• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.820-823
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• 2000

The characteristics of wire deflection, surface roughness and roundness were observed on changing discharge time for electrical discharge machining(EDM) of tungsten carbide in various conditions of thickness. The wire deflection was decreased as increasing discharge time and wire tension, the gap of deflection was decreased after thickness 60mm and discharge time of 6$\mu\textrm{s}$ due to the changing from fundamental mode to vibration mode. The deflection is the smallest at the water specific resistivity of 7.5 kΩ ㆍcm. The deflection is found to be decreased as increasing dwell time, and the result is due to the vibration of the pressure and the amount of the dielectric. The component of copper(Cu) and zinc(Zn), which is the main material of wire electrode, was observed for rough wire-cutting EDM of STD-11. This phenomena is found to be decreased as the number of EDM is increased. But it will be improved by changing the material and the shape of wire. The roundness of middle is found to be worse than that of upper and it is increased as the thickness of material is increased.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.537-542
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• 2000

Wire deflection, surface roughness and roundness were observed on changing discharge time for electrical discharge machining(EDM) of STD-11 in various conditions of thickness. The wire deflection was decreased as increasing discharge time and wire tension. The deflection is the smallest at the speed of wire of 10.6m/min and the water specific resistivity of 5k$\Omega$.cm. The deflection is found to be decreased as increasing dwell time. But if the water pressure is high, it is found not to be changed after the vibration of 4sec. The component of copper(Cu) and zinc(Zn), which is the main material of wire electrode, is observed for rough wire-cutting EDM of STD-11. This phenomena is found to be similar in spite of the change of EDM energy level. But it will be improved by changing the material and the shape of wire. The roundness of middle is found to be worse than that of upper and it is increased as the thickness of material is increased.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.203-210
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• 2004

This study reviewed various current methods of evaluating the toughness of steel fiber reinforced concrete specimens and criticized the use of various multiples of first-crack deflection to define toughness indices. The load-CMOD curve to determine toughness, instead of load-deflection curve, was used. The notched steel fiber reinforced concrete specimens With different water/cement ratio(0 35, 0.40, 0.45, 0 50) and fiber volume content(0.0%, 0 5%, 1 0%, 1.5%) were tested under third point bending.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.743-746
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• 2011

본 연구에서는 유한요소해석을 이용하여 차량속도 및 긴장재의 설계에 따른 CFTA 거더의 동적거동 및 동적증폭계수를 분석하였다. 긴장재의 해석변수로서는 긴장재의 양과 긴장력을 고려하였으며 차량하중은 도로교설계기준의 DB-24 하중을 선택하였다. 차량하중은 3축-2트랙에 작용하는 등가절점하중으로 변환하여 속도에 따라 시간함수로 모델링하였다. 긴장재의 양은 외측 �� 내측 덕트의 유무에 따라 변화시켰으며 긴장력은 설계긴장력의 0%에서 100%까지 25%씩 증가시켰다. 차량속도는 40km/hr에서 100km/hr까지 20km/hr씩 증가시켰으며, 해석결과 긴장재의 긴장력 변화는 거더의 동적거동에 영향을 주지 않았으며 초기처짐에만 영향을 주었다. 긴장재의 양에 따라서는 거더의 동적거동이 다르게 나타났으며 긴장재의 양이 적을 수록 동적처짐은 증가하였다. 이를 바탕으로 거더의 동적증폭계수(DAF)를 산출하였으며, 이 결과 긴장재가 없는 경우에도 도로교표준시방서에서 정한 기준 값보다 매우 작은 거동을 보였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.98-106
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• 2008

The strengthening in terms of efficiency, easy, economics is very popular method when it is applied to a damaged structures. The purpose of this study develops anchorage system that supports enough strengthening effect without any damage. In addition it is checked whether the method can be conveniently applied to structures. To verify strengthening effect a flexural experiments were performed. Four concrete beams were constructed and tested. Deflections, strains and modes of failure were recorded to examine strengthen of beams. Comparing crack load of each experimental data, yielding load, ultimate load, ductility index, and tendon stress were analyzed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.357-360
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• 2011

Machine tools of Gantry type have been performing machine work as a moving machinery. In a large machine tools, the machinery is moving with bed and it is structurally unstable. When the objects are processed, machine tools gets loads in the direction of Z-axis. In other words, the machine tools which become bigger was performed by the trend of complexation. It made that the increased machine weight can't be passed over. In order to enhance manufacturing precision, it needs to compensate Z-axis deflection of weight for machine tools. In this paper, Machine tools of Gantry type were miniaturized and deflection was measured by LVDT sensors. When deflection was measured, block mass weighted 50kg is moving on particular distance. Then, the displacement of fixed point and moving point is measured by recording telemeter.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.3
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• pp.241-247
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• 2015

Deflection and deformation occur easily in structures with long length, such as bridges and pipelines. Shape monitoring is required for ensuring their structural health. A fiber Bragg grating (FBG) sensor can be used for monitoring a large-scale structure because of its advantage of multiplexing. In this study, FBG sensors were used for monitoring a composite beam structure, and its strains were measured at multiple points. Thereafter, a shape estimation technique based on the strains was studied. Particularly, a three-dimensional shape estimation technique was proposed for accurate structural health monitoring. A simple experiment was conducted to verify the performance of the shape estimation technique. The result revealed that the estimated shape of the composite beam structure was in agreement with the actual shape obtained after the deformation of the specimen. Additionally, the deflection at a specific point was verified by comparing the estimated and actual deformations measured using a micrometer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1893-1899
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• 2010

A foxtail moves forward on a flat surface when pushed by a vertical force. The distance moved by the foxtail depends on the degree of deformation. We experimentally investigated the main parameters that influence the distance moved while varying the pushing force, area, and velocity. We then fabricated a nylon barb that mimics the foxtail barb and performed theoretical and experimental analyses of the displacement according to the acting force and the deflection. In addition, we investigated the relation between the displacement and the angle of a foxtail-like robot's leg by varying the clearance between the robot body and the inner surface of the pipe. To find the design parameters of the barb of the robot for tubular-type digestive organs and blood vessels, we studied the relation between the acting force and the elastic modulus while varying the leg diameter.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.245-248
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• 2008

Recently, much research has been conducted on FRP composite to replace steel. However, the concept of FRP girder filled with concrete has not been fully attempted. This study focuses on the analytical behavior of FRP girders filled with concrete. FRP girders usually have large deflection due to relatively low elastic modulus compared to steel members. However, in the previous experimental investigation on small sized modular beams, it has been verified that the displacement of FRP-girder filled with concrete is reduced and the strength is increased considerably. In this research, analytical investigations have conducted to verify the analytical method by comparing the results with tests. In addition, analyses on large girders assembled with small modules have been carried out to predict the feasibility before tests. The analytical results showed that the assembled FRP girders can be used as substitutes for steel girders.

• Korean Journal of Agricultural Science
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• v.23 no.2
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• pp.227-232
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• 1996

It is a tedious job to handle seedling trays in a green house with human hands because of their fluctuation when they are moving. A robotic gripper for handling a seedling tray has been developed., which has two fingers consisting of the vertical and horizontal bars. The maximum deflections at the center of the seedling trays were measured with various lengths of the horizontal bars. The length of 250 mm was revealed to be optimal one, resulting less than 15 mm deflection with a $540{\times}270mm$ seedling tray, which was acceptable for a practical use. For this study a LM system was adopted to move the fingers. To validate this system the robotic gripper was installed on a Cartesian robotic manipulator and their performance was tested several times with great success. The robotic manipulator used in this study was a general one, so a special one for this robotic gripper needs to be developed in future.