• Title/Summary/Keyword: Bending

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A Study on Characteristics of Bending Deformation in Cylindrical Die (원통형 다이를 이용한 굽힘의 변형특성에 관한 연구)

  • Kim, Yang-Woo;Lee, Dae-Su
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.4
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    • pp.59-66
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    • 2008
  • This paper has proposed a new parameter to interpret the effects of plastic deformation in bending of strips in cylindrical die and punch. With reference to the parameter, we have provided an insight on the separation between strips and punches, the occurrence of the multi-point bending during the process of deformation, the final shapes of strips, and the springback ratios. Also using the parameter, we have considered the different effects between the bending deformation in the cylindrical die and the bending deformation due to pure bending.

Characteristic responses of critical current in REBCO coated conductor tapes under tensile/compressive bending strains at 77 K

  • Diaz, Mark Angelo;Shin, Hyung Seop;Lee, Jae-Hun
    • Progress in Superconductivity and Cryogenics
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    • v.20 no.4
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    • pp.31-35
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    • 2018
  • When REBCO coated conductors (CCs) are applied to superconducting devices such as coils and magnets, they are subjected to deformation in various modes such as compression/tension bending, uniaxial/transverse tension and torsion. Despite outstanding performances by REBCO CC tapes, their electromechanical properties have been evaluated primarily under uniaxial tension, therefore data about the critical current ($I_c$) response in the compressive strain region are lacking. In this study, the characteristic responses of $I_c$ in REBCO CC tapes under bending strains in the range from tensile to compressive were evaluated. The springboard bending beam was used, wherein the CC tape sample was soldered onto the surface of the springboard. A Goldacker-type bending test rig, which lacks a support holding the sample during testing, was used as a comparator. Degradation in $I_c$ behaviors, including strain sensitivity, in differently processed REBCO CC tapes were examined based on the test rig used.

A Study on the Bending and Seismic Performance of High Performance Cold Forming Composite Beam

  • Choi, Young Han;Kim, Sung Bae;Hong, Hyung Ju;Kim, Sang Seup
    • International journal of steel structures
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    • v.18 no.5
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    • pp.1772-1783
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    • 2018
  • Nowadays, the researches about composite structure system are being implemented in various fields, and many steel structures are designed based on that. In this study, the bending and seismic performance of the newly developed high-performance cold forming composite beam are evaluated by several experiments. As a result of the bending performance test, the bending moment of beam was increased stably depending on the depth and plate thickness of beam, and it is considered that the bending moment can be evaluated by the equation of a composite beam design. As a result of the seismic performance test, it was verified that sufficient seismic performance was obtained despite the increase of a negative moment rebar and depth of beam. In addition, the nominal bending moment has obtained the strength above the plastic bending moment, and also the plastic rotation angle has satisfied the requirement of composite intermediate moment frame.

Development of an AFM-Based System for Nano In-Process Measurement of Defects on Machined Surfaces (가공면미세결함의 나노 인프로세스 측정을 위한 AFM시스템의 개발)

  • Gwon, Hyeon-Gyu;Choe, Seong-Dae;Park, Mu-Hun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.3
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    • pp.537-543
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    • 2002
  • This paper examines a new in-process measurement system for the measurement of micro-defects on the surfaces of brittle materials by using the AFM (Atomic Force Microscopy). A new AFM scanning stage that can also perform nano-scale bending of the sample was developed by adding a bending unit to a commercially available AFM scanner. The bending unit consists of a PZT actuator and sample holder, and can perform static and cyclic three-point bending. The true bending displacement of the bending unit is approximately 1.8mm when 80 volts are applied to the PZT actuator. The frequency response of the bending unit and the stress on the sample were also analyzed, both theoretically and experimentally. Potential surface defects of the sample were successfully detected by this measurement system. It was confirmed that the number of micro-defects on a scratched surface increases when the surface is subjected to a cyclic bending load.

A Study on the Bending Collapse at the Open Cross-Section Members with Experiment and Analysis (열린 단면 부재의 굽힘 붕괴 실험 및 해석에 관한 연구)

  • 이승철;강신유
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.4
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    • pp.132-139
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    • 2004
  • The open section members have been used as the members of vehicle such as automotives, airplanes and trains. When vehicles are crashed, these members have absorption of the energy and it is necessary for retainment of the survival space, and as the result, the prediction for the displacement of members in this case of the crash of vehicles is very important. The displacements of members in this case of the crash of automotives show combined aspect of both axial collapse and bending collapse. In the rollover accident when bending collapse happen, the collapse of each members is progressed by the plastic hinge which made from bending moment, and therefore the research for the behavior of members under bending moment after collapse is necessary to determine the internal energy which the members can absorb and the deformed shapes of the members on the step of design. In this paper, the characteristics of bending collapse at the members of the open cross-section were studied with experiment and numerical analysis. We made a comparative studied of the result of the experiment, and changed the axis according to the parallel-axis theorem.

Auto-Bending Manufacturing System for Boiler Tubes (보일러 튜브 자동벤딩 생산시스템 개발)

  • Lee, Hyun-Soo;Kang, Moon-Hyun;Park, Jun-Kon;Hur, Kwan;Sung, Joon-Suk;Heo, Wang-Soon
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.450-454
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    • 1997
  • This system is the automatic boiler tube bending equipment which has four heads for bending the tube and the carriage for moving the tube. The system consists of two frames for transporting each moving parts, high-frequency heating equipment for heating the tube in hot bending, control panel for inputting the job data operating, remote control unit for concetration and distribution of input/output, and the monitoring system which can establish unmanned operationby receiving the bending job data via LAN form a design teamwhich produces the job data and schedule based on master production plan and diagnoses bending data change, input, whole system status, and system malfunctions. By employing this system, 30% of production improvement was achieved was achieved comparing to the existing bending system.

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Bending Mechanism Analysis and Bending Coupler Optimal Design for Laparoscopic Surgical Instrument (복강경수술기구의 벤딩메커니즘 해석 및 벤딩커플러 최적설계)

  • Hwang, Dal Yeon;Moon, Dae Hoan;Choi, Seung Wook;Won, Jong Seok
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.4
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    • pp.434-441
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    • 2013
  • Bending motion has been used in the surgical instruments with bending structures and tendon mechanisms. A simplified bending angle amplification ratio between the proximal and distal bending joint was derived in this article. The bending structure of disk and rib in the proximal joint was analyzed based on finite element method with an emphasis on the circumferential uniformity of bending stiffness. Regarding the distal joint, optimal design and sensitivity analysis was done with four design variables of outer and inner diameter, rib height and rib width while maximizing the deformation under the stress distribution below the yield stress. Outer diameter and rib width are most critical to maximum deformation as the outer diameter and inner diameters are so to maximum equivalent stress.

A Study on the Extru-Bending Process of the Angle Product with 'Λ' Section Using Two Extrusion Billets (두 개의 압출빌렛을 사용하는 'Λ' 단면 앵글 구조재의 압출굽힘가공에 관한 연구)

  • Lee K. K.;Jin I. T.
    • Transactions of Materials Processing
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    • v.14 no.2 s.74
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    • pp.160-167
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    • 2005
  • In the present study about extru-bending of angle product, the bending of extruded angle products with the $'\Lambda'$ section and 'ㄱ', section can be obtained using two extrusion billets by the hot metal extru-bending machine with the two punches moving in the different velocity. The bending curvature can be controlled by the different velocity of billets through the two-hole container. This paper describes simulations and experiments of extru-bending process that can make bending during extruding by the difference of stem velocities. And they are applied to two kinds of dies, that is, one of them is conical dies with symmetry $'\Lambda'$ section and the other one is conical dies with asymmetry 'ㄱ' section. The results of the forming simulation by $DEFORM^{TM}-3D$ and results of experiments show that the bending phenomenon at the die exit during extrusion can be obtained with two extrusion billet by the two stems moving in the different velocity. And it was known that it is possible to design the structure of conical cavity of extrusion dies and to control the curvature of product through the simulation and experiment of extru-bending process.

The Effect of Exposure in Elevated Temperatures on Bending Properties of Wood

  • Park, Joo-Saeng;Lee, Jun-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.27 no.4
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    • pp.20-29
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    • 1999
  • Temperature has important effect on mechanical properties of wood. These effect needs to be understood and taken into account in the structural use of wood. Furthermore, the effect of cooling after exposing to high temperature must be explained. In this study, the effect of temperature, exposure time, specific gravity, and cooling on bending properties were investigated. The boundary temperatures at which bending MOE and MOR reduced rapidly were approximately $200^{\circ}C$ and $150^{\circ}C$, respectively. This boundary temperature was nearly constant with independence of species(specific gravity), exposure time, and cooling. Above the boundary temperature, the effect of exposure time was increased with temperature and the reduction of bending MOE and MOR for Japanese Larch with relatively higher specific gravity was smaller than that of Hem-fir. The recovery of bending MOE and MOR after cooling was also more significant above the boundary temperature than below. The degree of cooling effect was larger for MOR than MOE. Consequently, bending properties of wood in elevated temperatures should be considered in terms of the boundary temperature, $200^{\circ}C$ for bending MOE, $150^{\circ}C$ for MOR, and these boundary temperatures must be considered an important factor. Furthermore, to evaluate the safety of structure, the recovery after cooling should be considered.

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Cracking and bending strength evaluations of steel-concrete double composite girder under negative bending action

  • Xu, Chen;Zhang, Boyu;Liu, Siwei;Su, Qingtian
    • Steel and Composite Structures
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    • v.35 no.3
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    • pp.371-384
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    • 2020
  • The steel-concrete double composite girder in the negative flexural region combines an additional concrete slab to the steel bottom flange to prevent the local steel buckling, however, the additional concrete slab may lower down the neutral axis of the composite section, which is a sensitive factor to the tensile stress restraint on the concrete deck. This is actually of great importance to the structural rationality and durability, but has not been investigated in detail yet. In this case, a series of 5.5 m-long composite girder specimens were tested by negative bending, among which the bottom slab configuration and the longitudinal reinforcement ratio in the concrete deck were the parameters. Furthermore, an analytical study concerning about the influence of bottom concrete slab thickness on the cracking and sectional bending-carrying capacity were carried out. The test results showed that the additional concrete at the bottom improved the composite sectional bending stiffness and bending-carrying capacity, whereas its effect on the concrete crack distribution was not obvious. According to the analytical study, the additional concrete slab at the bottom with an equivalent thickness to the concrete deck slab may provide the best contributions to the improvements of crack initiation bending moment and the sectional bending-carrying capacity. This can be applied for the design practice.