• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.6
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• pp.607-613
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• 2008

A monitoring system for the subway structures using prestrained FBG sensors fixed with partially stripped fibers was developed. The sensor packages had pre-strain controllable fixtures. Tensile and compressive strain of the structure could be measured without slip. The FBG sensor system was applied to the concrete lining structure in Taegu subway. Near the structure, the narrow tunnel construction, for the electric power cables and telecommunication cables, started. We wanted to measure the deformations of the subway structures due to the construction by the FBG sensor. The applied sensors had the gauge length of 1 meter to overcome the inhomogeneity of the concrete material with enough length. In order to fix tightly to the structure, the partially stripped parts of the sensor glued to the package and slip phenomenon between fiber and acrylate jacket was prevented. Prestrain of the sensor was imposed by controlling the two fixed points with bolts and nuts in order to measure compressive strain as well as tensile strain. The behavior of subway lining structure could be monitored very well.

• Tunnel and Underground Space
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• v.18 no.4
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• pp.300-311
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• 2008

In this study, scaled model tests were performed to investigate the stability of three parallel tunnels. Seven types of test models which had respectively different pillar widths, tunnel sectional shapes, support conditions and ground conditions were experimented, where crack initiating pressures and deformation behaviors around tunnels were investigated. In order to evaluate the effect of pillar widths on stability, various models were experimented. As results, the models with shallower pillar widths proved to be unstable because of lower crack initiating pressures and more tunnel convergences than the models with thicker pillar widths. In order to find the effect of tunnel sectional shape on stability, the models with arched, semi-arched and rectangular tunnels were experimented. Among them rectangular tunnel model was the most unstable, where the arched tunnel model with small radius of roof curvature was more stable than semi-arched one. The model with rockbolt showed higher crack initiating pressure and less roof lowering than the unsupported model. The deformation behaviors of tunnels in the anisotropic ground model were quite different from those in the isotropic ground model. Futhermore, the results of FLAC analysis were qualitatively coincident with the experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.794-797
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• 2001

The basic design of today s rolling linear guides with rails is outlined in a French patent from 1932, it was not until the early 1970s that linear guides were commercialized. Progress with the numerical control of machine tools led to higher speed and accuracy of machines that exposed limitations of conventional sliding guides in terms of durability and response capability. As a result, rolling guides, having better high-speed performance and greater compatibility with electronics, began to be used widely. This paper examined theoretically and experimentally the influence of rail bolt tightening on the motion accuracy of linear guides. The rail of a linear guide is tightened and fixed to the base component by bolts. Naturally, the rail is an elastic body and the compression force generated by tightening the volts causes its deflection. Compromising motion accuracy, the rail deforms wavily in a longitudinal direction corresponding to the bolt pitch. The relation between rail position and deflection(sinking) amount caused by bolt tightening was analyzed through FEM analysis in this paper.

• Defense and Technology
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• no.10 s.164
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• pp.43-44
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• 1992

복합재 연소관과 노즐을 기계적 체결방법으로 결합하면 결합부위에서 재료의 불연속성과 기하학적 불연속성으로 인한 높은 응력집중이 발생해 구조적으로 매우 취약하게 됩니다. 복합재 연소관의 경우에는 내압을 받는 원통형 구조물이므로 기존의 평판에 대한 연구결과를 그대로 사용할수 없으므로, 이 글에서는 복합재 셀 구조물의 응력 및 파손 해석을 수행할수 있도록 1차전단변형 셀이론을 이용한 유한요소해석 프로그램을 개발하였습니다. 기계적체결부위의 모델링에 대해 검토하였으며 복합재료의 파손평가에 사용되는 여러가지 파손식을 적용해 비교하였습니다. 이 해석 방법을 이용해 복합재 연소관의 적층각, 볼트직경, 연소관의 끝단까지의 길이 등이 파손하중에 미치는 영향을 제시하였습니다

• Journal of the Korea Institute of Military Science and Technology
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• v.1 no.1
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• pp.189-200
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• 1998

본 연구에서는 얇은 마레이징강으로 제작된 천마 연소관에 브라켓이 용접되어 비행 날개를 볼트로 체결한 경우, 압력과 공력하중에 의해 브라켓 부위에 집중되는 응력의 해석기법을 정립하기 위하여 선형해석과 기하학적 비선형 해석을 수행하였다. 높은 압력에 의해 발생한 얇은 연소관의 면내 응력이 구조물의 강성을 증가시키는 응력의 강성보강효과(stress stiffening effect)를 고려한 기하학적 비선형 해석을 수행하여 선형해석 결과와 비교하였으며, 압력과 공력하중을 동시에 적용할 수 있는 복합하중시험기로 변형률을 측정하여 해석치의 정확성을 검토하였다. 얇은 연소관에 압력과 공력하중이 동시에 작용하는 경우는 응력의 강성보강효과를 고려한 기하학적 비선형 해석을 수행함으로써 보다 정확한 응력을 구할 수 있다는 결론을 얻었다.

• Journal of the Korean Vacuum Society
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• v.11 no.2
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• pp.81-86
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• 2002

With a specific model for the Helicoflex type metal gasket expected to be used in large ports of the KSTAR vacuum vessel, a sealing curve was obtained by measuring the flange tightening properties such as the correlations of the tightening torque(or linear load), displacement to the leak rate. From the experiment results it was found that the leak rate of the Helicoflex seal in the room temperature was bellow $2\times10^{-1}\textrm{mbar\cdot L/s}$ with a tightening torque of 2500kgf . cm using Ml8 bolts.

• Proceeding of KASS Symposium
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• 2006.05a
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• pp.182-188
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• 2006

This study propose cutting body portion-high strength bolts to improve deformation capacity of High strength bolts, which are the mechanical fasteners used for End-plate connection. And, we report that loading test results of steel beam-to-column connection using high deformation capacity-high strength bolts in accordance with SAC2000 loading program. As a result, the initial stiffness and the maximum strength of the connection using high deformation capacity-high strength bolts, are approximately the same in comparison with those of the end-plate connection using the existing high strength bolts. But the deformation capacity of the connection is more than twice as much as those.

• Transactions of Materials Processing
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• v.17 no.6
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• pp.407-411
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• 2008

A brake system in automobile is one of the important parts that directly affect the safety of passengers. Particularly, disk brake module is applied to almost all kinds of automobile brake system due to its remarkable braking power and braking distance. In the disk brake module of an automobile, the bolt for tire wheel is assembled to the disk brake hub by interference fit(bolt pressing process). The process induces small deformation whose range is within tens of ${\mu}m$ and this deformation may cause the runout badness of the whole disk brake module, and even braking problems such as judder or squeal phenomena which makes the loss of braking efficiency. In this study, bolt pressing fit into hub was simulated by $ANSYS^{TM}$, a commercial structure analysis program. Also, the aspect and the cause of hub displacement were analyzed and the solution for decreasing runout of hub was proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.4950-4955
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• 2012

A bolt manufacturing process is completed with continuous forging. Technical and economical success of each process will depend on the appropriate process design and metal mold design for each procedure. This study aims to analyze the moldings of first and second steps among the multi-step molding processes of SCM435 bolt by use of the finite element method in order to achieve the reasonable process. Since the processes of first and second steps analyzed by use of the finite element method consist of axial symmetry, the transformed configuration of material satisfy the dimensions expected in process. In addition, the uniflow line formed in material becomes smooth and consistent over the entire process. Therefore neither molding of material nor inherent defect is expected.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.125-133
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• 2014

In this study, experimental research was carried out to investigate the seismic and structural performance of precast concrete exterior beam-column joints using bolt type connection and prestressing method. A total of five full-scale exterior beam-column joints were constructed and tested under reversed cyclic loading, controlled by displacement. Results of the test are as follows: Energy dissipation capacity and pinching phenomenon of PC beam-column joints showed disadvantageous behavior compared to RC beam-column joints. However, drift capacity of the PC joint was excellent. Also, yield mechanism concentrated on embedded nuts was suitable as an exterior beam-column joint of lateral load resistance frame. Additional application of prestressing method was also very effective to control excessive pinching and cracking in the joint region, and thus improved an overall seismic performance of the PC joint.