材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
16 巻 , 160 号
選択された号の論文の10件中1~10を表示しています
  • 丹羽 義次, 小林 昭一
    1967 年 16 巻 160 号 p. 1-7
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 田中 道七, 山本 亮介
    1967 年 16 巻 160 号 p. 8-14
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    0.19%C炭素鋼板より, 板厚5.5mmの平滑平板試験片, 中央に円孔をもつ板状試験片, および両側にU溝をもつ板状試験片を作り, 定たわみの塑性疲労試験を実施し, 試験中の応力の変化と同時に試験片に発生したき裂の伝ぱの模様について観察した.
    切欠き試験片においては, 切欠き底に発生した各1本の疲労き裂が成長して最終的な切断に至る. しかし, 平滑試験片では多数の微細なき裂がほとんど同時に発生し別個に成長する. その中で両側端に発生した中の各1本のき裂が特に大きく成長して最終破断に至る. 各形状の試験片を通じてき裂長さが試験片有効幅の約25%に達するまでは, 試験片全体としての荷重負荷能力はほとんど低下しない. また, き裂長さXと公称ひずみ振幅εaおよび繰返し数Nの間にはX=K2εaμNλなる関係が見いだされ, ここでK2, μ, λは同一材料, 同一荷重条件では試験片形状による定数である. 一般にき裂伝ぱの初期においては切欠きの鋭い試験片ほどき裂成長速度は大きいが, その後の速度の増加する割合は切欠きの鋭いほど小さくなる傾向にある.
  • 西島 敏
    1967 年 16 巻 160 号 p. 15-20
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    A series of fatigue tests have been made to determine experimentally the size and notch effects of hollow specimens on the fatigue strength in reversed torsion. The hollow specimens were carefully machined out from one stock, composed of hot drawn low carbon steel pipe with 0.14%C, nearly satisfying the condition of geometrical similarity, that is, with their external and internal diameters of 41 and 31mm respectively for the large testpieces, and 8 and 6mm for the small. For the sake of comparison some solid cylindrical specimens were also prepared each with diameter of 8mm. Holes of several sizes were drilled reaching transversally to the central axis of the specimens. The material has been experimentally examined regarding the homogeneity of its quality with its static mechanical properties. Its agreement with the specimens annealed in vacuum has been established. In this experiments, size effect has been hardly observed in the testpieces of geometrically similarisize, and the notch effect of the drill holes has been determined as 1.6 and 2.7, for the diametral ratio of the drill holes and the specimens of 0.06 and 0.25, respectively.
  • 佐藤 四郎
    1967 年 16 巻 160 号 p. 21-25
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    The torsional fatigue test were carried out with specially prepared mild steels containing silicate inclusions.
    In order to investigate the initiation and propagation of fatigue cracks, the testing machine was stopped at intervals after additional cycling, and microphotographs were taken in the same area on the surface of the specimen.
    The results obtained are as follows:
    (1) The average ratio of torsional fatigue limits to rotating fatigue limits obtained at previous report is about 0.7.
    (2) The first cracks are formed within the first 5per cent of the lifetime. As is known, the fatigue cracks initiate at an earlier stage of the life to fracture.
    (3) The initial cracks are very often started from the surface at which no defects such as inclusions or cavities produced by the crumbling of these inclusions are microscopically found.
    It is thought that most of the cracks appeared on the surface of the specimen started from inclusions which are just below the surface.
    (4) The initial cracks mostly appear in the axial direction of the specimen.
  • 青山 咸恒, 並川 宏彦
    1967 年 16 巻 160 号 p. 26-31
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    The existence of decarburized surface layer affects the fatigue resistance of spring steel under cyclic load very much.
    In our previous experiment, fatigue resistance and the plastic deformation under cyclic load of spring steel were studied with non-decarburized and decarburized specimens by means of repeated plane bending.
    The plate specimens used were cut from the leaf spring stock of Si-Mn steel, approximately 6mm thick by 60mm wide, then quenched and tempered. In the half of the specimens, the surface remained as rolled and decarburized, and in another half the decarburized layers were removed by grinding.
    The test results obtained in several stress ratio showed that the endurance limit markedly decreased and the plastic deformation in the process of repeated bending increased in different manners, due to the existence of decarburized skin.
    In the present experiment, the behaviours of surface layer of decarburized and non-decarburized specimens under static or repeated bending were studied by X-ray diffraction method.
    First, the surface stresses of the both specimens in static uniform bending were measured by X-rays, at several loaded and unloaded steps, in tension and compression side separately. Then, the relations between the nominal bending stress, the measured stress by X-rays and the total surface strain were examined.
    In non-decarburized specimens, the nominal bending stress and the measured stress by X-rays kept linear relation till the nominal stress nearly reached the tensile yield point. In the decarburized specimens, however, the relation ceased to be linear at the nominal stress much lower than the apparent tensile yield point. The nominal stress, where the relation between the nominal stress and the measured stress by X-rays ceased to be linear, was defined as“the proportional limit of surface layer”. The fatigue ratio of the decarburized specimens, expressed in termes of reversed bending fatigue limit divided by“the proportional limit of surface layer”, well agreed to that of non-decarburized ones.
    Then, the half-value breadth of X-ray diffraction line was measured on the tension side surface of the specimens that failed in the above mentioned repeated bending test. The X-ray diffraction was made at the point adjacent to the fracture and 10mm distant from the fracture in the longitudinal direction.
    In case of non-decarburized specimens, the half-value breadth ratio (half-value breadth of failed specimen divided by the initial value of the specimen) obtained at the point 10mm distant from the fracture (b2/b0) was observed to be 0.9-1.0 in every stress ratio. The half-value breadth ratio in the fracture adjacent point (b1/b0) appeared to be smaller than b2/b0 under the reversed stress, and larger than b2/b0 under pulsating stress.
    In decarburized specimens, b2/b0 was observed to remain near unity when the maximum stress did not exceed 70kg/mm2, but became larger according as the maximum stress increased. And b1/b0 appeared to be larger than b2/b0 in any stress ratio.
  • 平 修二, 林 建吉, 田中 啓介
    1967 年 16 巻 160 号 p. 32-37
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fatigue process preceding the macro crack initiation in cold-rolled low-carbon steel specimens was investigated by the back reflection X-ray microbeam technique. The following results were obtained.
    (1) Formation and development of substructure were characteristic of the crystal deformation in fatigue process of cold-rolled specimens, having no relation to reduction percent of cold-rolling, similar to the case of annealed specimens. Therefore, it can be said that fatigue progress correlates with the degree of the formation and development of substructure, independent of initial degree of cold-rolling.
    (2) The mechanism of the development or formation of substructure in cold-rolled specimens, however, was different from that in annealed specimens in some respects. In the former case, the tendency that the dislocations introduced by cold-rolling moved to decrease the dislocation density within one subgrain and to make narrow the extended subgrain boundary became more evident as reduction percent increased.
    (3) Subgrain size tended to be smaller and total misorientation within one grain increased during the fatigue process, although those changes were not outstanding.
    (4) The micro lattice strain range within one grain (strain of 2nd kind), and that within one subgrain (strain of 3rd kind) showed a rapid decrease during the early stage in fatigue process. Their diminution became gradual in the next stage. The trend of the change in the micro lattice strain range corresponds to the change in half-value breadth during the fatigue, similar to the case of annealed specimens.
    (5) The dislocation density within one subgrain near the macro crack initiation was small, and equal to 2∼3×108lines/cm2, regardless of their reduction percent. The amount of increased dislocation density at subgrain boundary during the fatigue process of cold-rolled specimens was not widely different from that of annealed specimens.
    (6) The well-developed substructure is likely to play an important role in the macro crack initiation of cold-rolled specimens, as in the case of annealed ones.
    (7) During the fatigue process of cold-rolled specimens the degree of crystal deformation differred from grain to grain because of the difference in orientation factor, similar to the case of annealed ones.
  • 平 修二, 阿部 武治
    1967 年 16 巻 160 号 p. 38-45
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    In the previous paper, the authors studied on the deformation of polycrystalline copper by X-ray diffraction, and it was suggested that the difference in work-hardening rate of each grain due to its orientation played an important role in the deformation behaviour of polycrystalline copper. That is, in such metals as copper, the plastic anisotropy of crystals must be considered in the problem of plasticity of polycrystals.
    G.B. Greenough have introduced the relation between the microscopic residual stress among the grains resulting from the uniaxial tension (stress of the 2nd kind) and the residual lattice strains measured by the X-ray diffraction from several crystal planes perpendicular to stress axis. However, Greenough assumed, according to Taylor's theory, that the work-hardening of the grain depended only on the total shear strain on the slip planes, which does not seem to be adequate for such metals as copper. Furthermore, Greenough put assumptions that the total axial strain was equal in all grains under the loading condition and the crystal was elastically isotropic.
    In this paper, the basic relation between the strains measured by X-rays and the crystal plasticity was investigated in more general case, namely, in arbitrary state of mutual interference between the grains and for elastically and plastically anisotropic metals.
    The constraint ratio n was defined at the beginning as,
    Δε=n[Δε]Δσ=0
    where Δεand Δσ were microscopic strain and stress in a grain respectively, and were given as, Δε=ε-ε, Δσ=σ-σ, where ε and σ were the mean values of strains and stresses of all grains, respectively. Then, the case of n=0 corresponds to constant strain condition, while the case of n=1 to constant stress.
    Under the assumption that X-ray diffraction plane is at a right angle with tensile axis, the following two relations which give the X-ray measured strains Δεey associated with tensile loading have been found to hold (where Δεey is the mean value of Δεey for all the reflecting grains). First, in the loading condition,
    ΔεeyL=s12'·ΔF(ε)(1-nL)
    s12' shows the elastic compliance concerning the co-ordinate peculiar to the specimen, and ΔF shows the difference in work-hardening curve of a grain from its mean value of all grains, and nL shows the constraint ratio at the loading time. Next, after unloading the residual strain is given as,
    ΔεeyLU≅s12'{ΔF(ε)(1-nL)+Δs11'/(s11')2ε(1-nU)}
    where nU is the constraint ratio during the unloading process. From these results, it is considered that X-ray measurements have to be done in the loading condition as well as in the unloading one in order to get more information on the plastic property of polycrystals. It may be possible to know the value of constraint ratio n from X-ray measurements, if the value of ΔF (that is, the relation between crystal orientation and work-hardening curve) is known from the experiment on the single crystal.
    Discussion was also made on elastic anisotropy, and it was suggested that its effect was prominent in such strongly anisotropic metals as copper.
  • 福良 二郎, 藤原 晴夫
    1967 年 16 巻 160 号 p. 46-51
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    Successive calculating method is proposed for separation of Kα doublet and compared with customary methods such as Rachinger's and Fourier analysis.
    By this method it is not necessary to assume any type of function for the diffraction pattern and constancy of angular distance (Δ2θ) between corresponding points on each of the diffraction lines by Kα1 and Kα2 radiations.
    Some examples for Cr Kα (bearing steel) and Co Kα (α-brass) doublet and the tables of numerical value for calculation are given.
  • 山口 梅太郎
    1967 年 16 巻 160 号 p. 52-58
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    Specimens of 161 cylinders (30φ×60mm) and 113 circular disks (30φ×15mm) were prepared from a granite block. On these specimens, compressive and tensile strength of granite were measured by means of conventional compression and radial compression (Brazilian) test methods.
    All the data of the compressive strength were randomly devided into 32 groups, each of which was including 5 measurements. And also, all the data of the tensile strength were randomely grouped into 22 groups, each of which was including 5 measurements. On each group, the mean strength, the square-root of unbiased variance, and the 95% confidence limits of the mean strength were calculated. All the data were rearranged and were randomly devided into 16 groups for compressive strength and 11 groups for tensile strength, each of which was including 10 measurements. The calculation of the statistical values was also carried out for each.
    Increasing the number of specimens included in a group until the total number of 161 was reached for compressive strength, and the total number of 113 was reached for the tensile strength, the same process as above was repeated and the statistical values of each group were calculated.
    The values of mean strength, square-root of unbiased variance, and 95% confidence limits were plotted on graphs to the number of specimens included in a group.
    While the permissible differences to the total mean strength (1662kg/cm2 for the compressive strength and 104.4kg/cm2 for the tensile strength) were decided as the percentage deviation to the total mean strength.
    And then, the values of 95% confidence limits of the mean strength calculated above were compared with the permissible differences. Thus the number of specimens required for testing the strength of granite was decided upon the balance between the required confidence of the mean strength and the difficulty of specimen preparation.
    As conclusion of this experiment it was found that 20 specimens for compressive strength test and 10 specimens for tensile strength test were required to obtain mean compressive and tensile strength of granite which are within 15% to its true mean strength with 95% accuracy (it is assumed that the true compressive and tensile strength of granite is the mean value of the compressive strength of 161 specimens and the tensile strength 113 specimens of measured).
  • 1967 年 16 巻 160 号 p. 59-67
    発行日: 1967/01/15
    公開日: 2009/06/03
    ジャーナル フリー
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