• Title/Summary/Keyword: Bending

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Effect of Grain Angle on Bending Properties of Pinus densiflora (소나무재의 휨 가공성에 미치는 섬유경사각의 영향)

  • Kim, Jung-Hwan;Lee, Weon-Hee
    • Journal of the Korean Wood Science and Technology
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    • v.29 no.2
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    • pp.118-125
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    • 2001
  • In this study, it was examined the characteristics of bending property of red pine(Pinus densiflora S, et Z.) related to slope of grain. At first, we have investigated the characteristics of wood species for bending property. At second, it was examined the relationships between grain angle and its related bending property. Specimens were made following to grain angle $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $90^{\circ}$, respectively. Dimension of wood materials was $10mm(T){\times}20mm(R){\times}350mm(L)$. Microwave irradiation time for bending process was 30, 60, 90, 120 seconds. The result of this study were as follows ; 1. Grain angle of wood was closely related to Young's modulus on bending process. In the process of bending with various grain angle, wood bending was easily proceed on the high grain angle range. 2. However, the strength of bent wood was very weak when the grain angle was high. Therefore, it was considered suitable grain angle for bending was existed. 3. The characteristics of wood properties for wood bending were very different among wood species.

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Analysis on the Mechanism of Fluting in the Bending of Low Carbon Steel Sheets (저탄소강판을 이용한 굽힘 가공에서 발생하는 꺽임현상에 대한 발생 기구 해석)

  • Park, K.C.;Yoon, J.B.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2007.05a
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    • pp.336-339
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    • 2007
  • In order to investigate the cause of fluting in tangential bending of low carbon steel sheet, an analytic analysis, an experiment and a series of finite element analysis for bending process were done. The fluting in bended sheet was due to the yield point elongation of material. Due to the yield point elongation, unstable plastic hinge was occurred in course of bending of elastic perfectly plastic sheet. According to the analysis and computational results, lower yield point elongation than 5% was required to prevent fluting in $0.5{\sim}0.6t$ sheet in $15{\sim}20mm$ radius bending.

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2-Dimensional Finite Element Analysis of Forming Processes of Automotive Panels Considering Bending Effects (굽힘 효과를 고려한 자동차 패널 성형 공정의 2차원 유한 요소 해석)

  • 김준보;금영탁
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.6
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    • pp.27-38
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    • 1996
  • A two-dimensional FEM program, which considers bending effects in the membrane fromulation, was developed under plane strain assumption for analyzing forming processes of an arbitrarily shaped draw-die of automotive panels. For the evaluation of bending effects with membrane elements, the bending equivalent forces and stiffnesses are calculated from the bending moment computed using the changes in curvature of the formed shape of two membrane ones. The curves depicted with 3 nodes are described by a circle, a quadratic equation, and a cubic equation, respectively, and in the simulation of the stretch/draw sections of an automotive inner panel, three different description results are compared each other. Also, the bending results are compared with membrane results and measurements in order to verify the validity of the developed program.

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Sectional forming analysis by membrane finite elements considering bending effects (굽힘효과를 고려한 박막 유한요소에 의한 단면 성형해석)

  • Kim, Jun-Bo;Lee, Gwang-Byeong;Keum, Yeong-Tak
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.3
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    • pp.493-503
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    • 1998
  • The sectional forming analysis considering bending effects from the geometrically deformed shape of two linear membrane finite elements(called super element) was performed under plane strain assumption for analyzing forming processes of an arbitrarily shaped draw-die. For the evaluation of bending effects, the bending equivalent forces are calculated from the bending moment computed using the changes in the interior angle at the middle node of super element, and are agumented to the membrane stretch forces. In order to verify the validity of the bending formulation, the simulation results for the stretch, draw, and bend sections were compared with membrane analysis results and measurements.

Center Pillar Design for High Bending Collapse Performance (굽힘 붕괴 성능 향상을 위한 센터 필라 설계)

  • Kang, Sungjong;Park, Myeongjae
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.4
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    • pp.128-134
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    • 2013
  • High bending collapse performance (maximum resistance force and mean resistance force) of body center pillar is an important design target for vehicle safety against side impact. In this study, effect of the upper section shape and the thickness of outer reinforcement on bending collapse performance was investigated for the center pillar of a large passenger car. First, through bending collapse analyses using simple models with uniform section, an optimized center pillar upper section was chosen. Next, bending collapse performance for various models of the actual center pillar with changing the thickness of outer reinforcement were analyzed. The finally designed model showed distinctive enhancement in bending collapse performance nearly without weight increase.

An Experimental Study on Deep Collapse of Steel Tubes under Pure Bending (순수 굽힘 시험기를 이용한 연강 사각관의 굽힘 붕괴에 관한 실험적 연구)

  • KiM, C.S.;Chung, T.E.;Kang, S.Y.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.9
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    • pp.37-44
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    • 1997
  • In this paper the bending collapse characteristics of square and rectangular steel tubes were studied with the pure bending test machine which apply pure bending moment without imposing shear and tensile forces. Under pure bending moment, delayed buckling modes occur and depend on test length and shape of section. For delayed mode, the endrgy of bending moment is absorbed by strain hardening energy. The pre- dictions of maximum moment and moment-rotation angle curve from those concepts are in good agreement with experimental observations.

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A Study on the Development of the Continuous 3D Tube Bending Machine (연속 3 차원 튜브 벤딩장치 개발에 관한 연구)

  • Mun, Hyeon-Jun;Kim, Chung-Sup;Kim, Jong-Doo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.8
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    • pp.701-706
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    • 2008
  • A continuous 3D tube bending machine has been developed for industrial boiler panel production. The machine consists of a main bender, a sub bender, a side bender, tube feeding rollers and control system that includes data management system. Tube position is controlled by a numerical control system. The bending former can be easily replaced according to the shape of bending form. Reduction of working time and improvement of production capacity from the practice have been achieved by bending a long tube in the machine developed.

Ultimate Transverse Bending Strength Analysis of a SWATH Ship (SWATH선의 최종 횡굽힘강도 해석)

  • 박치모
    • Journal of Ocean Engineering and Technology
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    • v.6 no.2
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    • pp.103-112
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    • 1992
  • The calculation method which takes into account the shear lag effects on the ultimate transverse bending moment of a SWATH(Small Waterplane Area Twin Hull) ship has been developed. In case of the ultimate bending strength analysis of conventional monohull ships and general box girder structures, the hypothesis that plane section remains plane after bending can be employed but not in the case of the structures having wide flange. For the ultimate bending strength analysis of such structures, a new method which can take into account the effect of shear lag on the ultimate bending strength has been developed by adopting more reasonable assumption that warping distortion of the section takes place inthe same way as the actual stress distribution. Finally, the proposed method has been applied to a a SWATH cross deck structure.

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Estimation of Plastic Bending Moment of Offshore Pipelines (해저관로의 대변형 굽힘에 의한 소성 모멘트 추정)

  • 이종현;최한석;이승건
    • Journal of Ocean Engineering and Technology
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    • v.17 no.2
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    • pp.21-26
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    • 2003
  • The reel-lay method of submarine pipelines a continuous string of pipe coiled onto a reel. Assembly of this pipe that is string is accomplished onshore by welding, and nondestructive testing is carried out prior to coiling the pipe. The total length of pipes on the reel depends on the reel and pipe diameters. Pipeline installation is accomplished by uncoiling, straightening the pipe, and laying out the pipe string onto the seabed as the barge moves forward. Installation associated with coiling and uncoiling is related to the bending moment and strain relationship of the pipeline, A highgrade pipe material is required when the reel-lay method is used. This paper is concerned with the highly plastic bending moment of the pipeline, including the effect of ovality. Moment calculation in the pipe is accomplished by the numerical method, including the variable ovalities during the plastic bending of the pipe string. The new calculation method of the high plastic bending moment was applied to the reel-lay method.

An Experimental Study on the Cold Bending of Reinforcing Bar (철근의 Bending and Straightening에 대한 실험적 연구)

  • 조현우;최희복;강경인
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2003.05a
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    • pp.109-113
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    • 2003
  • In this experiment, we distribute the bending angle to 60$^{\circ}$, 90$^{\circ}$, 120$^{\circ}$, and we separate it in to two groups. One is straightening right after bending and the other is straightening after one week. The bars we will use are HD13 and HD16. The number of tests will be 60 times. In the case of HD16, the increase of bending angle decreased yield strength and maximum strength. And compared with thinner bars, HD16 showed bigger differences in yield strength and maximum strength when the 'being bent' duration got longer. So it shows that when we bend and after straighten a bar, stress change takes place on the surface of the bar. At the beginning it shows it's ductility after that it deforms while transforming it's character to destroying. And also, if we straighten a bar after bending, it doesn't get straighten like the original form. So it makes torsion and this torsion makes moments in different areas.

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