Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Volume 19 , Issue 207
Showing 1-18 articles out of 18 articles from the selected issue
  • Osamu KAWANO
    1970 Volume 19 Issue 207 Pages 1012-1021
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Small-Angle X-Ray Scattering (SAS) has wide application in the field of macromolecules, colloidal solutions etc., while its application to physical metallurgy is restricted. But the smaller particles than 100Å in metals and alloys can be analysed better by the SAS method than by electron microscopy. It was Guinier who first introduced SAS techniques to this field. He had studied the structure of small heterogeneities, named Guinier-Preston Zones. They have the same crystallographic structure as the matrix solid solutions. But it is clear from the theory of SAS that this method can be applied to detect the heterogeneities of atoms in the non-crystalline materials, as glass materials.
    The advantage in the application of SAS is the fact that lattice strains cause only minor changes of the diffracted intensity.
    In this summarizing report, it is intended to describe what can be clarified by the SAS method. The determination methods of average particle size, particle number, solute concentrations inside and outside particles, size distribution, shape, the concentration gradient at the particle surface and spacial distribution of particles are described with the theoretical background and some examples.
    SAS has also been applied to the analysis of lattice defects, as agglomeration of vacancies and dislocations. The scattering intensities with these defects are much weaker than with clusters of solute atoms. As the undesired diffraction effects, double Bragg scattering, incoherent Compton scattering, temperature scattering and fluorescent radiation must be considerd in the quantitative analysis.
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  • Takao HANABUSA, Haruo FUJIWARA
    1970 Volume 19 Issue 207 Pages 1022-1027
    Published: December 15, 1970
    Released: June 03, 2009
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    A stainless steel clad plate, consisting of a stainless steel plate and an other-kind-of-steel plate combined together by rolling, explosion or other technique, becomes equipped with both the properties of the clothing metal and of the base metal. Since reinforcing the base metal by clothing it with stainless steel to raise its resistance against corrosion and pressure has come to be in vogue in recent years for various purposes, the problems regarding the clothing metal have begun to attract attention, particularly with respect to the residual stress on its surface and the internal distribution of stress in it.
    In the present paper is presented the result of experiment made concerning the residual stress in the stainless steel clad plate which had been subjected to hot rolling in the clothing. Two specimens have been used, the SS41 base metal clad with the SUS28 stainless steel plate (RA material), and the SB42 base metal clad with the SUS38 stainless steel plate (RF material).
    The residual stress released by cutting the steel plates to clothe the base metal of RA and RF materials into small blocks was found to be within the range of ±6kg/mm2. The X-ray measurement of stress on the surface of the clothing SUS28 stainless steel plate and of stress distribution in its depth revealed that ca. 20kg/mm2 of compressive residual stress was generated in it, and that ca. 15kg/mm2 of tensile residual stress was generated in the SS41 base metal.
    This difference is considered to be due to the difference between SUS28 and SS41 in thermal expansion coefficient, and it is considered that there was plastic deformation of SUS28 while it was subjected to cooling in air. On the other hand SUS38 and SB42 were approximately equal in coefficient value, and so no residual stress was detected in RF material.
    From the result of measurement of the residual stress distributed in the plates and of the width of the diffraction line in them, it is supposed that the combination of the steel plates by rolled clothing is effected within very thin scopes of their respective layers.
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  • Takewo CHIKU, Shigetsune AOYAMA, Hirohiko NAMIKAWA, Kouzo SATTA, Syogo ...
    1970 Volume 19 Issue 207 Pages 1028-1034
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In order to make X-ray measurement of stress using oscillation technique, its optimum conditions were studied with respect to the grain size of the specimen and the geometrical conditions of the soller slit system. Investigation was also made of the influence that the oscillating angle, the oscillating speed and the time constant would have on the diffraction profiles or the stress determined by X-rays.
    The abnormality of diffraction profile of coarse grained specimen, caused by the geometrical conditions of the soller slit system, decreased by the oscillation of the X-ray optical system. And the number of grains, which contributed to the diffraction, increased by the oscillation technique. The diffraction profile obtained with the instrument became normal, when the range of oscillating angle was twice as large as the half breadth of the diffraction profile. And the peak position of diffraction profile could also be determined with ease.
    The periodic change of intensity was observed on the diffraction profile when the oscillation technique was used. This phenomenon was remarkable with the increase of incident angle ψ0. It was due to the difference of diffracted X-ray intensity for different angle in oscillation. When smaller oscillating angle than ±15°was chosen, however, the periodic change in intensity of the diffraction profile was kept sufficiently small under the time constant 8 or 16sec. which was what is generally used.
    The analytical results showed that the value of cosecθ obtained from the oscillation technique was not exactly proportional to that of sin2ψ. But the experimental results showed that the cosecθ-sin2ψ relations obtained in the oscillating condition became approximately linear. The stress value of Fe {211} determined by conventional sin2ψ method using the data of ±10° oscillating condition, appeared to be 4∼6% smaller than that obtained from the data of fixed condition. Sin2ψ method seems to be practically useful to determine the stress, even when the oscillation technique is adopted, supposing that the oscillating angle is not so large and the stress of the specimen is not so high.
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  • Hirohiko NAMIKAWA, Akio ISOGAI, Shigetsune AOYAMA, Takewo CHIKU
    1970 Volume 19 Issue 207 Pages 1035-1041
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Hereunder report is made of the studies pursued regarding application of multiple exposure technique to X-ray measurement of stress. In this technique, a film is repeatedly exposed to the diffracted X-ray in two or three positions. The distances from the specimen to the positions of exposure (R1, R2 and R3) are chosen as follows: R3-R2=R2-R1=R. If we express the distance from diffraction line obtained at R1 to that obtained at R2 by P, the diffraction angle θ is given by the following relation: θ=1/2tan-1(-P/R).
    In the present paper special emphasis is given on this technique which was employed in the X-ray measurement of stress in a coarse grained specimen, which gave spotty diffraction patterns on the film. An apparatus was devised for double exposure with interchangeable soller or double pin hole slit. The value R of the apparatus was put at 30mm. The value P was determined as the mean of several distances Pi between respective pairs of spots on the film which were diffracted from the same crystal. The standard deviation of diffraction angle θi of the spots is given by the following relation: θs=√1/iΣi1iφ, ψ)2.
    The origin of the error which can be induced in the measurement with multiple exposure technique was also discussed. The error in the measurement has been caused mainly by the divergence of X-ray, missetting of the film and inadequate measurement of Pi on the film. In the measurement of coarse grained specimen, divergence of X-ray is the main origin of the error. It is desirable therefore that the divergence angle in the use of soller slit will be as small as possible.
    The stress in the mild steel specimen with 50μ grain diameter was determined under bending load. The stress value obtained with this technique showed good agreement with that obtained by counter method using oscillation technique of X-ray optical system.
    Since there was no requirement for the use of reference material the diffraction line intensity from the specimen was free from any unfavourable affectation. The peak density of diffraction lines was subject only to the control of exposure time.
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  • Jyunichi ARIMA, Norio HOSOKAWA, Kazuo HONDA
    1970 Volume 19 Issue 207 Pages 1042-1049
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    It is well known that the constituent crystals of polycrystalline metals are anisotropic in the elastic and plastic deformation, on which various theories have higherto been proposed. Recently, some studies on the relation between the practical deformation behaviour of engineering materials and these theoretical models have been attempted. From this point of view, the authors have carried out their analytical investigations for the purpose of elucidating the deformation behaviour of the polycrystalline metals, and measured the X-ray elastic constants and changes in the integral breadth of carbon steels, copper and alluminium.
    There are practically, on the other hand, metallic materials of two phase alloys, such as carbon steels, α+β brasses, Al-Si alloys and titanium alloys. These alloys contain, however, pearlite in the case of carbon steel, the second phase that has different crystal structure, physical or mechanical properties as compared with the matrix phase. Consequently, it seems that the deformation behaviour of each crystal is closely related to the deformation mechanism of metallic materials which is too complicated to be thoroughly understood. For clarifying the strength of materials, it is necessary first to investigate how the second phase will affect the first during the deformation, and then to measure the elastic constants of each phase.
    The authors carried out a series of experiments using several kinds of two phase alloys for industrial use in order to clarify the essentials of the above-mentioned mechanism of deformation. In this paper, the results of the following experiments are reported. First the elastic constants of annealed 7-3 brass, 6-4 brass and Al-Si alloys were measured by using various kinds of X-rays, and then they were compared with the analytical results based on the elastic anisotropy of single crystals in connection with the mechanism of elastic deformation.
    Five kinds of materials were used in this experiment, that is annealed plate specimens of 7-3 brass, 6-4 brass, 90Al-10Si, 80Al-20Si and 70Al-30Si alloys. The characteristic X-rays were irradiated on the specimen surface through parallel beam slit with divergent angle of 0.25 degree, and the strains were measured by using the diffraction from (100), (110) and (111) atomic planes or equivalent ones. The specimens were stressed stepwise by the tensile testing machine, and at the several stages of applied stress, the X-ray beams were radiated to the center of the specimen surface in vertical and oblique incidence with several angles ψ. The strain was measured by the conventional sin2ψ method using counter technique. The value of the lattice strain εψ was calculated from the measurement of the diffraction angle of intensity distribution curve by using an automatic recorder. From the slope of εψ-sin2ψ diagram for several applied stresses, the εψ/σ-sin2ψ curve was drawn. by using the method of least square. From these slopes the elastic constants were calculated for each diffraction planes.
    The summaries of the present study are as follows.
    Fig. 5 shows εψ/σ calculated by the unniform local stress model (Reuss's model) and the uniform local strain model (Voigt's and Nagashima's model). According to the uniform local stress model, εψ/σ and sin2ψ are in linear relationship in full range and under no influence of volume fraction on the second phase. According to the uniform local strain model, however, deviation from the linear relationship is considerable in the small range of sin2ψ. This tendency is more conspicuous as the volume fraction of second phase is increased.
    On the α-phase of 7-3 and 6-4 brasses, in our experimental results, it means that the mechanism of elastic deformation is very close on
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  • P. D. Evenschor, W. Fröhlich, V. Hauk
    1970 Volume 19 Issue 207 Pages 1050-1051
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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  • Gerhard FANINGER
    1970 Volume 19 Issue 207 Pages 1052-1067
    Published: December 15, 1970
    Released: June 03, 2009
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  • Isao IWASAKI, Yasunori MURAKAMI
    1970 Volume 19 Issue 207 Pages 1068-1074
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Several studies have so far been reported on the distribution of elongation in individual grains of coarse grained aluminium specimen due to simple tension.
    In this study coarse grained flat aluminium specimens with grain sizes of about 2mm and 4mm were measured by the oscillating crystal method, specially using Cokα radiations for measurement of the six normal strains in random directions.
    From these measured strains and orientation of each crystal, longitudinal and lateral residual strains, principal residual strain, principal residual shear strain and the direction of principal maximum residual strains of individual grains were calculated based on the theory of elasticity.
    The experimental results obtained may be summarized as follows. The longitudinal as well as the lateral residual strains were in compression for smaller orientation function, and in tension for larger orientation function, their absolute values being proportional to the orientation function. Their principal maximum residual strains showed a similar tendency to the above longitudinal strains, while on the contrary their principal maximum residual shear strains showed an inverse trend. The angles between the direction of their principal maximum residual strain and longitudinal axis were larger for greater orientation function. These angles decreased with the increase of the applied strain. Both the defferences in their principal residual strains and their principal shear strains between the neighbouring grains were remarkable as the difference of orientation function increased.
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  • Kenkichi HAYASHI, Shun-ichi DOI
    1970 Volume 19 Issue 207 Pages 1075-1080
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The phenomenon of fatigue strength being increased by preliminary working has often been the subject of studies, and the increase of fatigue strength due to plastic deformation is thought to be a consequence of residual stress and micro structural change caused by plastic deformation, so that the fundamental relation between fatigue strength and residual stress or micro structural change is to be studied.
    In this paper, the effect of preliminary working on the fatigue strength of S45C steel is studied from the influences of residual stress and micro structural change caused by tensile and compressive deformations. As the result of the study, it is found that micro structural change is considered to be more responsible than residual stress for the increase of fatigue strength.
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  • Kenkichi HAYASHI, Yoshitaka NATSUME
    1970 Volume 19 Issue 207 Pages 1081-1085
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In the previous study the influence of induction hardened steel on its fatigue strength was investigated with respect to the hardened depth and residual stress. It is hard, however, to explain, on the bases of hardness and residual stress alone, the increase of endurance limit due to induction hardening. In the present paper it is intended to find out main factors that will contribute to improvement of fatigue strength.
    It is found that all the specimens tested have shown a linear relation existing between the endurance limit and the integral width of X-ray refraction line, regardless of the hardening methods, whether by progressive hardening or by static quenching. The specimen obtained from the integral width according to Hall's analysis has also shown a linear relation existing between its micro strain and particle size and the endurance limit. It is this micro strain and particle size evidently rather than the residual stress that have influence on the endurance limit of induction hardened steel.
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  • Masao TERASAWA, Yasuo YOSHIOKA, Katsutoshi ASAMI
    1970 Volume 19 Issue 207 Pages 1086-1092
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    As previously reported the present authors carried out experimental investigations on the fatigue fracture of tufftrided steel, with emphasis on observation of changes in residual stress due to cyclic stressing, by rotary bending using the cylindrical type specimen, and by reversed bending using the plate type specimen, and pointed out that no change was observed either in residual stress or in micro structure during the fatigue process. In the process of fatigue fracture there are three stages, the crack initiation, the crack propagation and the fracture, and the process appears only in the locally limited area of the tufftrided steel specimens.
    In order to clarify the mechanism of fatigue in tufftride treatment it is required that suitable experimental method will be devised for observation of the fatigue process within the limited area, and to meet this requirement the specimen for this experiment must be notched, so that the initiation of fatigue crack and its propagation may be easily observed. In view of the fact that the X-ray micro beam diffraction technique has many advantages for enacting observation of the changes in the microstructure within the limited area under cyclic stressing, the investigation on the tufftrided low carbon steel specimen was performed through observing the changes in the microstructure during the fatigue process, using the optical microscope by the X-ray micro beam diffraction method.
    The results obtained in this way are summarized as follows.
    (1) Under the same number of cyclic stressing to fracture crack occurs in the tufftrided specimen at its notch root in the earlier period of total fatigue life than in the non-tufftrided specimen, while crack propagation rate is lower in the tufftrided specimen than in the non-tufftrided specimen.
    (2) The area of plastic deformation in the vicinity of fatigue crack of the tufftrided steel is very small, and narrow straight slip lines in parallel are observed the area.
    (3) When the carbon steel is nitrified by tufftriding, the incomplete substructure are formed in the nitrified layer.
    (4) The increases of total misorientation, micro lattice strain and excess dislocation density and the decrease of subgrain size at the notch root are observed in the earlier period of total fatigue life. These variables are maintained, however, to stand almost at constant value even after the crack initiation.
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  • Shigeru KITAGAWA
    1970 Volume 19 Issue 207 Pages 1093-1097
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    As one of the X-ray studies of fatigued metals, the author adopted the transmission X-ray diffraction method in this study. Specimens of pure aluminum poly-crystals which were completely annealed were used, and they were fatigued by cyclic tension and compression strainings with a small fatigue test machine which was designed by the author. The test pieces were of the size of about 0.5mm in thickness, 2∼5mm in length and 6mm in width at the smallest section. For most of those fatigue tests, the strain amplitudes were considerably large, which could not be measured, then the fatigue lives were about 104 cycles. The surface of the fatigued specimen was observed at times with an optical microscope, which could be directed and adjusted in three dimensional bearings. It was noticeable that most of the fatigue cracks occurred at grain boundaries.
    In process of the fatigue test, the transmission X-ray diffractions of that specimen were exposed on a Laue camera. The X-ray source was of cobalt target, and the electron beam was 30kV and 8mA. A slit of 0.5mm in diameter was used for the X-ray beam. The asterisms of the diffraction patterns were measured statistically, and it was confirmed that the asterisms increased with increase in the number of strain cycles. It seemed that there were correlations between the asterisms and the fatigue damage, though no clear conclusion could be deduced.
    The fatigued specimens were further thinned by electrolytically polishing until about 0.1mm in thickness. In the transmission X-ray diffraction of the thinned specimen, it was clarified that the diffracted spots were isolated to fine spots which were elongated; and at the same time, the diffraction rings by the characteristic X-ray, CoKα, appeared. Since those diffractions were constructed of groups of many fine spots, it seems that the substructure or poly-crystallization developed in the grains of those specimens.
    An experiment was also performed of a specimen which was subjected first to tension of over 10% strain. It was then subjected to cyclic straining of small amplitude in tension and compression. Comparative study was made of the X-ray diffraction patterns (a) as the specimen was cyclically strained and (b) as it was statically strained. It was clarified that the diffractions of the statically strained specimen were completely broadened, and these broadened diffractions decreased as the result of cyclic straining. This phenomenon implies that microplasticstrains by the static straining in the grain differ from those by the cyclic straining.
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  • Kenkichi HAYASHI, Kuniji ICHIDA
    1970 Volume 19 Issue 207 Pages 1098-1104
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The study of fatigue behavior of metals at high temperature seems to be increasingly demanded by increasing requirement in various industries for use of metals at elevated temperature. According to the reports hitherto made about fatigue strength of metals subjected to heat, the fatigue strength falls with rise of temperature during the fatigue test, except for the effect of substitutional solution hardening called blue shortness. Such fatigue behavior is considered to be due to the rise of temperature facilitating the mobility of dislocation, though it is open to question whether the mobility of dislocation is the sole factor to determine the fatigue strength at elevated temperature or not.
    It has been reported that formation and development of sub-structures in the metals during their fatigue is closely related to fatigue fracture. In view of the fact that the rise of temperature facilitates rearrangement of dislocation and its polygonation, it is conceivable that its mobility may have relation to formation of sub-structures.
    In the present study, the influence of temperature on fatigue strength is studied from these view points by using a new fatigue testing machine for high temperature in inert gaseous environment, and by observing the micro-structure by means of an X-ray micro-beam.
    From the results of the experimental study the following conclusions have been derived.
    (1) The experiment at the room temperature shows that the fatigue life is longer in argon gaseous environment than in atmosphere when stress amplitude is comparatively high, but the environment almost ceases to make any difference when stress amplitude sufficiently falls.
    (2) The fatigue strength at high temperature both of S45C carbon steel and of 0.04%C low carbon steel, per hour in each respective fatigue cycle, falls gradually at first with rise of temperature up to ca. 200°C, and then tends to rise under the influence of blue shortness.
    (3) The rise of testing temperature has more effect on the crystalline grains on the surface of the specimens. They begin to show deformed diffraction arc of X-rays when temperature rises, but the grains, in which sub-structures are formed by the fatigue show but minor fractions of them.
    (4) With the exception of the temperature range of blue shortness, to the higher temperature the specimens are subjected, and to the higher stress amplitude, the shorter their fatigue life is, and the more sub-structures develop in them.
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  • Kenji HATANAKA, Noritoshi NAKAGAWA, Hideaki KAWABE, Tomoharu YAMADA
    1970 Volume 19 Issue 207 Pages 1105-1113
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Since transmission electron microscopy began to be applied to observations of the structure of dislocation that takes place during fatigue deformation process, many investigations on this field have been reported. Consequently it has been made clear that the dislocation structure in fatigued metals is greatly affected by the stress or strain amplitude and also by the stacking fault energy in face centered cubic metals.
    The authors have investigated the fatigue deformation process in 18-8 austenitic steel having very low stacking fault energy from the viewpoint of the morphology of microscopic slip line and the crystallographic micro-lattice strain, and have been able to clarify the features of fatigue deformation in the materials of low stacking fault energy to a certain extent. Hitherto only a few studies on dislocation structure in austenitic stainless steel have been reported by means of transmission electron microscopy. Therefore for the purpose of clarifying the behavior of dislocation in fatigue stressed 18-8 austenitic steel, electron microscopic observation was made of the specimens cycled variously at both low and high stress levels, and at the same time their dislocation structure in the course of their tension was also observed, and on the results of these observations the characteristic features of fatigue deformation in the materials of low stacking fault energy were examined.
    Some differences in dislocation structure during the fatigue process between at low and high stress levels were observed. In the former, dislocation bundles are formed at the very early period, and then those structures gradually develop into band structures composed of dislocation dipoles and elongated dislocation loops, and finally cell structures are built up, while in the latter the highly developed band structures and cell structures are observed, especially near at the grain boundary, in the earlier stage of fatigue process, and with the more stress cycles, these configurations gradually change into clear cell structures consisting mainly of dislocation loops. The cell structure at the time of micro-crack initiation is more distinct than that at low stress level. However, the cell structure in 18-8 austenitic steel is imperfect in contrast to those in iron and aluminum, namely cell walls are broad and the misorientations between cells are very small. Those differences can be explained by the ease of cross slip mechanism.
    The dislocation structure during the fatigue process is characterized by the band structures lying along {111} trace, while in the tensile deformation the uniform distribution of dislocations is a distinctive feature. As for the cell structures made in the fatigue and in the tensile deformation, the following differences are observed; in the former case the cell size is larger than in the latter, and the cell walls are mostly composed of the dislocation loops, rather than joggy tangled dislocations, and the cell structure in the former is more distinct than that in the latter.
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  • Shuji TAIRA, Teruyoshi TANABE, Keisuke TANAKA
    1970 Volume 19 Issue 207 Pages 1114-1120
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Many studies on fatigue crack propagation have hitherto been presented. Most of them are directed in search of the relation between the crack propagation rate and both the crack length and the applied stress range, that is, the crack propagation law. In one of these laws, the crack propagation rate has been estimated so far with a function of the stress intensity factor K, as the simplest and the most appropriate single variable which represents the elastic stress field around the crack tip. This method of approach is very exact and accurate in such a case as the crack length is short and the applied stress in fatigue is adequately small in comparison with the yielding strength. However, there may be other cases where the choice of K is inappropriate. We need therefore another approach on the basis of the propagation mechanism. Considering that the crack propagation rate can be determined by the distribution of plastic deformation, we have tried to estimate the law with new variables.
    In this study annealed plane specimens of 0.16% C low carbon steel with a shallow single edge notch were fatigued under completely reversed in-plane bending stress. The plastic deformation near the crack tip was examined by means of an optical microscope and the back-reflection X-ray microbeam Debye technique. The obtained results are summarized as follows:
    (1) The slip bands zone size ahead of fatigue crack tips is much smaller than the plastic zone size predicted from Dugdale's model. The relation is given by the following equation.
    ξ/l=0.032{sec(π/2σ/0.77σy)-1}
    where ξ, 1, σ and σy represent respectively the slip bands zone size, the crack length, the applied stress and the tensile yielding strength. The residual stress induced by fatigue will reduce the size of the plastic zone at the crack tips in cyclic stressing.
    (2) The crack propagation rate dl/dN is uniquely related to the slip bands zone size ξ ahead of the crack tips, as
    dl/dN=1.9×10-8ξ1.5
    regardless of the stress amplitude or the crack length.
    (3) The excess dislocation density Dm at the fatigue crack tip increses, and the subgrain size t decreases as crack propagation rate dl/dN becomes larger and their relationship is expressed as,
    dl/dN=5.2×10-30Dm2.6
    dl/dN=1.7×10-5t-3.3
    (4) The crack propagation laws estimated with the stress intensity factor are slightly but inevitably dependent on the stress amplitudes. These laws are independent of them, on the other hand, provided that we choose the representative quantities of the plastic deformation, for examples, the plastic zone size, the excess dislocation density or the subgrain size ahead of the crack tip as the single variable.
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  • Yunoshin IMAI, Shin-ichiro KUMAGAI
    1970 Volume 19 Issue 207 Pages 1121-1127
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Specimens of 0.38% C steel and Fe-25% Ni alloy were put to test of their low cycle fatigue properties, tensile and hardness, both in their quenched and tempered states. The maximum bending strain on their surfaces under which the fatigue was tested was controlled at 1.0∼1.6%. The X-ray diffraction and thin film electron microscopic methods and some other techniques were employed for the purpose. The results obtained may be summarized in two phenomena. One is similar to the contrast of annealed metals versus cold-worked metals, and the other is what is considered to characterize martensite.
    The low carbon 25Ni alloy in tempered condition presents remarkable variation in microstructure, but the differentiation is almost leveled by the fatigue, the phenomenon that is similar to the contrast of annealed metals versus cold-worked metals. The differentiation in microstructure is kept up in the 0.38% carbon steel in spite not only of tempering but also of low cycle fatigue process.
    The results obtained are not yet adequate enough to explain the correlation between the microstructural variation and the damage fraction in martensitic steels. The crack nucleation and fracture line in the 0.38% carbon steel and low carbon Ni alloy are often related longitudinally to the edges of the martensite leaves.
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  • Kazuyoshi KAMACHI
    1970 Volume 19 Issue 207 Pages 1128-1131
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    We had previously reported that X-ray patterns were affected in consequence of plastic deformation of iron and low carbon steels due to induction of hydrogen into them. We later learned that it was possible to effect electrolysis of the materials to formation of new phases and even of hydrides by charging them with current for an extended period of time. It became evident also that of the matrix phases thus formed, the body-centered cubic lattices were transformed into austenite of face-centered crystalline structure with lattice constant a=3.57A°, while others were transformed into ε' hydride with closely packed hexagonal crystalline structure of c/a=1.8. In order to investigate the mode of the lattice distortion under hydrogen charge, the constituent single crystals under hydrogen charge were submitted to the Laue photography, both normal and diverged. It was made clear from the study of these films obtained that the lattice distortions were due to discontinuity occurring between the crystals and the asterisms following them.
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  • S. Kawabata
    1970 Volume 19 Issue 207 Pages 1132-1141
    Published: December 15, 1970
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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