材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
36 巻 , 408 号
選択された号の論文の20件中1~20を表示しています
  • 酒井 達雄, 安井 秀昭, 田中 道七
    1987 年 36 巻 408 号 p. 915-921
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    A database on the fatigue strength of metallic materials was compiled by collecting the experimental fatigue data of the last 20 years in Japan on a nationwide scale as a project in JSMS Committee on Fatigue. In particular attention to statistical fatigue properties, the authors have been analyzing P-S-N characteristics of carbon steels for machine structural use in this database.
    When these fatigue data were plotted altogether on S-N coordinates, they were widely dispersed due to a wide range of strength levels of metals. The tensile strength σB was taken up as a typical parameter of the strength level, and the applied stress was normalized by σB. Then all the data were replotted as a σaB-N diagram. Thus we have all the data points yielded in a relatively narrow scatter band.
    By examining the effects of material and testing conditions on S-N property, it was found that all the S-N plots were successfully classified into the following four groups; (1) S10C-S15C, (2) S20C-S40C, (3) S45C-S58C (Quenched & Tempered), and (4) S45C-S58C (Except for Quenched & Tempered).
    Quantitative P-S-N characteristics were finally analyzed for each group based on the stress dependency of the fatigue life distribution. The theoretical results thus obtained were in good agreement with the statistical fatigue properties of respective groups of the materials.
  • ΔK一定試験による検討
    市川 昌弘, 中村 武夫
    1987 年 36 巻 408 号 p. 922-926
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The purpose of this paper was to decompose experimentally the variability of the fatigue crack propagation rate da/dN into two parts, the inter-specimen variability and the intra-specimen variability. Specifically, in order to separate σb2 and σw2 experimentally, fatigue crack propagation tests were conducted under the condition of constant ΔK, where σb2 and σw2 were the inter-specimen variance and the intra-specimen variance of logda/dN, respectively. The condition of constant ΔK was attained by use of the tapered double cantilever beam specimens. The material tested was the high strength steel HT60. By measuring the increment of the crack length Δa at regular cycle intervals of ΔN, da/dN was evaluated as da/dN=Δa/ΔN as in usual cases.ΔK was chosen as ΔN=5000 cycles. The technique of analysis of variance was applied to the test data to estimate σb2 and σw2. It was shown that σb2 and σw2 were of the same order. The F test also showed that the inter-specimen variability could not be neglected.
  • 権 在度, 中曽根 祐司, 北川 英夫
    1987 年 36 巻 408 号 p. 927-933
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The authers have been attempting to establish a proper method for predicting fatigue lives of structures which have been subjected to material degradation.
    For this purpose, the present paper describes a statistical investigation on the effects of material degradation on the crack initiation life and on the crack growth rate in a 2¼ Cr-1Mo (SCMV4) steel. The steel studied in this paper has been used in a plant having operated for over 60000 hours and subjected to material degradation due to temper embrittlement. The results obtained for the degraded steel were discussed in comparison with those for the recovered SCMV4 steel.
    The crack initiation life and crack growth rate in the degraded SCMV4 steel and in the recovered SCMV4 steel followed the log-normal distribution. The crack initiation life was shorter in the degraded steel than in the recovered one at a high probability. The crack growth rate da/dN was higher in the degraded steel at higher stress-intensity-factor-range ΔK levels at a high probability. At lower ΔK levels, on the other hand, the mean of da/dN was a little lower in the degraded steel; nevertheless, a larger variation in da/dN implies that da/dN can become higher in the degraded steel.
    A Monte Carlo simulation was made on the basis of the data obtained in the present experiments in order to determine the P-S-N diagrams for the degraded and the recovered SCMV4 steels. The obtained P-S-N diagrams statistically revealed that the fatigue life of the degraded steel was shortened at higher stress levels and that its variation became larger at lower stress levels. The larger variation in the life of the degraded steel is attributed to shorter fatigue life in the degraded steel than in the recovered steel at a considerably high probability, although the difference of the mean fatigue lives of the two steels became smaller at lower stress levels.
  • 古田 均, 白石 成人, James T.P. YAO
    1987 年 36 巻 408 号 p. 934-939
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    It has become important to evaluate the reliability of existing structures in order to establish a rational program for repair and maintenance. Since most of the existing structures may suffer from defect, corrosion and damage, it is necessary to account for their effects in the reliability analysis.
    In this paper, an attempt is made to develop a reliability analysis for damaged structures using fuzzy sets theory. Damage state is specified in terms of linguistic variables such as “slight”, “more or less”, “severe”, etc. which are defined by fuzzy sets. Using a fuzzy reduction factor, information of the damage state is introduced into the calculation of failure probability. A measure of structural redundancy is newly proposed based on the failure probabilities of damaged and undamaged structures. Several examples are presented to illustrate and demonstrate the applicability of the reliability analysis proposed herein.
  • 岡部 永年, 矢野 利行, 鎌田 功, 柏谷 英夫
    1987 年 36 巻 408 号 p. 940-946
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The impact fatigue tests were performed on glass-cloth reinforced epoxy resin laminates at various temperatures up to 200°C. From the experiments, the temperature-dependence of impact fatigue strength was clarified. The scatter of this strength at each temperature was statistically analyzed and its temperature-dependence was also clarified. The safety factor and the allowable stress for the laminates under service impact loads were. studied with regard to the influence of circum-temperature used, on the basis of reliability theory. The results obtained are as follows:
    (1) The impact fatigue strength σt of the laminates shows a scatter of logarithmic distribution at high temperatures and can be estimated statistically by the formula of σtNfmt=DtμtStu.
    (2) The parameters of impact fatigue property, mt and Dt, and the strength scatter St are dependent upon temperature. Both of mt and Dt can be estimated from the statistic (σB, SσB) of static tensile strength σB at room temperature (20°C).
    (3) The safety factor and the allowable stress of the laminates under service impact loads can be determined according to the expectative reliability with regard to the circum-temperature practically used. This result is very useful for the optimum structural design.
  • 下河 利行
    1987 年 36 巻 408 号 p. 947-953
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The objective of this study was to investigate the probabilistic certification method for the fatigue strength of composite structures systematically and then to propose the use of the combination of the scatter factor of life and the scatter factor of fatigue strength. The equations to express the mutual relationship between these two scatter factors and the combination of both factors were derived. Moreover, some calculation examples of the scatter factors were given by using the typical scatter parameters of fatigue life and fatigue strength obtained from the test results of carbon/epoxy laminate specimens. The assumptions made in this study were: (1) Fatigue tests of the composite structures provide an appropriate estimate of the central tendency of fatigue life, (2) the distribution form of fatigue life is the log-normal or two-parameter Weibull distribution, (3) the scatter parameters of fatigue life are known and independent of stress, (4) the shape of the S-N curve is linear on semi-logarithmic or double-logarithmic graph paper, and (5) the slope of the S-N curve is known.
  • 貞広 嘉和
    1987 年 36 巻 408 号 p. 955-959
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of dry-grinding by ball mill and vibration mill with an alumina vessel on the ESR spectra of zinc oxide powder has been studied. The ESR A(g=2.013), B(g=2.005), C(g=1.955) and C'(g=1.959) peaks were observed on the products which were heat-treated, preserved for a year in in vacuum, and surface-treated by aqueous HCl after grinding.
    The results obtained are as follows.
    (1) The C' peak corresponds with the broken-bonds formed on the surface of zinc oxide crystallites by cracking, and A peak corresponds with the dangling-bonds caused by dislocations in the crystallites.
    (2) The B peak consists of B'(g1=2.007, g2=2.005, g3=2.002) and B"(g=2.006, g//=2.003). B' peak corresponds with the oxygens combined to the broken-bonds formed on the surface and B" peak corresponds with the oxygens combined to the dangling-bonds on the dislocation in the crystallites.
  • 阿部 武治, 長岐 滋, 背戸 卓美
    1987 年 36 巻 408 号 p. 960-966
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Plastic deformation of metallic material with elliptic inclusions was studied by assuming the material composed of rigid-plastic solid with different yield stress and using a plane model of material with the staggered configuration of inclusions. The rigid-plastic finite element method was employed in the numerical calculation which is based on the upper bound theory in plasticity. Uniaxial and biaxial tensile stresses were assumed to be applied to the model material under the plane stress condition. The calculation was made on both cases where the inclusions are harder than the matrix and softer than the matrix.
    The influences of the aspect ratio, the yield stress ratio and the volume fraction of inclusions on the deformation behavior of the material were clarified. The deformation is much affected by the mutual restriction of deformation between the inclusion and the matrix. The mutual restriction is less under the biaxial applied stress than under the uniaxial stress. That is, the inclusion deforms independently from the matrix more under the biaxial tension than under the uniaxial tension. The mean flow stress of the material was also discussed based on the calculated strain distribution.
  • 戸谷 眞之, 桐岡 健
    1987 年 36 巻 408 号 p. 967-973
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The early stage of the stable mode III crack growth is theoretically analyzed. A tip of the initial crack is blunted by screw dislocations continuously distributed on two slip-planes inclined at equal angles to the crack. It is assumed that at some critical load level the crack starts to grow and that, with a small increase in the applied load, the crack extends over a small distance and then stops due to the formation of a secondary pair of slip-lines. The boundary value problem relevant to this growth step is formulated by use of the notion of the effective friction stress and solved. The increment of the crack shearing displacement at the site of the initial crack tip is expressed as a function of the crack growth distance and the increment of the applied load. It is found that the form of the function is identical with that previously obtained by J.R. Rice and E.P. Sorensen.
  • 大谷 隆一, 木南 俊哉, 村山 英明, 渡部 哲也
    1987 年 36 巻 408 号 p. 974-979
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    An accurate prediction of fatigue fracture at elevated temperatures depends on the elucidation of the small crack initiation and propagation behavior. Experimental studies on the small cracks, however, have been quite limited. In this study, two types of high-temperature low-cycle fatigue tests, C-P type of a trapezoidal stress waveform with tension hold and P-P type of a high-frequency triangular stress waveform, were conducted by using smooth specimens of 304 stainless steel, and the behavior of initiation and early growth of surface small cracks was observed continuously during the tests with a high-temperature microscope. Furthermore, a detailed study was made by the interrupted tests with the replicas or scanning electron microscopy. The results obtained are summerized as follows. (1) The crack of C-P type fatigue initiates at a grain boundary between two triple points as it opens uniformly and gradually. (2) The crack growth to the adjacent grain boundary in the early stage of C-P type fatigue is caused through the same process as the crack initiation, showing a stepwise and discontinuous manner. (3) The process mentioned at (1) is the process of growth and coalescence of voids on the grain boundary owing to the grain boundary sliding. (4) The crack initiation of P-P type fatigue takes place at the intersection of slip bands and a grain boundary, and most of the cracks propagate along the grain boundaries in the early stage of fatigue. (5) The crack growth rate of P-P type fatigue decreases suddenly when the crack tip comes near to the triple point. (6) The fracture mechanisms of C-P type fatigue and P-P type fatigue are quite alike to that of creep and that of low cycle fatigue at room temperature, respectively.
  • 鈴木 秀人, 大藪 優, 国尾 武
    1987 年 36 巻 408 号 p. 980-985
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Axial loading fatigue tests were carried out on high tension bolts made of boron steel and Cr-Mo steel. The initiation and the subsequent growth of micro fatigue cracks in the bottom of thread were examined through the micro-fractography using SEM.
    The results obtained were as followed:
    (1) The fatigue strength of boron steel bolts was quite superior to that of Cr-Mo steel bolts. For the stress ratio of the actual stress used in the engine to the mean stress, σam=0.2, the fatigue limit of boron steel bolts was 83MPa, while the other was 54MPa and 65% of the former.
    (2) Both boron steel and Cr-Mo steel showed almost the same monotonic and cyclic 0.2% proof stresses.
    (3) The fractography using SEM showed a remarkable difference in the initiation and subsequent growth of micro cracks in the bottom of thread between boron steel and Cr-Mo steel bolts. The fatigue fracture surface of boron steel bolt near the bottom of thread consisted of the former austenite grain boundary, while that of Cr-Mo steel bolt occured within the grain and did not correspond to the microstructure.
    (4) The former austenite grain size of boron steel was about twice as large as that of Cr-Mo steel. Based on the criterion that fatigue cracks initiate when the size of plastic zone at the bottom of thread exceeds the grain size, it was interpreted that the larger grain size of boron steel caused its higher fatigue limit.
  • 村上 理一, 津村 豪, 秋園 幸一
    1987 年 36 巻 408 号 p. 986-991
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The corrosion fatigue crack growth behavior in the butt welded joints of low carbon steel has been studied and discussed in relation to the welding residual stress and corrosion deposits.
    In air, the fatigue crack growth rate was scarcely influenced by the tensile residual stress, but the compressive residual stress reduced the fatigue crack growth rate. In seawater, the effect of compressive residual stress on the corrosion fatigue crack growth rate was less than that in air. When the stress ratio was increased, this effect was scarcely observed. However the occurrence of the wedging effect due to corrosion deposits was confirmed in seawater except the case of compressive residual stress at low stress ratio. When the crack closure occurred by the compressive residual stress in seawater, the corrosion deposits formed within fatigue cracks were fractured by contact with the closing crack planes, but they were formed again. Such an mechanism seemed to occur particularly in the compressive residual stress field. Thus, the corrosion fatigue crack growth rate in the compressive residual stress field was remarkably accelerated by the aggressive attack of seawater.
  • 田中 道七, 木下 賢一朗, 中山 英明
    1987 年 36 巻 408 号 p. 992-998
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper describes the fatigue crack growth and crack opening behaviors in impact fatigue of two alloy steels; one is a high strength low alloy steel HT-60 and the other is an austenitic stainless steel SUS316. Both of the alloy steels have almost the same ultimate tensile strength of about 600MPa. Major attention was paid to the microscopic crack opening behavior under impact fatigue load measured by means of the fine grating method. The results of the crack growth tests indicated that the crack growth rate in impact fatigue is higher than that in non-impact fatigue for SUS316 alloy steel, but not for HT-60 alloy steel. Such a difference in crack growth behavior between two steels was correlated to the following microscopic crack opening behavior of these steels: In the case of SUS316 alloy steel, both of the effective stress intensity range at a crack tip and the effective crack opening displacement behind the crack tip are larger for the crack propagated under repeated impact load than those for the crack under non-impact load, but in the case of HT-60 alloy steel, the difference in those values measured under impact and non-impact loads is relatively small comparing to the case of SUS316 alloy steel.
  • 角屋 好邦, 後藤 徹
    1987 年 36 巻 408 号 p. 999-1004
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to develop suitable non-destructive evaluation (NDE) methods for detecting the creep damage and estimating the residual life of the machine parts used at high temperatures, the metallurgical observations and hardness tests were conducted on the crept specimens and the long-term serviced samples of Cr-Mo-V Steel.
    The results obtained are summarized as follows:
    (1) The damaged grain boundary observation method, the void density method and the hardness method were proposed as the NDE methods based on the results of investigation on the crept specimens under the uniaxial constant stress condition.
    (2) Moreover, these NDE methods were found to be applicable to the parts subjected to long-term service under a multiaxial stress state.
    (3) Among these NDE methods, the damaged grain boundary observation method makes it possible to evaluate creep damage and residual life without creep rupture data. Therefore, this method is considered as the most suitable one.
    (4) However, since the NDE inspection of actual components should be conducted as quick as possible, a proper combination of the above various NDE methods is recommended.
  • 赤城 協, 神保 勝久, 中村 孝, 浦井 隆宏, 永井 文雄, 松尾 陽太郎
    1987 年 36 巻 408 号 p. 1005-1011
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    In this work, a proto-type high-pressure fatigue testing machine capable of generating high internal pressure and high frequency up to 15Hz with high efficiency was constructed first, and then it was used to carry out a repeated internal pressure test for A2017-T4 cylindrical specimens. It was found through Weibull statistics that there are three peaks in the time-strength distribution and each peak is closely connected with the fractographical feature. A new estimating method of fatigue limit using Weibull's location parameter was suggested.
  • 岡部 永年, 伊藤 洋茂, 平田 英之, 村松 正光
    1987 年 36 巻 408 号 p. 1012-1017
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Strength properties of Ceramics depend upon the shapes, sizes and location of initial flaws, and so they have the strength of significant different levels and dispersions owing mainly to the difference of testing modes or the shapes and sizes of specimens even though the material was taken from the same lot. Therefore, an estimating method for ceramic strength, based on a modified Weibull analysis, was studied in this paper for finding the common property parameters as material constants independent of testing methods or shapes and sizes of specimens. Common Weibull modulus m0 was estimated by Weibull analysis for the values of fracture strength normalized by a mean value of that by each testing method, and was applied to analyze the effective volume of specimens in each test. Finally the strength property parameter σ0 was derived from scale parameter. Weibull modulus m0 was treated as a determined value and the confidence of measured values was considered only about σ0. Consequently, by using these two parameters m0 and σ0, the fracture strength of ceramics can be estimated with regard to failure probability Pf, confidence level 1-γ and sample size n as follows.
    σf0m0√2nln(1-Pf)-1/Veffχ2(2n, 1-γ)
    The estimating method proposed in this paper is very useful for estimating the design allowable stress and determining safety factor in ceramic structural design based on reliability engineering.
  • 吉村 達彦, 伊藤 泰彦
    1987 年 36 巻 408 号 p. 1018-1020
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    It is important for a vehicle designer to predict the input load spectrum to vehicle parts. The statistical analysis of small traces in the recovery parts is one of the load prediction methods applicable for this purpose. But, there are two difficult points to analyze those data as follows.
    (1) The time when those traces took place is not given.
    (2) The statistical distribution of samples is not equal to the distribution of the population.
    In this report, the method to obtain the distribution of the population from the above-mentioned data is discussed.
  • 市川 昌弘, 高松 徹
    1987 年 36 巻 408 号 p. 1021-1024
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Evaluation of the elastic-plastic fracture toughness JIc using side-grooved specimens requires introduction of the so-called effective specimen thickness Beff. At present, three different equations of Beff are known. These are Beff=√B0BN, Beff=B0-(B0-BN)2/B0 and Beff=BN, where B0 is the gross specimen thickness (thickness apart from the side-groove) and BN is the net specimen thickness (thickness at the bottom of the side-groove). In ASTM Standard Test for JIc, Beff=BN is used for calculation of J, but its validity does not seem to have been fully confirmed. Thus, this paper examined experimentally which one is appropriate among the above three equations. Experiments were carried out using side-grooved compact tension specimens of 2024-T3 Al alloy. The net specimen thickness BN was chosen so that BN>25JIcfs was satisfied. J was calculated using the well-known formula J=(A/Bb)f(a/W). Substituting each of the above three equations of Beff for B, JIc was estimated and compared with the value of JIc as obtained from the non-side-grooved specimen. It was found that there exists a case in which Beff=√B0BN or Beff=B0-(B0-BN)2/B0 is more appropriate than Beff=BN. This result is useful in further investigations of the effective thickness.
  • 大津 政康
    1987 年 36 巻 408 号 p. 1025-1031
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The development of mathematical theory of acoustic emission (AE) is summarized, and a waveform analysis of the moment tensor solution is proposed. On the basis of the theory, vertical surface motions (AE) in the disbonding process of stainless overlay were simulated, determining source characteristics from the observation of a micrograph. It is confirmed that a simulated displacement agrees quite well with a detected AE waveform up to the arrival of reflection waves, including the scale of amplitude.
    To check the effect of the inclined angle on results of the deconvolution analysis, simulated waveforms were deconvoluted with error on the inclination angle. According to the results, unless the inclination angle is correctly known, the source time functions obtained may include considerable error except for a rise time. It implies that the determination of crack orientation is of significant importance, before attempting the deconvolution analysis.
    The applicability of the moment tensor solution was investigated by numerical experiments for inclined tensile and shear cracks. Simulated AE waveforms in a half space were employed, and then components were determined within 8% discrepancy. The results of the eigenvalue analysis show a great promise of the moment tensor solution for determining the crack type and the crack orientation.
  • 2. 設計の実例 ボイラ
    瀬戸口 克哉
    1987 年 36 巻 408 号 p. 1032-1038
    発行日: 1987/09/15
    公開日: 2009/06/03
    ジャーナル フリー
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