• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.6
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• pp.885-890
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• 2015

LLC resonant converter has been widely used because of its high efficiency and high energy density. In this paper, we designed a LLC resonant converter as the main power supply of the Nd:YAG pulse laser. First harmonic approximation (FHA) is used to model the LLC resonant converter. FHA equivalent circuit model and the transfer function of the LLC resonant converter is proposed. Soft start technology is also used to suppress the surge current. The laser output simulation test result is identical with the practical test, the laser energy of every pulse can reach up to 2.5J, and the pulse per second (PPS) can be adjusted from 6 to 18. The power system is verified stable and reliable by both of the simulation and experiment results.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.68-74
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• 2016

The Nd:YAG laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration, and has increased the automation and flexibility of an entire industry. Laser welding of dissimilar metals has been widely used to improve the wear resistance and corrosion resistance of industrial parts. The objective of this research is to investigate the influence of process parameters on the welding of SM45C and STS304 with CW Nd:YAG lasers. Bead-on-plate welding tests were carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding quality of the cut section, strain-stress behavior, and hardness of the welded part were investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.177-183
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• 2005

In this work, Inconel 600, Inconel 625 and Haynes 230 are welding using Nd:YAG laser and electron bear. These heat-resistant alloys are typically used for the liquid thruster. To examine, the affects of experimental parameters on weld ability, the plate welding of these materials were carried out using both Nd:YAG laser and electron bear. Also, the micro-structure, micro-hardness, and tensile strength of the specimens were analyzed. from the analysis of the experimental results of laser and electron beam welding, we have obtained the optimal welding conditions.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.107-110
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• 1997

We generated a diffraction free beam from Nd:YAG laser with an NBUR (negative branch unstable ring) resonator. The field inside the resonator had a plane wavefront and a homogeneous intensity distribution and the output beam through a scraper mirror of an annular type was used as a source. The outpur beam had an inner radius of 2.5 mm and an outer radius of 5 mm. In this experiment, we used a Fourier transformation lens with the focal length of 5 m to observe the far-field pattern. The lens was placed at a distance of the focal length from the scraper mirror and we found that the beam did not show any noticable diffraction over the distance of 13 m from the lens.

• Journal of Oral Medicine and Pain
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• v.22 no.2
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• pp.261-282
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• 1997

This study was undertaken to compare and investigate the wound healing process following Nd:YAG laser wounds and scalpel incisions of the rat tongue dorsal mucosa. Laser wounds were made parallel on the right side of tongue dorsum and scalpel incisions were made on the left side with 5mm length, respectively Visual inspection and immunohistochemistry with CD44 antibody after immediately, 6 hours, 1 day, 2, 4, 7, 11, 21 days after surgery were carried out. The results were as follows : 1. There was macroscopically no treat difference between laser wounds and scalpel incisions. 2. Laser wounds appeared as dry, bloodless and irregular grooves with carbonization and whitening of superficial tissues compared to sharp, straight and bleeding incisions using scalpel. 3. In the epithelium of rat tongue mucosa, CD44 expression in healing laser wounds and scalpel incisions were similar. 4. In the lamina propria and muscle layer, CD44 expression in healing laser wounds gradually increased earlier and decreased faster than scalpel incisions. Conclusively, it is suggested that pulsed Nd:YAG laser has more beneficial effect on the healing of wounded oral mucosa than scalpel in knew of CD44 expression.

• Journal of Oral Medicine and Pain
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• v.25 no.4
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• pp.403-411
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• 2000

The authors experienced a non-painful, elevated, dome-shaped lesion on lower lip in Korean male of 22-year-old and a non-painful, elevated, dome-shape lesion on left side of mouth floor in Korean female of 36-year-old. And diagnosed the lesions as a mucocele and a ranula respectively, based on the comprehensive evaluation of data obtained from history taking, clinical and radiologic examination and histopathological findings. In these cases, the authors removed mucocele and ranula using the pulsed Nd:YAG laser with advantage of good hemostatic effect, and so we could minimize improper tissue destruction during operation. The excisional wounds of lower lip and mouth floor had a good healing process without any symptom of pain and any signs of bleeding and infection.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.74-77
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• 2000

A pulsed Nd:YAG laser has been used in a wide variety of fields : measuring, material processing and so on. In a material processing, it is very important to control the laser energy density. A pulse repetition rate and a pulse width are regarded as the most dominant factors to control the energy density of laser beam. In this study, pulsed Nd:YAG laser system was designed and manufactured to control the laser output usefully and easily. This system adopted the sequential charge and discharge circuit is controlled by 80196 micro- processor. As a result, it is found that laser output is controlled minutely by changing laser input and pulse repetition rate, and usefully by using 80196 microprocessor.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.24-32
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• 2007

Laser surface hardening is beneficially used for surface treatment of structural steel. Due to very rapid heating and cooling rates, structural low-alloy steel(SCM4) can be hardened as self quenching. The aim of this research project is to improve the influence of the process laser parameters: laser power, spot size, surface roughness, and traverse speed. The laser beam is allowed to scan on the surface of the workpiece at the constant power(1095W), varying the traverse speed at 0.3m/min, 0.5m/min and 0.8m/min. The optical lens with the elliptical profile is designed to obtain a wide surface hardening area with uniform hardness. From the results of the experiment, it has been shown that the stable hardness is about 600$\sim$700Hv, when the laser power, focal position and the traverse speed are P=1095W, z=0mm and v=0.3m/min.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.51-59
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• 1994

We constructed travelling type Nd:YAG laser with a negative branch confocal unstable ring (NBCUR) resonator like a Newtonian telescope type using four flat mirror and two positive lenses. Annular output beam was obtained by using scraper mirror. This laser oscillator has 22 optical faces and optical alignment was done by equal inclination interferance method. We inserted a Faraday rotator of permanent magnet type designed in the laboratory for unidirectional operation. We obtained laser output energy of 80m.I with electrical input energy of 70 J. and we obtained that peak power of 0.5MW through Q-switching with BDN dye.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.636-644
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• 2006

Recently, there were some successful examples that the laser welding was introduced into production line. However, the spread of laser welding is not sufficient in many industries. There are several reasons why it is difficult to penetrate the laser welding into production lines. Because it is different from reflection, absorption and permeation of laser beam according to material and surface condition. Moreover, there are significant problems in processing such as absorption and scattering of beam by the induced plasma or plume. Therefore, understanding of mechanism on formation of weld defect in laser welding of the laminated core for motor is very important. In this paper, it was analyzed in terms of materials which was source of defect in laser welding and conventional arc welding. As a results of analysis, insulation coating film of the laminated core was judged to main factor of weld defect. it could be well aware as tracing carbon volume, and it was deduced that weld defect by insulation coating film was caused by difference of mechanism between the two heat sources.