材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
39 巻 , 443 号
選択された号の論文の17件中1~17を表示しています
  • 小林 英男, 荒居 善雄, 荒木 徹, 奥 達雄
    1990 年 39 巻 443 号 p. 1076-1081
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Effects of specimen size and initial notch on fracture toughness and fracture resistance characteristics were examined for three high strength graphite materials, IG-11, IG-110 and IG-110U. A characteristic R-curve behavior and specimen size requirements for fracture mechanics parameters were discussed. An effect of elevated temperature environment on the fracture toughness was also examined at elevated temperatures from room temperature upto 820°C in a vacuum environment. The temperature effect was discussed in comparison with the result at room temperature in an air environment. The results obtained are summarized as follows:
    (1) Graphite materials show a characteristic R-curve behavior in which the fracture resistance increases in the initial stage of crack extension near the initial notch tip, takes a constant value in the intermediate stage, and then decreases in the final stage near the specimen back face. The effect of initial notch is caused by an underestimation of the stress intensity factor, K, for a corner crack. It is shown that the true fracture resistance is constant and equals to the fracture toughness.
    (2) The stress intensity factor, K, is valid as the fracture mechanics parameter for the fracture toughness testing. A well-known specimen size requirement for the metallic materials can be extended to the graphite materials by replacing the yield stress by the tensile strength.
    (3) The fracture toughness increases slightly with increasing temperature in the vacuum environment and it has a larger value than that obtained at room temperature in the air environment. So, the fracture toughness and the fracture resistance obtained at room temperature in air can give conservative estimations for the evaluation of the structural integrity of the high temperature gas cooled reactor.
  • 浜田 晴一, 寺前 哲夫
    1990 年 39 巻 443 号 p. 1082-1088
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Ball contact damages were investigated on pressureless sintered SiC and Si3N4 ceramics. Impact tests were carried out using the air gun system. Three kinds of balls; steel, SiC and Si3N4, the size of which was 3mm in diameter, were used as projectiles, and four kinds of ceramics were used as target specimens of size 7.5×10×85mm. After the impact tests, three point bending tests were carried out to evaluate the residual strength of the specimens, and differences in failures with ball contact were discussed taking the results of numerical analyses into consideration.
    The results are summarized as follows;
    (1) The residual strength could not be estimated by the diameter of the ring crack.
    (2) SiC specimens with steel ball impact, and Si3N4 specimens with SiC ball impact showed the largest degradation of strength.
    (3) Distinction of fracture between SiC and Si3N4 specimens seemed to be caused by the differences in strength and fracture toughness of these materials.
  • 東郷 敬一郎, 大塚 昭夫, 高 紅維
    1990 年 39 巻 443 号 p. 1089-1094
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Behavior of ductile crack initiation from a crack under mixed mode I-II loading has been investigated on a weldable structural steel SM41A. Elastic-plastic fracture toughness tests were carried out on the single-edge-cracked specimens subjected to bending moment and shearing force. The ductile crack initiation from the mixed mode crack occurred in two types -fibrous-type and shear-type- depending on the loading mode. When the mode I component was more predominant, the fibrous-type crack was initiated by the coalescence of microvoids. On the other hand, under the mode II predominant loading, the shear-type crack initiation occurred by large shear deformation. The applicability of J-integral concept to the ductile crack initiation from a mixed mode I-II crack was examined. The condition of ductile crack initiation from a mixed mode crack was shown by contour line on the JI-JII diagram, JI and JII being the mode I and Mode II components of J-integral, respectively. The condition of crack initiation for mode II crack, JiII, was different in value from the condition of crack initiation for mode I crack, JiI.
  • 結城 良治, 鄭 南龍, 石川 晴雄, 中野 禅
    1990 年 39 巻 443 号 p. 1095-1100
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    This study investigates the problem of applying fracture mechanics to evaluation of the strength of adhesive joints, focusing on mixed mode fracture criteria. Various types of adhesive joint specimens with a crack in an adhesive layer were prepared for the static tests and fatigue tests. The adherend was acryl plate and epoxy plate and the adhesive was cemedine 1500 and EP-007. The energy release rates GI and GII for various adhesive joints were analyzed by FEM and modified virtual crack extension method. Comprehensive mixed mode conditions from pure mode I to nearly pure mode II were realized in this study. The fracture toughness results obtained showed a mixed mode fracture criterion peculiar to adhesive joints, which can be characterized by GI and GII. It was found that the fatigue crack growth rate in various adhesive joints can be well characterized by the total energy release rate range ΔGT. Therefore, different approaches are necessary for the fatigue crack growth and fracture toughness of adhesive joints under mixed mode conditions.
  • 服部 敏雄, 西村 朝雄, 村上 元
    1990 年 39 巻 443 号 p. 1101-1105
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    The stress and displacement fields at the close vicinity of a bonding edge show approximately the following singular behaviors.
    σ(γ)=Kλ (1)
    σ(γ): stress
    γ: distance from singularity point
    K: intensity of stress singularity
    λ: order of stress singularity
    Formerly we presented a new adhesive strength evaluation method using these two stress singularity parameters K and λ. In this paper, the strength estimation on resin cracking at the tab edge of LSI plastic package was attempted by using these stress singularity parameters. Crack initiation criteria using stress singularity parameters were measured on 90° notch specimens, plain specimens, fracture toughness tests and so on. Crack initiation behaviors of three types LSI plastic packages were analysed using these crack initiation criteria. These analytical results of delamination and crack initiation behaviors were compared with the heat-cycle experimental results.
    From these studies it was found that the intensity of stress singularity at the tab edge increased in accordance with the increase of delamination area of tab bottom, and this delamination area depended strongly on the tab size.
  • 横堀 寿光, 磯貝 毅, 横堀 武夫, 小泉 幸久
    1990 年 39 巻 443 号 p. 1106-1112
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Multiaxial fatigue tests were carried out to investigate the effect of stress components (Δσ, Δτ, σst., τst.) on fatigue crack growth.
    The test method was the combined tension and tortion one in phase loading by using thin-walled hollow cylindrical specimens with pre-cracks. The experiments were carried out under the condition of equal equivalent stress amplitude, Δσeq=√Δσ2+3Δτ2
    Under the condition of mixed modes, the fatigue crack growth rate increases remarkably with increasing stress ratio. This characteristics is due to the effect of static tensile stress σst. on Δτ.
    In this paper, the effect of static tensile stress was incorporated in the constitutive equation of fatigue crack growth rate under the mixed mode fatigue condition of Δσ and Δτ. Then, the following constitutive equation of fatigue crack growth rate including the effects of Δσ, Δτ, σst. and τst. was obtained.
    db/dN=AKIb)mA=(AR=0)1/r*
    r*={1+(σst/Δτ)1/2/7 (Region IIa) 1 (Region IIb)
    AR=0={2.16×10-5×0.230m (Region IIa) 3.64×10-5×0.147m (Region IIb)
    m={f21) (Region IIa) g21) (Region IIb)
  • 村上 敬宜, 古川 勝明, 白石 暢彦
    1990 年 39 巻 443 号 p. 1113-1118
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    A prediction method of service loading from striations on fracture surface is proposed. Although it is well known that striation spacing corresponds to the crack growth rate da/dN, it is not possible to determine Pmax and Pmin under service loading only from s. This is because the value of s is influenced not only by ΔK but also by the stress ratio R (=Pmin/Pmax).
    The new idea in this study for determination of Pmax and Pmin is based on the anticipation that the information on R must be included in the relative height of striation H to s. The results of fatigue tests on 2017-T4 Al Alloy CT specimens showed a definite correlation between H/s and R. The difficulty of the measurement of H was overcome by sectioning the specimens at an inclined angle and by measuring small distance using SEM.
    Striations under R=-1 were compressed and flat, and H/s was small. With increasing R, H/s became large. Therefore, the standard laboratory test results on the relationship between s and ΔK, and also that between H/s and R enables us to predict service loading from the fatigue fracture surfaces.
  • 城野 政弘, 菅田 淳
    1990 年 39 巻 443 号 p. 1119-1125
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue crack growth tests under Hi-Lo two-step, repeated two-step and programmed loadings were performed on grain-oriented 3% silicon iron in a high-resolution, field emission type scanning electron microscope, using a specially designed servo-hydraulic fatigue loading system, and direct, real time observations were made, partly with aid of image processing technique.
    Under Hi-Lo two step loadings, the relationships of crack growth direction and crack tip opening displacement to crack growth rates were found quite different from those of constant amplitude loading test. On the contrary, the relationship between crack tip opening displacement and effective stress intensity range under repeated two-step loading could be considered similar to that of constant amplitude loading. Moreover, the change of crack tip opening displacement was found to correspond well to the range-pair of stress intensity range. From the above mentioned observation results, microscopic and macroscopic controlling parameters of fatigue crack growth were discussed.
  • 町田 進, 吉成 仁志, 林 忠宏
    1990 年 39 巻 443 号 p. 1126-1132
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Structures are often subjected to various types of random loading in service. Hence fatigue crack propagation under random loading is one of practically interesting topics. This study aims at finding empirically a practical relation for predicting the fatigue crack propagation rate under different types of random loading from constant amplitude loading tests.
    The specimen used was CCT (center crack tension) one with 3.2mm thick, made of JIS SPCC mild steel. Several patterns of power spectrum with different band widths in frequency were used, and the mean stress level was changed from compression to tension to identify the crack closure effect. Cycle counting was made using “hysterisis loop method”. The constant amplitude loading test was carried out to compare with the random loading test. The stress range ΔSr of random loading was converted into the fixed value ΔSeq (equivalent stress range). By using this ΔSeq and considering the crack closure effect, a possibility has been shown that the fatigue behavior under random loading may be predicted from the constant amplitude loading test.
  • 原田 昭治, 秋庭 義明, 植田 隆浩, 矢野 満
    1990 年 39 巻 443 号 p. 1133-1138
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Cyclic stress- and strain-amplitude-controlled low-cycle fatigue tests were conducted on a pearlitic ductile iron (PDI). The effects of spheroidal graphite (SG) and matrix on the fatigue process were examined. The material tested showed cyclic hardening behaviour at an early stage of the fatigue life, irrespective of the cyclic loading condition. The fatigue lives in all tests satisfied the Manson-Coffin type of relation, which resembled the results reported in the previous report. In evaluating crack growth, no unique linear relationship between crack growth rate and cyclic J-integral value was obtained, which suggested the presence of crack closure effect induced by SG. Microscopic cracks were mostly initiated at SG. However, casting shrinkage in some cases played an important role as a crack initiation site.
  • 岩舘 忠雄, 阿部 敏広
    1990 年 39 巻 443 号 p. 1139-1144
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to study life prediction method of structural material for sea environment use, the field testing facility to measure the fatigue crack growth rate of the materials due to sea wave was developed. The tests of fatigue crack growth rate measurements using 3.5% Ni-Cr-Mo-V structural steels were performed in cathodic protection and free corrosion environments.
    The field test data were analized using the rainflow method and equivalent load (Peq) equation. When the yeild strength and the stress ratio increase, the fatigue crack growth rate increases. The fatigue crack growth rate of field test results was little different from indoor test results obtained using ASTM sea water. This difference may be caused by the change of stress ratio and frequency conditions. The crack growth rate of indoor test using field test conditions coincided well with the field test results. In observation of fracture surface of the specimens, fatigue crack containing intergranular fracture was observed. The higher yield strength material showed larger amount of intergranular fracture.
    This study demonstrates that the fatigue crack growth behavior in actual sea field environment can be obtained using indoor test data.
  • 大塚 尚武, 小林 隆夫, 渡士 克己, 菊池 政之
    1990 年 39 巻 443 号 p. 1145-1150
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fracture surface topography analysis (FRASTA) technique was applied to investigate the fatigue cracking of SUS304 stainless steel specimen at elevated temperatures. The specimen with single edge notch was subjected to 2603 cycles of fatigue at a constant strain range at 600°C. After the test, the topographic features of the conjugate fracture surfaces were compared using the FRASTA technique and fracture mechanics analysis was conducted. The analysis showed that a macroscopic fatigue crack was initiated at around 1000 cycles and then propagated at nearly a constant rate. These features and the expected crack growth rate coincided well with the experimental observation. This indicates that the FRASTA technique is applicable to the estimation of fatigue cracking at elevated temperatures.
  • 松原 雅昭, 高野 太刀雄, 岡村 弘之
    1990 年 39 巻 443 号 p. 1151-1156
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper describes an experimental study on pressurized thermal shock, PTS, problem by using a photoelastic technique for the purpose of confirming the validity of application of statically indeterminate fracture mechanics to the problem. The following points are made clear from the test results:
    (1) Thermal stresses obtained from the photoelastic test results agree well with those given by nonstationary thermal conduction analysis.
    (2) Bending moments obtained from observation of photoelastic fringes agree well with those given by nonstationary thermal conduction analysis. It was experimentally confirmed that bending moment occurred by constraint in such structure that bending deformation was restricted. The compliance of the end of specimen was quantitatively evaluated.
    (3) The good agreement was observed between the stress intensity factor obtained from observation of photoelastic fringes near a crack tip and that given by application of statistically indeterminate fracture mechanics which was described in the previous paper. It was confirmed that statically indeterminate fracture mechanics which was valid for theoretical evaluation of the stress intensity factor under PTS. Also by this experimental results, It was made clear that bending moment by constraint influenced significantly the stress intensity factor under PTS.
  • 鈴木 新一, 河内 雅弘, 加藤 宗寿, 中島 卓郎
    1990 年 39 巻 443 号 p. 1157-1161
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    Pulsed holographic microscopy was applied to take an instantaneous microscopic photograph of a rapidly propagating crack in PMMA. The crack was in the opening mode and its speed was at several hundred m/s. The crack and craze opening displacement, which are both called COD, were measured as a function of distance r from the craze tip within the region of r up to 8mm. The crack opening displacement was nearly proportional to √r, while the craze opening displacement deviated from the curve of √r. The crack tip opening displacement (CTOD) was determined from the measured COD data, and the dynamic stress intensity factor KI(v) was also obtained. Furthermore, the value of J-integral was calculated by assuming small scale yielding. It happens that cracks which have the same KI(v) value and crack speed show different COD profile in the craze layer.
  • 石井 明, 佐々木 茂美, 越智 保雄, 林 広佳
    1990 年 39 巻 443 号 p. 1162-1166
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    An experimental visual inspection technique using the slit light for the detection of cracks in/on alumina ceramics circuit boards has been presented. Since the alumina ceramics has a well light-diffusible property over all of visible wavelength range, it is difficult to detect cracks in the material by an ordinary inspection with the human eye or optical microscope observation with coaxial illumination. In the present technique, the surface of the specimen placed on a X-Y stage is illuminated from a proper direction by the slit light, which is adjusted to a small width with several condensing lenses, and the line image of the surface is sensed by a CCD line sensor camera through an object lens and inputted into the image device as intensity signal. The X-Y stage, which is driven by pulse motors with high accuracy, is used for the mechanical scanning for obtaining the two dimensional image of the surface.
    As for the results, under specific observing conditions, including the camera position relative to the slit light, the incident angle to the surface, and the width of the slit light, some characteristic intensity changes were found not only around the crack, but also on the edge of the board and of the installation holes for IC parts. The optimum condition for the detection of the crack was experimentally examined. In order to interpret these features, a simple model is proposed, and it is clarified that the light uniformly diffused into the specimen gives rise to the characteristic pattern due to the reflection at the crack surface. Finally, utilizing these characteristic patterns, one image processing algorithm, which detects only cracks in the ceramics board and has a possibility to process in high speed, is presented.
  • 大路 清嗣, 久保 司郎, 阪上 隆英, 安田 章二, 藤下 健一
    1990 年 39 巻 443 号 p. 1167-1172
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
    A simple method was proposed for determining the length and depth of a semi-elliptical surface crack embedded in a conductive body from several D.C. potential readings. This method was based on the comparison between measured potential values and calculated potential values obtained by boundary element electric field analyses. For each measured potential value a characteristic line could be calculated, which represented the possible combinations of crack shape parameters, i.e. the length and depth of the semi-elliptical surface crack. These crack shape parameters were estimated on a least squares basis from the intersections of the characteristic lines corresponding to several potential readings. A sensitivity matrix was introduced to predict errors involved in the estimation from errors in the potential measurements. The evaluation of this matrix enabled us to determine the optimum combination of locations of measuring probes for the estimation. This method was applied to the monitoring of the length and depth of surface cracks propagating under fatigue loadings. It was found that the present method was quite useful for the estimation of the length and depth of surface cracks. The sensitivity matrix was also found to be useful for evaluating the errors of the estimation.
  • 麹谷 信三
    1990 年 39 巻 443 号 p. 1173-1179
    発行日: 1990/08/15
    公開日: 2009/06/03
    ジャーナル フリー
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