• Nuclear Engineering and Technology
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• v.23 no.1
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• pp.1-11
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• 1991

The objective of this study is to investigate the effect of weld line on the mechanical strengths and the process of weld line elimination in the Zircaloy-4 resistance upset welding for the fabrication of heavy water reactor fuel rods. The weld current and the amount of upset increased linearly with the main heat, in which two relations between them were derived. It was found that the threshold to obtain sound weld was 50% of main heat in terms of weld upset size, mechanical strengths and weld line elimination. The weld microstructure of resistance upset welds of Zircaloy-4 comprsied basketweave, Widmanstatten and martensite respectively by changing the main heats. Dimples on uniaxially fractured surface at weld line in the Zr-4 welds were larger and deeper compared with those on biaxially fractured surface. It was also found that the process of the weld line elimination in the resistance upset weld of Zircaloy-4 could be divided into three stages in terms of the presence of many pores, their shrinkage and elimination, and the shrinkage of the original weld interface with increasing weld currents.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1399-1406
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• 2011

As a result of the examination analyzed loop type of Detecting the Broken Rail Monitoring System as a part of prevention of train derailment, installed in the Seoul Metro No. 2 subway line 98.51m section which is Samsung to Seolleung, we found that it is possible to detect crack location(Thermit welding: 48.18m) within the margin of error of ${\pm}1m$ accurately As analysis of the first day, third day, fifty day, and seventh day periodically, we found that Fresnel reflection happened where the crack location 48.18m. However other 3 branches show loss by bending of optical cable(spread reflection from the outside impact).

• Transactions of Materials Processing
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• v.8 no.1
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• pp.7-13
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• 1999

In this study, side panels were developed using the laser-welded tailored blank (T.B.) of both the same thickness and different thickness. At first, the formability of the same thickness T.B. was investigated to compare with one of the non-welded panel with respect to weldline movement and strain distribution in blank during the stamping process. Based on these results, we determined the weld line positions and the die step for T.B. forming of the blanks composed of different thickness combination. Then we made some stamping tryouts with selected types of blanks to investigate the formability of T.B. of the different thickness. During the tryouts, wrinkles were found in the a-pillar lower region which is under the deformation mode of the shrink flange. In the b-pillar region, fractures were also found. These defects have been reduced and corrected by controlling the blank design, the die faces and process parameters.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.908-917
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• 1995

The constant .DELTA.K fatigue tests are performed in SS41 and its weldments to investigate crack opening behavior and fatigue crack propagation behavior at each parts of weldment and its boundary layer. The weldments were annealed after welding for the purpose of relieving residual stress. Every weldments has notch at weld metal zone, and fatigue crack propagates from weld metal zone to vase metal zone perpendicular to weld line. The Laser ISDG method is used in order to determine the crack opening ratio, this method is more precise than indirect measurement method, and faster and easier than other direct measurement method.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.69-74
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• 2001

In this Paper are described the indirect induction heated boiler and induction heated hot air producer using the voltage-fed series resonant high-frequency inverter which can operate in the frequency range from 20kHz to 50kHz. A specially designed induction heater, which is composed of laminated stainless assembly with many tiny holes and interconnected spot welding points between stainless plates, is inserted into the ceramic type vessel with external working coil. This working coil is connected to the inverter and turbulence fluid through this induction heater to moving fluid generates in the vessel. The operating performances of this unique appliance in next generation and its effectiveness are evaluated and discussed from a practical point of view.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2253-2261
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• 2002

Recently the hydroforming technology has drawn a lot of attention because of its capability to produce high quality and light weight parts. In the present study, the tube expansion - one of the simplest hydroforming processes, has been investigated in order to understand fundamental phenomena such as deformation characteristics and effect of process parameters. As a result, the most important process parameters, which determine the state of stress at the expanded zone, were found to be pressure and die displacement. If the stress becomes equi-axial tension at the zone, necking occurs at some distance from the weld line and develops into a crack along the axial direction. Some aspects of mechanical property measurements as well as distributions of hardness and microstructure are also discussed in this paper.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.633-638
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• 2012

The doctor blade is a core part of a laser printer and directly influences the printing quality. The main specifications for doctor blades ate for them to be precise and durable. It is necessary to study an automatic production system for doctor blades in order to obtain high-efficient manufacturing processes. In this paper, the technology and the design of the automatic production line has for manufacturing doctor blades has been researched. The automated manufacturing process consists of five steps, which are the supplying of raw material, shearing, bending, bracket supplying, and the laser-spot welding process. The proposed automatic manufacturing system allowed for faster and more reliable production of doctor blades.

• Journal of the korean Society of Automotive Engineers
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• v.3 no.1
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• pp.19-26
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• 1981

자동차제조에 있어서의 용접은 신뢰성 양산과 생력화에 대응하여 접합 조립하는 방법으로 특이한 분야를 형성하여 발전되었다. 예를 들면, 자동차의 생산은 기본적으로 양산체제를 갖추고 있 어서, 일반적으로 노동집약형 산업이라고 불리어지며 그 제조공정을 보면 stamping press 공정과 같이 용접공정도 비교적 장치산업적인 분야로 빠르게 자동화나 성인화 내지 무인화로 진행되고 있다. 자동차용접은 사람이 portable spot welder로 한점씩 용접하지만 양산에 대비한 합리화와 안정화를 위하여 다점용접 (multi spot weld)라는 자동화공법의 도입이 불가피하며 금일의 자 동차생산에 있어서 상식화가 되고 있다. 이것은 한개의 차체라면 차형의 대조 또는 press panel의 수에 따라 차이가 조금 있으나 약 4-5 천점의 점용접이 필요하기 때문에 여러 가지 반송장치와 조합하여 대규모의 line설비로 발전되어 가고 있다. 이와 같이 용접공정의 자동화는 생산성을 높이는 반면에 전용성이 높기 때문에 설계변경에 대한 초기투자의 용접설비 대부분을 갱신하여야 하는 새로운 투자의 필요문제가 증대되었다. 이러한 전용설비에 대한 유연성을 가미한 자동차로 지향되어, 그 한 방법으로 산업용 robot가 도입되었다. 근래에 와서는 자동차제조에 있어서 새 로운 용접기술을 합리적으로 효과있게 적용하는 기술이 금후의 연구과제라 하겠다.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.57-64
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• 2004

This study deals with the prediction of defect location which can be occurred in structure. The existing methods was very difficult to be applied to predict it, because of complex numerical formula. The triangulation method proposed in this study can predict the source location easily with small amount of data. The arrival time of wave can be directly converted into the distance between sensors. For this purpose, the propagation velocity was measured by Rayleigh wave, and the propagation behavior was analyzed. The welded workpiece is adapted to investigate for the consideration of jointed part in structure, The propagation velocity of signal was measured in welded workpiece and the revised algorithm of source location was proposed.

• Proceedings of the KWS Conference
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• v.43
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• pp.213-215
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• 2004

Water jet propulsion system has high efficiency on middle to high speed, and it provides better safety than conventional screw propeller because it has not projected propeller and rudder. So many leisure boat and high-speed ferries use this propulsion system. We developed water-jet propulsion unit for small planning boat, and launched that in the boat, after that we tested water-jet unit in the lake. As a result, we certify heat dissipation at the bearing housing and reverse duct's shape for neutral position are important at the design, and alignment water-jet unit and keel line are important at the launching, and ship's resistance performance and jet's propulsion performance also are needed to consideration.