• Title/Summary/Keyword: Reverse Moment

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Analysis and Process Design of Hot Pipe Bending Process With Small Bending Radius (작은 곡률반경 파이프 벤딩을 위한 열간 파이프 벤딩공정 해석 및 설계)

  • 류경희;김동진;김병민;이동주
    • Transactions of Materials Processing
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    • v.10 no.4
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    • pp.329-337
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    • 2001
  • The finite element simulation model and the program to calculate the reverse moment have been developed to analyse the stress state and deformation of pipe bending using local induction heating with small bending radius in this study. The reverse moment that is to be applied on the bending arm to control the wall thinning ratio of the bending outside to within a particular value. Even though the demand of pipes with small bending radius is increasing in power plants and ship buildings, the welded elbows are still widely used. The bending process with or without a reverse moment acting on the bending arm has been simulated. The reverse moments calculated from the developed program are in good agreement with the finite element simulations and the experiments.

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An Optimum Design of Pipe Bending Process Using High Frequency Induction Heating and Dynamic Reverse Moment (고주파 유도가열 및 동적 반력 모멘트를 이용한 파이프 벤딩 공정의 최적설계)

  • Lee, H.W.;Jung, S.Y.;Woo, T.K.;Kim, C.
    • Transactions of Materials Processing
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    • v.19 no.2
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    • pp.79-87
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    • 2010
  • The Pipe bending process using high frequency local induction heating is an advanced technique to bend pipes with a small bending radius and a large diameter. Even though the pipe bending process is a quite widespread engineering practice, it depends heavily upon trial and error method by field engineers with several years of experience. So it is necessary to develop an integrated methodology for optimum design of the pipe bending process. During hot pipe bending using induction heating, outward wall thickness of a pipe is thinned due to tensile stress and the reduction of wall thickness is not allowed to exceed 12.5%. Taguchi method and dynamic reverse moment is proposed to maintain a reduction ratio of thickness within 12.5%, when D/t ratio is high. An application of the proposed approach was compared with those of the finite element analysis and has good in agreements.

Process Design of the Hot Pipe Bending Process Using High Frequency Induction Heating (고주파 유도가열을 이용한 열간 파이프 벤딩 공정 설계)

  • Ryu, Gyeong-Hui;Lee, Dong-Ju;Kim, Dong-Jin;Kim, Byeong-Min;Kim, Gwang-Ho
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.9
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    • pp.110-121
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    • 2001
  • During hot pipe bending using induction heating, the wall of bending outside is thinned by tensile stress. In design requirement, the reduction of wall thickness is not allowed to exceed 12.5%. So in this study, two methods of bending, one is loading of reverse moment and the other is loading of temperature gradient, have been investigated to design pipe bending process that satisfy design requirements. For this purpose, finite element analysis with a bending radius 2Do(outer diameter of pipe) has been performed to calculate proper reverse moment and temperature gradient to be applied. Induction heating process has been analyzed to estimate influence of heating process parameters on heating characteristic by finite difference method. Then pipe bending experiments have been performed for verification of finite element and finite difference analysis results. Experimental results are in good agreement with the results of simulations.

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A Study on Reducing Rolling Mode Effect in High-Sensitivity Optical Pickup 3-axis Actuator (고감도 3축구동 액츄에이터를 위한 Rolling Mode 저감 연구)

  • 김영중;홍삼열;김진아;최인호
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.775-779
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    • 2003
  • Recently, a new type actuator using multi-pole magnet has been developed for high-density and high-speed disk drive, which can be achieved higher sensitivity than a conventional actuator for applying one-pole magnet. However, it is very difficult for the actuator of multi-pole magnet to meet simultaneously the optimal design condition for reducing rolling mode effect and improving driving sensitivity because the force center is different from the mass center In this paper, First We propose the new shape coil for tracking which can reverse moment additionally in tracking motion, Next we achieve the optimal design to reduce phase disturbance and peak gain at the rolling mode frequency. Finally, the validity of the proposed methods is proved from experimental results.

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Changes of Ground Reaction Forces by the Change of Club Length in Golf Swing (클럽의 길이 변화에 따른 골프 스윙의 지면반력 변화)

  • Sung, Rak-Joon
    • Korean Journal of Sport Biomechanics
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    • v.17 no.2
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    • pp.31-40
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    • 2007
  • Proper weight shifting is essential for a successful shot in golf swing and this could be described by means of the ground forces between the feet and ground. It is assumed that the ground forces would different according to the club used because the length and swing weight of each club is different. But, in present, it is not clear what changes are made by the change of clubs and this affect the swing motion. Therefore this study focused on the investigation of the changes of the ground forces and ground reaction forces (GRF) by the change of club length. The subjects were three professional male golfers. Four swings (driver, iron 3, iron 5, and iron 7) for each subject were taken by two high speed video cameras and two AMTI force platforms were used to measure the GRF simultaneously. Kwon GRF 2.0 and Mathcad 13 software were used to post processing the data. Changes of the three major component of GRF (Vertical, lateral, anterior-posterior force) at 10 predefined events were analyzed including the maximum. Major findings of this study were as follows. 1. Vertical forces; - There were no significant changes until the top of backswing. - Maximum was occurred at the club horizontal position in the downswing for both feet. The shorter club produced more maximum forces than longer ones in the left foot, but reverse were true for the right foot. - Maximum forces at impact shows the same patterns. 2. Lateral forces; Maximum was occurred at the club horizontal position for both feet, but there were no lateral forces because the direction of two forces was different. Maximum force pattern by different clubs was same as the vertical component. 3. Anterior-posterior forces; - This component made a counter-clock wise moment about a vertical axis located between two foot until the club vertical position was reached during the backswing, and reverse moment were produced when the club reached horizontal at the downswing. - Also this component made a forward moment about a horizontal axis located in the CG during the fore half of the downswing, and a reverse moment until the club reached vertical at the follow through phase. Maximum was occurred at the club vertical in the downswing for both feet. The longer club produced more maximum forces than shorter ones for both feet.