材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
62 巻 , 5 号
選択された号の論文の10件中1~10を表示しています
論文
  • 政木 清孝, 亀島 洋平, 久森 紀之, 佐野 雄二, 秋田 貢一, 菖蒲 敬久
    2013 年 62 巻 5 号 p. 297-304
    発行日: 2013/05/15
    公開日: 2013/05/20
    ジャーナル フリー
    In order to investigate the effects of laser peening on high cycle fatigue properties of (α+β) type Ti-6Al-4V alloy, rotating bending fatigue tests were carried out. The laser peening conditions were a spot size of 0.8mm in diameter, a pulse energy of 200mJ and an irradiation pulse density of 38 pulse/mm2. The fatigue properties were not improved with these conditions of laser peening ; even though the material was hardened to some extent and high level compressive residual stresses were induced in the near-surface layer. Because the reason that the fatigue properties were not improved was considered the notch effect of surface roughness introduced by laser peening, further fatigue tests were performed with laser-peened specimens followed by surface polishing. However, the fatigue lives of polished specimens were shorter than those of unpolished specimens, unexpectedly. Considering the peening effects such as surface roughness, hardness and residual stress, the reasons for arriving at the unexpected results would be the influence of the strain-induced transformation of β phase into α' martensite and a larger yield strength in tension than that in compression due to the HCP structure of α phase of titanium alloy.
  • 藤山 一成, 水谷 芳樹, 谷口 嘉規, 來海 博央
    2013 年 62 巻 5 号 p. 305-310
    発行日: 2013/05/15
    公開日: 2013/05/20
    ジャーナル フリー
    Creep damage evaluation by EBSD (Electron BackScatter Diffraction pattern) method was conducted on the austenitic stainless steel SUS304HTB widely used as the boiler tube material. Creep damage was imposed under the condition of 650℃ /130MPa and 700℃ /75MPa for preparing various interruption time samples. The longitudinal mid-section of specimen was observed by EBSD equipment and then IPF (Inverse Pole Figure) maps, KAM (Kernel Average Misorientation) maps, GROD (Grain Reference Orientation Deviation) maps were made for damaged samples. IPF maps showed the increasing inhomogeneity incrystal orientation within each grain as the time fraction increased. Area averaged parameters of KAM and GROD, i.e., KAMave and GRODave showed monotonically increasing trend with creep time fraction. Compared with KAMave, GRODave showed better performance for insensitivity of EBSD pixel step size. As GRODave showed excellent proportionality with creep strain except for rupture stage, the linear relationship was used as the conversion function into creep strain. Using this relationship, it was suggested that creep void diameter was proportional to the creep strain derived from local GRODave measurement method proposed here. Therefore, GRODave could be a good measure for estimating the strains around creep voids and the void growth mechanisms of SUS304HTB.
  • 吉川 高正, 稲葉 忠司, 橋本 結衣, 横尾 優哉, 徳田 正孝
    2013 年 62 巻 5 号 p. 311-318
    発行日: 2013/05/15
    公開日: 2013/05/20
    ジャーナル フリー
    The yield surface and the deformation mechanism of the extruded AZ31 magnesium alloy rod at room temperature were studied. The uniaxial tensile, compressive and pure shear tests with the simultaneous observation of the microstructure were carried out for specimens sampled along different directions in an extruded rod. In the plane-stress condition within the plane perpendicular to extrusion, the yield surface almost fits the Tresca's criterion for isotropic materials, because of the activation of the basal slip or {10-12} twinning, regardless of the loading direction. The deformation mechanism with higher critical resolved shear stress than those of basal slip or {10-12} twinning is driven by the tensile loading parallel to extrusion, due to the texture with the direction of its c-axis perpendicular to tensile direction. Therefore the tensile yield stress for this direction increase more than compression or shear, and the twinning pattern at the yield for tensile loading does not appear.
  • 古西 和夫, 北根 安雄, 伊藤 義人
    2013 年 62 巻 5 号 p. 319-326
    発行日: 2013/05/15
    公開日: 2013/05/20
    ジャーナル フリー
    This paper presents a study on performance of piled jetty steel pipe repaired by steel patch plate. In this study, repaired steel pipes of piled jetty are modeled. The whole model of piled jetty is analyzed by finite element method. In FE model, shell elements, pipe elements, beam elements and spring elements are used. The bi-linear force-displacement relationship is used for spring elements to represent horizontal resistance of soil. Variation of corrosion thickness is modeled by using actual data of corroded steel pipe. From numerical results, the buckling behavior of repaired steel pipe of piled jetty is clarified. It is shown that a required thickness of patch plate is larger than thickness reduction to achieve the same level of ductility performance in the repaired pipe as intact pipe.
  • 宮本 慎太郎, 細川 佳史, 皆川 浩, 久田 真
    2013 年 62 巻 5 号 p. 327-334
    発行日: 2013/05/15
    公開日: 2013/05/20
    ジャーナル フリー
    This study measured the amount of the solid phases in the hardened cement specimens immersed in pH2.0 sulfuric acid solution, hydrochloric acid and mixed acid (sulfuric acid : hydrochloric acid = 2 : 8 and 8 : 2 in molar ratio) in order to discuss the chemical transformation behavior of cement hydrate deteriorated by these acids. As a result, it is obvious that the cement hydrates deteriorate due to the dissolution of Portlandite by the action of proton as well as the chemical alteration of AFm phase by the action of anion. In case of the sulfuric acid acted, Monosulfate and Monocarbonate transformed into Ettringite by the action of SO42- which permeated from the outside solution. On the other hand, in case of the hydrochloric acid acted, Monosulfate transformed into Friedel's salt via Kuzel's salt by the action of Cl- which permeated from the outside solution. Furthermore, in case of the mixed acid, Monosulfate and Monocarbonate preferentially transformed into Ettringite instead of Kuzel's salt or Friedel's salt. As a result, in the case of mixed acid, it was shown that Cl- may permeate to the depths more compared with the case of HCl independently since the amount of fixation of Cl- near the exposed surface becomes small by generating of Ettringite.
  • 坂井田 喜久, 矢代 茂樹, 吉田 始
    2013 年 62 巻 5 号 p. 335-341
    発行日: 2013/05/15
    公開日: 2013/05/20
    ジャーナル フリー
    In order to determine the mechanical and x-ray elastic constants of carburized case layer in chrome molybdenum steel, three thin bend bar specimens with a thickness of about 0.3mm were cut from the carburized block after quenching by wire-electrical discharge machining. Carbon content and hardness gradients of block were measured before cutting. Thin bend bar specimens were subjected to four-point bending loads. The elastic strains were monitored using a strain gauge cemented on the tensile surface. Under each bending loads, the 2θ-sin2ψ diagram from 211 plane of ferrite or martensite was also measured by x-ray. In the case of thin bend bar specimen, apparent Young's modulus determined from the slope in the applied stress versus monitored strain curve was relatively smaller than that of the ordinary bend bar specimen. In this study the monitored strain was corrected by the thickness of gauge base including glue. As a result, Young's modulus of case layer was larger than that of the interior, because of increased carbon content and resulting martensite transformation of carburized layer. Young's modulus of the interior at the total case depth was smaller than that of starting material. X-ray elastic constants, EX/(1 + νX) and EX/νX, of thin specimens were determined from the changes of the slope and intercept in sin2ψ diagram with the applied stress. X-ray elastic constants of case layer were larger than that of starting material. The absolute value of stress constant, K, of case layer was also larger than that of starting material. It was found that up to 25 percent of the residual stress might be underestimated in our case if the stress constant, K, of starting material was used in x-ray stress measurement.
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