• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.13-18
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• 2001

This paper deals with finite element analysis for free vibration and forced sine vibration of Ka- and Ku- bend antenna structures using MSC/PATRAN/NASTRAN. The structures are designed to satisfy minimum resonance frequency requirement in order to decouple the dynamic interaction of the satellite with the spacecraft bus structure. From the forced sinusoidal vibration, we have observed output acceleration versus input in X-,Y- and Z- direction, based on base excitation using large mass method. The results of finite elements analysis can be used as the reference data for the experimental test of satellite antenna, resulting in the reduction of cost and time by predicting and complementing experimental data.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.05a
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• pp.31-36
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• 1998

It is very important to have exact informations on the properties and characteristics of the sintered steel as a new material of machine elements. The bending fatigue tests are performed for sintered steel bend specimens and spur gears, which are notched by using a slicing blade. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester Consequently, the S-N curves are obtained and the fatigue strength. is compared with flaw depth. Accordingly, this study presents the fatigue strength of sintered spur gears, the critical notch depth of sintered steel and the effects of flaw depth on the bending fatigue strength. The enhancement of fatigue strength due to carburized treatment is clarified.

• Journal of the Korean Society of Visualization
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• v.1 no.2
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• pp.38-46
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• 2003

An experimental investigation was performed to study the turbulent characteristics of swirling flow a 90$^{\circ}C$ circular tube for Re = 10,000, 15,000 and 20,000. 2D-PIV(Particle Image Velocimetry)technique was employed to measure the fluctuation velocity field. The results include spatial distributions of mean velocity vectors, turbulence intensity and turbulence kinetic energy. The axial and radial turbulence intensities, and kinetic energy profiles show double-peak structures in the inlet region of the 90 degree bend and the profiles are disappeared along the test tube with decaying the swirl intensity.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.34-40
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• 1998

It is very important to have exact informations on the properties and characteristics of the sintered steel as a new material of machine elements. The bending fatigue tests are performed for sintered steel bend specimens and spur gears, which are notched by using a slicing blade. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester. Consequently, the S-N curves are obtained and the fatigue strength is compared with flaw depth. Accordingly, this study presents the fatigue strength of sintered spur gears, the critical notch depth of sintered steel and the effects of flaw depth on the bending fatigue strength. The enhancement of fatigue strength due to carburized treatment is clarified.

• Structural Engineering and Mechanics
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• v.45 no.1
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• pp.19-32
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• 2013

Cracking at low temperatures is one of the frequently observed modes of failure in asphalt concretes. In this investigation, fracture tests were performed on cracked asphalt concrete subjected to pure mode I and pure mode II loading at different subzero temperatures. An improved semi-circular bend (SCB) specimen containing a vertical crack was used to conduct the experiments. The SCB specimens produced from the gyratory compacted cylindrical samples were compressively loaded, and critical stress intensity factors, $K_{If}$ and $K_{IIf}$, were then calculated using peak loads obtained from the tests. The experimental results showed that with decreasing the temperature, mode I and mode II critical stress intensity factors increased first but below a certain temperature they both decreased. It was also found that at a fixed temperature, the mode II fracture resistance of the asphalt concrete was higher than its mode I fracture resistance.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.327-329
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• 2006

In this paper, the cutting qualities by laser dicing and fracture strength of a silicon die is investigated. Laser micromachining is the non-contact process using thermal ablation and evaporation mechanisms. By these mechanisms, debris is generated and stick on the surface of wafer, which is the problem to apply laser dicing to semiconductor manufacture process. Unlike mechanical sawing using diamond blade, chipping on the surface and crack on the back side of wafer isn't made by laser dicing. Die strength by laser dicing is measured via the three-point bend test and is compared with the die strength by mechanical sawing. As a results, die strength by laser dicing shows a decrease of 50% in compared with die strength by mechanical sawing.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.40-44
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• 2015

The fatigue behavior of thermal butt fusion in safety class III high-density polyethylene (HDPE) buried piping for nuclear power plants was investigated using load-controlled bending fatigue on four-point bend test specimens. Based on the results, the presence of thermal butt fusion beads was confirmed to reduce the fatigue lifetime in the low- and medium-cycle fatigue regions while having a negligible effect in the high-cycle fatigue regions.

• Computational Structural Engineering
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• v.11 no.4
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• pp.383-390
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• 1998

0.93m/sec의 평균속도는 변위제어 삼점휨 실험된 콘크리트 보의 하중-변위 측정결과를 선형탄성파괴역학모델과 가상균열모델에 기초한 유한요소법으로 분석하였다. 두 모델 모두 실험결과와 잘 일치하며, 균열성장길이가 약 60∼70㎜가 될 때까지 안전된 균열성장을 보이다 불안정한 균열성장에 의해 파손되었다. 선형탄성파괴역학모델에 의한 수치해석 결과 에너지해방률은 균열성장길이에 비례해서 증가하였으며, 최대값(202N/m)에 이르게 되면 일정한 값을 유지하였다. 가상균열모델에 기초한 수치해석결과 이 연구에 사용된 하중속도와 시험편의 크기에 대해 70㎜의 완전한 파괴진행대가 평성되었으며, 이는 기존의 정적 실험결과에 대한 수치해석 결과보다 상당히 작은 값이었다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.1
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• pp.96-101
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• 2001

In designing the greenhouse structures, snow and wind loads must be estimated on the basis of the probability of occurrence of snow or wind storms of a given intensity. The recurrence interval chosen depends on the standard durable years and safety factors of the greenhouse. This study was carried out to find the standard durable years of pipe framed greenhouses. Bend test for metallic materials was conducted on samples of galvanized steel pipes being used in greenhouse frames. A secular change of collapse loads and flexural rigidity for galvanized steel pipes were analyzed with the parts buried in the ground and exposed in the atmosphere. From those experimental results and corrosion rate of galvanized film, the standard durable years for pipe framed greenhouses are estimated as follows ; the small scale pipe houses of movable type is 7∼8 years and the large scale pipe houses of fixed type is 14∼15 years.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.587-588
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• 2006

The stress corrosion cracking (SCC) susceptibility of Alloy 600 MA, Alloy 600 TT, Alloy 800, and Alloy 690 TT were investigated in a deaerated 0.01 M solution of sodium tetrathionate using reverse u-bend test samples at $340^{\circ}C$. The results showed that SCC occurred in all alloys, excluding Alloy 690 TT. The SCC susceptibility decreased with an increase in the chromium content of the alloys. The results of the deposits and spectra taken from an energy dispersive X-ray system confirmed the existence of a reduced sulfur causing SCC.