圧力技術
Online ISSN : 1347-9598
Print ISSN : 0387-0154
ISSN-L : 0387-0154
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42 巻, 6 号
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論文
  • オリフィス下流部に局所減肉を有する配管の破損挙動
    高橋 宏治, 安藤 柱, 木村 祐介, 川戸 和臣, 久恒 眞一, 長谷川 邦夫
    2004 年 42 巻 6 号 p. 310-317
    発行日: 2004年
    公開日: 2005/01/25
    DOIhttps://doi.org/10.11181/hpi.42.310
    ジャーナル フリー
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    Monotonic four-point bending tests were conducted using pipe specimens having orifice undergoing local wall thinning. The effects of local wall thinning on the fracture behaviors of pipe were investigated. Local wall thinning was machined on the inside of pipes in order to simulate erosion⁄corrosion metal loss. The configurations of the eroded area were l=100mm in eroded axial length, d⁄t=0. 5 and 0. 8 in eroded ratio, and 2θ=180°in eroded angle. The area undergoing local wall thinning was subjected to either tensile or compressive stress. Failure type could be classified into ovalization, local buckling, and crack initiation, depending on eroded ratio, and stress at the eroded area. Three-dimensional elasto-plastic analyses were also carried out using the finite element method, which is able to accurately simulate fracture behaviors. The crack initiation point could be successfully predicted by the criterion proposed by Miyazaki et al. .
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  • 単一過大荷重負荷後の疲労き裂伝ぱに及ぼすき裂先端の塑性域について
    真壁 朝敏, 宮崎 達二郎, Anindito PURNOWIDODO, 屋富祖 建樹
    2004 年 42 巻 6 号 p. 318-327
    発行日: 2004年
    公開日: 2005/01/25
    DOIhttps://doi.org/10.11181/hpi.42.318
    ジャーナル フリー
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    ABSTRACT: In most practical cases, the retardation of fatigue crack propagation has been observed after applying single overload. However, it was found that the fatigue crack growth rate actually accelerated after a tensile overload under a negative value of baseline stress ratio. This type of crack propagation behavior was related to the change of the compression residual stress to tensile residual stress distributed in the vicinity of the crack tip after an overload. In the present investigation, it was discussed that the number of delay and acceleration cycles of crack propagation were associated with a creating mechanism of static plastic zone, which influenced the residual stress state in front of the crack. In addition, the extent of fluctuation of the crack opening stress level related to the extent of the overload-affected zone. Also, it was found that the residual fatigue crack propagation life was influenced by the applied overload level and the conditions of applied cyclic stress after overloading.
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  • V-Mod. 2. 25Cr-1Mo鋼の500°Cクリープ強度の支配因子
    長谷川 泰士, 梅木 進, 川副 文宏, 岡山 豊, 吉田 卓
    2004 年 42 巻 6 号 p. 328-336
    発行日: 2004年
    公開日: 2005/01/25
    DOIhttps://doi.org/10.11181/hpi.42.328
    ジャーナル フリー
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    A creep strengthening mechanism of the 2. 25Cr-1Mo-0. 25V steel at 500°C and 550°C was precisely discussed by using of the creep rupture and deformation test results. According to the analyses of the precipitates through TEM observation of thin foil and carbon replica, M23C6, M2C and MC type carbides were identified. Through the theoretical Slorovits' void strengthening stress calculation by measured VC precipitation density at lath boundary of the bainitic structure, the creep rupture strength was estimated about 200 MPa, and the lath structure recovery resistance seemed to determine the creep strength.
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  • フランジ継手締付け指針の開発
    辻 裕一, 高木 知弘, 澤 俊行
    2004 年 42 巻 6 号 p. 337-346
    発行日: 2004年
    公開日: 2005/01/25
    DOIhttps://doi.org/10.11181/hpi.42.337
    ジャーナル フリー
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    A guideline for bolted flange joint assembly has been published as an HPIS technical report, in which bolts are tightened in the clockwise-pattern sequence and the tightening torque is 100% of the target torque in all steps except for an install step. This paper describes analytical and experimental backgrounds of the guideline. Numerical simulations of bolt-up procedure by using three-dimensional finite element analysis are systematically executed for JPI flange joints of various nominal sizes and classes. The number of bolt-up passes required to achieve uniform bolt preloads is determined in order to avoid excessive iterations of tightening operation. Tightening tests using various sizes of the flange joint demonstrate that HPIS procedure achieves comparable uniformity in bolt preload and in flange alignment with ASME PCC-1 procedure. The guideline developed is able to achieve accurate preloads consisting with assembly efficiency for practical use.
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