• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.42-44
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• 2007

Methods of repair welding are different to production welding for welding position, welding process, welding power source, heating methods. This study investigated proper the welding process used the welding process SMAW and GTAW in the weldment of inconel filler metals. Mechanical test showed that SMAW and GTAW process had higher mechanical properties than those of material specification. Both SMAW and GTAW welding process can appy the repair welding. In comparison, GTAW welding process had more higher mechanical properties in the weldment.

• Journal of Welding and Joining
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• 제31권2호
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• pp.57-62
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• 2013

Magnesium has good castability and limited workability, so its products have been manufactured by almost casting processes. In this study, a pulsed Nd:YAG laser was used to butt-weld the sand casting magnesium alloys. And the effect of welding conditions such as peak power, pulse width, welding speed was evaluated in detail. As a result of this study, large underfill and plenty of spatter taken place under the conditions with high peak power. Thus, it is recommended to use low peak power and long pulse width to obtain good welds with deep penetration. It is also confirmed that the welding speed and pps(pulse per second) are directly connected at weld defects such as underfill, porosity.

• Journal of Advanced Marine Engineering and Technology
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• 제36권8호
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• pp.1069-1075
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• 2012

레이저는 고밀도 열원으로써, 입열을 최소화하면서 고속용접이 가능한 장비이다. 특히 최근 상업화된 고출력 파이버 레이저는 특유의 발진원리 때문에 높은 빔품질과 소형화된 시스템이 가능하다. 이러한 장점들로 인해 파이버 레이저는 LNG 카고탱크에 대해 선박 내부에서 용접이 가능한 가장 적합한 열원이라고 판단된다. 따라서 본 연구에서는 선박산업에 레이저 용접기술을 적용하기 위해 파이버 레이저를 이용하여 LNG 선용 스테인리스강의 용접을 진행하였다. 연구에서 사용한 재료는 카고탱크에 사용되고 있는 오스테나이트계 스테인리스강인 두께 1.2mm의 STS304L였다. 레이저 출력 및 용접속도를 변화시켜가면서 겹치기 및 맞대기 용접을 실시한 후 용입특성을 분석하여 최적의 접합조건을 도출하였다. 그 결과 용접부에서 모재보다 우수한 기계적 성질을 얻을 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.245-256
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• 2014

I-core sandwich panel that has been used more widely is assembled using high power $CO_2$ laser welding. Kim et al. (2013) proposed a circular cone type heat source model for the T-joint laser welding between face plate and core. It can cover the negative defocus which is commonly adopted in T-joint laser welding to provide deeper penetration. In part I, a volumetric heat source model is proposed and it is verified thorough a comparison of melting zone on the cross section with experiment results. The proposed model can be used for heat transfer analysis and thermal elasto-plastic analysis to predict welding deformation that occurs during laser welding. In terms of computational time, since the thermal elasto-plastic analysis using 3D solid elements is quite time consuming, shell element model with multi-layers have been employed instead. However, the conventional layered approach is not appropriate for the application of heat load at T-Joint. This paper, Part II, suggests a new method to arrange different number of layers for face plate and core in order to impose heat load only to the face plate.

• Journal of Welding and Joining
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• 제17권1호
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• pp.116-123
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• 1999

The $CO_2$ welding with 100% $CO_2$ shielding gas is commonly used because of its cost and efficiency. Arc phenomena of the $CO_2$ welding is influenced by various factors such as chemical compositions of welding wire, shielding gas, welding condition and welding power source etc. In this study, arc phenomena is investigated by using two type of FCW(titania type, semi-metal type). Then, the welding quality and optimum welding condition can be selected. From this study, the following results were obtained; 1) In low current range(140A), FCW up to welding voltage(22V) resulted in a typical short circuit transfer. 2) In high current range(320A), the arc stability in titania FCW of a typical globular transfer is better than that of semi-metal FCW.

• Journal of Welding and Joining
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• 제32권2호
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• pp.63-69
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• 2014

Dual laser heat sources were used for polymer based material joining. An infrared camera and thermocouple DAQ system were used to correlate the temperature distribution to computer simulation. A 50 degree tilted pre-heating laser source was acting as a heating source to promote the temperature to minimize thermal shock by the following a welding heat source. Based on the experimental result, the skin depth was empirically estimated for computer simulation. The offsets of 3mm, 5mm and 10mm split by weld and preheat were effectively used to control the temperature distribution for the optimal laser joining process. The closer offset resulted in an excessive melting or burning caused by sudden temperature rising. The laser power was split by 50%, 75% and 100% of the weld power, and the best results were found at 50% of preheating. To accurately simulate the physical laser beam absorption and joining optical properties were experimentally measured for the computer FEM simulation. The simulation results showed close correlation between theoretical and experimental results. The developed dual laser process is expected to increase productivity and minimize the cost for the final products.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.556-559
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• 2001

In this paper, we proposed AC/DC boost converter to improve input current harmonic reduction in SMAW(shielded metal-arc welding). The proposed harmonic reduction with the boost converter design and the UC2854 integrated circuit which controls the converter, The topology of welding power supply is made of a pair of boost converter and welder half-bridge IGBT inverter. The voltage arc is modeled by a variable resistance in series with a voltage source. The results has been confirmed by PSIM simulation tool. The simulation results show that input at current is nearly sinusoidal with low harmonic contents and sinusoidal input current waveform at high power factor.

• Journal of Welding and Joining
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• 제21권6호
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• pp.26-32
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• 2003

Arc welding process has indicated that it suffers from many flaws. It's because requirement of products is diverse and factors which affects the quality is also various. Therefore, in order to stabilize the welding process, it is important to choose a proper welding machine for the each process, and to evaluate the welding process capability of each machine. In this study, rational and simple index to evaluate the welding machine was set the coefficient of resistance variation through the arc stability examination such as spatter generation weight and bead configuration uniformity etc. And the method to evaluate the process capability index was developed by application of 6$\sigma$.

• Journal of Welding and Joining
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• 제28권2호
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• pp.27-31
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• 2010

Generally, angle pieces at the corners of cargo tank of membrane type LNG carrier ship are manually welded, due to their various shapes and positions. In this study, a GTA welding robot system was developed in order to improve productivity, which consists of a 7-axis manipulator, a system controller, a GTA welding power source, and peripheral devices. The welding system is characterized by capabilities of welding corrugated work pieces as well as 90/135 degree linear work pieces, and controlling the entire weld cycle automatically. The developed system was field tested on actual work pieces and its performance was proven to be successful.

• 전기의세계
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• 제11권
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• pp.14-17
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• 1963

정확하게 control된 pulse의 용도는 과학과 공업이 발달될수록 날로 많아져 가고 있는데 그의 일부는 대전력을 취급하는 경우로서, Radar에 대한 응용을 들 수 있다. 한편, 요지음 gallium-arsenide등 반도체 diode를 사용해서 Laser action을 일으킬 수 있다는것이 발견되어 G.E. 및 IBM등에서 개발되고 있다. 이 경우에, continuous emission도 가능하지만 흔히, intermittent operation을 시켜야 할 때가 많기 때문에 timed pulse source가 필요하게 된다. 또 한편, spot welding의 경우에도 이러한 pulse source가 필요하게 된다. 이들을 크게 나누어 source를 AC로 할 경우와 DC로 할 경우가 있는데, 전자의 경우는 thyratron을 사용할 경우가 많게 될 것이다. DC의 경우나 AC의 경우에나 잘 shape되고 time된 pulse source를 만들어 놓으면 진공관이나 thyratron이나 같은 모양으로 drive할 수 (thyratron의 경우는 trigger)있을 것이기 때문에, 이러한 pulse source를 만들 필요가 있게 된다.