• Title/Summary/Keyword: Pipe Bending

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Effect of Bend Angle on the Collapse Behavior of Locally Wall Thinned Pipe Bends (감육 곡관의 붕괴거동에 미치는 곡관 굽힘각의 영향)

  • Na Man-Gyun;Kim Jin-Weon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.10 s.253
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    • pp.1269-1275
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    • 2006
  • The purpose of this study is to investigate the effect of bend angle on the collapse behavior of locally wall thinned pipe bends. For this purpose, the present study performed three-dimensional finite element analysis on the 30-, 60-, and 90-degree pipe bends with local wall thinning at the center of intrados, extrados, and crown, and evaluated the collapse moment for different thinning dimensions under closing- and opening-mode bending with a constant internal pressure. The results showed that, for intrados and extrados wall thinning, the reduction in the collapse moment due to local wall thinning became significant with decreasing bend angle of pipe bends. This effect of bend angle was enhanced with increasing thinning dimensions, and it was clearer fur opening-mode bending than for closing-mode bending. For crown wall thinning, however, the effect of bend angle was unclear and was less sensitive to the change of wall thinning shapes.

Evaluation of Local Allowable Wall Thickness of Thinned Pipe Subjected to Internal Pressure and Bending Moment (내압과 굽힘하중하에서 감육배관의 국부허용두께 평가)

  • Kim, Jin-Won;Park, Chi-Yong;Kim, Beom-Nyeon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.1
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    • pp.81-88
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    • 2001
  • This study proposed an analytical method to evaluate a local allowable wall thickness (LAWT) for locally thinned pipe subjected to internal pressure and bending moment. In this method, the stresses in the thinned region were calculated by finite element analysis and plastic collapse was applied as a failure criterion of thinned pipe. Using this method, LAWT for a simplified thinned pipe was evaluated with variation in axial extent of thinned area, and it was compared with allowable wall thickness provided by previous pipe wall thickness criteria. The results showed that the LAWT was lower, about 50%, than that calculated by construction code or ASME Code N-597, and it was higher, about 2 times, than that estimated by evaluation model based on pipe experiments. In addition, LAWT was decreased with increasing axial extent of thinned area and saturated with further increase in axial extent. And, the variation in LAWT with axial extent of thinned area depended on type of load, especially a magnitude of bending moment, considering in the evaluation.

The effects of stability of the tunnel reinforced by rebar steel pipe (철근보강형강관이 적용된 터널의 안정성효과에 대한 연구)

  • Kim, Sang-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.12 no.5
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    • pp.389-397
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    • 2010
  • This paper presents the effects of the tunnel stability using rebar steel pipe which is the steel pipe reinforced by rebar. In order to carry out this research, not only the theoretical and experimental study for bending stiffness of normal steel pipes and rebar steel pipes but also numerical analysis of tunnel stability are performed. It is clearly found from the results that 65% of bending stiffness of the rebar steel pipe is larger than that of the normal steel pipe. The results obtained from the numerical analysis of tunnel stability show that about 10% of tunnel stability is increased in case of the rebar steel pipe. The rebar steel pipe, therefore, may be very useful to develope the tunnel stability economically.

Practical estimation of the plastic collapse limit of curved pipes subjected to complex loading

  • Yan, A.M.;Nguyen, D.H.;Gilles, Ph.
    • Structural Engineering and Mechanics
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    • v.8 no.4
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    • pp.421-438
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    • 1999
  • In this paper a practical limit load estimating procedure is proposed for general pipe-elbow structures subjected to complex loading (in-plane and out-of-plane bending, internal pressure and axial force). The explicit calculating formulae are presented on the basis of theoretical analysis combined with numerical simulation. Von Mises' yield criterion is adopted in both analytical and numerical calculation. The finite element examination shows that the method provides a simple but satisfactory prediction of pipe structures in engineering plastic analysis.

Study on Optimization of Temperature Jump-Bending Process for Reducing Thickness Attenuation of Large-Diameter Steel Pipe (대구경 곡관 두께감소율 제어를 위한 온도점프 벤딩 공정의 최적화에 관한 연구)

  • Xu, Zhe-Zhu;Kim, Lae-Sung;Jeon, Jeong-Hwan;Liang, Long-Jun;Choi, Hyo-Gyu;Lyu, Sung-Ki
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.4
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    • pp.21-27
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    • 2015
  • Induction bending is a method that allows the bending of any material that conducts electricity. This technology applies a bending force to a material that has been locally heated by an eddy current induced by a fluctuating electromagnetic field. Induction bending uses an inductor to locally heat steel through induction. This results in a narrow heat band in the shape to be bent. In general, the reduction of thickness attenuation of a large-diameter steel pipe is not allowed to exceed 12.5%. In this paper, in order to meet the standard of thickness attenuation reduction, a non-uniform heating temperature jump-bending process was investigated. As a result, the developed bending technique meets the requirements of thickness attenuation reduction for large-diameter steel pipes.

Fatigue Failure Behavior of Pipe Bends with Local Wall-Thinning Under Cyclic Bending Condition (반복굽힘 조건에서 감육 곡관의 피로손상 거동)

  • Yoon, Min-Soo;Kim, Jin-Weon;Kim, Jong-Sung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.10
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    • pp.1227-1234
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    • 2012
  • In this study, fatigue tests were carried out using real-scale pipe bend specimens with wall-thinning defects under a cyclic bending load together with a constant internal pressure of 10 MPa. The wall-thinning defect was located at the extrados and the intrados of the pipe bend specimens. A fully reversed cyclic in-plane bending displacement was applied to the specimens. For the pipe bends with wall thinning at the extrados, an axial crack occurred at the crown of the pipe bend rather than at the extrados where the defect was located. In addition, the fatigue life was longer than that of a sound pipe bend predicted from the design fatigue curve in ASME Sec.III, and it was less dependent on the axial length of the wall-thinning defect. For the pipe bends with wall thinning at the intrados, a circumferential crack occurred at the intrados. In this case, the fatigue life was much shorter than that of a sound pipe bend predicted from the design fatigue curve, and it clearly decreased with decreasing axial length of the wall-thinning defect.

A study on the field application of high strength steel pipe reinforcement grouting (고강도 강관 보강 그라우팅의 현장 적용성에 관한 연구)

  • Shin, Hyunkang;Jung, Hyuksang;Ryu, Yongsun;Kim, Donghoon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.4
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    • pp.455-478
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    • 2019
  • In this paper, we conducted experimental investigation on the field applicability through the verification of reinforcement effect of the steel pipe reinforcement grouting using high strength steel pipe. SGT275 (formerly known as STK400) steel pipe is generally applied to the traditional steel pipe reinforcement grouting method. However, the analysis of tunnel collapse cases applying the steel pipe reinforcement grouting shows that there are cases where the excessive bending and breakage of steel pipe occur. One of the reasons causing these collapses is the lack of steel pipe stiffness responding to the loosening load of tunnels caused by excavation. The strength of steel pipe has increased due to the recent development of high strength steel pipe (SGT550). However, since research on the reinforcement method considering strength increase is insufficient, there is a need for research on this. Therefore, in this study, we conducted experiments on the tensile and bending strength based on various conditions between high strength steel pipe, and carried out basic research on effective field application depending on the strength difference of steel pipe through the conventional design method. In particular, we verified the reinforcement effect of high strength steel pipe through the measurement results of deformed shape and stress of steel pipe arising from excavation after constructing high strength steel pipe and general steel pipe at actual sites. The research results show that high strength steel pipe has excellent bending strength and the reinforcement effect of reinforced grouting. Further, it is expected that high strength steel pipe will have an arching effect thanks to strength increase.

A Study on the Deformation Characteristics of Gas Pipeline under Internal Pressure and In-Plane Bending Load (내압과 굽힘하중을 받는 가스배관의 변형특성에 관한 연구)

  • Jang, Yun-Chan;Kim, Ik-Joong;Kim, Cheol-Man;Jeon, Bub-Gyu;Chang, Sung-Jin;Kim, Young-Pyo
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.15 no.2
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    • pp.50-57
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    • 2019
  • This paper investigates deformation characteristics of gas pipeline using the in-plane bending experiment and finite element analysis of a pipe bend. The effect of the bending angle and internal pressure on the deformation characteristics is analyzed. The pipe bend used in this study is API 5L X65 (out diameter: 20 inch) material with the thickness of 11.9 mm. The maximum load, displacement at maximum load, angle and local strain of 90° pipe bend are obtained from the in-plane bending experiment. Comparison between FE results and experimental data shows overall good agreements. In addition, the deformation characteristics of 22.5° and 45° pipe bend are calculated using the finite element analysis. As a result, the effect of the bend angle on the deformation characteristics is discussed.

Characteristics of Structural Behavior of Unplasticized Polyvinyl Chloride (PVC-U) Pipe Buried Underground (지중매설 경질폴리염화비닐관의 구조적 거동)

  • Kim, Sun-Hee;Cheon, Jinuk;Kim, Eung-Ho
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.6 no.4
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    • pp.16-23
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    • 2015
  • The industrialization and urbanization forced to increase the density of pipelines such as water supply, sewers, and gas pipelines. The materials used for the existing pipe lines are mostly composed of concretes and steels, but it is true that the development for more durable and efficient materials has been continued performed to produce long lasting pipe lines. Recently, underground pipes serve in diverse applications such as sewer lines, drain lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, etc. In this paper, we present the result of investigation pertaining to the structural behavior of unplasticized polyvinyl chloride (PVC-U) flexible pipes buried underground. In the investigation of structural behavior such as a ring deflection, pipe stiffness, 4-point bending test, experimental and analytical studies are conducted. In addition, pipe stiffness is determined by the parallel plate loading tests and the finite element analysis. The difference between test and analysis is about 8% although there are significant variations in the mechanical properties of the pipe material. In addition, it was found by the 4-point bending test there is no problem in the connection between the pipes by coupler.

A Study on the Deformation of O.D 245mm Off-shore Plant Pipe by Induction Bending (고주파 벤딩을 통한 직경 245mm 해양플랜트 배관의 변형에 관한 연구)

  • Joo, Yi-Hwan;Kim, Namyong;Kim, Dong-Seon;Lyu, Sung-Ki
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.8
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    • pp.72-78
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    • 2022
  • Bending using high-frequency induction heating is used to bend pipes and sections, and is currently widely applied in industrial fields such as power generation facilities, ships, onshore plants, and offshore plants. The purpose of this study is to study the manufacturing process and design technology of high-frequency bending of pipe to make the best pipe design arrangement. Although various studies are being conducted in the field of high-frequency bending, more research is needed on high-frequency bending of pipes for ship building and offshore plants. The purpose of this study is to review the feasibility of production design using 3D model tool of S3D and AM(PDMS), and to review and improve bending thickness reduction, reduction rate, and roundness.