• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2138-2140
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• 2000

송전선, 변전소, 발전소 등의 전력설비에 있어서 애자장치의 오손은 지락사고나 코로나 유발에 의한 환경장애 등의 원인이 되고 있어 염분에 의한 애자장치의 오손 대책이 설비 관리에 있어서 중요한 부분을 차지하고 있으며, 이를 위해서는 염분 오손도의 측정이 선행되어야 한다. 본 논문에서는 염분 오손도를 상시 자동으로 측정할 수 있는 방법으로서 제안되고 있는 전자식 애자 이용법, 열전 반도체를 이용한 전도도 측정법, Nd:YAG 레이저법, 레이저 광센서와 프리즘을 이용한 염분 오손도 측정법, 정전용량 검출센서를 이용한 염분 오손도 측정법, 백금 전극을 이용한 누설전류 측정법과 같은 염분 오손도 측정법을 소개하고자 한다.

• Korean Journal of Materials Research
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• v.6 no.6
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• pp.636-643
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• 1996

공진기형 제 2고조파소자(SHG)는 레이저 빔의 에너지 밀도가 높아 고내구성 박막이 필요하다. 본 연구에서는 광학박막 재료로 고융점 산화물인 ZrO2, TiO2, SiO2를 사용하였다. 반응성 스퍼터링 방법으로 제작한 ZrO2, TiO2, SiO2 박막을 XRD, SAM을 사용하여 분석하였고, 박막의 광학적 특성을 평가하였다. SHG 소자의 KTP 및 Nd:YAG 결정의 반사방지막(A/R 코팅)구성은 ZrO2와 SiO2를 사용하여 컴퓨터로 계산하였는데 기본파인 1064nm와 제 2고조파인 532nm에서 각각 0.1%, 0.5%이하의 반사율을 갖도록 하였다. 또한 고반사막(H/R 코팅)의 경우 1064nm에서 99.9%의 반사율을 갖도록 TiO2와 SiO2로 디자인하였다. 제작한 광학박막의 광학적 특성, 레이저 내구성(laser damage threshold), 온습도 안정성 실험 등을 통해 광학박막을 평가하였다.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.109-113
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• 2007

Laser welding process for wing of a guided weapon is studied. Nd;YAG pulse laser beam is used to weld the skin(STS304, thickness: 1mm) to frame(AMS 5398) of wing. Optimal laser welding condition is obtained from the mechanical testing and observation of the welded joint.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.64-71
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• 2009

Recently as ultrasonic medical devices are gradually developed, many of those require smaller and more precision coaxial cables in the probe. So, the use of micro coaxial cable becomes an efficient solution for ultrasonic machine. However, there are many difficulties in stripping micro coaxial cable by traditional mechanical process. In this paper we use the Nd:YAG laser for the efficient striping of conduct wire of cable. Through some experiments, we found that there is a new possibility in the proposed method. Also, we propose a pre-process of the cable before stripping in order to enhance the performance.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.1
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• pp.67-76
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• 2013

We present an innovative real-time laser welding monitoring technique employing the correlation analysis of the plasma plume optical emission generated during the process. The plasma optical radiation emitted during Nd:YAG laser welding of S45C steel samples has detected with a Photodiode and analyzed under different process conditions. The discrete DC voltage difference, filter methods and wavelet transform has been used to decompose the optical signal into various discrete series of sequences over different frequency bands. Considering that wavelet analysis can decompose the optical signals, extract the characteristic information of the signals and define the defects location accurately, it can be used to implement process-control of laser welding.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.167-172
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• 2013

Titanium dioxides nanoparticles coated aluminum oxide powders were fabricated by pulsed laser deposition (PLD) with Nd : YAG laser at 266 nm. The Pulse laser energy is 100 mJ/pulse. During the irradiation of the focused laser on the $TiO_2$ target, Ar gas is supplied into the chamber. The gas pressure is varied in a range of $1{\times}10^{-2}$ to 100 Pa. Titanium dioxides nanoparticles deposited aluminum oxide powders were characterized by using energy dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HR-TEM), in order to understand the effect of Ar background gas on surface morphology and properties of the powders. The coated $TiO_2$ nanoparticles had nanosized spherical shape and the crystallite sizes of 10~30 nm. The morphology of coated $TiO_2$ nanoparticles is not affected by gas pressure. However, the particle size and crystallinity slightly increased with the increase of gas pressure. According to this technique, the size and crystallinity of nanoparticles can be easily controlled by controlling pressure during the laser irradiation.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.428-433
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• 1993

The second harmonic of Q-switched Nd:YAG laser beam with gaussian mode is cut off by pinhole of a certain radius and its central portion passed through pinhole is focused by converging lens. It is confirmed that the shape of this beam in focal region is central symmetric but non-gaussian. Change of transmittance due to self-focusing is investigated by scanning (z-scan) $CS_2$ of 1 mm thickness in the focal region. It is found that the observed results can be consistently explained by Fresnel theory within 1.5% accuracy and efficiency of self-focusing depends on spatial shape of incident beam.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.410-413
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• 2003

We have developed the measurement system for the high power laser The absorber is made of gold-plated copper cavity. The calibration heater is using a manganin(CuMn12Ni ; Isabellenhutte) coil, and output power is measured by using of resistance bridge with composed manganin and copper coil. Developed system can measure for 5∼1000w laser output power range. Calibration factors are 489.13 J/mV at 100W range and 489.13 J/mV at 500W range. Correction factors are 0.99 at 100W range and 1.006 at 500W range.

• Laser Solutions
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• v.14 no.1
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• pp.19-24
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• 2011

This work reports the results for laser shock peening of duplex stainless steel (22% Chromium - 5% Nickel) using a pulsed Nd:YAG laser (wavelength = 532nm, pulse width = 8ns). for the application to high-capacity pumps for seawater desalination plants. By properly selecting the process parameters such as laser intensity of 10GW/$cm^2$, laser pulse density of 75pulse/$mm^2$, and $100{\mu}m$ thick aluminum foil as an absorbent coating layer, the surface hardness of duplex stainless steel could be enhanced by 26%, from 256HV to 323HV with little changes in surface morphology and roughness. The depth of laser shock peened layer was measured to be around 2mm. The large enhancement of surface hardness is considered to have high practical importance in minimizing abrasive and corrosive deterioration of pump parts.

• Laser Solutions
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• v.11 no.4
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• pp.7-12
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• 2008

Laser Transformation Hardening(LTH) is one branch of the laser surface modification processes. A lot of energy is needed for the LTH process to elevate workpiece surface to temperature of the austenite transformation($A_3$), which results from utilizing a beam with a larger size and lower power density comparatively. This study is related to the surface hardening for the rod-shaped carbon steel by the high power diode laser whose beam absorptivity is better than conventional types of lasers such as $CO_2$ or Nd:YAG laser. Because a beam proceeds on the rotating specimen, the pretreated hardened-phase can be tempered and softened by the overlapping between hardened tracks. Accordingly, the longitudinal hardness measurement and observation of the micro structure was carried out for an assessment of the hardening characteristics. In addition, a hardening characteristics as a hardenability of materials was compared in the point of view of the hardness distribution and hardening depth and width.