• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.907-913
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• 2017

The performance of a spark jet driven by pulsed-arc plasma was investigated experimentally for various energy input. A high-speed jet (about 330 m/s) was obtained by rapid gas heating produced by 37 mJ of deposited energy per pulse. The peak velocity and penetration distance of the jet were proportional to the deposited power and the deposited energy per pulse, respectively. A smaller orifice diameter produces a higher velocity jet at lower energy levels. For the same deposited energy, higher-current pulses produce a higher jet velocity than higher-pulse-width pulses. A total deposited energy of about 10 mJ per pulse with a pulse duration of about $10{\mu}s$ was found to be the optimum for energy- efficient operation.

• Journal of the Korean institute of surface engineering
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• v.38 no.5
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• pp.193-197
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• 2005

Highly c-axis oriented Zinc oxide (ZnO) films were successfully deposited at room temperature by oxygen ion-assisted pulsed filtered vacuum arc. The effect of oxygen gas ratio ($O_{2}/O_{2}+Ar$ on the preferred orientation, surface morphology and resistivity of the ZnO films were investigated. Highly crystalline ZnO films with (002) orientation were obtained at over $13\%$ of oxygen gas ratio. Increasing oxygen gas ratio up to $80\%$ was found to improve crystallinity of the films. From hall measurements, it was found that the film has n-type characteristic and carrier concentration and its mobility were closely related with oxygen gas ratio. Minimal resistivity of $3.6{\times}10^{-3}{\Omega}{\cdot}cm$ was obtained in the range of $20\%$ to $40\%$ of oxygen gas ratio.

• Journal of Welding and Joining
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• v.31 no.2
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• pp.4-15
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• 2013

The laser/arc hybrid welding process is a new process combining the laser beam and the arc as welding heat source. The laser beam and arc influence and assist one another. By application of hybrid welding, synergistic effects are achievable, and disadvantage of the respective processes can be compensated. The laser-arc hybrid welding process has good potential to extend the field of applications of laser technology, and provide significant improvements in weld quality and process efficiency in manufacturing applications. This review analyses the recent advances in the fundamental understanding of hybrid welding processes using the works of the data base of Web of Science (SCI-Expanded) since the 2000 year. The research activity on the hybrid welding has been become more actively since 2006, especially in China, presenting the most research papers in the world. Since the hybrid welding process was adopted in manufacturing of the automobile in Europe in the early of 2000's, its adopting is widely expanded in the field of manufacturing of automobile, ship building, steel construction and the other various industry. The hybrid welding process is expected to advance toward higher productivity, higher precision, higher reliability through the mixing of high power and flexible fiber laser or disk laser and digitalized pulsed arc source.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.89-93
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• 2002

A study of noticeable improvement in welding speed in thin-plate Type 304 stainless steels gas tungsten arc (GTA) welding was investigated. The welding speeds were increased to more than 3m/min, up to 8m/min. During the welding, Direct Current Straight Polarity (DCSP) and pulsed current GTA welding processes were carried out, respectively. The appropriate high speed welding parameters were established while achieving a high quality weld. After this, Erichsen test and tensile test were performed. The results obtained wert summarized as following: ultra high speed welding for thin-plate Type 304 could be satisfactorily welded with high speed from 3m/min to 8m/min in both DCSP and pulsed GTA welding; Increasing welding speed was found to decrease the ductility, tensile strength md elongation of welded joint; The optimal frequency would be 200Hz-500Hz for high speed welding in pulsed current welding; DCSP welding could obtain the better results of Erichsen test and tensile test than those of pulsed current welding obtained.

• Journal of Welding and Joining
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• v.27 no.1
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• pp.59-64
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• 2009

In order to determine the One-Drop One-Pulse(ODOP) condition of the pulsed gas metal arc(GMA) welding, the drop detaching phenomenon during the peak time is investigated using the force-displacement model. The drop detaching criterion is established based on the displacement of the pendant drop, and the forces exerted on the drop are calculated using the Modified Force Balance Model(MFBM). The effects of wire melting on the drop size and force are included in the force-displacement model. While the peak current has most significant effects on the drop detaching time, the initial drop mass prior to the peak time also influences drop transfer. The calculated results show good agreements with the experimental data, which implies that the ODOP condition can be predicted using the force-displacement method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1483-1491
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• 2001

Enhancement of pulsed-laser ablation by an artificially deposited liquid film is presented. Measurements of ablation rate, ablation threshold, and surface topography arc performed. Correlation between material ablation and photoacoustic effect is examined by the optical beam deflection method. The dependence of ablation rate on liquid-film thickness and chemical composition is also examined. The results indicate that photomechanical effect in the phase explosion of liquid is responsible for the enhanced ablation. The low critical temperature of liquid induces explosive vaporization with localized photoacoustic excitation in the superheat limit and increases the ablation efficiency. Experiments were carried out utilizing a Q-swiched Nd:YAG laser at near-threshold laser fluences with negligible plasma effect (up to ∼100 MW/cm$^2$).

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1800-1803
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• 2002

The pulsed power system was widely making use good of many industrial and environments. The pulse generator generally required for short pulse duration and high peak value was forced to consider its volume and economy. In this paper, this system is designed and fabricated which has a compact size of pulse generator with switched MOSFET. We have studied the removal of rust material using Arc discharging in pulsed power system. It have tested their characteristics by adjusting variable voltage charging and pulse repetition rate. As a result, We can eliminate rust materials with this device.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2242-2244
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• 1999

Recently, An important research field of pulsed power is high voltage, high power generation with exploding wire opening switch. Another point of view exploding wire effects have been researched for generation of the pulsed high pressure shock wave. Theoretical considerations of the shock pressure generation along with experiment results are presented in this paper and. Some experimental results of hard rock fracturing show the possibilities of commercial using.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1981-1983
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• 2000

In this paper, the arc resistance of INPIStron is presented. It is need to the design of Pulsed power system and simulation on the circuit of pulsed power system with INPIStron switch. It is also possible to use this parameter to the part of discharge characteristics of Xenon lamp and the device with electrical discharge.

• Journal of Welding and Joining
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• v.34 no.4
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• pp.48-54
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• 2016

The use of Zn coated steel has increased in the automotive industry due to its excellent corrosion resistance. Conventionally the BIW(body-in-white) structure and the hang-on parts have been made of Zn coated steel and more recently Zn coated steel began to be applied in the chassis parts. During gas metal arc (GMA) welding of the chassis part, lap fillet joint used to be adopted but spatter generation and porosities are most important concerns. In the industrial applications, an intentional joint gap was made to avoid the weld defects but it is not easy to control the size of joint gap. In this research, gas tungsten arc (GTA) is combined with GMA welding where GTA precedes GMA. As pulsed arc was adopted as GMA, GTA was oscillated along the longitudinal direction by pulsing GMA, but the arc oscillation did not disturb the molten droplet transfer of GMA welding. By increasing the distance between GTA and GMA, the length of weld pool increased and porosity could be reduced. Moreover porosity in the welds was fully removed when the distance between two arcs was 15 mm.