• 소성∙가공
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• 제29권4호
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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.

• 한국산업융합학회 논문집
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• 제25권5호
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• pp.827-833
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• 2022

In this study, the prediction of the bending angle for the 350 A bellows-type expansion joints and the structural stability according to the load were determined. The stability of the 2km piping system was predicted by applying the allowable bending angle of the expansion pipe joint obtained from the analysis. The maximum bending angle was calculated through bending analysis of the bellows-type expansion joints, and the maximum bending angle by numerical calculation was about 1.8°, and the maximum bending angle of the bellows obtained by comparing the allowable strength of the material was about 0. 22°. This angle was very stable compared to the allowable bending angle (3°) of the expansion pipe joint regulation. By applying the maximum bending angle, the allowable maximum deflection of the 2 km pipe was about 3.8 m. When the seismic load was considered using regression analysis, the maximum deflection of the 2km pipe was about 142.3mm, and it was confirmed that the bellows-type expansion joints and the deflection were stable compared to the allowable maximum deflection of the pipe system. These research results are expected to present design and analysis guidelines for the construction of piping and the development of bellows systems, and to be used as basic data for systematic research.

• Journal of the Korean Wood Science and Technology
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• 제29권2호
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• pp.118-125
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• 2001

본 연구에서는 소나무의 고부가적 이용을 위한 휨가공 특성을 조사하였다. 먼저 휨가공에 영향을 미치는 수종 특성에 대하여 조사하였다. 다음으로 섬유경사각과 휨가공 특성의 관계에 대하여 조사하였다. 시험편은 섬유경사각 $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $90^{\circ}$와 치수 $10mm(T){\times}20mm(R){\times}350mm(L)$로 제작하였다. 휨가공 전의 고주파조사 시간은 30, 60, 90, 120초로 하였다. 본 연구의 결과는 다음과 같다. 1. 섬유경사각의 크기는 휨가공에 있어 탄성계수와 높은 상관이 있었으며, 섬유경사각이 커질수록 휨가공 성능이 크게 증가하였다. 2 강도적인 측면을 고려할 때, 지나치게 큰 섬유경사각은 강도가 약하기 때문에 휩가공채의 용도에 따라 적당한 섬유경사각의 크기가 조정되어야 할 것으로 판단되었다. 3. 휨가공성은 수종에 따라 현저하게 차이가 있는 것으로 조사되었고 수종특성이 명백히 존재하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.277-280
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• 2003

It was investigated that the "ㄱ" type angle product could be bended with a curvature during extrusion by extru-bending process. The bending process for the "ㄱ" type angle product can be developed by the hot metal extru-bending machine with the two punches moving in the different velocity. Because of non-symmetry of product, it is important to design the ruled surface contour of dies cavity for the welding and bending with two billets. So it is designed that the multi-hole container has two non-symmetric holes and non-symmetric contour of dies entrance. The results of the experiment show that "ㄱ" type angle product can be bended by the extrusion process and that the curvature of the product can be controlled by the velocity of punch and that the defects such as the distortion of section and the thickness change of the product and the folding and wrinkling of the product did not happen after the bending processing by the extrusion bending machine.

• 한국안전학회지
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• 제20권2호
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• pp.18-25
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• 2005

This study performed finite element analysis on the pipe bend with various bend angles under loading conditions of internal pressure and combined pressure and bending, to investigate the effect of bend angle on the collapse behavior of pipe bend and on the stress state in the bend region. In the analysis, the pipe bends with bend angle of $5\~90^{\circ}$ were considered, and the bending moment was applied as in-plane closing and opening modes. From the results of analysis, it was found that the collapse moment of pipe bend increases with decreasing bend angle. As the bend angle decreases, also, the equivalent stress at intrados region increases regardless of bending mode. Under closing mode bending especially, the increase in stress at intrados is significant so that the maximum stress region moves from crown to intrados with decreasing bend angle.

• 대한물리의학회지
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• 제9권4호
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• pp.425-432
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• 2014

PURPOSE: The purpose of this study was to investigate that the differences in sternocleidomastoid muscle activity, neck rotation angle, neck lateral bending angle and neck lateral bending onset time between conditions with and without visual biofeedback during neck rotation. METHODS: Ten male and four female adults with condition of forward head posture were recruited in this study. Subjects conducted to left and right maximal neck rotation under the conditions with and without visual biofeedback. During neck rotation, kinematic data of neck rotation, neck lateral bending movement, and electromyography activities of bilateral sternocleidomastold muscles were collected. Differences in dependent variables between conditions with and without visual biofeedback were analyzed using paired t-test. RESULTS: There were significant decreases in lateral bending angle, while lateral bending movement onset time was delayed significantly when applying visual biofeedback (p<.05). However, there were no significant differences in the activation of left and right sternocleidomastoid muscles and neck rotation angle between conditions with and without visual biofeedback (p>.05). CONCLUSION: These findings suggest that visual biofeedback may be effective for axial rotation of cervical spine during neck rotation in adults with forward head posture.

• 자동차안전학회지
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• 제11권1호
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• pp.40-47
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• 2019

First, three point bending analysis for the inclined press door impact beam was carried out to investigate inclination angle effect on the maximum strength with varying support distance. Next, for the system model with spring elements representing body stiffness at door mounting area, the bending structural behavior of impact beam mounted on vehicle was estimated. The mounting distance and inclination angle were changed and the beam bending buckling strength was presumed at the head displacement below which spring stiffness change has little effect on the load. Finally strength ratio to predict the bending buckling strength of impact beam mounted on vehicle from three point bending maximum strength of fixed support distance was suggested.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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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

• 국제물리치료학회지
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• 제7권2호
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• pp.1051-1055
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• 2016

The purpose of this study was to investigate the effect of the screen size of smart devices on the bending angle of the cervical spine. The subjects of this study were 30 healthy adults(15 men and 15 women) who used smartphones and tablet PC(personal computer). The changes in the bending angle of the upper and lower cervical spine were measured in the subjects after they had used a smartphone and a tablet PC for 300 seconds each. To make sure that all subjects began in the same starting position, an angle-measuring instrument was used to set the angles of the ankle, knee, hip, and arm joints to 90 degree. The subjects were asked to keep the trunk straight. They were asked to hold a smartphone in their hand and to bend their neck so that they could look down at the screen. Once they began using the smartphone in this manner, they were free to change their posture. We used a paired t-test to compare the bending angle of the cervical spine on subjects who used smartphones and tablet PC in the long-term and short-term there production error of cervical and the significance level was cervical. The results showed that, when using a smartphone and a tablet PC for 300 seconds, there was no significant difference in the bending angle of the upper cervical spine(p>.05), although there was a significant difference in the bending angle of the lower cervical spine(p<.05).

• 소성∙가공
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• 제32권4호
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• pp.221-227
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• 2023

While tube bending is a conventional forming technique, it is still used to make curved products for load-bearing members or aesthetically pleasing parts in various manufacturing industries such as automotive, aerospace, and others. Whole or local deformation of the final product such as springback, distortion, or local buckling are of interest in metal forming or precision manufacturing. In this paper, the factors affecting the cross-sectional deformation are explored. A 5-axis stretch bending machine was used for two-dimensional bending with extruded AA6082-T4 rectangular tubes. Three different bending sequences were employed: stretch before bending, stretch after bending, simultaneous bending and stretch. Furthermore, by considering both the stretch and bending angle, cross-sectional deformation was also analyzed. It was observed that employing stretch bending techniques can effectively reduce cross-sectional deformation and contribute to overall quality enhancement. Through this study, it was revealed that these factors have an impact on the cross-sectional deformation of the tubes.