• Journal of Welding and Joining
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• v.22 no.1
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• pp.58-64
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• 2004

The control of the weld bead shape is important in laser welding of the small parts. The effects of laser welding parameters on the weld bead shape in the pulsed Nd:YAG laser welding of STS 304L material were investigated. Shielding gas type, flow rate, pumping voltage, pulse frequency, pulse width, focal position and overlap distance were selected as laser welding parameters. Experiments were designed and conducted using the Taguchi method which was a statistical experimental method. The weld bead width, penetration, area and aspect ratio were measured and analysed as the weld bead shape properties and the welding parameters were optimized to maximize the weld aspect ratio. Weld aspect ratio were greatly affected by the pulse width, pumping voltage and pulse frequency, and somewhat by the overlap distance, and little by the shielding gas type, flow rate and focal position. A confirmation experiment were conducted using the optimized welding parameters.

• Current Optics and Photonics
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• v.3 no.3
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• pp.243-247
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• 2019

We have developed a compact, wavelength-selectable, Q-switched Nd:YAG laser at mid ultraviolet for chemical warfare agent detection. The fundamental wave at 1064 nm is delivered by a pulsed solid state laser incorporating with a square-type Nd:YAG rod in a resonator closed by two crossed Porro prisms for environmental reliability. The output energy at 213 nm ($5{\omega}$) and 266 nm ($4{\omega}$) by ${\chi}^{(2)}$ process in the sequentially disposed BBO crystals are measured to be 6.8 mJ and 15.1 mJ, respectively. The output wavelength is selected for $5{\omega}$ and $4{\omega}$ by a motorized wavelength switch. The energy ratio of the $5{\omega}$ to the $4{\omega}$ is varied from 0.05 to 0.85 by controlling the phase matching temperature of the nonlinear crystal for sum-frequency generation without change of the output pulse parameters.

• Medical Lasers
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• v.10 no.3
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• pp.185-188
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• 2021

Onychomycosis is the most common disease of the nail, with a worldwide prevalence of 5.5%. It causes local pain, paresthesia, and cosmetic problems and decreases the patients' quality of life. Conventional treatments include the administration of topical and systemic agents. However, factors such as subungual hyperkeratosis and biofilm formation may affect the efficacy of these treatments. Moreover, side effects associated with systemic agents are a major concern for patients. Therefore, various novel treatments are being developed; among them, photodynamic therapy (PDT) and Nd:YAG laser are promising, and several studies have demonstrated the efficacy and safety of PDT and laser therapy. Here, we report the efficacy and tolerability of PDT combined with 1064-nm Nd:YAG laser therapy and topical efinaconazole for the treatment of three patients with refractory onychomycosis.

• Medical Lasers
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• v.8 no.1
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• pp.32-34
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• 2019

Postinflammatory hyperpigmentation (PIH) is a reactive hypermelanosis of the skin that occurs as a result of variable inflammatory processes, such as trauma, and many inflammatory conditions. Although a range of modalities of managing PIH have been reported, the treatment of PIH is challenging. In this report, a patient with PIH was treated using picosecond-domain Nd:YAG lasers. After three sessions of 1,064-nm picosecond-domain Nd:YAG laser treatment, the patient showed almost complete improvement with no remarkable side effects or recurrence over the duration of six months. Overall, 1,064-nm picosecond-domain Nd:YAG laser can be used effectively and safely for treating pigmented lesions in the dermis, particularly PIH, in Asian patients.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.626-631
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• 2002

This paper describes the weldability and mechanical behavior of JIS S45C medium carbon steel (corresponding to KS SM45C and SAE 1045) for machine structures in CW Nd:YAG laser welding. ill general, medium carbon steels have a limited application to the industrial fields in spite of good mechanical characteristics. This is due to welding difficulty because of the high carbon contents and impurities in this material. Therefore, in this study the laser weldability of medium carbon steel with adjusted contents of S and P has been investigated in order to extend the application to medium carbon steels. Several experiments and numerical simulations have been conducted to determine the characteristics of mechanical behavior in CW Nd:YAG laser welds. The results of the simulations concur with the experiment results. From the result of this study, the application possibility of CW Nd:YAG laser welding to medium carbon steel has been confirmed. Also, the appropriateness of mechanical behavior simulation has been verified to analyze and predict the welding phenomena.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1703-1705
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• 2001

The pulsed Nd:YAG laser is used widely for materials processing and medical instrument etc. It is important to control the laser energy in those fields using a pulsed Nd:YAG laser. In this paper, constant-frequency current resonant half-bridge inverter and Cockcroft-Walton circuit are used to charge the energy storage capacitor variably. This laser power supply is designed and fabricated which has no high-voltage transformer, less switching losses, compact size and capability in varying the laser output power. Also, the output characteristics of this Nd:YAG laser system are investigated. The tested results are described.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.720-728
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• 2011

Lap joint welding conducts low carbon steel plates using a 2.0kW continuous wave Nd:YAG laser beam. The specimen is composed of thin plate of 20 sheets. Process Variables contain two controlled parameters of the laser power and the welding speed. In order to quantitatively examine the characteristics of the lap welding, the welding quality of the cut section, stain-stress behavior, and the hardness of the welded part are investigated. The weld width difference between the top and the bottom because the welding speed is increased. The reason, cooling rate is decreased because of fast welding speed. When the heat input is higher, larger volume of the base metal will melt and the welding heat has longer time to conduct into the bottom from the top. The microstructure and tensile properties of the joints are investigated in order to analyze the effects of heat input on the quality of laser welded specimen. From the results of the investigation, We observe that welding quality is good for the laser power of 1800W, and laser welding speed from 1.8m/min to 2.2m/min.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.629-635
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• 2006

Manufacture of motor by laser has been studying realization that was demands on market for lightening and miniaturization. Moreover. early in the 1980s. manufacture of parts for automobiles by laser welding was already successfully introduced. The purpose of this study was to develop production technology of the high quality laminated stator core for motor by pulsed Nd:YAG laser heat source. In the event of adjusting defocus and voltage to control humping in laser welding of the laminated core. sound bead could be obtained. but deep penetration was not. Therefore. explosive evaporating plasma was controlled by adjustment of peak power on pulse width. Particularly, because explosive evaporating plasma induced high peak power, made molten metal in keyhole scatter. a suitable adjustment of peak power was required to obtain sound bead. As a results of experiment. sound bead and deep penetration could be obtained.

• Journal of the Korean institute of surface engineering
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• v.45 no.4
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• pp.143-150
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• 2012

Laser cleaning have been found to be a useful cleaning tool to remove contaminants without inducing damage to the substrate and making secondary pollutant. In this study, the effect of Nd:YAG laser cleaning system, emitting at 1064 nm and 532 nm, on acrylic resin applied onto copper coupons and pieces of bronze was investigated. The samples after laser cleaning tests were examined using microscopy, FT-IR, SEM-EDS. As a result, the acrylic resin could be removed from most of the samples at low laser energy density. Laser wavelength 532 nm was more effective than 1064 nm because of using lower laser energy density, which could reduce heat damage to substrates. Although the acrylic resin was easily removed, it revealed melted surfaces and removed bronze patina which must remain. The problems should be solved by future studies using different laser system or laser wavelengths.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.660-666
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• 2003

The purpose of this study was to investigate the inhibitory effect of Er:YAG laser against the intraoral acid producing bacterium of S. mutans. Bacterial pellet containing S. mutans KCTC 3065 was irradiated by Er:YAG laser having a $650\;{\mu}m$ diameter beam by non-contact mode. Irradiated parameters were 50mJ, 10Hz and exposure time were 1s, 3s, 5s, 7s, 9s respectively. We obtained the following results of relative growth rate and acid-producing ability of S. mutans by culturing for 48hrs. 1. The growth rate of S. mutans was decreased in the group of laser irradiation compared to the control group(P<0.01). 2. The growth rate at laser irradiation group of 7s, 9s irradiation time was decreased significantly compared to the laser irradiation group of 1s, 3s, 5s irradiation time, until 12 hours(P<0.05). After 24 hours, all groups of laser irradiation were not found to be statistically different in each other. 3. The acid-producing ability of S. mutans was inhibited for a certain duration by irradiation of laser. In summary, the growth rate and acid producing ability of S. mutans decreased according to laser irradiation. This effect was directly related to the amount of irradiation time. These results suggested that Er:YAG laser had an growth inhibition effect on S. mutans.