材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
40 巻 , 458 号
選択された号の論文の16件中1~16を表示しています
  • 幡中 憲治, 石本 靖
    1991 年 40 巻 458 号 p. 1410-1414
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    The cyclic stress-strain response was numerically calculated for commercially pure copper using an analytical method derived from the concept of dislocation dynamics.
    The shape of the stress-strain hysteresis loop was mainly controlled by one of the constants included in the expression of internal stress. Consequently, the hysteresis loop was quantitatively described very well by choosing this constant properly.
    Both the cyclic stress-strain curves determined from the companion specimen method and the incremental strain-step method were in good agreement with the ones calculated under the respective cyclic straining conditions.
    The cyclic frequency dependency of cyclic stress-strain response was calculated through the proposed analytical method, and the effect of cyclic frequency on the fatigue life was successfully evaluated.
  • 横幕 俊典, 杵渕 雅男, 蓑方 康郎
    1991 年 40 巻 458 号 p. 1415-1421
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Ultra-low carbon steel containing phosphorus and copper (P-Cu steel) has both a higher fatigue limit and better crack propagation resistance than conventional low carbon steels with the same tensile strength. In this paper, the mechanism for improving the fatigue properties of P-Cu steel is discussed on the basis of microscopic observations by electron microscope and measurements of crack closure behaviour for small and long fatigue cracks. The excellent fatigue limit and small-crack propagation resistance in P-Cu steel can be attributed to solution hardening caused by phosphorus and precipitation hardening caused by ε-Cu. On the other hand, the superior resistance to long-fatigue crack propagation was caused by grain coasening which occurs with reduction of carbon content, leading eventually to roughness-induced crack closure.
  • 高尾 健一, 楠川 量啓
    1991 年 40 巻 458 号 p. 1422-1427
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue tests were carried out on a notched specimen of an annealed commercially pure titanium under push-pull loading, in order to clarify fatigue notch characteristics, especially the reason why the metal is extraordinarily insensitive to notch in fatigue. The initiation and initial growth of a crack at the notch root area were observed successively with optical-and scanning-electron-microscopes using a replication technique. Observations have shown that the fatal crack starts propagating as a single crack only after one-grain-size cracks initiate at several neighboring grains and then join with each other. Crack opening displacements (CODs) were also measured for similar cracks. Measurements have shown that CODs are small and unchange almost before joining, but at joining they increase abruptly and then monotonously with a number of cycles. It is suggested that pure titanium has a very thick surface layer relating to crack initiation, leading to extraordinarily low sensitivity to notch. The behavior is considered to be mainly attributed to the strong constraint for microscopic plastic deformation between adjacent crystals, because pure titanium has a hcp crystal structure and has only a few number of slip systems.
  • 城野 政弘, 菅田 淳, 濱崎 俊彰
    1991 年 40 巻 458 号 p. 1428-1434
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue crack growth tests under constant amplitude and repeated two-step loadings were performed on a 3% silicon iron in air and vacuum, using a specially designed servo-hydraulic fatigue loading system, and direct, realtime observations were made.
    Macroscopic fatigue crack growth appearances under repeated two-step loadings both in air and vacuum were found similar to those under constant amplitude loadings. And macroscopic crack deflections, which were observed under non-stationally variable amplitude loading such as high-low two-step loading, were not observed under repeated two-step loadings except those occurred at the grain boundaries of the materials. It was found that the relationship between effective stress intensity range ΔKeff and crack growth rate under repeated two-step loadings coincided with that of constant amplitude loading in air and vacuum. Also the crack tip opening displacement, CTOD, was found to be a good parameter in expressing the fatigue crack growth rate under repeated two-step loadings, suggesting the similarity of the relationships between ΔKeff and CTOD under constant amplitude and stationally variable amplitude loadings. The fatigue crack growth resistance in vacuum was superior to that in air.
  • 村田 雅人, 向井 喜彦
    1991 年 40 巻 458 号 p. 1435-1441
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Crack closure behavior in fatigue crack propagation process is induced by plastic deformation near crack. In the present paper, the effect of plastic deformation on fatigue crack closure in low strength material and its welded joint was studied. The results obtained are as follows. Crack closure was caused by plastic deformation near crack surface. Generally, the crack opening ratio in high yield strength material was higher than that in low yield one. This tendency results from a low degree of deformation near crack surface. In addition, in welded joint, the crack propagation rate was higher than the mother metal, though the crack opening ratio was almost 1 by the effect of residual stress. This was explained by the effect of restraint for plastic deformation, which was induced by the existence of compressive stress field ahead of crack.
  • 太田 昭彦, 前田 芳夫, 町田 進, 吉成 仁志
    1991 年 40 巻 458 号 p. 1442-1446
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue crack propagation properties of welded joints under random loading were investigated in air and synthetic sea water. The fatigue crack closure did not occur for whole excursion of loading, because the stress ratio around crack tip became high due to the tensile residual stresses around crack tips. That is, the applied range of stress intensity factor coincided with the effective range of stress intensity factor. The fatigue threshold in synthetic sea water was about a half of that in air. The fatigue crack propagation rates under random loading could be well estimated by the results obtained from constant amplitude tests assuming a linear cumulative damage law. That is da/dn=CKeqmKthm}, where ΔKeq={Σ(ΔKim·ni)/Σni}1/m, ni=0 at ΔKi≤ΔKth or ni=ni at ΔKiKth.
  • 阿部 孝行, 金澤 健二
    1991 年 40 巻 458 号 p. 1447-1452
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    High-cycle fatigue behavior of JIS SUP spring steels was discussed from a point of view of effects of non-metallic inclusions on fatigue strength and on behavior of fatigue crack initiation and propagation. Hardness of the materials ranged from HV 420 to HV 520. Fatigue tests were carried out in air environment up to 108 cycles under conditions of rotating bending and reversed torsion.
    The results obtained are as follows:
    (1) Relationship between hardness (HV) and rotating bending fatigue strength (σwb: MPa) for steels where fatigue cracks initiated from the specimen surface independently of inclusions is described by σwb=1.71HV. This relationship is considered as that for inclusion-free high strength steels.
    (2) Stage I cracks were observed to start in multiple directions from a fatigue crack initiation site near an inculsion under a rotating bending condition. The size of the State I crack is larger than that of the inclusion itself.
    (3) Under reversed torsion, fatigue fracture occurred from Stage I cracks initiated at a parallel plane to the specimen axis, where no inclusion could be observed.
    (4) For both types of fatigue tests, Stage I cracks initiated under a shear stress larger than τa =0.85HV, which is a half of the rotating bending fatigue strength of inclusion free steels. As it was not confirmed whether non-propagating cracks existed on the specimen surface endured 108 cycles or not, endurance limit for crack initiation was not determined.
    (5) The value of stress intensity factor at a tip of Stage I crack is an important factor or Stage I crack to start propagating as Stage II crack.
  • 中村 眞行, 服部 敏雄, 坂田 寛, 石塚 達郎
    1991 年 40 巻 458 号 p. 1453-1458
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    In fretting fatigue, it has been known that the contact edge is shifted inward because of wear. The effect of the contact edge shift on crack propagation behavior is considered here to predict accurate fretting fatigue life. The stress intensity factor (KI) for fretting fatigue crack was calculated by using the contact pressure and frictional stress distributions. They were analyzed by finite element method. The S-N curves of fretting fatigue were predicted by using the relationship between the calculated stress intensity factor range (ΔKI) and the crack propagation rate (da/dN) obtained from CT specimens. Fretting fatigue tests were performed on Ni-Mo-V steel specimens. The S-N curves of experimental results were in good agreement with the analytical results obtained by considering the contact edge shift.
  • 大川 功, 高橋 秀夫, 都丸 高道, 三角 正明
    1991 年 40 巻 458 号 p. 1459-1465
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper discusses the stress-based evaluation of fatigue life under both in-phase and out-of-phase combined loading conditions. Load controlled fatigue tests were performed on a low carbon steel under combined push-pull and completely reversed torsion in the intermediate to high cycle regime. Phase differences between two loadings were 0°, 45° and 90°.
    Experimental data showed that the increase of phase difference resulted in the increase of fatigue life under combined loadings. This may be explained by the decrease of plastic strain range due to material hardening in out-of-phase conditions.
    Gough's ellipse quadrant was generalized to out-of-phase loadings by taking account of the phase differences. This criterion can be easily applied but slightly overstimates the actual life. A modification of Lee's criterion, which was also an extension of Gough's equation, showed good agreement with the observed life. Furthermore, Brown-Miller's theory expressed in terms of the shear and normal stresses on the maximum shear plane was applied to out-of-phase fatigue. As a result, the fatigue lives under push-pull, torsion and combined in- and out-of-phase loadings were well correlated by Brown-Miller's criterion.
  • 誉田 登, 外山 和男
    1991 年 40 巻 458 号 p. 1466-1471
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Materials for construction tend to be used in more harsh environments nowadays. Much effort has been spent already in order to understand the effect of environment on fatigue strength. Especially, the environmental effect on fatigue crack propagation behavior has been clarified in many combinations of materials and environmental conditions. However, each step of the corrosion fatigue process has not been evaluated in detail. In this study, each period from initiation and growth of corrosion pits to initiation and propagation of corrosion fatigue cracks is estimated. Material used was a carbon steel HT60 of 630MPa class tensile strength. A micro-drilled notch was introduced at the surface of test specimen by machining. The notch of 80μm diameter, which imitated corrosion pits was expected to fill the role of concentrated stress sites. Test environments were 3.5 weight percent NaCl solution and 1.33×10-4Pa air in a chamber of scanning electron microscope (SEM). Fatgue tests were conducted under a load ratio of 0.1 at a frequency of 1.5Hz in NaCl solution and at 20Hz in a vacuum. While under continuous observation by SEM, a crack which reached 20 to 30μm in length was defined as fatigue crack initiation. A regression equation, with an accuracy within a factor of 5, for fatigue crack initiation life was derived for both environments. It became clear that the effect of stress and notch shape on initiation life was smaller in NaCl solution than that in a vacuum. In addition a relationship between stress intensity factor, calculated from shadow figure of notch, and crack initiation life was deduced. In NaCl solution, the initiation life of corrosion pits was estimated to be quite short, and a ratio of fatigue crack initiation life to total failure life was about 35% regardless of stress intensity factors.
  • 鳥居 太始之, 本田 和男, 太田 陽介
    1991 年 40 巻 458 号 p. 1472-1478
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    A method was proposed which evaluates crack opening stress distribution and stress intensity factor from the crack opening displacement distribution near a circular-hole. The fatigue crack and the low-temperature annealed crack emanating from the hole were prepared and the crack opening displacements were measured along their faces. The difference in the crcak opening stress distribution between the fatigue and the annealed cracks was used to estimate the residual stress distribution along the fatigue crack. They showed the compressive residual stresses near the hole and the crack tip, but the tensile ones between them, which were caused by cyclic deformation near the hole and subsequently redistributed due to fatigue crack propagation. The stress intensity factors estimated from the fatigue crack opening displacements were smaller than those calculated from the applied stress and were closely related to the change in fatigue crack propagation rate.
  • 小川 武史
    1991 年 40 巻 458 号 p. 1479-1484
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue crack growth in polycrystalline magnesia has been investigated at room temperature using a combined loading technique, in which compression load is applied to the ligament of the compact specimen in order to stabilize the crack growth. Measurement of the crack length was performed continuously by the surface film technique, in which the change in crack length was monitored by a thin layer of carbon on the surface which encompasses the region of fracture. The propagation of a crack leads to a break in the carbon film which is atomically bonded to the surface of specimen. Crack grew stably under cyclic tension loading with the maximum stress intensity factor Kmax lower than fracture toughness. Initially, the growth occurred in each cycle, but it became discontinuous in the following cycles. The continuous monitoring of crack length revealed that the crack grew quickly in a single cycle at Kmax over several tens of microns and arrested until the next growth occurred. The crack growth mechanism is discussed in terms of a wake effect of the fatigue crack, and the role of cyclic loading in the crack growth of ceramics is suggested.
  • 佐竹 忠昭, 菅野 幹男
    1991 年 40 巻 458 号 p. 1485-1490
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    The melt-sintered Al-Al2O3 dispersion-strengthened alloy has been fatigued in plane bending at the resonant frequency for the second-order mode of oscillation to study the micromechanism of fatigue crack growth. Specimens were annealed at 373K for 1hr to obtain the structure for recovery stage heat treatment, having the average cell size of 0.7μm in diameter. Fatigue damage was examined by optical and scanning electron microscopy. It was found from the microstructural observations that the fracture surface morphology with fatigue crack growth was classified into three categories depending on ΔK values: in ΔK<5MPa√m the granular mode of fracture covered over fracture surfaces, in 5<ΔK<10MPa√m striation-like marking and microcracking were observed together with the granular mode, and in ΔK>10MPa√m the granular mode has been hardly observed. The ΔK≈5MPa√m seemed to be the critical value at which the striation-like marking and microcracking appeared on fracture surfaces. It was concluded that fatigue damage concentrated on cell boundaries. The results obtained are discussed in connection with the effect of the Al2O3 particles dispersed in cells on dislocation motion.
  • 菅原 宏人, 大塚 昭夫, 天野 岳彦
    1991 年 40 巻 458 号 p. 1491-1496
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Static and cyclic fatigue tests were made on glass, glass ceramics and silicon nitride under static tensile loading and tension-compression cyclic loading at various stress ratios between R=-1 and 1, by using an apparatus specially designed with a device to minimize the load eccentricity. Crack growth tests were also made under static loading and cyclic loading in order to obtain the crack growth rate da/dt, as a function of stress intensity factor K. Test results on smooth round bar specimens show that almost no effect of stress cycling was seen on silicon nitride A and borosilicate glass, while appreciable degradation in strength due to cyclic loading was observed on glass ceramics and silicon nitride B. The relation, da/dt versus K, of small cracks obtained from the tensile test on smooth round bar specimens showed higher values than those of large cracks obtained from the crack growth tests. The increase in crack growth rate due to cyclic stress was observed in both silicon nitride B and A, in the latter of which no effect of stress cycling was observed in the tests on smooth round bar specimens.
  • 鳥山 寿之, 村上 敬宜, 牧野 泰三
    1991 年 40 巻 458 号 p. 1497-1503
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
    Nonmetallic inclusions cause relatively low fatigue strength for high strength steels and also cause a large scatter of fatigue strength. A method of inclusion count on the basis of statistics of extreme is proposed to evaluate material quality. By combining the new inclusion counting method and fatigue strength prediction equation proposed by Murakami et al., the lower bound of scatter band of fatigue strength can be predicted. The square root of the projection area of inclusion √area is the crucial parameter both in inclusion counting and fatigue strength prediction.
    The detabase of cumulative frequency of the maximum inclusion size √areamax of various commercial steels is presented. The scatter bands in rotating-bending fatigue strength of back up roll steel are estimated by the proposed method and are comfirmed to be in good agreement with the experimental results.
  • 田村 博
    1991 年 40 巻 458 号 p. 1504-1509
    発行日: 1991/11/15
    公開日: 2009/06/03
    ジャーナル フリー
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