材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
36 巻 , 407 号
選択された号の論文の19件中1~19を表示しています
  • 柏谷 賢治, 井上 靖雄, 佐藤 幸雄, 松山 晋作
    1987 年 36 巻 407 号 p. 786-791
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to clarify the mechanism of initiation of rolling contact fatigue cracking, so called shelling, on the running surface of rails in railway track, the characteristics of the deformed rail surface layer have been investigated by means of electron microscopes (SEM, TEM) and X-ray apparatus comparing the rolling-contacted test pieces and cold-rolled test pieces. A texture is formed as a result of the simple slip deformation of crystals in the deformed surface layer of rails used in track and the rolling contact fatigue-tested rails. This texture disappeared at the topmost surface because of the occurence of some random plastic deformation. On the contrary, the texture of the cold-rolled test pieces results from the complex slip deformation of crystals and does not disappear at the surface.
  • 田中 啓介, 松井 英治, 栗村 隆之, 秋庭 義明
    1987 年 36 巻 407 号 p. 792-798
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    The X-ray elastic constants of sintered polycrystalline alumina (with 99% purity) were measured for the diffraction planes (1. 0. 10) and (220) by using Cr-Kα radiation and for (146) and (4. 0. 10) by using Cu-Kα radiation, and the results were compared with the theoretical values obtained from the elastic constants of a single crystal on the bases of Reuss and Voigt models. The measured value of E/(1+ν) (E=Young's modulus, ν=Poisson's ratio) got smaller in the order of (146), (1. 0. 10), (220), (4. 0. 10). This order agreed with the theoretical prediction, although the value itself was smaller than the predicted value. Further comparsion of E and ν between the theory and the experiment indicates a necessity for making a suitable polycrystal model including the second phase or pores.
  • 小倉 敬二, 三好 良夫, 川口 真広
    1987 年 36 巻 407 号 p. 799-804
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    A new simplified technique was proposed on X-ray fractographic analysis of the fatigue fracture surface. The technique is based on the experimentally determined σr(Y) versus Kmax relation, where σr(Y) is the residual stress on the fracture surface after the removal of a thin layer whose thickness is Y, and Kmax is the applied stress intensity factor. It was found that σr(Y) is correlated with Kmax under a fixed stress ratio by such an equation as,
    σr(Y)/σy=Q·Kmaxq·(1-Yp)2,
    where ωp=α(Kmaxy)2, and Q, q and α are constants. The unkown value of Kmax was found to be successfully estimated from the measurable single value of σr(Y) by the above equation.
    The proposed technique was tested for the fatigue fracture surface which was made under a corrosive enviroment. The estimated value of Kmax was in good accordance with the actual applied value.
  • 三嶋 忠夫, 七山 幸夫, 広瀬 幸雄, 田中 啓介
    1987 年 36 巻 407 号 p. 805-809
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fracture toughness tests of bluntly notched specimens of sintered alumina were conducted under three point bending. The effect of notch-tip radius on the toughness value was first studied, and then the residual stress beneath the fracture surface was measured by the X-ray method. The depth of the plastic zone left on the fracture surface was determined on the basis of the residual stress distribution. The main results obtained are summarized as follows:
    (1) The stress intensity factor Kρ at the initiation of crack extension was related to the initial notch-tip radius ρ by
    Kρ=K0(1+ρ/ρ0)1/2
    where K0 and ρ0 are material constants. This was derived through the concept of the fictitious notch-tip radius proposed by Tanaka and Hirose.
    (2) The residual stress on the fracture surface measured by X-rays was tension. The tensile residual stress gradually diminished and changed into compression as the depth increased. At a certain depth the residual stress became almost zero.
    (3) The size of plastic zone ωy was determined from the residual stress distribution beneath the fracture surface. The size was related to the fracture toughness Kρ and the bending stress σB by the following equation.
    ωy=0.048(KρB)2
  • 岸本 秀弘, 上野 明, 河本 洋, 近藤 真司
    1987 年 36 巻 407 号 p. 810-816
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    In the case of strength design of ceramic parts, it is important to consider residual stress. The purpose of this study is to solve some problems related to such residual stress in ceramics.
    The residual stress on the Si3N4 surface prepared with several different treatments was measured by X-ray technique using a prototype Vanadium X-ray tube. V-radiation is suitable for getting a strong diffraction profile at a high diffraction angle and a shallow effective penetration depth for Si3N4. A new method developed by Yoshioka et al. was employed for analysis. In this method of analysis, the residual stress just on the surface and the stress gradient can be calculated. As a result, high compressive surface residual stress up to 1165MPa and the stress gradient of 154MPa/μm were observed on the heavily ground surface. In the case of the surface polished with wet cloth, the residual stress was -111--141MPa and the stress gradient was 14-27MPa/μm. When the above values are compared with the values obtained from the ordinary sin2ψ method, it is clear that the stress gradient near the surface must be taken into account in these cases. In order to evaluate the depth of the deformed layer of a surface ground with the cutting depth of 15μm, the residual stress was measured every time after the surface was removed by 2μm each by sputtering technique. When the surface was removed up to 8μm, the residual stress became undetectible and the half value breadth of diffraction profile converged to a constant value. It was concluded that the depth of the deformed layer of the ground surface was 8μm. Finally, it was made clear that the effective penetration depth of the V-radiation is shallow enough to evaluate the residual stress on the ground Si3N4 specimen.
  • 田中 啓介, 栗村 隆之, 松井 英治, 秋庭 義明
    1987 年 36 巻 407 号 p. 817-822
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    The X-ray elastic constants of sintered silicon nitride were measured for the diffraction plane (323) by using Cu-Kα radiation and for (411) by using Cr-Kα radiation. The values of E/(1+ν) (E=Young's modulus, ν=Poisson's ratio) were nearly identical for both planes, and were larger than the mechanically measured value. The residual stress on the lapped and ground surfaces was measured both with (323) and (411) diffractions. The measured values were all compression. The compressive stress for (411) plane was three to four times larger than that for (323) plane, which indicated a steep decrease of compression in the subsurface layer. The compressive residual stress in the direction perpendicular to the grinding direction was about twice the value in the grinding direction.
  • 松井 久明, 吉岡 靖夫, 師岡 利政, 長谷川 賢一, 中島 哲夫
    1987 年 36 巻 407 号 p. 823-829
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Recently, a synchrotron radiation source (SR) has become available as an excellent X-ray source. X-rays from SR (XSR) have following features: (1) high intensity, (2) optional wavelength with narrow width is obtained when monochromater is used, and (3) small divergency. These provide the accurate stress measurements on many (hkl) planes in the higher Bragg angle region since the X-rays with optional wavelength can be selected. Such features of SR are most suitable for the stress analysis for materials having preferred orientations.
    In this study, the stress in cold rolled steel specimens having the preferred orientation was measured by X-rays from the synchrotron radiation source. The results obtained are summarized as follows:
    (1) The diffractions from (211), (220) and (321) planes were obtained separately with high accuracy in a short time.
    (2) The stress in the textured steels was evaluated by an analytical method utilizing more than one diffraction plane belonging to one zone axis. This was found to be a suitable method for the stress analysis by use of XSR because the stresses in various lattice planes can be obtained with the same accuracy.
    (3) The X-ray elastic constant measured experimentally agreed well with the analytical value calculated from single crystal compliances.
  • 小林 俊郎, 新家 光雄
    1987 年 36 巻 407 号 p. 831-839
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 市川 宏, 早瀬 登久治, 永田 陽一, 寺西 春夫, 石川 敏功
    1987 年 36 巻 407 号 p. 840-846
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    High strength continuous SiC fibers are synthesized from polycarbosilane. The fiber which consists of ultrafine grain crystallites of β-SiC has high tensile strength at high temperatures in air. But, the behavior of the fiber after exposure for long time at high temperatures, has not been investigated yet. Therefore, the changes of strength and structure of the SiC fiber after exposure were studied by measuring tensile strength, analyzing X-ray-diffraction, scanning electron microscopical observation, and chemical element analysis. The SiC fibers were exposed at 800 to 1400°C, for 0.5 to 1000hours, in air or argon gas atmosphere. The strength and structure of the fibers were measured at room temperature. The results obtained are summarized as follows: (1) The SiC fibers maintained the strength higher than 2GPa after exposure at 800°C for 1000 hours, at 1000°C for 100 hours and at 1200°C for one hour in either atmosphere. (2) The strength decreased at temperatures above 1200°C. (3) At 1400°C in argon gas, the decrease of strength results from the crystal growth and the escape of CO gas formed by the interaction of C and O contained in the fibers. (4) At 1400°C in air, the decrease of strength results from the cracks of the SiO2 skin formed around the fiber.
  • 中島 孝慈, 藤城 郁哉, 武藤 進
    1987 年 36 巻 407 号 p. 847-853
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    In the preceeding study on the effect of hydrostatic pressure on the flow stress of polycrystalline cadmium, it was indicated that the rate of increase of the flow stress Δσ/σ due to 600MPa was larger than that of the shear modulus ΔG/G due to the same pressure. In the present study, tensile tests were made under hydrostatic pressures of 10 and 600MPa on cadmium single crystals of four different orientations.
    The results obtained are summarized as follows.
    (1) The yield stress for the slip in the basal plane increased by 6.9% at 600MPa and this amount of the rate of increase was in good agreement with ΔG/G of 7.0% on the basal plane. The value of Δσ/σ for the basal slip increased monotonically with an increase of strain.
    (2) A non-basal slip system operative in cadmium crystals was {1122} ‹1123›. The vaule of Δσ/σ for this slip was 16 to 18% and it was considerably larger than ΔG/G of 4.9% on the {1122} plane. Further, a decrease in the strain hardening rate due to high pressure occured in the high strain range near to the maximum load point.
    (3) In the extention along ‹0110› and ‹1120›, Δσ/σ for the deformation twinning was smaller than those for the basal and the {1122} ‹1123› slip. Especially in the ‹0110› crystals the flow stress σ and Δσ/σ for the slip within the twin block were well consistent with those for the {1122} ‹1123› slip.
  • 成田 舒孝, 東田 賢二, 喜多 秀樹
    1987 年 36 巻 407 号 p. 854-860
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Low temperature brittleness of Fe-Si alloy crystals was investigated in connection with the twin formation. In tensile tests at 77K, most of Fe-Si alloy crystals used exhibited the brittle fracture of {100} cleavage type except for crystals oriented near a ‹111› axis where the stress factor for twinning is rather small. The values of resolved shear stress on the twinning system at brittle fracture were in good agreement with those of twinning stress which were obtained from the compression tests at 77K. After the brittle fracture, deformation twins were observed on the side and fracture surfaces of crystals. SEM observation on the brittle fracture surfaces showed that the site of crack initiation exists on the ‹011› type intersection of deformation twins. To improve the low temperature ductility of Fe-Si crystals, dislocation substructures such as the sub-boundary and mobile dislocations were introduced into the crystals by the pre-deformation of two stages at 1160K and room temperature. The pre-treated crystals deformed in tension at 77K up to the strain larger than 10%, followed by ductile fracture. Computer simulation for the initiation and growth of a crack showed that the plastic relaxation around a twin-crack system is enhanced by lowering the twin growth rate and by increasing the mobile dislocation density as well as dislocation mobility so as to inhibit the crack extension.
  • 戸伏 壽昭
    1987 年 36 巻 407 号 p. 861-865
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Uniaxial stress relaxation of celluloid softened by heating was observed experimentally The experiments consisted of the constant strain (single step) and the gradually stepup strain tests. The representation of stress relaxation was evaluated by the single integral nonlinear viscoelastic model up to the third order of strain. The main features obtained are summarized as follows:
    (1) For the constant strain test, though residual stress at a certain duration after application of strain increases in proportion to strain in the range of small strain, it decreases with an increase in strain above a certain level of strain. The prediction of stress relaxation by the model with third order of strain agrees with the observed data. The relaxation function in the equation is represented by a power function of time. An exponent of time in the function decreases with an increase in strain.
    (2) For the gradually stepup strain test, the variation of stress which occurs instantaneously under the change of strain is almost constant for the number of steps. Residual stress at the end of each step increases with the number of steps, and the hardening of the material appears. For stress relaxation on stepup strain, the recovery of the material with the number of steps appears at the same time. The prediction of stress relaxation by the model with simple modification of super-position principle does not agree with the observed data.
  • 飯田 誠, 宮野 靖, 後藤 昌生
    1987 年 36 巻 407 号 p. 866-870
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Impact properties of moldings made by Reaction Injection Molding (RIM), which are integral-skin foams and have sandwich structures consisting of high density skin and low density core layers, were investigated by Charpy impact tests. A remarkable difference in failure mode was observed depending upon the layer composition. The failure modes were classified as: (1) tensile fracture-type and (2) buckling fracture-type. The Charpy impact value of the buckling fracture-type became over two times greater than that of the tensile fracture-type. In addition, the layer composition at which the fracture mode changes from the tensile fracture to the buckling fracture was predicted by using the static flexural properties of the moldings at comparatively low temperatures and the reciprocation law of time-temperature.
    The results obtained can be used as a sound guide to determine the optimum layer composition for the structural design of moldings concerning impact properties, and should be valuable when such moldings are applied to light-weight and thermal-insulated housing.
  • 間島 保, 飛田 拓郎, 君塚 嘉康, 中澤 一
    1987 年 36 巻 407 号 p. 871-877
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    The interference effect of double symmetrical U-shaped notches of unequal notch depth and/or unequal notch radius on the strengths were investigated experimentally. The notch pitch range in which the general yield strength is reduced was able to be predicted by using the upper and lower bound theorems. The X-shape extension of plastic deformation occurred in the notch pitch range influenced by the interference effect. The notch tensile strength was also reduced by the interference effect. The magnitude of the reduction of notch strength ratio and the notch pitch range influenced by the interfarence effect were almost equal to thoes of the general yield stress ratio, or the ratio of the general yield stress at the net section of the notched bar to that of the smooth bar. The nominal mean stress at the net section at fracture was also reduced by the interference effect. The fracture along the inclined plane connecting two notches situated diagonally was caused by the X-shape extension of plastic deformation in the notch pitch range showing the strong interference effect. The fracture at the net section occurred in the notch potch range showing the weak interference effect. The difference in notch depth has much stronger influence on the interference effect than the difference in notch radius does.
  • 田村 暢重, 中村 宏, 堀川 武
    1987 年 36 巻 407 号 p. 878-883
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Previously the authors carried out fatigue tests under such conditions as (1) variable loadings, (2) superposed waveform loadings and (3) intermittent waveform loadings, and applied these test results to estimate the fatigue lives of actual machines. Although many fatigue test results have been published, the data for the notched specimens, especially in the case of rotating bending, about crack initiation and crack propagation under variable loadings are very few. Therefore, in order to contribute to the study of this problem, the authors have carried out the fatigue tests for the notched specimens under two-level multiple block loadings.
    The conclusions obtained from the test results are summarized to the following two points.
    (1) Modified Miner's law predicts the fatigue life too short, especially in the long life range.
    (2) It is, for the time being, a neccessary and inevitable expedient to predict the fatigue life by extending the S-N curve downward in a straight line and by adopting σeq* and Σni*, in which n2β is substituted for n2 in the conventional formulas of equivalent stress σeq and total repeated numbers Σni.
  • 日和 千秋, 岡田 慎一郎, 中川 隆夫
    1987 年 36 巻 407 号 p. 884-888
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    In the present report a particular attention is given to the fact that the fatigue damage of cloth GRP is caused by the lowering of fiber strength. From such a viewpoint, measurements were made on the residual strength of the GRP specimens and the strength of the constituting fiber strands in order to clarify the change in fiber strength during fatigue. It was found that the crack length obtained from Griffith strength agreed well with the predicted value calculated from the damage. Fatigue tests were made on the altered specimens whose weft strands were covered with polymer sheets. The warp strands were found to be protected from suffering damage by wefts at woven intersections. The fatigue strength increased by 2.26 times of the original value (at the 107-th cycles.), and thus it was possible to prepare the cloth GRP of high fatigue strength.
  • 武藤 睦治, 坂本 勲, 綾 健次
    1987 年 36 巻 407 号 p. 889-895
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Welded joints, especially electron beam welded joints have significant heterogeneity of mechanical properties. Fracture mechanics parameters, for example J and COD, have been applied for homogeneous materials. The applicability of these parameters to heterogeneous welded joints has not yet been made clear. In the present study, fracture toughness tests were carried out on HT80 steel EB welded joints and the process of ductile crack initiation was observed in detail. Elastic-plastic FEM analysis of the welded joints was also carried out.
    In the HAZ-type specimen, a large crack tip opening displacement was observed in the base metal region, the strength level of which was lower than that of the weld metal. The main reason for the low JIc-value of the HAZ specimen seemed to be that plastic deformation concentrates in the base metal region due to the heterogeneity of strength. The path-independency of the J-integral holds approximately for heterogeneous welded joints in the range of the yield stress ratio of the base metal and the weld metal up to 1.74. It may be possible, therefore, to evaluate the fracture toughness by using the J-integral even in the case of heterogeneous welded joints.
  • 武藤 睦治, 坂本 勲, 鴨志田 信浩
    1987 年 36 巻 407 号 p. 896-902
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fracture toughness tests of specimens with arbitrary-shaped cracks were carried out. The Kc-estimation based on the published standard cord for assessing defects was significantly conservative. The one based on the proposed method for assessing defects, where the reduced circular crack with an area equivalent to an arbitrary-shaped crack was introduced, was reasonable and in good agreement with the KIc-value.
    Ultrasonic tests of specimens with arbitrary-shaped embedded cracks were carried out. The estimating equation of the defect radius γei was given as 2γei=W×10(V-β'/α') where W is the path length, V the relative peak echo hight, β' and α' constants. The defect radius evaluated by using the estimating equation was coincident with the actual equivalent radius of reduced circular crack in the scatter range of ±50%.
  • 北川 正樹
    1987 年 36 巻 407 号 p. 903-909
    発行日: 1987/08/15
    公開日: 2009/06/03
    ジャーナル フリー
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