue limit by coaxing effect and the increase in crack length becomes greater.
    (5) The coaxing effect of an aged material is more remarkable in the case where the non-propagating micro-crack under the first stress level is short.
  • 鎌田 敬雄
    1980 年 29 巻 317 号 p. 150-154
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    A rotating bending specimen and three types of flexural bending specimens of SC49 were tested to investigate the relationship between rotating and flexural bending strengths. Tufftrided specimens were also tested to examine the effect of surface treatment on the relationship.
    Rotating and flexural bending strengths coincide fairly well with each other, though the hourglass-shaped flexural bending specimen manifests a little bit longer life than any other rotating and flexural bending specimens. The longer life of the hourglass-shaped flexural bending specimen is brought about by the smaller plastic strain range induced.
    A slight difference between the lives of the rotating bending and the hourglass-shaped flexural bending specimens, observed even when the test data is arranged with the plastic strain range versus the number of cycles to failure, seems attributable to the shorter period of crack propagation caused by load-amplitude-controlled loading, and the higher probability of failure due to the larger volume of the surface layer exposed to maximum stress in the rotating bending specimen.
    The lower strength of the tufftrided rotating bending specimen compared with the tufftrided flexural ones, especially in the life range less than around 105 cycles, seems due to the facts that the tufftrided surface layer is easily affected by the higher temperature caused by the larger volume of heat generation and the smaller area of heat radiation in the rotating bending specimen, and that the strengthening effect of tufftride treatment is smaller in circular specimens than in rectangular ones.
  • 菊川 真, 城野 政弘, 近藤 良之, 山木 隆生, 山田 和久
    1980 年 29 巻 317 号 p. 155-161
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue crack propagation tests in a pure plane strain condition were performed by realizing a concentric circular crack propagation on the round-bar specimen with a circumferential notch under direct loading, and the crack propagation rate and crack closure behaviors were investigated by using the unloading elastic compliance method. In addition, the crack propagation behavior under a nearly plane strain condition could be examined for a wide range of K by using the compact-type specimen with side-groove of a proper configuration.
    Two-step tests of Hi-Lo loading were carried out on the both specimens and retardation behaviors of crack propagation were investigated. It was found that there existed more than two reasons for retardation. One of them is the change of crack opening level due to the change in loading level, and the retardation observed in the relatively high K region could be explained by the effective stress intensity factor. However, the retardation in the low K region was found not to be explained only by the change of crack opening level.
  • 駒井 謙治郎, 山地 謙二, 遠藤 吉郎
    1980 年 29 巻 317 号 p. 162-167
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The influence of gas atmosphere including vacuum on the fatigue crack growth rate da/dN has been investigated. da/dN decreased monotonically with decreasing partial pressure of water vapor pH2O. This was attributed to hydrogen embrittlement due to the residual water vapor. Although oxidation is inhibited in a harder vacuum, the crack rate decreased slightly. The fatigue fracture toughness was minimum in moist air and increased monotonically with decreasing pH2O. The fracture surface obtained in both moist or room air showed mostly a cleavage-like pattern and the facets of uneven crack surface were close to {100} orientation. In dry air, Ar and a vacuum of 10-3Pa, clearly defined striations were observed, whilst in a harder vacuum striation-like patterns, extrusions and flat planes appeared. In dry air, Ar and vacuum, {100} crack planes with <110> crack tip direction were observed on almost 50% of the fracture surface. These results suggest the occurance of crack extension by an alternating shear proposed by Pelloux.
  • 大南 正瑛, 今村 龍三
    1980 年 29 巻 317 号 p. 168-173
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effects of vacuum environment and grain size on the minimum creep rate and creep rupture properties of a commercial pure copper were examined experimentally in vacuum of 0.3torr and 6×10-4torr, and in air at 320°C. In air, the minimum creep rate decreased with increasing grain size in the range of smaller grain size, but in vacuum the creep rate decreased with increasing grain size. In the range of large grain size, on the other hand, the phenomenon was quite contrary. That is, the creep rate increased with increasing grain size in air, but decreased with increasing grain size in vacuum.
  • 坂巻 清司, 稲田 貞俊
    1980 年 29 巻 317 号 p. 174-180
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The relation between micro-cracks and transition temperature was examined on low carbon steels containing lamellar pearlites. Specimens were pulled to fracture at different speeds at various testing temperatures below room temperature. Fractured specimens were observed under a microscope.
    Four distinct temperature ranges were observable from the initiation mechanisms of microcracks. Below the transition temperature TC, at which the fracture stress decreased abruptly in the temperature range of nil-ductility, micro-crack were initiated in ferrite by cracking of boundary cementites and lamellar cementites. In the temperature range from TC to TB (nil-ductility transition temperature), micro-cracks were initiated at the intersection of deformation twins and at the barriers such as grain boundaries and pearlite colonies. In the temperature range from TB to TD (ductility transition temperature), different types of the initiation of micro-cracks were observed. In the vicinity of TB, micro-cracks were initiated at the ferrite boundaries and the boundaries between pearlite colonies and ferrites, but at the temperature near TD, lamellae of cementite parallel to the tensile axis were fractured and the cementite cracking grew into void to fracture. Above the temperature TD, fracture was advance by voids and the voids tended to become larger with increasing temperature.
  • 菊池 昌利
    1980 年 29 巻 317 号 p. 181-186
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    It is known as“Liquid Metal Embrittlement (LME)”that fracture stress, elongation and reduction of area can be markedly reduced when a solid metal is coated with a certain liquid metal and then immediately deformed in tension.
    In this study, LME of some steels contacting with liquid zinc was examined using a special tensile apparatus. The materials used were SS41, SB42, SM50A and STK55 steels. Tensile tests were carried out in 460°C liquid zinc, and fractographic features of LME cracking were examined.
    The results obtained are as follows:
    (1) Stress-elongation curves of tensile tests in liquid zinc at 460°C were similar to those in air at 460°C, but rupturing elongations in liquid zinc were reduced to 30-40% of those in air. At the same time elongation and reduction of area were reduced to 11-41% and 14-32%, respectively.
    (2) In liquid zinc at 460°C, elongation of SB42 and STK55 steel specimens pickled in 10% H2SO4 solution was reduced to 50% compared with that of #120 grinder finished one. Other materials also showed some changes in elongation and reduction of area depending upon their surface condition.
    (3) The yield point, tensile strength and elongation of hot dip zinc galvanized steels at room temperature became higher than those of materials not galvanized, but reduction of area was not affected.
    (4) Intergranular facet patterns were predominant on the surface cracked by liquid zinc embrittlement of steels.
  • 池尻 忠夫
    1980 年 29 巻 317 号 p. 187-191
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    In this paper, the arc resistance tests of synthetic resins were carried out in various gas insulators such as N2, CO2, SF6 and air, and the effects of species of gas and their pressure on arc resistance were investigated.
    The effects of various gases on the process of arc deterioration were also discussed. The AS TM D495 standard arc resistance testing method was used. The maximum pressure of the gas was 4ata.
    The increase of arc resistance in gas such as N2 and CO2 was noticed. In the high pressure gas, several cases appeared: the case with an abrupt decrease in arc resistance, the case with a V-or N-letter type curve against the increase in gas pressure. The increase of gas pressure did not always result in the increase of arc resistance. The arc resistance remarkably increased SF6 under 2∼4ata. except silicone glass.
    There are no inherent difference in the arc resistance in gas insulators between D.C. supply and A.C. supply.
  • 西松 裕一, 山口 勉
    1980 年 29 巻 317 号 p. 192-197
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The failure lives of rock were observed under constant uniaxial tensile stress, and the results were analyzed on the assumption that the failure process of rock is a stochastic process. When the logarithms of probability of survival were plotted against the failure lives, a curve opening upwards was obtained on P-t diagram. This upwards concave curve on P-t diagram means that the failure process is neither serial nor cumulative, but consists of parallel Poisson's processes of 1st order.
    It is suggested that this upwards concave curve is caused from the stochastic dispersion of the rate constant of failure by various factors, rather than the coexistence of a few parallel failure processes with definitely differen trate constants of failure. The experimental errors such as the deviation of loading axis, fluctuation of humidity, etc., and the dispersion of a few macroscopic pre-existing cracks are suggested as the important factors among those affecting failure.
    Based on the test results., the probability distribution of the rate constant of failure was graphically analysed, and expressed as a discrete distribution of four rate constants.
    On the assumption that the failure process under constant load is not different from that under constant rate of stress, the fluctuation of uniaxial tensile strength of rock was estimated from the probability distribution of failure lives of the same rock under constant tensile stress. The estimated coefficient of variation of uniaxial tensile strength was not much different from the one obtained by the uniaxial tension test.
  • 小林 英男
    1980 年 29 巻 317 号 p. 198-203
    発行日: 1980/02/15
    公開日: 2009/06/03
    ジャーナル フリー
feedback
Top