材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
29 巻 , 316 号
選択された号の論文の17件中1~17を表示しています
  • 山田 敏郎, 多田 和弘, 鹿野 裕
    1980 年 29 巻 316 号 p. 2-8
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fatigue life of 0.09%C Al-killed steel under program loading of multiple repeated two step stresses, which were composed of a over-stress and a under-stress, was investigated.
    The predicted fatigue life was calculated from the basic fatigue damage of one stress cycle: exp(Aσ+D) and the fatigue damage function: exp(Aσ+D)·exp(-mσpN'), by applying the authors' prediction method for fatigue life and endurance limit of metals under service loads1).
    It was found that the predicted fatigue life and endurance limit of the Al-killed steel were in good agreement with the tested values when the adequate values of m and p were applied.
    In the previous study1), it was reported that Aσα should be used as the basic fatigue damage for predicting the fatigue life of 0.11%C rimmed steel under the same program loading. The present study showed that exp(Aσ+D) is adequate as the basic fatigue damage in the case of Al-killed steel. Therefore, either Aσα or exp(Aσ+D) must be chosen depending upon the kind of metals in order to predict their fatigue lives.
    The crack growth rate was analyzed by the use of stress intensity factor and the ratio of the period of crack growth to the total life was obtained by counting the beach marks on the surface of fractured specimens.
    The scattering of fatigue lives in the neighborhood of fatigue limit under program loading was analyzed.
  • 福田 収一
    1980 年 29 巻 316 号 p. 9-12
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    The sensitivity study of linear fracture mechanics parameters in the estimation of fatigue life has been carried out in this paper with the aim of improving the estimation accuracy and serving for the rationalization of structural design, maintenance and inspection.
    Since the method of probabilistic sensitivity analysis which is known as the first-order-second-moment format seems to be quite difficult to apply in this case due to the lack of appropriate data, this paper describes the alternative method of deterministic sensitivity analysis which is also based on the first order approximation. The degree of importance of each linear fracture mechanics parameter can be easily evaluated by comparing the corresponding values of the partial derivative. This paper presents the evaluation equations for the case where ΔK can be approximated as ΔK=Δσ√πa, and it is shown that for 2<n≤4 and a2>>a1 condition, the degree of importance of linear fracture mechanics parameters on fatigue life is in the order of n>Δσ>C≥a1>a2, if C and n are evaluated independently. The same conclusions were obtained from two numerical examples for other conditions.
    As the result of this analysis, the parameter n turns out to be most influential on fatigue life, so that it is considered quite important to evaluate n as precisely as possible in order to prevent fatigue failure or to rationalize structural design, maintenance and inspection.
  • 鶴井 明
    1980 年 29 巻 316 号 p. 13-16
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    On the basis of crack propagation and crack arrest mechanisms, the distribution characteristics of fatigue endurance limit for the notched specimens of steel were investigated and an explicit expression for the distribution function was obtained. The calculated distribution function, which utilizes the parameters estimated from the experimental data of the depth of non-propagating cracks in the notched specimens of Cr-Mo steel, seemed to be a satisfactory one. The distribution function obtained was found to be skewed to the left.
  • 疲労寿命分布の母数推定に関連して〔続報〕
    酒井 達雄, 田中 道七
    1980 年 29 巻 316 号 p. 17-23
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    In reliability analysis of machines and structural members, it is important to clarify the fatigue life distribution of these engineering items, and Weibull distribution is often accepted as the original distribution of the fatigue life. Although various kinds of estimation procedures have been developed on three parameters of Weibull distribution, the statistical properties of each estimated parameter still remain unsolved for any estimation method.
    The authors performed the parameter estimation by means of several methods and discussed on the distribution characteristics of estimates of Weibull parameters. In this study, three different kinds of estimation were made on each parameter of Weibull distribution, and, the estimates obtained from the respective methods, including those given in the previous paper, were compared with each other in particular attention to statistical properties such as convergency or distribution of estimates. Finally, the most preferable method for parameter estimation of Weibull distribution was selected and quantitative discussions were also performed on the sample size required to determine, experimentally, the parameter of the original distribution.
  • 西島 敏
    1980 年 29 巻 316 号 p. 24-29
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    Statistical fatigue data of various materials at different conditions are increasingly required by engineers for reliabillity design purposes. The present paper describes a new way of analysing fatigue data, which is promising to take out maximum statistical informations from ordinary small sample test results. The method is essentially based on examining the distribution in relative strength deviation of individual test data, evaluated against the mean strength at the considered life level. The Probit analysis using weighting coefficients, under the condition of a known variation coefficient, is quite suitable for the mean strength estimation. Starting with a provisional variation coefficient, the test data could be transformed into a set of relative deviation values in strength; a real variation coefficient is then evaluated according to the theory of multiply censored order statistics.
    The proposed method could also be used most effectively in analysing a pile of small sample data sets plotted on a common strength scale, e.g., the ratio against tensile strength of the material.
  • 繊維含有量および温度依存性
    藤井 太一, 前川 善一郎, 土谷 敬一
    1980 年 29 巻 316 号 p. 30-36
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    Glass fiber reinforced cement (GRC) made by incorporating discontinuous random glass fibers into cementitious matrix is nowadays regarded as a useful material for civil engineering applications in order to increase the tensile strength and fracture energy, and to provide some degree of ductility in the behavior of the material. Since commercial composite materials possess generally a considerable scatter in their mechanical properties, understanding of the source and nature of the variability in GRC is considered to be very important for better utilization of this material. In this study, the mechanical behavior of GRC with various fiber contents was investigated in tensile tests from -30°C to 200°C. The main results obtained are summarized as follows;
    (1) The tensile strength distribution of GRC can be represented by a normal or Weibull distribution as same as those of other composite materials.
    (2) The stress-strain relation of GRC consists of two stages. The slope of the relation remains linear in the first stage. The subsequent change in the slope is caused by the pull-out of fiber and the microscopic failure of matrix. The fiber content and test temperature are found to have significant effects upon these mechanical behaviors.
    (3) The average and the coefficient of variation of the tensile strength of GRC were calculated by use of the law of mixture of strength and were found to agree with the experimental data. Furthermore, the influence of the constituent material on the strength of GRC was discussed.
  • 丹羽 一邦, 米沢 政昭, 大場 史憲, 室津 義定, 津村 俊弘
    1980 年 29 巻 316 号 p. 37-43
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    An optimum design problem was treated to determine a structure having a minimum structural cost or weight under the constraint on the allowable failure probability of the structure. A design method was proposed, which attains the optimum solution to the problem by sequentially solving a subproblem. The result was compared with that using SUMT (Sequential Unconstrained Minimization Technique) combined with a conjugate gradient method. Furthermore, the effects of the statistical correlation between the failure modes, the buckling failure mode of compression members, and the configuration of structures on the resulting optimum design of simple structures were discussed.
  • 中易 秀敏, 広瀬 浩一, 森 健一, 加瀬 滋男
    1980 年 29 巻 316 号 p. 44-50
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    A reliability and maintainability analysis by the Monte Carlo simulation technique is presented for the structural systems constructed with several subsystems and subjected to cyclic loading. Preexisting cracks in a subsystem grow up under the cyclic loading until the length of one of them reaches a critical value and the failure of the subsystem occurs.
    The structural system is inspected periodically by nondestructive methods. Whenever a crack is detected during the inspection, the structural strength of the system is renewed by the repair or replacement of the implicated member.
    The failure and maintenance of a model for analysis is simulated by the Monte Carlo technique developed for a special purpose. The recommended procedure enable us to evaluate the effect of inspection number on the reliability and availability of the system, and to find out the optimum policy for maintenance. A method of parameter sensitivity analysis is also described which gives the best way to improve the reliability and availability of structural systems.
  • 山本 義秋, 河本 実
    1980 年 29 巻 316 号 p. 51-56
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    When the results of fatigue tests are to be examined, it is important to represent S-N curves by numerical expressions. In the present study, various methods of representing the S-N curves by numerical expressions proposed in the past were examined. Emphasis was given to evaluate the characteristics and appropriateness of the conventional methods of expressing them.
  • 三浦 精, 遠藤 和宏, 浜島 和雄
    1980 年 29 巻 316 号 p. 57-61
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    It is known that at room temperature the tensile stress-strain curve of an aluminum single crystal having <100> tensile orientation becomes flat after about two percent elongation (this flat region of the stress-strain curve is named Stage IV). In the previous paper, the propagation of clustered slip accompanied by prominent cross slip was observed in the Stage IV region of curve.
    In the present study, the <100> oriented aluminum single crystals were tested in tension at various temperatures so as to clarify the influence of temperature on the deformation mechanisms in Stage IV.
    At 203K, a few clustered slip lines accompanied by prominent cross slip occurred, but they did not propagate in the entire region of the specimen, and the stress-strain curve became flat only from about ten percent elongation. In the crystal stretched at 77K, the cluster did not propagate at all from the both ends of the specimen, and so the stress-strain curve did not become flat.
    On the other hand, the wavy coarse slip was observed and the stress-strain curve became flat from about 0.5 percent elongation at 473K. It was suggested that these wavy slip lines were produced by frequent repetition of cross slip on two {111} planes and also possibly on {110} plane having the same slip direction.
    It was confirmed that the occurrence of Stage IV is caused by the propagation of the clustered slip accompanied by prominent cross slip and is much influenced by the temperature of deformation due to the easiness of cross slip.
  • 田中 啓介, 藤山 一成, 中村 研
    1980 年 29 巻 316 号 p. 62-68
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fracture toughness tests of a structural low-carbon steel SM41B were conducted at low and ambient temperatures. The electrical potential method was successfully used for determining the crack nucleation point and the amount of crack extension. The effect of test temperature on the fracture toughness JIc was discussed in correlation with the results of X-ray diffraction observation of plastic strain on the fracture surface. The plastic strain measured on the fracture surface in the close vicinity of pre-fatigue cracks was found to be proportional to the fracture toughness divided by the flow stress, thus to the crack-tip opening displacement. The fracture surface strain increased with crack extension in the cases of dimple fracture and was nearly constant in the cases of cleavage fracture. The change of fracture surface strain with crack extension corresponded to the resistance change of material. A more detailed examination indicated that the fracture surface strain was given by the sum of strains accumulated before and after the mechanical instability for fracture.
  • 中山 英明, 金山 幸雄, 式田 昌弘
    1980 年 29 巻 316 号 p. 69-74
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    As one of the investigations to reveal the effect of impact load on the fatigue behavior, i.e., fatigue life, fatigue crack initiation and propagation, a series of fatigue tests was conducted with a cantilever type rotating bending fatigue testing machine equipped with an impact loading device under two sorts of program load patterns; one is the impact program load condition in which the maximum bending stress followed by the transitional decaying vibrational load appears by an impact load at the rise time of the primary stress and another the ordinary periodical 2-step program load condition.
    Here, annealed 0.23%C carbon steel specimens with a small hole on the plane of the minimum sectional area were used to observe the behavior of fatigue crack initiation and propagation during the fatigue process. The experimental results were discussed from two points of view; the equivalent number of overstressing cycles and the cumulative damage in the modified Miner's rule concept.
    From the comparison of the equivalent number of overstressing cycles for crack initiation with that for fatigue failure, it was concluded that the impact program load pattern like the one in this experiment is more detrimental to propagate fatigue cracks than to initiate those. Such a fatigue behavior in the impact program condition is also recognized from the discussion based on the cumulative damage in the modified Miner's rule concept, that is, the ratio of the cumulative damage for crack initiation to that for fatigue failure takes generally a higher value than the value in nonimpact fatigue load conditions.
  • 下河 利行, 浜口 泰正
    1980 年 29 巻 316 号 p. 75-81
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    The relationship between the S-Ñ curve, where Ñ is the median fatigue life, and empirical fatigue life distributions obtained from a fairly large number of specimens has been analyzed using two groups of data, i.e., five data for steels and seven data for aluminum alloys collected from published papers and books. The distribution shape of fatigue life is found to be related to the shape of the S-Ñ curve in the neighborhood of the test stress level. To compare the quantitative relationship between the scatter of fatigue life and the slope of the S-Ñ curve in various test data, the test stress levels were standardized by the median fatigue strength at 105 cycles in each data, and the standardized S-Ñ curves, where“standardized”means the use of such standardized stress levels, were drawn. The standard deviation of log-life in either steels or aluminum alloys has an obvious linear relation on double logarithmic graph paper with the slope of the standardized S-Ñ curve at the test stress level. The distribution of the median fatigue strength corresponding to each fatigue life obtained at one stress level is normal in shape and its standard deviation is approximately constant regardless of test stress levels in each data.
    On the basis of these results, a method for estimating fatigue life distribution was developed when available information is limited either to a simple S-N curve only or to the original fatigue life data for the construction of such an S-N curve.
  • 松山 高康, 冨高 精蔵, 土肥 祥壮
    1980 年 29 巻 316 号 p. 82-87
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of hydrogen on the ductility of tantalum single crystal was investigated in the temperature range of 77-396K using a variety of techniques including observation by the S.E.M., tensile testing, X-ray radiography, and electric resistivity methods. The solid solution of hydrogen in tantalum was shown to be highly ductile at temperatures above 300K. The ductility of the solid solutions decreased rapidly at temperatures below 300K, and was minimum at about 200K. The fracture mode was cleavage at the temperatures in the region of ductility minimum, while it was ductile at temperatures near 77K. The factors affecting the above embrittlement are considered to be inhomogeneous distribution of hydrogen in the specimen and formation of stress induced hydrides. The ductility near 77K may be caused by very slow diffusion of hydrogen at that temperature.
  • 前田 修, 片山 祐三, 小林 正人, 田中 一雄
    1980 年 29 巻 316 号 p. 88-93
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    CFRP insert molding method was proposed for application to mechanical components such as print hammers used for an ultra high speed line printer. In this technique, CFRP sheet acts as an insert and is surrounded with resin injected by the transfer molding method. The main problems of this method are (1) poor adhesion between insert and injected resin when a hardened insert is employed, and (2) insert strength drop due to fiber misalignment, which appears when resin is injected into cavities with slightly hardened insert. This paper describes the results of investigation on these problems and impacts strength of print hammers made by the CFRP insert molding method.
    The results obtained are summarized as follows.
    (1) The interfacial shear stress between insert and injected resin can be determined by measuring the force requird to pull out an insert sheet embedded in matrix resin. The interfacial shear stress increased by molding the CFRP sheet at 150°C for 3 minutes and coating a bonding agent on the CFRP sheet.
    (2) Fiber misalignment of insert was avoided by employing cross CFRP and low pressure resin.
    (3) The printing life time of print hammers made from the treated insert by the CFRP insert molding method was about 103 times that of the print hammers made from the untreated insert.
  • 門側 幸宏, 山手 有
    1980 年 29 巻 316 号 p. 94-98
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
    To obtain the glass-forming condition of the binary mixtures consisting of alkali (Li, Na, or K) and magnesium nitrates, the dehydration processes were investigated by means of thermogravimetry.
    The reaction rate of initial dehydration and the water content of dehydrated mixture were measured for 18 samples, of which compositions are shown in Table I. The results shown in Table II indicated that the both measured values were not correlated directly to the glass-forming ability.
    However, the glass-forming was not observed if the rate constant of dehydration was less than 0.12. On the other hand, the concentration of alkali nitrates had a significant effect to the glass formation. Unless the concentration of alkali nitrates exceeded a certain value in each binary system, the glass-forming did not take place (see Fig. 8-10).
    Therefore, it is concluded that the glass-forming may be restricted to the following two conditions; (i) the dehydration rate constant is more than 0.12 and (ii) the concentration of alkali nitrates exceeds a certain value in each binary system.
  • 1. 疲労破面と転位組織
    片桐 一宗, 粟谷 丈夫
    1980 年 29 巻 316 号 p. 99-105
    発行日: 1980/01/15
    公開日: 2009/06/03
    ジャーナル フリー
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