• Title/Summary/Keyword: Bending

### A Discussion on Measurement of Springback Ratio Using Winding Bend (감아굽힘 시험장치의 제작과 스프링백 비의 시험법에 대한 역학적 검토)

• 김용우
• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.95-101
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• 2000
• To measure springback ratio of thin sheet or plate, winding bend rig is made. It bends a specimen with keeping its curvature constant and measures the bending angles before and after release of bending load. To check the performance of the bend rig, we calculated the bending moment by two ways which are based on simple beam theory. One is that the bending moment is calculated by using the results of bending test, and the other is that the moment is calculated by using the results of tensile tests. The former may entails the effect of the friction between bending pin of the rig and the surface of specimen, but the latter does not contain any effects of the friction since the bending moment is obtained by using tensile tests. Nevertheless, the values of the two bending moment shows the same level of bending moment, which implies that the friction does not influence on the value of springback ratio in spite of the presence of friction within the cope of the test performed in this experiment.

### Forming Simulation of the Extrn-Bending Process of the Angle Product with '${\wedge}$' Section ([ '${\wedge}$' ]단면 앵글 구조재의 압출굽힘 가공에 관한 성형해석)

• Lee K. K.;Jin I. T.
• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.346-349
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• 2004
• In the previous experimental study about extru-bending of angle product, the bending of extruded angle products with the '${\wedge}$' section and 'ㄱ' section can be abtained 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 simulation of extru-bending process by the difference of punch velocities. The result of the forming simulation by $DEFORM^{TM}-3D$ shows that the bending phenomenon at the die exit during extrusion can be abtained by the two punches moving in the different velocity. And it is possible to design extrusion dies and to control the curvature of product through the simulation of extru-bending process by analysis

### Pre-Bending Analysis of Tie-Bar for Hydroforming (Hydroforming을 위한 Tie-bar의 예비굽힘성형 해석)

• 강대철;전병희;성부용
• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.255-261
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• 2000
• Tube bending is one of the conventional manufacturing process. Recently, tube bending was highlighted in automotive industry by hydroforming. Tube hydroforming process is divided into pre-bending process and hydroforming process. It's initial state is very important in die cavity of first hydroforming process. So tube bending is important factor of the hydroforming process. In this paper, two pre-bending simulations, by a rotary draw bending machine and a bend die. This paper presents the simulation results in pre-bending process that is used to form an automotive part, tie-bar.

### Production of CO2 Laser Forming Machine for Bending of Sheet Metal Using the FE-Analysis (유한요소해석을 이용한 박판 벤딩용 CO2 레이저 성형기 제작)

• Ko D.C.;Lee C.J.;Kim B.M.
• Transactions of Materials Processing
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• v.15 no.4 s.85
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• pp.319-325
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• 2006
• The laser forming process is a new flexible forming process without forming tools and external force, which is applied to various fields of industry. Especially, applications of the laser forming process focused on cutting, welding and marking process. In this paper, the laser bending process of sheet metal which is heated by laser beam and formed by internal stress is simulated by using thermo elastic-plastic analysis model. Based on the result of FE-analysis, the laser bending machine is made to obtain reliable data for sheet bending. Under the same condition as FE-analysis, the laser bending experiment has been performed to ver 펴 the result of FE-analysis and good agreement has been obtained between FE-analysis and experiments. Additional laser bending experiments have been performed to evaluate the laser bending machine.

### A Study on the Bending Properties of Fabrics for Korean Women's Clothes (부인용 한복지의 굽힘특성에 관한 연구)

• 성수광
• Journal of the Korean Home Economics Association
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• v.26 no.1
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• pp.11-19
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• 1988
• Bending properties of 168 commercial silk fabrics and polyester fabrics for korean women's clothes were tested by KES-F system. Samples were classified into for summer, fall & winter fabrics. In this study, bending regidity(B) and bending hysteresis(2HB) were measured, then 2HB/W, {{{{ SQRT { 2HB/W} }}}}, 2HB/B which are concerning to formation of weared clothes and transformation behavior were investigated. fabrics for korean women's silk clothes for fall & winter were compared with fabrics for japanese kimono clothes on the bending properties. The results were as follows : 1. The bending regidity of silk fabrics were higher than polyester fabrics and bending hysteresis of fall & winter fabrics were higher than summer fabrics. 2. The 2HB/W and {{{{ SQRT { 2HB/W} }}}} of polyester fabrics were lower than silk fabrics. 3. the silk fabrics for summer clothes were the least in 2HB/B. 4. Silk fabrics for korean women's clothes were almost the same in bending rigidity, bending hysteresis and thickness of fabrics for japanese kimono clothes, but weight of the silk fabrics were lower to fabrics for jpanese kimono clothes.

### Analytic Factor Effects Analysis of Bending Process of Double Pipe for Tube-Hydroforming using Experimental Design (실험계획법을 이용한 튜브 하이드로 포밍용 이중관 벤딩 공정의 해석적 요인 효과 분석)

• Shim, D.S.;Jung, C.G.;Seong, D.Y.;Yang, D.Y.;Park, S.H.;Kim, K.H.;Choi, H.H.
• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.310-313
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• 2007
• This paper covers finite element simulations to evaluate the bending limit of double pipe for tube-hydroforming. The tube-hydroforming process starts with a straight precut tube. The tube is often prebent in a rotary draw bending machine to fit the hydroforming tool. During the bending the tube undergoes significant deformation. So forming defects such as wrinkling, thinning and flattening are generated in the tube. Consequently we analyzed the effect of process parameters in rotary draw bending process and searched the optimized combination of process parameters to minimize the forming defects using orthogonal arrays. The characteristic to evaluate the effects of the process parameters is the bending angle which wrinkling is generated, we define the bending angle at that time as bending limit. Of many process parameters, the process parameters of the bending process such as gab between inner and outer tube, boosting force, dimensions of mandrel were analyzed. And we observed the deformation modes of bent double pipe at specific bending angle in each parameter combination.

### Effect of Fibre Blend Ratios and Twists on the Bending Behavior of 2 Folded Staple Yarns (II)-Bending Properties of Folded Yarns- (섬유의 혼합율과 꼬임 구조가 2합 방직사의 굽힘 특성에 미치는 영향(II)-합사의 굽힘 특성-)

• Kim, Han-Seong;O, Ae-Gyeong;Kim, Seung-Jin
• Textile Science and Engineering
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• v.30 no.7
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• pp.485-495
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• 1993
• The bending propertied of the 2 folded yams such as the bending rigidity, the coercive couple, the hysteresis energy and the residual curvature with various wool/polyester blend ratios and with variations of the single and 2-folded yarns twists were stylied for analyzing twist characteristics, inter and intra frictional effects. The value of the experimental specific bending rigidity of two folded staple yarns were in the range of 1.2 and 2.5 times of the estimated values, and the experimental specific bending rigidities of 2 folded yarns divided by the power of 1.2 of its linear density were almost same as the experimental specific bending rigidities of single yarns. The experimental specific bending rigidities of the 2 folded staple yarns were found to show the maximum values in the range of the same twist between the single and 2 folded yarns with increasing 2 folded yarn twist with fixed single yarn twist. The values of the coercive couple, the residual curvature and the hysteresis energy of the 2 folded staple yarns showed almost sane tendency as that of the specific bending rigidity. Maximum bending rigidity to wool/polyester blend composition was shown around the range of same blend composition, and maximum bending recovery was also shown in this range, then coercive couple and hysteresis energy were increased with polyester colnposition.

### A Study on the Derivation of Springback Compensation Angle Trend Line in Tube Bending (튜브 벤딩시 스프링백 보정각 추세선 도출에 관한 연구)

• Lee, D.Y.;Oh, S.G.;Choi, B.S.
• Transactions of Materials Processing
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• v.29 no.4
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• pp.188-193
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• 2020
• Piping work of large ships or offshore plants is often done in a narrow and confined space, requiring precise bending and safety. In order to realize an accurate bending angle, it is very important to predict and correct a deformation that may be caused by elasticity in the bending process, that is, an angular deviation due to springback. Therefore, by using CAE analysis to develop a correction angle model for springback based on multiple tube bending angles and using trend line data derived from this correction angle model, at bending the tube as the diameter of the base former and the tube outer diameter change, the springback compensation angle at any angle can be obtained. In this study, the bending mechanism was analyzed to increase the bending precision, and a correction angle model was developed and a trend line was derived in consideration of springback occurring in the bending process. In order to derive a more accurate and reliable trend line, a tube tensile test was performed, and the reliability of the corrected angle trend line was verified by comparing the bending angle measurement and analysis results with a 3D scanner.

### Development of Measurement Device for Bending Stiffness of Footwear (신발의 굽힘강성 측정 장비의 개발)

• Lee, Jong-Nyun
• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1078-1084
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• 2011
• In design of sport footwear, bending stiffness of its toe part is an important factor though it can be hardly measured. This paper introduces a device for measuring the bending stiffness. The device is simply designed with aluminum frames, one AC motor, two load-cells, one encoder and control hardwares. The mechanism measuring the bending moment of a shoe is described. Then, it was used to observe how the midsole material and design of a sports shoe affect on its bending stiffness. For the experiments, various specimens prepared, where each midsole of the specimens is different in terms of material, thickness and hardness. With those specimens, experiments were performed by using the device and then the bending stiffness was computed by applying the least square curve fitting after the bending moment data were measured. The specimen with Poly-urethane(PU) midsole has the higher bending stiffness than the one with Phylon(PH) midsole, and the midsole thickness affects more on the bending stiffness than the midsole hardness. Based on those results, it can be concluded that the measurement device can provide consistent bending stiffness data to sports footwear and the bending stiffness of a footwear measured by the developed device can be used as a major parameter in the footwear design.

### A Comparative Study on the Kinematic Factors and GRF with Poombalbki Types in Taekkyon (택견 품밟기 유형에 따른 운동학적 변인과 지면반력 차이 분석)

• Oh, Seong-Geun;Ryu, Ji-Seon
• Korean Journal of Sport Biomechanics
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• v.20 no.1
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• pp.57-65
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• 2010
• Korean traditional martial arts Taekkyon has a unique stepping method, Poombalbki. The purpose of this study was to investigate kinematic factors and ground reaction forces on two types of Poombalbki, one of which use knee bending and the other use chiefly hip bending. Six male taekkyoners who are the students of Y University participated in this study. Positions and velocities of CoM, the elapsed times of each phase, angles and angular velocities of low limb joints, and GRFs were analyzed for this study. The results were as follows; CoMs of whole body, trunk, and head were more posteriorly positioned in performing hip bending Poombalbki than knee bending one. Horizontal velocities of those were slower in performing hip bending Poombalbki. A player stayed more shortly within range of his opponent in performing hip bending Poombalbki. The vertical and horizontal components of GRF of forward-stepping foot were smaller in performing hip bending Poombalbki(p<.05). In conclusion hip bending is useful strategy, because A player is farther from his opponent, he stayed more shortly within range of his opponent, and the smaller weight is loaded on his front foot in performing hip bending Poombalbki than knee bending one.