材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
36 巻 , 409 号
選択された号の論文の17件中1~17を表示しています
  • 岩崎 親裕, 猪飼 靖, 松田 勝
    1987 年 36 巻 409 号 p. 1046-1052
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    A new procedure is demonstrated to estimate fatigue damage from the viewpoint of internal stress and effective stress. Constant effective stress fatigue tests were carried out in order to get the ES-N (effective stress vs. number of cycles to failure) curve, which was similar to the S-N curve in its shape. Based on the ES-N curve, the cumulative damage or the cumulative cycle ratio was estimated using the fatigue test data under the constant stress amplitude and under the manifold multiple repeated stress in two stress levels.
    The main results are as follows:
    (1) The relationship between the effective stress and fatigue damage was independent of load history.
    (2) The values of cumulative cycle ratio for the broken specimens based on the ES-N curve were around 1. On the other hand, the values for the unbroken specimens were small, and those values were saturated in the early stage of their fatigue process. These estimations based on the ES-N curve were superior to those based on the Miner's rule (S-N curve).
    (3) It is important that the maximum stress in service is held below the critical effective stress (fatigue limit represented by effective stress) in designing a structural member to be used over a long period.
  • 大川 功, 三角 正明, 榎本 信助
    1987 年 36 巻 409 号 p. 1053-1059
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    To investigate the effect of loading frequency on fatigue strength of age-hardenable steel, rotating bending fatigue tests were carried out under two different frequency conditions (3000 and 300rpm) by using the low-temperature quenched rimmed steel. Hardness change and crack propagation were observed during the fatigue process under both loading frequency conditions.
    The main results obtained were as follows;
    (1) At a high cyclic stress region, the effect of loading frequency on fatigue life was not observed. However, at lower stresses, the fatigue life in 300rpm became longer and eventually the fatigue limit in 300rpm became higher than that of 3000rpm.
    (2) The rate of increase in hardness with number of cycles was larger in 300rpm than in 3000rpm. This was mainly caused by the time dependence of age-hardening.
    (3) As the cyclic stress was lowered, the fatigue crack growth in 300rpm became slower than that in 3000rpm. Near the fatigue limit in 300rpm, a long non-propagating crack was found at a relatively low number of cycles.
    (4) The fatigue behavior mentioned above might be explained as follows; the effect of strengthening of material due to age-hardning on fatigue appears remarkably in 300rpm when cyclic stress is low, owing to the enough time available for ageing than in 3000rpm.
  • 高尾 健一, 西谷 弘信
    1987 年 36 巻 409 号 p. 1060-1064
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    Cracking behavior has been investigated through successive observations on the surfaces of five steels, an alpha brass, an age-hardened Al-alloy and a pure titanium, with particular emphasis on the relation between the crack initiation process and the notch sensitivity in fatigue.
    Two types of crack initiation process were observed. One was the process where cracking starts at a very small region compared with a grain diameter, as observed on an Al-alloy. The other was the one where a fatigue crack initiates not at a point but at a definite region having the size comparable to the grain diameter, as observed on other metals.
    The difference in cracking characteristics was related to the thickness of surface layer. The notch sensitivity based on fatigue crack initiation decreased with increasing thickness. An Al-alloy with the thinnest thickness had the highest sensitivity, whereas a pure titanium the lowest. For a sharp notch, however, a non-propagating crack appeared, so that the fatigue limit did not decrease drastically with increasing notch sharpness, leading to rather low sensitivity. The fatigue strength of the notched members can be uniquely assessed from the relation between the reciprocal of notch root radius and the elastic maximum stress at the fatigue limit, based on the new “Linear Notch Mechanics” concept.
  • 村上 敬宜, 松田 健次
    1987 年 36 巻 409 号 p. 1065-1070
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of understress in two-step stress fatigue tests on fatigue life was investigated with emphasis on the behavior of small cracks.
    In fatigue under variable amplitude loading, two critical stresses play important roles in fatigue damage prediction. One is the fatigue limit σw defined by the failure of a specimen containing a small crack, and the other is the critical stress σwi which is the threshold value for fatigue crack initiation from the small crack. It should be noted that both σw and σwi are the function of crack size and accordingly the degree of contribution of understress σL to fatigue damage varies at every moment with the variation of crack size, i.e. crack propagation. The equations to predict σw and σwi were derived here as the function of crack size.
    If the value of σL is lower than σwi defined on the basis of crack length l, the repetition of σL does not contribute fatigue damage. However, if the crack propagates due to the repetition of overstress σH and the value of σwi decreases below σL, σL starts to contribute to fatigue damage. This fact explains the reason for a wide scatter of the values of cumulative fatigue damage D of modified Miner's rule obtained in previous studies. A method is also discussed to predict the lower limit of D.
  • 城野 政弘, 菅田 淳
    1987 年 36 巻 409 号 p. 1071-1076
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue crack growth tests were carried out under constant amplitude, repeated two-step and random loadings by using the test specimens which have a longitudinal residual stress due to water cooling from a high temperature. Crack length and crack closure were measured by using the minicomputer-aided unloading elastic compliance method.
    The crack opening stress intensity, Kop, under varying loadings was found to be controlled by the maximum stress intensity range-pair, (ΔrpK)max, and its actual stress ratio, R', which is defined as R'={(K)min+Kr}/{(K)max+Kr}, where (K)max and (K)min are the maximum and minimum applied peak stress intensity in the varying loading respectively, and Kr is the stress intensity factor induced by the residual stress. And also, Kop was found to coincide with the constant amplitude test results having the identical stress intensity range ΔK and stress ratio R with (ΔrpK)max and R'.
    The linear accumulation law of crack growth in terms of the effective stress intensity rangepair, ΔrpKeff, was confirmed to give a good estimation of the fatigue crack growth rate under varying loadings even in the residual stress field.
  • 橘内 良雄, 小林 英男, 成本 朝雄, 石塚 鉄夫, 飯田 國廣, 吉久 悦二
    1987 年 36 巻 409 号 p. 1077-1083
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fatigue crack growth behavior in butt-welded joints of STS42 steel was examined using compact type (CT), center-cracked tension (CCT) and single edge cracked (SEC) specimens, and the effects of specimen configuration, thickness, crack orientation and location of weld line in the specimens on the fatigue crack growth rate in the welded joints were examined in connection with welding residual stress.
    The fatigue crack growth rate in the CCT specimen was similar to or slightly higher than that in the base metal, whereas the crack growth rate in the CT or SEC specimen decreased considerably as compared with that in the CCT specimen, except for the CT specimen with a notch on the weld line. The crack growth rate increased slightly with increasing specimen thickness, regardless of specimen configuration. In the case of the CT specimen with perpendicular crack orientation with respect to the weld line, the crack lengths of the both sides of the specimen surface were often different each other. The side with an advanced crack front corresponded to the backing side with finishing pass. When a crack existed within the region of initial compressive residual stress field, the overall distribution of residual stress did not change appreciably. The effect of welding residual stress on the crack growth rate was the same as that of stress ratio on the growth rate of the base metal. The crack growth rate in the welded joints was correlated with the effective stress intensity factor range, ΔKeffR, which was estimated by superposition of the respective stress intensity factors for the residual stress field and for the applied stress, regardless of specimen configuration and distribution of residual stress in the specimens.
  • 小林 英男, 荒居 善雄, 中村 春夫
    1987 年 36 巻 409 号 p. 1084-1089
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fatigue crack growth emanating from fastener holes is believed to have caused the failure of the rear pressure bulkhead of the crashed Boeing 747 jumbo jet plane. To evaluate the initial flaw criticality at fastener holes, the fatigue crack growth tests were conducted for plate specimens with drilled holes which simulate fastener holes. The initial flaws of 1.27mm in size were induced in the holes as required by the damage tolerance design.
    The results of fatigue crack growth characteristics and the through-holes fatigue lives were compared with analysis. Finally, the fatigue failure analysis of the bulkhead of the crashed plane was attempted.
    The following are the results obtained.
    (1) When the flawed hole is adjacent to the sound holes, the fatigue cracks from the flaws are arrested at the sound holes and crack reinitiation cycles are satisfactorily long.
    (2) On the other hand, when two or three adjacent holes are flawed, the specimen shows a drastic reduction in life. This case is found to give the quantitative simulation for the fatigue failure of the bulkhead of the crashed plane.
    (3) If the damage tolerance design or the in-service inspection based on this had been adopted, it is judged that the fatal failure would not have occured.
  • 鈴木 謙一, 深倉 寿一, 柏谷 英夫
    1987 年 36 巻 409 号 p. 1090-1096
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    Axial-strain controlled fatigue tests of stainless steels (SUS 304L, SUS 316L and WM-X) and aluminum alloys (A5083-O and A5356) were conducted at 4K with the strain rate of 0.4%/s and the strain ratio of -1. The fatigue tests at 77 and 300K were also conducted for comparison. The TIG weld metal of stainless steel (WM-X) showed cyclic strain-hardening at 4 and 77K, and cyclic strain-softening at 300K, although other materials showed cyclic strain-hardening at 4, 77 and 300K. It seemed that the strain-induced martensitic transformation influenced the cyclic stress responce of stainless steel. In the fatigue life range of 1000 cycles or more, the fatigue resistance, that means the strain capability at given cycles of fatigue life, of SUS 304L, SUS 316L, WM-X and A5083-O at 4K were nearly equal to or a bit higher than that at 77K. At 4K, the fatigue resistance of SUS 316L was higher than that of SUS 304L, but lied in the middle of a scatter band by a factor of 2 among base metals of stainless steels in literatures. The fatigue resistance of A5083-O was the lowest in a scatter band by a factor of 1.4 among base metals of aluminum alloys in literatures. At 4K, the fatigue resistance of WM-X was almost equivalent to that of SUS 304L and was lower than that of SUS 316L by 20%, being away below that of base metals of stainless steels at 300K. However, the fatigue resistance of the MIG weld metal of aluminum alloy (A5356) was lower than that of A5083-O by 45%, being closer to that of base metals of aluminum alloy at 300K. One must be careful to use the weld metal A5356 at 4K.
  • 岡田 庸敬, 服部 修次, 山岸 真一郎
    1987 年 36 巻 409 号 p. 1097-1103
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fatigue tests were conducted for high-strength steels, HT50 and HT80, in laboratory air, in ion exchanged water and in synthetic seawater, systematically. Three types of the notched specimens were used: shaft specimens with a groove, with a transverse hole and with a shoulder fillet. The results obtained were as follows:
    (1) Synthetic seawater reduced the fatigue strength considerably. However, the strength in the synthetic seawater decreased slightly with an increase of αk (stress concentration factor) in comparison with that in laboratory air or in ion exchanged water.
    (2) A notch reduced the fatigue strength remarkably in laboratory air and in ion exchanged water in the order of the specimens with a hole, with a shoulder fillet and with a groove, and HT80 was more sensitive to the notch than HT50.
    (3) The increase of βk (fatigue notch factor) with increasing αk was smaller in synthetic seawater than that in laboratory air, but it was much larger than that in ion exchanged water.
  • 駒井 謙治郎, 入船 佳津一
    1987 年 36 巻 409 号 p. 1104-1109
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The corrosion fatigue crack growth rate of dual-phase stainless steel SUS329J1 has been measured in synthetic sea water at various stress ratios and stress cycle frequencies under free corrosion and a cathodic potential. In air the roughness-induced wedge effect enlarges the region II in the load-strain hysteresis loop. In synthetic sea water, the corrosion products-induced wedge effect under free corrosion and the Ca and Mg deposites-induced wedge effect under a cathodic potential are conspicuous, thereby enlarging the region II and raising Kop. Under free corrosion the stress assisted dissolution accerelates the crack growth rate at a low ΔKeff. In addition, at a high ΔKeff at R=0.1 and f=0.17Hz the crack growth rate is much more accerelated due to hydrogen embrittlement. Under a cathodic potential, ΔKth is remarkably high. But the crack growth rate is much accerelated due to hydrogen embrittlement in terms of ΔKeff.
  • 大塚 昭夫, 森 要, 吉田 貴司
    1987 年 36 巻 409 号 p. 1110-1115
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The characteristics of fatigue crack initiation and growth of two high strength aluminum alloys (2017-T3, T4 and 7075-T6) under mode II loading have been investigated in 3.5% saltwater by the four-point-shear test method. The mode I fatigue crack growth tests have also been carried out for the same alloys in 3.5% saltwater and in air. 2017-T3, T4 and 7075-T6 aluminum alloys showed mode II growth in 3.5% saltwater as in air under the conditions of higher ΔKII than a certain critical ΔKII and of a sharper notch than a certain critical sharpness. The minimum value of ΔKII for mode II growth (ΔKII-threshold for mode II growth) increased in 3.5% saltwater compared with that in air. An appreciable effect of environment was observed not only on the da/dNKI relation but also on the fractograph of mode I fatigue crack growth in 7075-T6. In both alloys, little effect of environment was found on the minimum value of ΔKII for mode I crack growth, on the da/dNKII relation or on the fractograph of mode II fatigue crack growth.
  • 前川 一郎, 柴田 博司, 小林 朗
    1987 年 36 巻 409 号 p. 1116-1121
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    Bending fatigue experiments were carried out for Al2O3-ZrO2 and Al2O3 ceramics under a pulsation of trapezoidal loading at 288 and 873K. In order to evaluate the fatigue damage, the degree of phase transformation of dispersed ZrO2 from the tetragonal to monoclinic phase was studied by means of X-ray analysis, and the crack length at Vicker's indentation was measured. The results obtained were summerized as follows;
    (1) The fatigue life was comparatively short but a clear fatigue limit could be seen at both temperatures for Al2O3-ZrO2, although such a fatigue limit could not be seen for Al2O3. From these results, it is considered that fatigue fracture originates at microcracks around the dispersed ZrO2.
    (2) The crack length formed at a Vicker's indentation on the tensile side of each specimen surface after the repeated pulsation of loading was much longer in the longitudinal direction than in the transverse direction.
    (3) No increase in the phase transformation of dispersed ZrO2 due to the pulsation of loading was observed at both 288 and 873K.
    (4) In order to explain the difference in indentation crack length, a simple model was proposed.
  • 岸本 秀弘, 上野 明, 河本 洋
    1987 年 36 巻 409 号 p. 1122-1127
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to make it clear whether the cycle-dependent crack propagation would occur in ceramic materials under a cyclic load, the crack propagation rate was measured using compact tension specimens made of sintered Si3N4 at room temperature under ambient condition. In this study, the crack propagation rate da/dt, which ranged from 10-10m/sec to 5×10-4m/sec, was measured under static loads and cyclic loads in the form of square wave. In the case of cyclic loads, the hold time at the maximum and minimum loads was equal. The crack propagation rate da/dt was equal to 2f×da/dN, where da/dN is given in m/cycle and f, in Hz.
    Crack propagation tests were carried out at 1.1Hz and at various stress ratio R=1, 0.4, 0.2, 0.1, R being the ratio of the minimum load to the maximum load. The results showed that, as R decreased, da/dt increased consistently and KImax at da/dt=2×10-10m/sec decreased. In other words, as the load amplitude became large, the effect of cycling of the load became more damaging.
    Further tests were carried out at constant R (0.1) and at three levels. of f, f=0.01Hz, 0.1Hz, 1.1Hz. As f increased, da/dt increased. Even under the condition of f=0.01Hz, crack propagation was accelerated by cycling of the load, as compared with da/dt under a static load. The f-da/dt diagram was constructed from the above data in order to distinguish the cycle-dependent crack propagation from the time-dependent crack propagation. In the range where KImax was small (<3.57MPa√m), only the cycle-dependent crack propagation occurred. It is important to recognize that 3.57MPa√m is smaller than the threshold KImax under a static load. When KImax became larger than 3.57MPa√m, the time-dependent crack propagation appeared. In this region, both of the cycle-dependent crack propagation and time-dependent crack propagation existed. In the range where KImax was large (>4.34MPa√m), the time-dependent crack propagation was predominant.
  • 星 実泰, 中村 宏
    1987 年 36 巻 409 号 p. 1128-1133
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to investigate the fatigue life of notched specimens under combined bending and torsion which were acting at different frequencies, a testing machine was deviced, and some experiments were carried out on three types of notched carbon steel specimens.
    In the same way as that proposed in the previous paper, a modified Findley equation including the correction factor of different frequencies R1/t was used as the criterion of fatigue life, (σ/σN)1/ψN+(R1/t·τ/τN)2=1
    where σN, τN=fatigue strengths at N cycles
    ψNNN
    R=the frequency ratio of torsion to bending
    t=the gradient of the S-N diagram of torsion
    It was found that the method was applicable to the notched specimens also.
  • 児玉 昭太郎, 三沢 啓志, 大住 勝彦
    1987 年 36 巻 409 号 p. 1134-1138
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    X-ray fractography is a technique for analysing the cause and mechanism of fracture from the information obtained by X-ray irradiation on the fractured surface. It has been shown that a good correlation exists between the residual stress on the half value breadth of diffraction profile and the stress intensity factor that had caused the fracture. X-ray fractography has been successfully applied for the in-service fracture of many types of fracture. However, in some cases the residual stresses on the fatigue fractured surface in service are compressive, which have not been found in the laboratory experiments so far.
    In the present study, fatigue experiments were carried out on 0.5% carbon steel to investigate the stress condition that produces compressive residual stress on the fractured surface. The specimen was a center notched rectangular plate of 8mm thick, and a wide range of stress ratio Rminmax were applied from tensile to compressive, namely R=0.50, 0.25, 0.20, 0.00, -1.67, -2.33, -2.40 and -3.00. From the results of experiments, it was found that, when the stress ratio was -3.00 and the minimum stress was -150MPa, the residual stress on the fractured surface became compressive. Since the minimum stress is far smaller than the compressive yield stress, the cause of the compressive residual stress was considered to be the result of crack closure. In this case, the crack opening ratio U=(σmaxop)/Δσ, where σop is the crack opening stress, was about 0.3 and almost constant through the crack length.
  • 二瓶 正俊, 西島 敏, 今野 武志, 下中 外茂夫, 林 美昭, 高木 義彦
    1987 年 36 巻 409 号 p. 1139-1144
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    A random load fatigue testing system, equipped with a computer to control any frequency distribution of random wave, was newly developed. This controlling system mainly consisted of three parts: a random wave generator based on the matrix method, a rain-flow counting system and an error matrix creator for a digital gain control.
    Fatigue tests were carried out under the Gaussian type block- and random-loading waves, to evaluate the control capability and performance of the newly developed system. It was found that the controlling system acts well and the fatigue life under random loading is shorter by half than that under block loading having the same frequency distribution of the loads.
  • 藤山 一成, 木村 和成
    1987 年 36 巻 409 号 p. 1145-1151
    発行日: 1987/10/15
    公開日: 2009/06/03
    ジャーナル フリー
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