材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
37 巻 , 420 号
選択された号の論文の21件中1~21を表示しています
  • 西橋 秀一, 篠塚 正宜
    1988 年 37 巻 420 号 p. 984-988
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The response variability of structures is generally caused by random loading and/or random structural properties. Recently, attempts to deal with interpretation of material properties as a problem of random fields have received considerable interest from engineers and researchers, and the finite element analysis combined with a Monte Calro simulation technique or perturbation method has been proposed to evaluate the response variability of structures.
    In this paper, the response valiability of linear structures under spatial variation of elastic properties (in this case, flexibility) is investigated. Utilizing a Green's function formuration, the mean square statistics of statically determinate beams and, more importantly, statically indeterminate beams are determined in a simple integral form which can be readily evaluated by the numerical method in negligible computer time.
    Using the fixed end beam model under uniform loading, the response variabilities of beam end moment and deflection were expressed in terms of random variables which were mutually correlated and were evaluated using the First-Order Second-Moment method. Due to the generality of the present approach, it seems feasible to treat a larger system (e.g. multi-bay/multi-story frames) with acceptable numerical effort. Finally, the safety indices for the beam midspan deflection and end moment were evaluated using two standard method (i.e. Lagrange's multiplier method and Advanced First-Order Second-Moment method).
  • 古田 均, 白石 成人
    1988 年 37 巻 420 号 p. 989-995
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper attempts to apply the concept of fuzzy sets theory to the reliability analysis of redundant structures with damage. Damage state is represented in terms of fuzzy sets which specify several linguistic variables such as “severely damaged”, “moderately damaged”, “slightly damaged”, etc. In the formulation of the reliability analysis, information regarding the damage state can be introduced coupling with the PNET method. While the PNET method is useful to calculate the system reliability of structures, it requires to identify all the possible failure mechanisms. As the number of failure mechanisms increases, it becomes more difficult to find all the possible failure mechanisms. To overcome this problem, we employ a technique proposed by Ishikawa et al. which can provide us of the sufficient number of dominant failure mechanisms. A numerical example is presented to illustrate the method proposed herein.
  • 鶴井 明, 田中 泰明
    1988 年 37 巻 420 号 p. 996-1002
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    As the first step for a probabilistic LBB (Leak Before Break) evaluation, the random propagation of surface cracks of semielliptic type was investigated by considering the randomness of loading and material properties. First, by the use of a Markov approximation metod, the joint probability density function of surface length and depth of a surface crack was derived in a closed form, under the assumption that the shape of surface crack is always semi-elliptical and the well-known Paris' fatigue crack propagation law is applicable for its propagation in both surface and depth directions.
    Next, a failure criterion for the two-dimensional crack propagation was constructed. Based upon this criterion, the so-called residual life distribution was theoretically derived by the use of the crack length density function. Finally, a more detailed form of the residual life distribution function under stationary random loading was studied under the condition that the material property was not random, and its qualitative behavior was clarified by numerical calculations.
  • 城野 政弘, 菅田 淳, 宮崎 健一, 大森 武
    1988 年 37 巻 420 号 p. 1003-1009
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Reversed plane bending fatigue tests were conducted on two kinds of structural steels, JIS S35C and SCM435. The behavior of small surface cracks were continuously sampled by replica technique, and their probabilistic properties were investigated. The distributions of fatigue crack initiation life and fracture life were found to be represented by log-normal distributions. The fatigue crack growth rate of S35C in the range of crack length from 0.1mm to 3mm could be expressed by the equation of da/dn=C·σa7.7·a1.3, where σa and a are the stress amplitude and a half of surface crack length, respectively. It was found that the distribution of coefficient C also obeyed a log-normal distribution and its variance was nearly constant irrespective of magnitude of stress amplitude and crack length. Some trials to estimate the distribution of fatigue crack growth life were made based upon the above mentioned experimental results of growth rate.
  • 市川 昌弘, 秋田 敏, 高松 徹, 松村 隆, 佐藤 守夫, 西島 敏
    1988 年 37 巻 420 号 p. 1010-1016
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    With an aim to establish a probabilistic model for fatigue crack growth rate da/dN from a reliability engineering point of view, a DC electrical potential system was developed to measure the crack length automatically as a function of the number of repeated cycles during fatigue tests. The crack length measured at an arbitrary interval of the number of stress cycles was fed into a personal computer, and processed in real time. This personal computer was also used to control the applied load precisely. To examine the performance of the system developed, preliminary tension-tension fatigue tests were carried out on the center-cracked specimens of 2024-T3 Al alloy under the condition of the constant stress range and the constant stress ratio. The relation between the electrical potential and the crack length was first determined using four specimens, and a sixth order polynomial was obtained for this relation. Then, statistical data of da/dN were obtained using eighteen specimens. The scatter band of the log da/dN vs. logΔK plot of the whole data was narrower than that in our previous tests in which a travelling microscope was used for crack length measurement. This result shows that the electrical potential system developed works well. The maximum error of the system in crack length measurement was about 50μm. The coefficient of variation of the crack propagation life was also smaller in the present test than in the previous test. This is considered due to that the applied load and the temperature were controlled more precisely than in the previous test. Thus, the system developed enables to obtain statistical data of the fatigue crack growth rate accurately and efficiently.
  • 三道 弘明, 中川 隆夫, 藤井 進, 谷尻 裕之
    1988 年 37 巻 420 号 p. 1017-1021
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    In statistical analyses of life data, the Bayesian approach regards parameters of the underlying life distribution as random variables to cope with the uncertainty included in estimates of these parameters as well as to make use of the prior information. The Bayesian method also enables us to deal with the reliability of a product or a part as a random variable since the reliability is expressed as a function of the parameters. This indicates that the reliability can be guaranteed to be larger than a specified value in terms of probability by adopting the Bayesian method.
    Based on this idea, the present study considers a method for analyzing fatigue life data which usually include censored data, assuming a log-normal distribution as the underlying life distribution. The proposed method provides an estimate for the fatigue life whose reliability can be guaranteed to be larger than a specified value with specified probability. Numerical examples are also examined to clarify the characteristics of the proposed method and to show its effectiveness. Through the examination of numerical examples, it is verified that the proposed method provides conservative estimates for both complete data and censored data. It is also shown that the proposed method considerably reflects the specified guarantee probability for complete data, but guarantees the reliability with larger probability than the specified for censored data.
  • 三木 光範, 室津 義定, 酒井 利彦
    1988 年 37 巻 420 号 p. 1022-1028
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    A database for the mechanical properties of advanced composites was developed. The data were obtained from the research and development project of composite materials for future industries supported by the Ministry of International Trade and Industry (MITI). This paper deals with the statistical analysis of the tensile and flexural strengths of fiber reinforced plastic (FRP) based on this database.
    The present analysis consists of the following three parts: (1) the calculation of basic statistical properties, the calculation of parameters of Weibull distribution, and the testing of goodness-of-fit for the primary populations where the sample size is larger than 10, (2) the clarification of the effects of various factors such as hybridization, discontinuousness of fibers, temperature, thermal aging, orientation, and matrix properties on the mean strength and the variation, and (3) the clarification of statistical properties of the parameters of the strength distribution.
  • 松原 雅昭, 岡村 弘之
    1988 年 37 巻 420 号 p. 1029-1035
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper presents an application of Fracture Mechanics for a statically indeterminate structure to a pressurized thermal shock (PTS) problem of pressure vessel of PWR. This method is efficient to clarify the mechanical characteristics of PTS event. The following results were obtained:
    1) Stress intensity factor (K) under PTS is affected by the compliance of the shell of pressure vessel.
    2) The bending moment occurred by flexural constraint is important for K under PTS.
    3) As a new test method of PTS simulation with high precision, 4-point bending of a plate with axial load is proposed.
  • 宮田 隆司, 大塚 昭夫, 奥山 彦治
    1988 年 37 巻 420 号 p. 1036-1042
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effects of stress state on ductility and fracture appearance in shear type ductile fracture of aluminium alloys 2017-T4, 5052-0 and a structural steel SM50B were investigated in comparison with those in fibrous ductile fracture. Thin walled cylindrical specimens were used for the tests under combined tension-torsion loading to obtain the shear fracture under various biaxial states of stress. Fractographic observation showed the micro-void nucleation and growth played an important role in shear fracture as well as in fibrous fracture. Ductility in shear fracture varied with the stress triaxiality (or the stress ratio of tension to torsion) and took a smaller value than in fibrous fractures. Shear fracture always occurs preceded by macroscopic shear band formation and the variation of ductility with stress triaxiality can approximately be explained by the micro-void nucleation and growth model in shear band. Whether the shear fracture precedes the fibrous fracture depends on the material and geometrical configuration of the specimen.
  • 新保 實, 植木 正憲, 宮野 靖, 石原 昌作, 藤田 毅
    1988 年 37 巻 420 号 p. 1043-1049
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The compressive strength of partially stabilized zirconia with 4-8mol% yttria was investigated in a relatively wide range of temperature. In each yttria-added material, the amount of metastable tetragonal (T) phase decreased with increasing yttria content and this was accompanied by fracture strength decrease by decrement of the T phase. The strength also decreased with increasing test temperature in the experimental range, and the magnitude of the temperature dependence became less important with increasing yttria content. In the case of 4mol% yttria stabilized zirconia, the fracture strain increased with temperature up to 450°C, but beyond this temperature, it decreased with increasing temperature. However, in the case of 6 or 8mol% yttria added zirconia, the fracture strain decreased monotonically with temperature. The fracture mode in the compression test could be roughly classified into three categories in a simple map representing the relation between yttria content and test temperature. Although almost all of the stress-strain curves retained their linearity until fracture occured, a peculiar shape of the curve exhibiting yield point and subsequent plastic deformation was observed in 4mol% yttria stabilized zirconia tested at temperatures between 400°C and 500°C.
  • 康井 義明, 塚村 清
    1988 年 37 巻 420 号 p. 1050-1056
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The buckling behavior associated with composite plates containing a cut-out portion is a deeply interesting engineering problem. Here the buckling strength of cross-ply laminated rectangular plates with a cut-out under axial compression was demonstrated by numerical analysis. The composite materials treated were carbon-fiber/epoxy (CFRP) and glass-fiber/epoxy (GFRP) plates. The configuration of cut-out was a square hole having round corners or a circular hole which is centrally located in the FRP plate.
    Because of the complexities of the problem, respective geometry and material properties, the finite element method with automatic mesh divisions was used both for the prebuckling stress state and the buckling phase. The buckling loads for various cut-out dimensions and buckling pattern modes for different aspect ratios of rectangular plates were elucidated in the present study.
  • 竹下 達郎, 松尾 圭造, 杉林 俊雄, 池上 皓三
    1988 年 37 巻 420 号 p. 1057-1063
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The strength evaluation of adhesive scarf joints under tensile load was investigated both analytically and experimentally. The scarf joints were constructed by two adherends of glass cloth laminated plastic (GFRP) and metal (carbon steel, brass, copper, or aluminium alloy). The adhesive was epoxy resin. The strain and stress distributions in the joints were analyzed by applying the elastic finite element method. The analytical strain distributions were in good agreement with the experimental ones.
    The strength of the joints was predicted by applying the strength laws to the adherends, adhesive layer and their interfaces. The joint strength depended on the adhesive strength or interfacial strength for short overlaps, and depended on the strength of metal adherend for long overlaps. The overlap length have little effect on the initial failure stress of the joints for the case of the adherends of copper, brass and aluminum alloy.
  • 岩本 正治, 自念 榮一, 鈴木 惠
    1988 年 37 巻 420 号 p. 1064-1070
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to investigate microscopically the effects of crystallinity and temperature on the fatigue crack growth behavior of polypropylene, the microfractographs were discussed based on the fatigue crack growth curves (a-N curves).
    The results obtained were as follows:
    (1) Two kinds of damage zone occurred at the crack tip during the fatigue crack growth process: The one in which the spherulite structure is broken down and the other not so. It was found that the former zone was accompanied with an intrusion on the specimen surface and crazes appeared in the bottom of intrusion at 20°C. However, it was difficult to find the crazes at temperatures below 0°C.
    (2) The effects of crystallinity and temperature on the fatigue crack growth behavior were studied by microfractographs for the cases showing three different shapes of macroscopic a-N curves. In the case where the a-N curve showed the step-wise shape, the voids occurred in the transition from the decelerated zone to the accelerated zone of crack growth and the crack grew discontinuously. Furthermore, a different and peculiar fracture surface appeared at the non-propagating zone as well as at the accelerated zone. The specimen in which the stable crack growth hardly took place and the unstable fracture occurred suddenly, showed the flat and brittle fracture surface.
  • 伊原 千秋
    1988 年 37 巻 420 号 p. 1071-1076
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The growth behavior of small fatigue cracks is clearly different from that of long fatigue cracks. In this paper, a growth law of small fatigue cracks is proposed based on the stochastic damage accumulation model for long fatigue crack growth. It contains the following three parts. (1) The growth rate of small crack growing in a grain is proportional to some power of the process region which is limited by the grain boundary. (2) A transgranular small crack propagates into the next grain over the grain boundary, when the stress is beyond the fatigue limit. (3) A small crack growing through the noncontinuum propagation begins the continuum one, when the plastic zone size of crack tip becomes larger than the average grain size. Many experimental facts about small fatigue cracks are explained on the basis of this growth law.
  • 小倉 敬二, 三好 良夫, 西川 出, 中尾 康孝
    1988 年 37 巻 420 号 p. 1077-1083
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Near threshold fatigue crack growth and closure of a low carbon steel (0.18%C) with the duplex microstructure of ferrite-martensite were investigated. The highest value of 12MPa√m in the fatigue threshold stress intensity range, ΔKth, was obtained on a sample whose microstructure contained globular martensite in ferrite matrix with 47% in the volume fraction of martensite, among all the samples tested in the study. The threshold value, however, was less than those reported on AISI1008 and Fe/2Si/0.1C steels by Ritchie and his coworkers. No significant increase in ΔKth was observed in the microstructure where a continuous martensite phase encapsulated islands of ferrite. It was concluded that the excellent fatigue crack growth resistance at threshold in duplex steels was attributed to the optimum combination of the true crack growth resistance, ΔKeff, th, and the crack opening level, Kop.
  • 結城 良治, 秋田 清司, 岸 成人
    1988 年 37 巻 420 号 p. 1084-1089
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue tests have been conducted on the cruciform flat specimens of a stainless steel with a center crack by using a high-cycle biaxial fatigue test facility, in order to investigate the effect of biaxial stress on the fatigue crack growth properties ΔKI-da/dN. From the comprehensive experiments, no effect of biaxial stress was found on ΔKI-da/dN relation, if the crack was large and the stress level was low. However, a significant effect of biaxial stress appeared when the crack was small and the stress level was high.
    In this paper, the critical region where the effect of biaxial stress appears was clarified quantitatively, based on the crack length measured and the stress level used in the biaxial fatigue tests.
    Moreover, the effect of changing biaxial stress condition on the fatigue crack growth properties ΔKI-da/dN was investigated. Significant acceleration of the crack propagation was observed just after the uniaxial or equibiaxial stress condition was changed into the shear stress condition. This acceleration cannot be explained by the crack closure and one of the reasons for this acceleration seems to be the change of plastic zone shape at the crack tip.
  • 小寺沢 良一, 納所 孝至
    1988 年 37 巻 420 号 p. 1090-1096
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    High temperature low-cycle fatigue crack propagation behaviour of SUS 304 stainless steel under typical four types of reversed loading patterns (P-P, P-C, C-P and C-C type) was investigated, and the results were discussed in the light of fracture mechanics and electron fractography. The stress intensity factor range ΔK failed to describe the crack propagation behaviour adequately. In the case of loading with tension hold (i.e. C-P and C-C type), the crack propagation rate was successfully correlated with the modified J-integral J and agreed with the static creep crack propagation rate. The crack propagation rate for all of the four types of loading was successfully correlated in terms of the cyclic J-integral range ΔJ, and it was unnecessary to separate ΔJ into ΔJf and ΔJc. The crack propagation rate for the types of loading without tension hold or with short tension hold time (i.e. P-P and P-C type, and C-P and C-C type with comparatively short tension hold time) was successfully correlated with ΔJf, and that long tension hold time (i.e. C-P and C-C type with comparatively long tension hold time) was successfully correlated with ΔJc. The fracture surfaces of the case where the crack propagation rate was correlated with ΔJf were predominantly transgranular fatigue type, that is, fracture morphology and correlating fracture mechanics parameter (ΔJf) were of the same type (fatigue type). On the other hand, those of the case where crack propagation rate was correlated with ΔJc were transgranular fatigue type or intergranular creep type or mixed type depending on the condition, that is, fracture morphology and correlating fracture mechanics parameter (ΔJc) were of different type in some cases.
    There was no significant effect of creep-fatigue interaction on the crack propagation under the combined creep and fatigue conditions, and crack propagation may be assessed by a simple summation of fatigue component and creep component.
  • 下平 益夫, 松岡 三郎, 升田 博之, 西島 敏
    1988 年 37 巻 420 号 p. 1097-1103
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Near-threshold fatigue crack growth properties and fractographic features in 3% NaCl aqueous solution were studied for high tensile steels SM50B and HT80, carbon steel S45C and stainless steels SUS304 and SUS403, under the condition where crack closure did not occur. The results obtained are summaried as follows:
    (1) In air, fatigue crack growth properties were independent of the type of materials. The threshold values, ΔK, were equal to about 2.5MPa·m1/2.
    (2) Under the freely corroding condition in 3% NaCl solution, fatigue crack growth properties at a frequency of 30Hz coincided with those in air, when the stress intensity range, ΔK, was higher than 3MPa·m1/2. However, the ΔKth values were about 1MPa·m1/2 for high tensile and carbon steels, and about 1.7MPa·m1/2 for stainless steels.
    (3) Decrease in frequency from 30Hz to 0.3Hz resulted in a sixfold acceleration of crack growth rate under the freely corroding condition.
    (4) Under cothodic protection, fatigue crack growth properties including threshold were coincident with those in air at both frequencies of 0.3 and 30Hz.
    (5) Under the freely corroding condition, the crystallographic fracture mode was observed near the threshold for stainless steels, while the fracture surfaces were dissolved for high tensile and carbon steels.
    (6) Under cathodic protection, the fracture mode was transgranular at the region of ΔK<5MPa·m1/2, while the intergranular cracking was formed at the region of ΔK≥5MPa·m1/2.
  • 津田 大, 伊藤 太一郎, 中山 豊
    1988 年 37 巻 420 号 p. 1104-1110
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    The improvement of mechanical properties by a thermomechanical treatment (TMT) has been investigated on a Ti-added Cu-Ni-Al alloy. Characteristics in microstructure and rolling texture were examined in relation to the mechanical properties.
    In the thermomechanically treated Cu-Ni-Al-Ti alloy, the hardness, 0.2% proof stress and ultimate tensile strength reached the maximum values of 275Hv, 120kg/mm2 and 121kg/mm2, respectively.These values were much higher than those obtained in similarly treated Cu-Ni-Al alloys. The hardness increment of 100Hv obtained by cold rolling for the Cu-Ni-Al-Ni alloy was extremely higher than that of 60Hv for a Cu-Ni-Al alloy.
    The transmission electron microscopy of the preaged and cold rolled Cu-Ni-Al-Ti alloy indicated that deformation proceeded only in matrices and the concentrated stress in matrices leads mechanical twinning. X-ray pole figures on {111} reflection showed that the rolling texture was changed into an alloy type from a pure metal type observed in a Cu-Ni-Al alloy.
  • 芳賀 裕, 中島 正久, 四十宮 龍徳
    1988 年 37 巻 420 号 p. 1111-1117
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
    Cadmium sulfide (CdS) was encapsulated in the styrene-acrylonitrile copolymers (C-St·AN-CdS) by the encapsulating polymerization process. The compositions of the encapsulating copolymer and homocopolymer were determined by the elementary analysis. The monomer reactivity ratios were obtained by the Fineman-Ross method, and the reaction behavior of the copolymerization was investigated. The monomer reactivity ratios for the encapsulating copolymer were considerably different from the value of the ordinary St-AN radical copolymerization, and those for the homocopolymer were almost the same.
    The photocurrent of C-St·AN-CdS increased considerably, as compared with CdS alone, in a particular range of the AN composition ratio. C-St·AN-CdS showed the maximum relative sensitivity at the AN composition ratio of 9.7mol%. Furthermore, the dark current-voltage characteristics, the light intensity dependence of photocurrent, and the damping characteristics of photocurrent were measured, and the photoconductive mechanisms of these C-St·AN-CdS were discussed.
  • 後藤 徹
    1988 年 37 巻 420 号 p. 1118-1124
    発行日: 1988/09/15
    公開日: 2009/06/03
    ジャーナル フリー
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