材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
35 巻 , 389 号
選択された号の論文の20件中1~20を表示しています
  • 瀬口 靖幸
    1986 年 35 巻 389 号 p. 95-105
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 佐藤 清
    1986 年 35 巻 389 号 p. 106-108
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The influences of loading rate on fracture toughness, internal bond strength and bending strength, and the effect of notch root radius on fracture toughness were experimentally studied at room temperature for a medium density fiber board.
    The results obtained are summarized as follows:
    (1) Fracture toughness Kc is independent of both loading rate and notch root radius.
    (2) Internal bond strength is independent of loading rate.
    (3) Bending strength increases with increasing loading rate.
  • 小林 康男, 吉田 進
    1986 年 35 巻 389 号 p. 109-113
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Characteristics of fatigue crack growth in DP (with dual-phase, ferritic-martensitic microstructure) steel sheets have been investigated. SPHC (hot-rolled mild steel) sheets also have been examined for the purpose of comparison. For the both materials, the variation in fatigue crack growth rate (da/dN) with stress intensity factor range (ΔK) was measured by using CCT specimens, as well as the threshold values of ΔK by using CT specimens.
    From the results of these measurements, m in the formula of Paris, da/dN=CK)m, was determined as 3.5 for DP steel as well as for SPHC steel. The threshold values (ΔKth) at R=0.1 were shown as 6.5MPa·m1/2 and 5.7MPa·m1/2 for DP and SPHC steels, respectively.
    It is concluded that the characteristics of fatigue crack growth in DP steel sheet with a microstructure where a continuous ferrite matrix encapsulates islands of martensite are little different from those in conventional mild steel sheets.
  • 津田 大, 伊藤 太一郎, 中山 豊
    1986 年 35 巻 389 号 p. 114-119
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Mechanico-thermal treatment (MTT) is one of the effective methods to improve mechanical properties of alloys. In the present study, an improvement in mechanical properties of Cu-7.5 at%Ni-2.5 at%Al alloy by MTT was undertaken in comparison with those of simply aged specimens.
    By MTT, hardness, 0.2% proof stress (σ0.2) and ultimate tensile strength (UTS) have increased at room temperature, and arrived their maximum values by ageing for a remarkable shorter time than those of simply aged specimens. The important point is that σ0.2, UTS and total elongation are much improved at the elevated temperature as high as 500°C.
    To study the origin of strengthening by MTT, thin foils were observed in a transmission electron microscope. In MTT specimens, the deformed structure disappeared perfectly and recrystallized to fine grains by ageing at 500°C for 0.1hr. In contrast with simply aged specimens, very small precipitates were observed within these grains, and the discontinuous precipitates around grain boundaries were scarcely observed. These characteristics in the microstructure would contribute to the strengthening of MTT specimens.
  • 辻 宜秀, 喜田 義宏, 井戸 守
    1986 年 35 巻 389 号 p. 120-125
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    As a fundamental study of grinding mechanism, a single grit grinding test was performed, and the effects of heat treatment condition of steel on the metal removal mechanism and chip shape were investigated. The relation between the cutting speed or the shape of tool and the chip shape formed under different heat treatment conditions was also examined.
    After the chip forming process in the single grit grinding had been frozen by a quick stop device, the chip shape and material behavior ahead of the rake face were observed on the cross section of the chip through optical and electron microscopes.
    It was found from the detailed observations that, in the case of thin chip (about 30μm in thickness), slips cause by secondary shear occurred inside the chip and the temparature of the shear plane rose so high as to soften the steel. Next moment, a white hardened layer was formed on the slip plane as the result of rapid cooling. In quenched steel, as the chip was pushed out to the tool face, it became thin and long by the removal mechanism of workpiece. The chip shape developed into a flow type in the normalized steel, and a shear type in annealed steel under the condition of a cutting speed of 460m/min and an apex angle of 100°. As the cutting speed increased, the chip became smaller, and as the apex angle of cutting edge increased, the chip became longer and wider in all of the three conditions of heat treatment used in this test.
  • Fe2O3,NiO,Cr2O3およびMnO2の影響
    三浦 嘉也, 高橋 克明, 浅田 雅之
    1986 年 35 巻 389 号 p. 126-132
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fundamental electrochemical behavior of molybdenum was investigated in a commercially important glass (Na2O-CaO-SiO2) with various additives such as Fe2O3, NiO, Cr2O3 and MnO2 by means of linear potential sweep voltammetry at 1400°C. The molybdenum-glass interface after polarization was also analysed by EPMA.
    The cathodic current in the initial applied potential region was larger in the additive-containing glass than in the glass with no additive. The additives were reduced predominantly to the metallic state at the initial potential but reduced together with silicate anions at higher potentials and made alloys with Si and Mo.
    The additives were more or less effective to promote oxidation of molybdenum. Fe3+ ions oxidized molybdenum to MoO2 by the reaction 2Fe2O3+Mo=4FeO+MoO2G=-35.2kcal/mol). Ni2+ ions showed marked oxidizing power by the reactions 2NiO+Mo=2Ni+MoO2G=-26.4kcal/mol) and 3NiO+Mo=3Ni+MoO3G=-10.6kcal/mol). Cr6+ and Mn3+ ions should also have marked oxidizing power but the respective redox equilibrium in the soda-lime-silica glass seemed to be shifted to the lower valence states. Therefore, the oxidation of molybdenum by Cr and Mn ions was depressed.
  • 曽我 直弘, 田中 勝久, 大田 陸夫
    1986 年 35 巻 389 号 p. 133-137
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Phosphate glasses containing a large amount of chromium oxide were prepared and their chemical durability was examined. Among various phosphate glasses, metaphosphate glass was chosen as the base glass composition because of its chemical stability. The maximum amount of chromium oxide included in the glass was found to be 23mol%.
    The chemical durability of these chromium oxide-containing phosphate glasses was excellent. Particularly, the alkali resistance of phosphate glass was imporved by the addition of chromium ions. Both the weight loss and dissolution of chromium ions for the best glass were almost zero in 1N sodium hydroxide aqueous solution after immersing it for 12 hours at 70°C. The fact that these metaphosphate glasses excelled other phosphate glasses in water, acid or alkali resistance was explained based on the difference in glass structure.
  • 宮田 昇, 武田 真一, 神野 博
    1986 年 35 巻 389 号 p. 138-144
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The slow growth characteristics of indentation-induced microcracks in soda-lime-silica glass were investigated. Vickers indentations were made on glass specimens at loads of 4 and 7 kgf, respectively, in both air and water environments at room temperature, and the extension of median/radial and lateral cracks was monitored by optical microscopy over a long period of time after indentation. Fractographic features of the post-indentation slow crack growth were also examined on specimens subsequently broken from the indentation-induced flaw under bending. Although a theory suggests that a logarithmic plot of the median/radial crack size vs. the time after unloading should give a linear relation, the crack growth data in both air and water environments could not be represented by a single straight line over the entire range of time followed. In air environment, a characteristic slow-down in growth rate of the median/radial crack was observed at about 0.5 to 1 hours after unloading. This may be caused by a relaxation of the effective residual stresses resulting from an appreciable extension of lateral crack. The post-indentation slow crack growth behaviour in moist environments was interpreted in terms of median/radial-lateral crack interaction effects. A possible use of the post-indentation crack growth data for fatigue parameter evaluation of glass was also discussed.
  • 和田 千春, 庄子 哲雄
    1986 年 35 巻 389 号 p. 145-151
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper describes the relationship between fracture toughness and initial tangent modulus, i.e., Young's elastic modulus in tension, of granitic rock. ASTM standard specimens for notched three-point-bend and compact tension tests, which contained various levels of water or were subjected to thermal cycle, were used to correlate fracture toughness to Young's modulus. Furthermore, fracture toughness tests were carried out at high temperature and in pressurized water environment to evaluate the fracture and deformation behaviors under a simulated condition of geothermal reservoir.
    Based on the linear elastic fracture mechanics, elastic modulus was precisely measured for granitic rock samples by means of a compliance calibration technique prior to fracture toughness tests. Fracture toughness was determined by means of AE technique from an abrupt increasing point of AE activity.
    The results obtained in this study indicate that a significant increase in fracture toughness (KiAE) appears with increasing elastic modulus (E) and fracture toughness has a simple linear relationship with elastic modulus. Theoretical consideration based on the atomic scale fracture model by Gilman can give an adequate explanation to this relationship between KiAE and E.
    It is suggested that the effect of water content on the elastic modulus and fracture toughness can be interpreted as the result of internal friction on the micro-crack plane. An optical microscopic study led to a conclusion that the decrease in elastic modulus and fracture toughness with increasing temperatue is due to the increase in thermally-induced micro-crack in the rock sample. The result obtained at high temperature/pressurized water environment may be attributed to highly activated chemical reaction at the crack tip.
  • 白石 哲郎, 曽山 義朗, 森 慎之助
    1986 年 35 巻 389 号 p. 152-157
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue tests were made on pre-cracked specimens of polycarbonate under two-step loading and the effects of stress change on fatigue crack propagation and closure were investigated. Fatigue life was also examined and discussed. The main results obtained are summarized as follows:
    (1) Remarkable acceleration of fatigue crack propagation was found to occur at the first cycle after the stress increase. The acceleration factor of crack propagation was much higher than that in metals.
    (2) Retardation of fatigue crack propagation was observed when the stress was decreased, and the maximum retardation was found to occur immediately after the stress decrease.
    (3) The crack opening ratio U measured at the specimen surface was not affected appreciably by the stress change. This fact suggested that the acceleration and retardation in polycarbonate could not be attributed to the crack closure behavior.
    (4) The value of cumulative cycle ratio was smaller than unity in the case of stress increase, but was larger than unity in the case of stress decrease. This can be explained by the crack propagation curves and the acceleration or retardation behavior of fatigue crack propagation.
  • 山崎 利春, 千葉 和夫, 市川 以知郎
    1986 年 35 巻 389 号 p. 158-164
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue tests of Al/epoxy moulded joints were conducted and the effect of specimen geometry on the fatigue strength was studied. The test specimens used in the experiment were butt-joints, grooved butt-joints and slant butt-joints under bending, and butt-joints under tension.
    The stress state for each specimen geometry under fatigue load combined with residual thermal stress was analyzed by elastic FEM, and all the fatigue data were found to be expressed with a single narrow S-N band when they were plotted in terms of the stress component perpendicular to the interface.
    The fracture surfaces were also examined and it was shown that the fatigue fracture developed through the four stages starting from stable debond growth along the Al/adhesive interface to the final fracture of epoxy resin.
    The mechanism for stepwise transition of the four stages was discussed using fracture mechanics parameters.
  • 大規模降伏下でのき裂とモードII形き裂
    伊原 千秋, 清水 啓之, 加藤 久敦
    1986 年 35 巻 389 号 p. 165-169
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Previously a stochastic model for damage accumulation was proposed to obtain an expression for the fatigue crack propagation rate in small scale yielding. In this paper, the model is used to derive the propagation laws of (1) fatigue cracks in large scale yielding and (2) mode II fatigue cracks. The theoretical results show a good agreement with the experimental data. This suggests an extensive applicability of the present model. On these theoretical bases, it is concluded that the fatigue crack propagation rate is proportional to some power of the fracture process region size.
  • 桜井 茂雄, 宇佐美 三郎, 梅沢 貞夫, 宮田 寛
    1986 年 35 巻 389 号 p. 170-175
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    To assure high-temperature component safety and reliability, a life prediction method has been developed. The method is based on the micro-crack growth rate and the microcrack distribution.
    Strain controlled low-cycle fatigue tests were carried out on the plain specimens of SUS 316 at 923K in air and the initiation and growth behavior of surface micro-cracks were observed.
    The results obtained are summarized below.
    (1) The creep-fatigue life is governed by micro-crack growth.
    (2) A linear relationship is observed between the logarithms of main surface crack length and the life ratio, N/Nf, for various strain loading conditions.
    (3) The distribution of micro-crack length obeys the Weibull distribution.
    Moreover, the maximum crack length in an area larger than the sample area can be estimated with a help of the statistics of extremes. Therefore, the remaining life of high-temperature components may be accurately predicted by measuring the distribution of surface micro-crack length in critical parts.
  • 八木 晃一, 金丸 修, 久保 清, 田中 千秋
    1986 年 35 巻 389 号 p. 176-182
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The understanding of long-term behavior and life prediction under creep-fatigue loading conditions are important subjects. It is considered that life prediction under creep-fatigue loading conditions should be related to the creep properties, because the long-term creep-fatigue behavior might be dominated by the creep properties. It was found from the combined creep-fatigue loading tests on SUS 316 stainless steel that the fracture criteria were correlatable to the creep fracture modes of the static creep tests performed under the creep loading condition of the combined creep-fatigue loading tests. A new life prediction method was proposed according to this result.
    In order to verify this life prediction method, the fatigue tests with tensile strain holding wave form were carried out on SUS 316 stainless steel at 550, 650 and 750°C.
    The predicted rupture life agreed well with the observed one. This life prediction method was more accurate than the method in which the life is predicted using only one fracture criterion (ex. φcf=1). The dominant fracture modes under creep-fatigue loading conditions could be predicted using this method.
  • 服部 博, 北川 正樹, 大友 暁
    1986 年 35 巻 389 号 p. 183-189
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of thermal aging on the high temperature low-cycle fatigue properties of Ni-base superalloys, Inconel 617 and Hastelloy XR, was studyed at High Temperature Gas-cooled Reactor (HTGR) temperatures (950-1000°C). The strain controlled low-cycle fatigue tests were conducted under a symmetrical triangular wave form for Inconel 617 at 700°C and 1000°C, and for Hastelloy XR at 950°C. Two aging conditions, namely 1000°C for 3000 hours and 700°C for 200 hours, were employed for Inconel 617. One condition of 950°C for 1000 hours was employed for Hastelloy XR.
    In the both materials aged at HTGR temperatures, the low-cycle fatigue lives increased remarkably in comparison with the lives of as-received (solution heat treated) materials. This beneficial effect might be caused by the cohering and coarsening of carbide precipitates at grain boundaries. On the other hand, the fatigue life of Inconel 617 aged at 700°C was not influenced by the thermal aging.
  • 中島 正貴, 加藤 容三, 中村 和司
    1986 年 35 巻 389 号 p. 190-195
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Constant maximum stress intensity (Kmax) fatigue tests were carried out to obtain the near-threshold characteristics in fatigue crack growth of high strength steel. Specimens were loaded in in-plane bending at various Kmax under hydrogen supply and in room air. Fractographic observations were made on the fracture surfaces at the near-threshold regions.
    The results obtained are as follows;
    (1) The threshold stress intensity factor range (ΔKth) obtained under hydrogen supply was equivalent substantially to that in room air with an exception of the region of Kmax>KISCC under hydrogen supply.
    (2) ΔKth decreased linearly with an increase in stress ratio (R). In this regard, the effective value of the threshold stress intensity factor range (ΔKeffth) was constant, ΔKeffth≈3MPa√m, in the region of R<0.7. On the other hand, in the region of R>0.7, ΔKth decreased with increasing R. From these results, it is noted that the design based on ΔKth obtained at lower R is dangerous even in room air.
    (3) On the fractographic observations at the near-threshold region, the striation-like pattern occupied the major portion of the fracture surfaces in the region of R<0.7. On the other hand, in R>0.7, the proportion of intergranular facet increased with R.
    (4) It is confirmed that the constant-Kmax fatigue test is suitable for the determination of ΔKth.
  • 小寺澤 啓司, 内田 仁, 長田 良文, 山田 巌
    1986 年 35 巻 389 号 p. 196-202
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effects of cold work on Hydrogen induced cracking (HIC) and hydrogen embrittlement (HE) of iron single crystal were studied by cathodic charging tests with or without loading. The hydrogen induced cracks were produced at six kinds of {110} planes in the annealed specimen, while those cracks were produced at both primary and secondary slip planes in the prestrained one.
    When the stress more than the threshold one was applied, many hydrogen induced cracks were produced at the (110) plane, which was nearly perpendicular to the loading axis, in both the annealed and prestrained specimens. These hydrogen induced cracks connected each other with dimple or quasi-cleavage cracks, and then the specimen finally fractured due to hydrogen embrittlement.
  • 中野 詔彦, 長谷川 澄子
    1986 年 35 巻 389 号 p. 203-207
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    A heat cycle test equipment was designed and assembled, and it was used to perform the fatigue test of CFRP as one of the environmental element tests for evaluating the durability of composite materials in thermal environments. The main results obtained are as follows.
    (1) For CFRP, lowering of flexure strength was most remarkable in the environment comparable to the condition on the fracture critical curve of stress-temperature, when subjected to heat cycle fatigue under creep stress.
    (2) The maximum degradation was found when the high temperature side of the heat cycle temperature range was near Tg.
    (3) The degradation of CFRP with heat cycle fatigue indicated the following behaviors depending upon the combination of stress and temperature range.
    (a) Type showing a remarkable degradation in the early stage.
    (b) Type showing a gradual degradation.
    (c) Type showing little degradation in the early stage.
  • 岩永 弘之, 沖 猛雄
    1986 年 35 巻 389 号 p. 208-214
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Pitting corrosion, which affects the fracture of stainless steel in corrosive environments, is an electrochemical phenomenon. There are still many unanswered questions with respect to the pitting corrosion and, furthermore, there is no well-established inhibition method for the pitting corrosion at present. Stainless steel was adopted as the testing material in this experiment, and the state of formed pits was examined on the rectangle section specimen and the chamfering specimen in deaerated 3%NaCl solution under various constant loads by changing the holding time of pitting potential which was determined from the anodic polarization curve. The results obtained are as follows.
    (1) The formation of pits proceeded gradually and led to deep pits with increasing holding time of pitting potential, and it was expressible as a function of time. The process of deep pit formation differed from SUS 304 and SUS 430. The pitting formation was promoted and accelerated by the presence of stress. Deeper pits were formed under the applied stress above the yield point in particular and this phenomenon became more pronounced at high setting potentials.
    (2) The number of pits changed with increasing holding time of pitting potential and applied stress. The appearance of pitting corrosion on SUS 304 was different from that on SUS 430. The pits on SUS 304 were distributed all over the specimen surface, and they were numerous and shallow. But the pits on SUS 430 were localized in a certain area of specimen surface, and they were small in number and deep.
    (3) The chamfering specimen had a tendency to inhibit the pitting formation to a certain extent. In addition, the surface condition (roughness) seemed to be the major factor on the pitting formation.
  • 1. 疲労研究の歴史と現代的ニーズ
    西岡 邦夫, 田中 道七
    1986 年 35 巻 389 号 p. 215-221
    発行日: 1986/02/15
    公開日: 2009/06/03
    ジャーナル フリー
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