• 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.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.988-997
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• 2012

Laser surface hardening is one of core technologies to enhance various characteristics such as the strength, hardness, toughness, abrasion resistance, and fatigue resistance for the mold material. This paper focuses on testing characteristics of the laser heat treatment according to the preheating parameters in case of the SM45C medium carbon steel. In this paper, we assume that the power and travel speed of the laser are 1,800W and 0.5m/min, respectively, and the range of the preheating temperature is $50^{\circ}C{\sim}300^{\circ}C$. From the result of the test, we observed that the hardness width and depth are enhanced as the temperature is increased. Also, the best average hardness was 751.7Hv for the temperature of $100^{\circ}C$.

• Journal of Welding and Joining
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• v.31 no.2
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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 the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.539-547
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• 2010

Laser shock peening is useful to improve fatigue characteristic of multiple number of metals and alloys. This process induces a compressive residual stress on the metal surface, and when tensile load is applied, growth of crack is delayed and which changes the characteristic of the metal surface. It is an innovative surface treatment technique for strengthening metals. Specimens of SM45C are used in this study. The effect of an inertial tamping layer on the residual stress field using laser shock peening setup and Nd:YAG laser power is evaluated. Residual stress distribution measured by X-ray diffraction. As a result of this study it can be presented that following condition of Nd:YAG laser power and inertial tamping layer parameters, compressive residual stress is generated on the surface of the SM45C. Results to experimental data indicate that laser shock peening has great potential as a means of improving the mechanical performance of the metal surface.

• The Optical Journal
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• s.100
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• pp.30-33
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• 2005

인도의 레이저 시장은 총 5,676 백만 달러로 추정된다. 이중 산업용이 가장 많은 51%, 그 다음이 의료용으로 38%, 나머지는 각종 연구소에서 이용되는 과학 연구용으로서 11%를 차지한다. 사용되는 레이저의 종류에 따라 분류하면 CO2레이저가 포함된 기체 레이저가 전체의 반이 넘는 52%, Nd:YAG 레이저가 포함된 고체 레이저가 43%, 나머지는 반도체 레이저로서 5%를 차지한다.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.777-783
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• 2001

This paper is mainly concerned with the state of the practical developments of a constants PWM bridge type resonants DC-DC suitable converter for Nd:YAG Laser with a Microprocessor. (PIC16C54 & 8051) The use of IGBT power supply with feedback control of flashLamp currents imparts a advantages to Nd:YAG Laser for materials processing. these include the alility to tailor the pulseshape and modify pulse parameters on a pulse- by pulse basis. And Correct choice of pulseshape can enhance the repeatability of the process. as higher power IGBT became available, act ive pulseforming power supplies will find greater user in deep hole drilling machine By Using certain control tecniques, utililized in designing Pic16c54 from Microchip technology and Intel 8051, also Mornitoring from Microsoft Visual Basic 5, And it allowed us to designed and fabricate ahigh repel it ion rate and high power(HRHP) pulsed Nd:YAG laser system, As a result of that, the current pulsewidth could be contort led 200s to 350s(step 50s) , and the pulse repetition rate could be adjusted 500pps to 1150pps. In addition, in the case of one laser head consisting of a Nd:YAG laser rod and two flashlamps , the maximum laser output of 240w was produced at the condition of 350s and 1150pps, and that of about 480w was generated at the same condition when two laser heads were arranged in cascade.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.514-517
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• 1996

Zero current switching(ZCS) series resonant converter is used to control laser power density in a pulsed Nd:YAG laser power supply. The high power and high repetition rate paused Nd:YAG laser is designed and fabricated to control current pulse width and pulse repetition rate in the double elliptical laser oscillator. In order to find out operational characteristics of pulsed Nd:YAG laser, the electrical properties of driving power supply and laser output power are investigated and experimented by changing of the current pulse width from 200uS to 350uS(step 50uS) and pulse repetition rate range of 500pps(pulse per second) to 1150pps. From that result, we obtaind maximum efficiency of 1.83% and maximum laser output or 220W at the condition of 350 uS and 1150pps with one Nd:YAG rod), and obtained that of more than 400W with two laser head connecting series.

• Journal of Oral Medicine and Pain
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• v.23 no.1
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• pp.1-9
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• 1998

The aim of the study was to evaluate the anesthetic Effecs of pulsed Nd:YAG laser irradiation to the oral mucosa and the teeth. Twenty subjects who didn't have a history of significant systemic or current oral disease were included in this study. All the subjects were divided randomly into the experimental group and the control group with 10 for each group. Pain thresholds were measured with Weighted Needle Pinprick Sensory Threshold Test for the mucosal surface of lower lip and with electric pulp test for the upper right central incisor respectively, before and immediately after pulsed Nd:YAG laser irradiation in the condition of 2 watt, 20pps for 2 minute at 10mm distance. The experiment was double-blinded clinical trial. The results were as follows : 1. The mean pain threshold of the mucosal surface of lower lip for Weighted Needle Pinprick Sensory Threshold Test was 2.94(1.00g for the contral group respectively, and there was no statistical difference between two groups. 2. The mean pain threshold of the mucosal surface of lower lip was significantly increased immediately after pulsed Nd:YAG laser irradiation. 3. The mean pain threshold of the upper right central incisor for eledtric pulp test was 34.50(4.97V in the experimental group and 34.00(13.08V in the control group respectively, and there was no statistical difference between two groups. 4. The mean pain threshold of the upper right central incisor was significantly increased immediately after pulsed Nd:YAG laser irradiation.

• Journal of Oral Medicine and Pain
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• v.25 no.1
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• pp.129-144
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• 2000

The purpose of this study was to examine dentin surface changes of extracted sound third molar specimens which were etched with 10% maleic acid and irradiated at $7-140J/cm^2$ with $CO_2$ and at $156-280J/cm^2$ with Nd:YAG laser. The results were as follows. 1. Dentin surfaces etched with 10% maleic acid and then irradiated at below of $42J/cm^2$ with $CO_2$ laser showed the retentive morphology for resin restoration. 2. Dentin surfaces irradiated at below of $42J/cm^2$ with $CO_2$ laser showed the increased acid-resistance. 3. Dentin surfaces irradiated at $218-280J/cm^2$ with Nd:YAG laser showed the retentive morphology. 4. Dentin surfaces irradiated at $218-280J/cm^2$ with Nd:YAG laser and etched 10% maleic acid and then $218-280J/cm^2$ with Nd:YAG laser showed the increased acid-resistance.

• Journal of Surface Science and Engineering
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• v.46 no.5
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• pp.197-207
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• 2013

In the midst of increasing importance of modern cultural assets, especially, most modern bronze objects are exposed to outdoor environment, and as the objects are corroded steadily due to environmental factors the objects lost their original colors on the surface. We performed artificial patinas on the bronze sample per each color of red, black and green and checked cuprite and tenorite which are detected from actual bronze corrosion by analyzing the components. In addition, we applied the existing corrosion removal methods of grinder and sand blaster on a similar sample of bronze mirror per injection pressure and performed comparative analysis on the result with Nd:YAG laser. As a result of Nd:YAG laser cleaning artificial patina from bronze samples, all of the patinas were removed by laser wavelength 1064 nm better than 532 nm. Upon applying to a similar sample of bronze mirror, the artificial patina could be selectively removed from substrates without surface damage when Nd:YAG laser was conducted other than the existing removal method, and so it showed the possibility of application.