Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Volume 32 , Issue 361
Showing 1-20 articles out of 20 articles from the selected issue
  • Yasuo SASAKI, Toshiya HIRATA
    1983 Volume 32 Issue 361 Pages 1069-1082
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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  • Osami KOBORI, Gosaku KAWAI, Yukio IWASHIMIZU
    1983 Volume 32 Issue 361 Pages 1083-1088
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The acousto-elastic effect in a rolled plate of copper was studied experimentally from the measurements of the velocity and the amplitude of ultrasonic waves. A specimen with its axis perpendicular to the rolling direction was prepared from the plate for uni-axial tension tests, and ultrasonic waves with the frequency of 5MHz were transmitted into it along the thickness direction. For the velocity measurement, the sing-around method (S. A. method) was used. The results show that stress causes a linear change in all three velocities of independent waves, two of which are transverse waves polarized along and perpendicular to the stress axis. The amplitude of a transverse wave was also measured to analyze the birefringence due to structural anisotropy and stress (P. H. method). This shows that the anisotropy is slight, and that the velocity difference of two polarized transverse waves varies in proportion to the stress applied. Thus it is ascertained that the acousto-elastic results obtained by the two methods are consistent quantitatively, and that the copper plate used in the present work shows a linear stress-dependency of velocity as seen in alminium and steel.
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  • Hiroo MIYAIRI, Masashi WAKABAYASHI, Minoru TANAKA
    1983 Volume 32 Issue 361 Pages 1089-1095
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Recently, the constitution of fiber reinforced plastics became very complicated and diversed with the development of new fiber reinforcements. The superior properties of these materials have promoted other applications. Especially, carbon fiber reinforced plastics have attracted much attention as a new type of advanced composites.
    In this paper, the flexural behavior and impact properties of CF/GF hybrid composites having the polyester resin matrix were examined through the measurements of dynamic mechanical properties of these hybrid composites by using the pendulum and falling weight impact test methods. The flexural energy was obtained from the results of statical and dynamic testing and was compared with each other. Fracture modes of these hybrid comosites having different constitutions were observed and were compared with those of glass reinforced plastics. Then, the flexural and impact properties of CF/GF hybrid and GRP composite metarials were discussed.
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  • Keizo KISHIDA, Kenji NAKAGAWA
    1983 Volume 32 Issue 361 Pages 1096-1101
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The main purpose of this study was to establish an experimental method determining the dynamic fracture toughness of material at high loading rate. The experimental procedure used was based on the split Hopkinson bar technique that gives a load-displacement curve for each dynamic test. The dynamic stress intensity factor was evaluated from the dynamic strain measured by a small strain gage at the vicinity of the crack. Dynamic and static tests were conducted on 2017-T4 and 7075-T651 Al alloys using specimens of the same shape under loading rates of 1.0×106MPa√m/s and 0.2MPa√m/s, respectively. It was clarified that the fracture toughness of these materials was considerably reduced with increasing loading rate. This result was consistent with the fractographical observation using SEM.
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  • Katsumi MIZUTANI, Yoshio TANAKA, Mamoru IDO, Morihiko TANISAKI
    1983 Volume 32 Issue 361 Pages 1102-1107
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Material removal in orthogonal cutting of ceramics was previously found to be characterized by a trajectory of crack which unstably extends downwards from the region near the tool tip. It was also shown that the crack extended to some distance, re-extended after a pause, and finally turned upwards to emerge out at the free surface. The unstable extension of crack was satisfactorily elucidated in terms of the stress field in the region near the tool tip, but its subsequent extension, especially that to the free surface, still remains unsolved.
    This paper confines attention to the stress field which prescribes the trajectory of a crack just after its pause and its upward extension. Photoelastic model plates of diallyl phthalate having a machined pre-crack at the region near the tool tip were orthogonally cut at a relatively low speed (0.1mm/min). The main results obtained are as follows.
    (1) The feature that a newly initiated crack extends more downwards from the tip of the precrack and turns upwards immediately after some turbulence in the region near the tool rake face is typical and quite similar to that of ceramics.
    (2) A new crack initially extends in the direction which is determined by the stress singularity detectable by isochromatic fringes near the tip of the pre-crack. The trajectory of its subsequent extension is also determined by the isoclinic fringe loops which are formed in such an elliptical vortex generated at the tip of the pre-crack so as to follow a line connecting the farthest ends of the ellipses. In the region far from the tip of the pre-crack, the crack extension is scarcely affected by the pre-crack, and therefore the direction of crack extension is perpendicular to that of the maximum tensile principal stress in the model without any pre-crack.
    (3) The upward extension is caused under the condition that the stress intensity factor KII of the crack becomes negative. This condition is realized when some fracture takes place in the region above the extended crack.
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  • Hisakichi SUNADA
    1983 Volume 32 Issue 361 Pages 1108-1113
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The materials used in this investigation were 1.43%C-1.88%Cr and 1.86%C-1.62%Cr steels. Both steels were worked either by hot forging between 1370K and 970K or by isothermal rolling at 950K. The forged structure was composed of pearlite and carbide particles, while the rolled structure showed finer carbide particles distributing in ferrite matrix. Tension tests were performed at (α+Fe3C) region in nitrogen gas by varying cross-head speeds.
    The results obtained are as follows;
    (1) The forged strucure gave less elongation and relatively higher strength at room temperature than the rolled one.
    (2) The elongation of 1.43%C-1.88%Cr steel was remarkably improved by quenching after rolling and the value was attained 220% at 4.1×10-4s-1. Not only fine grains and finer carbide particles, but also equiaxied grains without working effect were necessary for higher deformability at low strain rates.
    (3) The fracture surface of the as-worked structure at room temperature showed a quasi-cleavage pattern without elongation, while the fracture pattern of the quenched structure after rolling, which showed higher elongation, changed into dimple and flat surface like interface sliding mixed dimple with increasing test temperature.
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  • Yasuyoshi IWAI, Junichi ARIMA
    1983 Volume 32 Issue 361 Pages 1114-1118
    Published: October 15, 1983
    Released: June 03, 2009
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    In the previous paper, the results of delayed fracture tests on Cr-Mo high strength steel (SCM 435) subjected to plastic deformation by surface-treatments were presented and the influence of surface roughness and compressive residual stress due to surface-treatments were discussed.
    In this study, cantilever bending delayed fracture tests and static bending tests were performed to examine the effect of hardness on the delayed fracture strength of SCM 435 surface-treated specimens. The methods used for surface-softening were decarburization and induction heating, and those for surface-hardening were nitriding, carburizing and induction hardning. The results for these specimens were compared with those without surface-treatment.
    The main results obtained are as follows;
    (1) The delayed fracture life of the decarburized specimens was largely prolonged under high applied stress.
    (2) In the case of the induction softened specimens after the heat-treatment, the delayed fracture limit increased remarkably without reducing static strength level so much.
    (3) On the other hand, the susceptibility to hydrogen embrittlement for all the surface-hardened specimens mentioned above increased and it was affected by both hardness and its distribution in the vicinity of the surface. The effect of compressive residual stress caused by surface-treatments was not recognized.
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  • Nobuo OGATA, Koukichi YOSHIDA
    1983 Volume 32 Issue 361 Pages 1119-1124
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In order to evaluate the effect of thermal history on environmental stress cracking (ESC), three different thermal conditions were employed for preparation of the samples. These samples were fractured under methanol environment by using two loading conditions; one was dynamic and the other was static. The relation between the stress intensity factor range ΔK and the cyclic crack growth rate aN was investigated under dynamic loading conditions. Similarly, under static loading conditions, the relation between the stress intensity factor K and the crack growth rate a was investigated. The log aN vs. log ΔK curve was markedly influenced by the thermal history of the samples. The same trend was observed under static loading conditions. From these investigations, it is found that the high ESC resistance of the quenched sample can be well represented by using the fracture mechanics concepts. Furthermore, the mechanism for the high ESC resistance was discussed by using the Williams theory. It is proposed that the high ESC resistance of the quenched sample is caused by the marked relaxation of stress in the failure zone.
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  • Shunich YONEZAWA, Koji YAMAKAWA, Shiro YOSHIZAWA
    1983 Volume 32 Issue 361 Pages 1125-1131
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The relationship between hydrogen embrittlement behavior and hydrogen content was studied on SCM 435 steel by employing the technique of fracture mechanics. The hydrogen content of specimen, which was measured with a modified electrochemical technique, was varied by using different electrolytes and additives as well as by changing catholic polarization. The specimens used had different tensile strength, prior austenite grain size and thickness. An increase of hydrogen content caused a decrease of KISCC and an increase of crack growth rate at stage II, (da/dt)II. In the range of tensile strength from 150 to 180kg/mm2, log-log plots of hydrogen content against KISCC or (da/dt)II showed a linear relation. It was concluded that both KISCC and (da/dt)II were determined only by the hydrogen content and were independent of the composition of electrolyte or catholic polarization.
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  • Takeshi NAITO, Keisuke HANAI, Hideo UEDA, Masao KIKUCHI
    1983 Volume 32 Issue 361 Pages 1132-1136
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Torsional fatigue tests were conducted on induction hardened steel samples with various case depths to evaluate the relation between case depth and fatigue strength. Smooth specimens of 24mm in diameter were used and the optimum case depth for torsional fatigue strength was 7mm.
    The site of origin of fatigue fracture was found to change from the case/core boundary to the surface at 7mm in case depth.
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  • Masahiro JONO, Masahiro HANAI, Makoto KIKUKAWA
    1983 Volume 32 Issue 361 Pages 1137-1143
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Repeated two-step tests which composed of a large number of cycles of understress with or without tensile mean stress and the intermittent overstress were carried out on smooth specimens of a 0.38% carbon steel. The effects of frequency ratio of overstress to understress in one block on the cyclic plastic strain and the fatigue damage by the stress below fatigue limit were investigated. The main results obtained are as follows;
    (1) The frequency ratio of overstress to understress affected the cyclic plastic strain, and the smaller ratio caused the larger plastic strain range-pair corresponding to the high level stress and the smaller plastic strain range-pair to the low level stress.
    (2) The effect of frequency ratio of overstress to understress was found not only in the relationship between the plastic strain range-pair and the fatigue life but also in that between the stress and the fatigue life. It was concluded that the effect of frequency ratio on fatigue life could not be explained only by considering the variation of the plastic strain range-pair due to stress interaction.
    (3) Although the fatigue damage amount per one cycle of low level stress did not change largely when the number of low level stress cycles, n2, was less than about 102 cycles, the larger n2 decreased the damage amount. And the fatigue damage during one block of low level stress cycling became saturated at a certain number of cycles of n2 and the damage could not accumulate any more beyond it.
    (4) In the multi-step loadings the saturation of fatigue damage during understressing was sometimes disturbed and the fatigue life prediction based on the results of repeated two-step tests where the saturation of damage existed might be dangerous.
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  • Yuji KIMURA, Takeshi KUNIO
    1983 Volume 32 Issue 361 Pages 1144-1149
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Since fatigue is essentially the manifestation of continuous local fracture caused by cyclic stressing, it has been pointed out that fatigue shows the statistical characteristics reflecting the stochastic feature of each fatigue process. Thus, the factors governing this fluctuation can be studied on the basis of both extreme theory and the stochastic process theory. The similar fluctuation also appears in the fatigue crack propagation process, and consequently a number of crack growth curves may be obtained.
    In this paper, the Monte-Carlo simulation was conducted by assuming the microstructural heterogeneity model as well as the stochastic process model of fatigue crack propagation, and the factors governing the statistical fluctuation in the fatigue crack propagation process were investigated.
    The results show clearly that such a factor as the difference in resisting power of structure caused by the change in size distribution of structural units like crystal grains, influences considerably the stochastic feature of the fatigue crack propagation process.
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  • Shigeo TAKEZONO, Masahiro SATOH, Katsuhiko TAKITA
    1983 Volume 32 Issue 361 Pages 1150-1156
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The fatigue crack propagation behavior of S35C steel plates having initial residual stress was studied. Fatigue crack propagation tests under a constant stress intensity factor range, ΔK, were carried out, and the effect of initial residual stress on crack propagation was examined. The initial residual stress was given to the specimens by pure bending. A FEM elastoplastic analysis of fatigue crack growth was made, and the relation between the mechanical quantity calculated from the analysis and the crack propagation rate was discussed.
    The results obtained are summarized as follows:
    (1) The influence of initial residual stress on fatigue crack propagation depends on the loading stress and the stress ratio, and it is difficult to estimate the propagation rate from only the initial stress distribution.
    (2) For the materials having initial residual stress the fatigue crack propagation rate is not related to the stress intensity factor range, ΔK, but closely related to a strain range at the crack tip, Δεymax.
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  • Yasufumi IMAI, Tomokazu MATAKE
    1983 Volume 32 Issue 361 Pages 1157-1161
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The shape of small surface cracks and their growth rate data are reported for the smooth axial specimens of annealed S40C steel subjected to alternating two-load level push-pull fatigue. Alternation of high and low load cycling caused different appearances on the fracture surface, from which the crack shape at each loading period can be determined. Surface cracks, after their surface length exceeding 0.2mm, were approximately semi-elliptical and kept the ratio of the depth to half the surface length to be 0.7∼0.9 during growth. The crack growth rate in the depth direction was well correlated down to 10-10m/cycle with the stress intensity range ΔK. On the other hand, by using the strain-based intensity range ΔKε, the growth rate at both the elastic and the fully-plastic regions was well represented by a single relation. From the quantitative comparison between ΔJ, proposed by Dowling, and EKε)2, it is shown that E(ΔKε)2 gives a rough approximation of ΔJ and hence ΔKε may be used as a correlation parameter for fatigue crack growth even under fully-plastic conditions.
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  • Takeshi NAITO, Hideo UEDA, Masao KIKUCHI
    1983 Volume 32 Issue 361 Pages 1162-1166
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Rotating bending fatigue tests were conducted on the gas carburized specimens with internal oxides and non-martensitic microstructure beneath the surface. The fracture surface and the axial section at the fatigue fracture origin were observed using a scanning electron microscope. The following results were obtained.
    (1) The S-N diagram of gas carburized steel with internal oxides and non-martensitic microstructure revealed two knees on its curve. The test results appeared to be divided into two groups: a group with the number of cycles to failure Nf under 105, and that with Nf over 106.
    (2) The fractographic feature of the group with Nf<105 was intergranular fracture from the surface to the depth of 25μ, followed by transgranular fracture reflecting martensitic microstructure.
    (3) For the group with Nf>106, fracture surface inclined about 45° to the specimen axis was observed. This surface was smoothened by rubbing each other with another surface during the fatigue test. The depth of the inclined smooth fracture surface reached to the depth of 100μ from the surface. It was concluded that the inclined smooth fracture surface consisted of the Stage 1 cracks and Stage 2a cracks.
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  • Kazuo KUWABARA, Akito NITTA, Takayuki KITAMURA
    1983 Volume 32 Issue 361 Pages 1167-1173
    Published: October 15, 1983
    Released: June 03, 2009
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    In order to investigate the behavior of thermal low-cycle fatigue crack initiation in a smooth bar of low-alloy steels, out-of-phase and in-phase thermal fatigue tests were carried out at a temperature range from 573K up to 823K in an air environment, and fatigue cracks generating in the interrupted and failed specimens were observed by means of optical and scanning electron microscopes. Also, by using a Cr-Mo-V forged steel, load-controlled low-cycle fatigue tests at 823K were performed inside a scanning electron microscope (SEM) with a vacuum environment of about 7mPa for the purpose of in situ observation of the surface cracking behavior.
    The results obtained were summarized as follows:
    (1) In general, the low-alloy steels showed such a character that failure life (Nf) in out-of-phase thermal fatigue was shorter than that in in-phase at low strain ranges. This was found from the results of the interrupted tests to be due to earlier crack initiation in out-of-phase thermal fatigue.
    (2) The fracture mode in both out-of-phase and in-phase thermal fatigue was of transgranular type, but the characteristic of crack initiation was different. Surface cracks generated much more easily in out-of-phase, while cracking in in-phase was apt to occur from internal inclusions, such as MnS.
    (3) The fatigue test results inside the SEM indicated that surface oxide scale cracked so easily (below 0.01Nf) under cyclic loading. Furthermore, many surface oxide scale cracks were observed in the out-of-phase thermal fatigue failed specimens, and the fatigue cracks in the underlying metal were also found to correspond to the oxide cracks. On the other hand, such oxide crack was hardly observed in the in-phase thermal fatigue failed specimens. These findings led to the environmental effect that the surface oxide cracks accelerated the early nucleation of fatigue cracks.
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  • Hiroshi IIZUKA, Haruhiko FUJITA, Manabu TANAKA
    1983 Volume 32 Issue 361 Pages 1174-1180
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Cyclic creep tests under reversed stress and combined creep-fatigue tests were carried out on SUS 304 stainless steel at 700°C in air. Creep stress was hold for 10hr per one cycle in all the tests, and the fatigue loading inserted in creep-fatigue tests was the strain controlled triangular wave shape one. The creep behavior was examined in each test and a reasonable life prediction method under creep-fatigue conditions was discussed.
    When creep stress was reloaded in cyclic creep or creep-fatigue tests, a transient creep was observed in each cycle and the steady-state creep rate changed in each test as compared with the monotonic creep. These behaviors were attributed to the combined effect of the inelastic strain range for reversed stress after creep loading (Δεcp) and that for fatigue loading (Δεpp). Thus the steady-state creep rate was influenced by creep stress as well as by the inelastic strain ranges of Δεcp and Δεpp. Though the acceleration of steady-state creep rate was observed in both cyclic creep and creep-fatigue tests, there existed a certain correlation between the creep rate and the creep damage. This relation was found to be identical with that of monotonic creep data.
    The rupture life of creep-fatigue tests was predictable within the factor of 2 by the linear damage rule using the above relation. The life prediction method by strain range partitioning gave also a good rersult, when based on the Δεcp-Ncp relationship that was calculated from the relation between the steady creep rate and the rupture life mentioned above.
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  • Katsushi TOKUNAGA
    1983 Volume 32 Issue 361 Pages 1181-1186
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The corrosion product formed on iron in a selenious acid solution was studied by combining immersion tests and instrumental analyses such as ESCA, IMMA, electron microscopy and FT-IR spectroscopy. The product formed after exposure for a short period (2∼5min) was mostly FeSeO3·nH2O with a small amount of Fe3O4 or γ-FeOOH. On the other hand, after exposure for a long time (20hr), the product was iron selenite hydrate only. The corrosion product formed at room temperature (25°C) consisted of dark-green spherical small crystallites, while that formed at a relatively high temperature (60°C) consisted of dark-pinkish well-developed crystals with needle-shape. These two corrosion products had essentially the same composition. The outermost part of the product contained a small amount of impurities and adsorbed contaminants such as H, B, C, Na, Mg, Al, Si, K, Ca and Cu. These contaminants are probably not significant constituents of the corrosion product.
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  • Kenjiro KOMAI, Hideji YAGI, Kichiro ENDO
    1983 Volume 32 Issue 361 Pages 1187-1193
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Pin-on-disc type wear tests have been conducted on steel under dry friction and the influence of Cr-content on its transition behavior from severe to mild-wear are discussed. In order to achieve mild-wear, the formation of a sufficient amount of oxide as well as that of work-hardened hard surface layer to hold the oxide layer is indispensable. The addition of Cr to steel produces two opposite effects on mild-wear: one to promote hardening and the other to inhibit oxidation. The range of severe-wear is enlarged by oxidation inhibition, and thus the Cr addition is harmful to T1-transitional load. On the other hand, the range of mild-wear is enlarged by hardening promotion and thermal softening inhibition, and the Cr addition is desirable to T2-transitional load. The increase of hardness by heat treatment contributes to the maintenance of oxide films and enlarges the range of mild-wear.
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  • K. Ogura
    1983 Volume 32 Issue 361 Pages 1194-1199
    Published: October 15, 1983
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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