材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
34 巻 , 384 号
選択された号の論文の20件中1~20を表示しています
  • 島田 尚一, 井川 直哉
    1985 年 34 巻 384 号 p. 1003-1011
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 井野 幸雄, 在原 豊
    1985 年 34 巻 384 号 p. 1012-1018
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fractography is a very useful method to examine the fracture history of a failed element. But in many cases the fracture surface has been scaled in the working environment or corroded before prepairing to observe. Therefore, the fracture surface must be often cleaned before the observation.
    In this report the fracture surface which had been scaled during low cycle fatigue testing at 288°C in pure water was examined. In order to strip off the surface scales, the following five methods were employed; (1) ultrasonic vibration in 3% HCl solution, (2) ultrasonic vibration in 5% diammonium hydrogen citrate solution, (3) ultrasonic vibration in 5% NaOH solution, (4) ion sputtering method and (5) blank replica method. There was no trace of stripping off the scales by the NaOH solution, ion sputtering method and blank replica method, but the scales were stripped off by HCl solution and diammonium hydrogen citrate solution. The vibration in 3% HCl solution seemed to restore the original fracture surface.
    The corrosion fatigue fracture mostly started at the surface pitting corrosion. Therefore, it was very important to investigate the growth behavior of pitting corrosion for the study of corrosion fatigue mechanism. So, the feature, size and number of pitting corrosion on the surface of fatigue specimens at high temperature in pure water were investigated. The total number of pitting corrosion examined were about 1000. It was observed that the pitting figure was complicated at the initial stage, but it changed to circuler as it grew. The pitting size distribution at the occurance of fracture was expressible by an exponent function. It was concluded that the probability density function of pitting size distribution was strongly affected by the testing strain rate.
  • 小田 明, 宮川 英明
    1985 年 34 巻 384 号 p. 1019-1024
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Explosion hardened austenitic manganese cast steel has been tried for railroad frogs and crossings recently. In the present study, by using a long size tapered block which had the shape and dimensions similar to those of the nose-rail of crossing and was explosively hardened at the faces of its head, the residual stress, hardness distribution and microcracks in the hardened layer were examined.
    The summary of the results is as follows:
    (1) A high tensile residual stress existed in the hardened surface layer, and the stress value decreased gradually from about 2000MPa near the detonating point to about 275MPa at the end of hardened layer. At the side of the head the stress distributed comparatively uniformly. The high tensile stress at the hardened surface decreased rapidly in the inner layer near the detonating point, and the change of stress was small at the end of explosion.
    Hardness at the surface of hardened layer decreased gradually from the location near the detonating point toward the end of explosion, but on the contrary it increased gradually in the inner layer. These variations of residual stress and hardness depended on the dimension of cross section and the setting method of explosive.
    (2) The microcracks produced at the hardened surface may promote wear in the practical use, but may not cause failure of the rail.
  • 平井 恒夫, 今井田 豊
    1985 年 34 巻 384 号 p. 1025-1030
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The underwater electrical discharge forming method makes use of energy generated by an impulsive high current discharge across a pair of electrodes, which are usually bridged by an initiating wire. It is necessary to consider various phenomena for the study of this process, such as the exploding wire phenomena, generation and propagation of shock waves, interaction and reflection of the waves at the workpiece and the behaviour of workpiece deformation. The magnitude and form of the pressure waves propagated in water have a particularly significant influence on the deformation process. It is difficult to apply numerical analysis to the underwater hydrospark forming process because of many unknowns, such as the form of the pressure wave, the conversion mechanism from pressure wave to stress wave and the stress-strain characteristics at high strain rate. Numerical analysis have been carried out in the past by assuming a particular pressure wave form at the surface of the workpiece, but the problem has not been solved with consideration of the interaction between water and workpiece. In the present paper, a finite element method was applied to the electrohydraulic forming of circular tubes, with consideration of those interactions. Comparison was made with the experiments. The results obtained were qualitatively in good agreement with the experimental ones.
  • 武藤 睦治, 坂本 勲, 井上 昌弘, 岩本 利一
    1985 年 34 巻 384 号 p. 1031-1036
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fracture toughness tests of embedded crack specimens produced by using the diffusion welding method were performed to investigate the method of assessment for embedded defects near surface.
    It was found that for l/re>0.5 (where l is the ligament width and re the radius of reduced circular crack with an area equivalent to that of an elliptical crack), the K-value can be estimated by supposing that a reduced circular crack is in the center of the specimen, and for l/re≤0.5, it can be evaluated by supposing that a semicircular surface crack with an area equivalent to that of an elliptical crack exists. The present method of assessment of defects needs to detect only the area and position of defects, while the standard codes published require the precise shape and dimensions of defects. This suggests that a convenient method of assessment of embedded defects can be developed when incorporated with ultrasonic inspection which gives the area of crack easily.
  • 御牧 拓郎, 橋本 敏, 三浦 精
    1985 年 34 巻 384 号 p. 1037-1040
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The major objective of the present paper was to study the effects of grain boundary and interphase boundary on stress corrosion cracking (SCC) in duplex (α+β)-brass polycrystals and to clarify the SCC mechanism in this alloy which is widely used. For this purpose, SCC experiments were carried out on a Cu-41.0 wt%Zn alloy in ammoniacal vapor at 298±5K. Although a few cracks were observed at the (α/α)-grain boundaries, SCC of the (α+β)-brass polycrystals was found to be transgranular, and cracks were initiated from the β-grain surface. No crack initiation was observed at the (α/β)-interphase boundaries nor at the (β/β)-grain boundaries. It was found that cracks propagated along the β-phase in the vicinity of the (α/β)-interphase boundaries, but did not propagate at the interphase boundaries themselves. It is concluded that the susceptibility to SCC decreases in the following order; β-grain surface, (α/α)-grain boundary, α-grain surface, and (β/β)-grain boundary or (α/β)-interphase boundary.
  • 御牧 拓郎, 大西 正哉, 橋本 敏, 三浦 精
    1985 年 34 巻 384 号 p. 1041-1045
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to study the effect of grain boundary on stress corrosion cracking (SCC) of α-brass, SCC tests were carried out on Cu-30.6 at%Zn alloy bicrystals in ammoniacal vapor at 303±2K. The susceptibility of the grain boundary to SCC was found to be higher than that of slip step sites in the present bicrystals with an about 15° off-coincidence Σ=13b boundary surface energy although it has been regarded to be as high as that of the so-called general boundary. Tubular pits which are considered to be initiated by the mechanism proposed by Pickering and Swann were mostly observed at the grain boundary and rarely on the crystal surface. Fine cracks propagating along the trace of {110} or {111} in the grain interior were observed not to grow into the main crack responsible to fracture.
  • 御牧 拓郎, 青木 英明, 橋本 敏, 三浦 精
    1985 年 34 巻 384 号 p. 1046-1050
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of grain boudary on the stress corrosion cracking (SCC) behavior of β-brass (Cu47.3 at%Zn) bicrystals was investigated. SCC tests were carried out in ammoniacal vapor at 303±2K, under a wide range of stress levels, i.e. 41.3-97% of the yield stress measured in a component single crystal.
    In all the specimens tested, SCC was observed even under lower stress levels. The fracture mode was found to be transgranular. Cracks were found to be initiated at the bottom of fine grooves in the crystal surface but not at the grain boundary. The time to fracture for the bicrystals was more prolonged than that of a component single crystal.
  • 御牧 拓郎, 植田 信雄, 橋本 敏, 三浦 精
    1985 年 34 巻 384 号 p. 1051-1056
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of interphase interface between the α(fcc)- and β(bcc)-phases in the Cu-Zn system on stress corrosion cracking (SCC) was studied by employing the two-phase (α/β)-brass bicrystals produced by a solid-solid diffusion method. SCC tests were conducted under various stress levels in ammoniacal vapor at 303±2K.
    It was found that the β-phase was more susceptible to SCC than the α-phase and the (α/β)-interphase interface was hardly attacked. Some cracks initiated from the corrosion pits in the β-phase were observed to propagate transgranually into the α-phase across the (α/β)-interphase interface. Intergranular fracture at the (α/β)-interphase interface has never been observed in the present experiment.
  • 小寺澤 啓司, 内田 仁, 長田 良文, 山田 巌
    1985 年 34 巻 384 号 p. 1057-1063
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effects of applied stress and cold work on the hydrogen embrittlement of iron have been examined by constant load tests under cathodic charging.
    The results obtained are summerized as follows.
    (1) Hydrogen embrittlement of the annealed iron specimen was induced by applying a stress higher than the yield one. This result indicates that the mobile dislocations play an important role for hydrogen embrittlement of annealed iron.
    (2) With the prestrained iron specimen, hydrogen embrittlement occurred even at an applied stress less than the yield one. This result means that the dislocations induced by preplastic deformation play an important role for hydrogen embrittlement of prestrained iron.
    (3) The quasi-cleavage fracture which was characterized by petal-like pattern was recognized on both annealed and prestrained iron. In this case, the average diameter of facets decreased with increasing prestrain. On the other hand, the density of facets increased with increasing prestrain. It is suggested that the inclusions and the dense regions of dislocations contribute to the susceptible nucleus for hydrogen cracking.
  • 熱処理硬さの異なるS45C鋼平滑丸棒の場合
    金山 幸雄, 中山 英明, 岡部 永年, 森 忠夫, 桜井 靖也
    1985 年 34 巻 384 号 p. 1064-1069
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    A series of impact fatigue tests were conducted for structural carbon steel JIS. S45C of different hardness ranging from HV 166 to HV 534. In order to investigate the S-N characteristics over a wide range of stress cycle, two types of impact fatigue testing machines were used; one is an impact cylinder falling type with the loading rate of about 0.5 Hz, and the other is a vibro-motor type with the loading rate of about 60 Hz.
    Discussions were made on the configuration of S-N curves, the fracture pattern and the effect of the difference in impact stress pattern on the fatigue life in relation to the hardness of each specimen. The main results are summarized as follows; firstly, the fatigue strength under a triangular stress pattern applied in this study was higher than that under a rectangular stress pattern with duration of the peak stress of about 0.8msec. Secondly, the S-N curve had an obvious transitional number of the stress cycle and fracture surface patterns were found to be entirely different between in front and in rear of the transition point, that is, the ductile fatigue fracture appeared in the low cycle region and the ordinary one in the high cycle region. Besides, this transition point had a tendency to transfer from the high cycle region to the low cycle region as the hardness increased.
  • 真武 友一, 今井 康文, 大浦 秀樹
    1985 年 34 巻 384 号 p. 1070-1075
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The rotor axes in low pressure turbines and generators in service are occasionally subjected to such a loading that a few overloads happen to be overlapped to the steady state repetition of low level stresses. Unless understanding the influence of overloads, therefore, the fatigue design of turbine rotors will not be completed. Such loadings supposedly give rise to an extreme acceleration of fatigue crack growth. In this paper, by employing the same material as usual low pressure turbine rotors', heat-treated 3.5Ni-Cr-Mo-V steel, the influence of overloads on the fatigue damage in the crack initiation and growth stages was investigated in alternating two-load level fatigue tests. The base block consisted of axial reversed strain cycling Δεp=0.5% as overloads and constant stress cycling σa=421MPa (above the fatigue strength) or 372MPa (below the fatigue strength) as a baseline loading.
    Contrasting to the previous investigation on an annealed S40C steel, the material exhibited cyclic softening in the low cycle fatigue test whereas the induced plastic strain during the low cycle fatigue stage disappeared gradually in the course of the following base line loading; the application of overloads always reduced the crack initiation life. The failure life was also reduced shorter than the predicted from Manson's double linear damage rule with using the fatigue properties of virgin material. The crack growth retardation, which may be induced by the application of overloads in the crack growth stage, was not observed on this material unlike on the previous carbon steel.
  • 佐藤 建吉, 藤井 孟, 児玉 昭太郎
    1985 年 34 巻 384 号 p. 1076-1081
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The crack propagation behavior in fretting-fatigue of A2024-T3 strip-typed specimens was investigated under the repeated stress of 60MPa with three different stress ratios, namely R=0.33, 0, and -0.33, and the contact pressure of 50MPa. The crack length a, the effective stress intensity factor range ΔKeff proposed by J. Schijve, and the maximum stress intensity factor Kmax were plotted as a function of crack propagation rate da/dN. It was seen that the crack propagation behavior in fretting-fatigue was affected by the stress ratio, and was able to be divided into two stages. In ‘SI-stage’ where the crack length is up to about 0.5mm, the da/dN in fretting-fatigue was very high compared with that in unfretting-fatigue, but with crack growth the da/dN in fretting-fatigue decreased markedly in the order of decreasing R. In ‘SII-stage’ the da/dN in fretting-fatigue increased with crack growth, and was higher than that in unfretting-fatigue for R=0.33, lower for R=-0.33, and almost the same for R=0. This behavior was interpreted by the reduction of fretting effect with crack growth and by the crack surface contact due to slantwise crack characterized in fretting-fatigue and shear lips characterized in A2024-T3.
  • 八木 晃一, 久保 清, 金丸 修, 田中 千秋
    1985 年 34 巻 384 号 p. 1082-1088
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to clarify the relation between creep damage and fatigue damage concerning the rupture life of SUS 316 stainless steel under combined creep-fatigue loading, the behaviors of surface cracks and internal cavities were examined metallographically. The defects were measured quantitatively, and the relation between the defects and the test condition was discussed.
    The fracture under combined creep-fatigue loading at 550°C was caused mainly by the formation, growth and linkage of wedge-type intergranular cracks. They were associated with the hardening of matrix due to strain aging under creep loading and fatigue loading. The rupture life under combined creep-fatigue loading at 650°C was determined by the growth of surface cracks under fatigue loading in the combined creep-fatigue loading test. The fracture at 750°C was caused by the inter-granular growth of surface cracks, which were affected by the formation of internal cavities at the surface crack tip.
  • 伊原 千秋, 三澤 哲也
    1985 年 34 巻 384 号 p. 1089-1092
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    A stochastic approach to creep crack propagation is proposed in consideration of random propagation resistance. It is based on a propagation law of small creep cracks. Through adding the Gaussian white noise to propagation resistance of the propagation law, a stochastic differential equation of Itô type is derived. This stochastic differential equation plays an important role in our stochastic propagation approach. A sample path and life distribution of creep crack propagation are derived according to the approach. These theoretical results are compared with the experimental data for type 304 stainless steel.
  • 森 信儀, 遠藤 隆士, 河上 護
    1985 年 34 巻 384 号 p. 1093-1098
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Although the wear characteristics and mechanism of boronized steels have been reported, there is no report in which the X-ray method was applied to study the wear process of boronized steels. The authors have reported in the previous paper that the surface compressive residual stress and half-value breadth changed during the fatigue process.
    In the present study, the Amsler type wear tests of boronized steels was carried out. The X-ray method was successfully applied to measure the changes in surface residual stress and half-value breadth during the wear process, and the relationship between the changes of X-ray parameter and the structures was investigated.
    The results obtained are summarized as follows;
    (1) Boronized steels had higher wear resistance than non-boronized steels. Wear loss was unaffected by the surface compressive residual stress value that was dependent on the thickness and the type of boronized layer.
    (2) As the wear distance became more, the half-value breadth of X-ray parameter increased. The X-ray method was applied effectively as a nondestructive detecting method of wear damage accumulation. The half-value breath increased corresponding to the extent of work hardening at the area near the wear surface.
    (3) In these experimental conditions, plastic flow was difficult to occur in the boronized layer. It is considered that when the depth of residual boronized layer becomes less than 20-30μm, plastic flow occurs in the matrix under boronized layer.
  • 村上 惇, 松下 裕臣, 吉識 忠継, 新保 正樹
    1985 年 34 巻 384 号 p. 1099-1104
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The morphology of phase-separation and the mechanical properties of amine cured rubber-modified epoxy resins were investigated.
    The results of the dynamic mechanical properties and the microscopic observations indicated that the epoxy-rich matrix phase was plasticized by the dissolved rubber and the rubber-rich domains were dispersed homogeneously in the epoxy-rich matrix.
    The rubber-modification of epoxy resins enhanced the fracture toughness against crack initiation and caused the crack arrest. The size of the plastic-deformed region at the crack tip was correlated well with the fracture toughness against crack initiation according to Dugdal's equation.
    From the fatigue crack propagation (FCP) tests at a low frequency it has been shown that the presence of rubber domains introduces the interfacial debonding between the domain and the matrix as the result of stress response, which promotes the FCP at the low stress intensity factor range.
  • マイクロコンピュータによる指数付けとステレオ投影図出力システム
    伊藤 修, 橋本 敏, 三浦 精
    1985 年 34 巻 384 号 p. 1105-1109
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    A new automatic system to analyze the orientations of the crystallographic axes of arbitrarily oriented cubic crystals using the back-reflection X-ray Laue method has been developed. The system consists of a tablet digitizer to input the coordinates of Laue spots, an usual microcomputer to index Laue patterns and a plotter to output stereographic projection.
    The accuracy of the analysis was remarkably improved in comparison with the traditional method of indexing with Greninger chart and Wulff net; it is estimated to be less than 0.1-0.2° in consequence of optimizing the rotation of standard projection and compensating the distance between specimen and film by computation. The time required is about ten minutes.
  • 1985 年 34 巻 384 号 p. 1110-1114
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 2. 高速変形に対する材料の構成式
    中川 憲治, 岸田 敬三, 谷村 眞治
    1985 年 34 巻 384 号 p. 1115-1120
    発行日: 1985/09/15
    公開日: 2009/06/03
    ジャーナル フリー
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