• Title/Summary/Keyword: Laser Power

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Effects of laser power on hardness and microstructure of the surface melting hardened SKD61 hot die steel using Yb:YAG disk laser (Yb:YAG 디스크로 레이저 표면 용융 경화된 SKD61 열간금형강의 경도와 미세조직에 미치는 레이저 출력의 영향)

  • Lee, Kwang-Hyeon;Choi, Seong-Won;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.33 no.3
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    • pp.54-61
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    • 2015
  • In this study, effect of laser power on hardness and microstructure of SKD61 Hot Die steel of which surface was melted and hardened with Yb:YAG disk laser was investigated. Beam speed was fixed at 70 mm/sec and distance between them was 0.8 mm about Laser surface melting. The only thing that was changed laser power. Laser powers were 2.0, 2.4 and 2.8 kW. No defect was found under all conditions. As the laser power increased, the penetration depth were deepened and the bead width was also widened. There was no hardness deviation of fusion zone at same laser power and it was higher than that of heat affected zone. In addition, the more laser power increased, the more hardness in fusion zone decreased. Fusion zone was macroscopically dendrite structure. However, core matric in dendrite was lath martensite of 100 nm size. There were $M_{23}C_6$ of 500 nm and the VC and $Mo_2C$ of a nano meters on boundary of dendrite.

Heat transfer analysis for optimization of recording mark on Compact Disk-Recordable (추기형 광디스크에서 최적 기록마크 생성을 위한 열전달 해석)

  • Hong, S.K.;Lee, J.D.;Shin, J.M.;Go, S.R.;Lee, K.H.;Cho, H.H.
    • Proceedings of the KSME Conference
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    • pp.589-595
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    • 2001
  • The present study conducted heat transfer analysis in multi-layer of CD-R. It is necessary to analyze heat transfer during the recording process to find optimum power and write strategy in CD-R. This study investigated effects of several parameters such as recording speed, laser power, layer thickness and thermal property. The calculated results presented temperature distribution in the multi-layer and detailed information of recording characteristics. Optimum laser power was estimated, comparing an optimum mark length with the calculated mark lengths. The results showed that the optimum laser power was influenced significantly by the layer thickness and the thermal properties of the dye.

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Fabrication of Micro Carbon Structures and Patterns with Laser-assisted Chemical Vapor Deposition (레이저 국소증착을 통한 미세 탄소구조물 및 패턴 제조)

  • 정성호;김진범;이선규;이종현
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.914-917
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    • 2002
  • Fabrication of micro carbon structures and patterns using laser-assisted chemical vapor deposition is studied. Argon ion laser and ethylene were used to grow micro carbon rod through pyrolytic decomposition of the reaction gas. The influence of reaction gas pressure and incident laser power on the diameter and growth rate of the micro carbon rod was experimentally investigated. The diameter of micro carbon rods increases linearly with respect to the laser power but is almost independent of the reaction gas pressure. Growth rate of the rod changes little with gas pressure when the laser power remains below 1W. When the carbon rod was grown at near threshold laser power, a very smooth surface is obtained on the rod. By continuously moving the focusing lens in the direction of growth, a micro carbon rod with a diameter of 28 ${\mu}{\textrm}{m}$ and aspect ratio of 100 was fabricated.

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인공심장판막의 현황

  • 김형묵
    • Journal of Biomedical Engineering Research
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    • v.10 no.2
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    • pp.94-96
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    • 1989
  • Explosive evaporative removal process of biological tissue by absorption of a CW laser has been simulated by using gelatin and a multimode Nd:YAG laser. Because the point of maximun temperature of laser-irradiated gelatin exists below the surface due to surface cooling, evaporation at the boiling temperature is made explosively from below the surface. The important parameters of this process are the conduction loss to laser power absorption (defined as the conduction-to-laser power parameter, Nk), the convection heat transfer at the surface to conduction loss (defined as Bi), dimensionless extinction coefficient (defined as Br.), and dimensionless irradiation time (defined as Fo). Dependence of Fo on Nk and Bi has been observed by experiment, and the results have been compared with the numerical results obtained by solving a 2-dimensional conduction equation. Fo and explosion depth (from the surface to the point of maximun temperature) are increased when Nk and Bi are increased.To find out the minimum laser power for explosive evaporative removal process, steady state analysis has been also made. The limit of Nk to induce evaporative removal, which is proportional to the inverse of the laser power, has been obtained.

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Growth Characteristics of Micro Carbon Structures Fabricated by Laser-Assisted Chemical Vapor Deposition (레이저 국소증착법에 의한 탄소 미세 구조물의 제조시 성장특성에 관한 연구)

  • Kim, Jin-Beom;Lee, Seon-Gyu;Lee, Jong-Hyeon;Jeong, Seong-Ho
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.7
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    • pp.106-115
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    • 2002
  • Growth characteristics of micro carbon structures fabricated by laser-assisted chemical vapor deposition are studied. Argon ion laser and ethylene were used as the energy source and reaction gas, respectively, to grow micro carbon rod through pyrolytic decomposition of the reaction gas. Experiments were performed at various conditions to investigate the influence of process parameters on growth characteristics such as the diameter or growth rate of the micro carbon rod with respect to reaction gas pressure and incident laser power. Reaction gas pressure in experiments ranges from 200 to 600Torr and the incident laser power from 0.3 to 3.8W. For these conditions, the diameter of the rod increases linearly with respect to the laser power but is almost independent of the reaction gas pressure. Growth rate of the rod changes little with gas pressure when the laser power remains below IW. For a constant reaction gas pressure, the growth rate increase with Increasing laser power, but the rate of increase decreases gradually, implying that the chemical vapor deposition condition changes from a kinetically-limited regime to a mass-transport-limited regime. When the carbon rod was grown at near threshold laser power, a very smooth surface is obtained on the rod. By continuously moving the focusing lens in the direction of growth, a micro carbon rod with a diameter of 287${\mu}{\textrm}{m}$ and aspect ratio of 100 was fabricated..

Laser Micro-machining Process-monitoring Technologies (레이저 미세가공 공정 요소 모니터링 기술)

  • Sohn, Hyon-Kee;Lee, Jae-Hoon;Hahn, Jae-Won;Kim, Ho-Sang
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.2
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    • pp.34-39
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    • 2010
  • In order to achieve and maintain dimensional accuracy in laser micro-machining, dominant parameters such as laser power and laser focus position need to be monitored and controlled real time. Also, in order to selectively machine multi-layered materials, the material being presently machined need to be recognized. This paper presents an auto-focusing (AF) module to keep laser focus on a large-area surface; a real-time laser power stabilizing module based on optical attenuation; and a laser-induced breakdown spectroscopy (LIBS) module. With these monitoring modules, position error in laser focus on a 4" silicon wafer was kept below $4{\mu}m$, initially $51{\mu}m$, and laser power stability of a UV laser source was improved from 1.6% to 0.3%. Also, the material transition from polyimide to copper in machining of FCCL (flexible copper clad laminate) was successfully observed.

Effects of Average Power on Laser Cladding of Hypereutectic Al-Si Alloy on Al 1050 Alloy (Al 1050 합금에 과공정 Al-Si 합금의 레이저 클래딩에서 평균출력의 영향에 대한 연구)

  • Lee, Hyoung-Keun
    • Journal of Welding and Joining
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    • v.29 no.2
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    • pp.88-93
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    • 2011
  • This study produced hypereutectic Al-Si clad layer on 1050 Al alloy by a novel laser cladding method. Pure Si powder was mixed with organic binder to make fluid paste which could be screen-printed on the 1050 Al alloy plate. Pulsed Nd:YAG laser was irradiated on the Si paste layer to melt and alloy with Al substrate. Different laser power of 99 W, 179 W and 261 W, was used to see the difference of the microstructure, composition and hardness of the clad layers. When laser power of 179 W was used, the clad layer had overall Si content of 38wt% and composed of fine primary Si particles and fine eutectic phase. At laser power of 261 W, the clad layer had overall Si content of 24wt% and composed of mainly fine eutectic phase. Vickers hardness of HV176.7 and HV150.3 on the clad layer was obtained at laser power of 179 W and 261 W, respectively.

Photopolymer Solidification Phenomena Considering Laser Exposure Conditions in Micro-stereolithography Technology (마이크로 광 조형에서 레이저 주사조건에 따른 광 경화성수지의 경화현상)

  • 이인환;조동우;이응숙
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.3
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    • pp.171-179
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    • 2004
  • Micro-stereolithography technology has made it possible to fabricate a freeform 3D microslructure. This technology is based on conventional stereolithography, in which a UV laser beam irradiates the open surface of a UV-curable liquid photopolymer, causing it to solidify. In micro-stereolithography, a laser beam of a few $\mu m$ diameter is used to solidify a very small area of the photopolymer. This is one of the key technological elements, and can be achieved by using a focusing lens. Thus, the solidification phenomena of the liquid photopolymer must be carefully investigated. In this study, the photopolymer solidification phenomena in response to variations in the scanning pitch of a focused laser beam was investigated experimentally. The effect of layer thickness on the solidification width and depth was also examined. These studies were conducted under the conditions of relatively lower laser power and relatively higher scanning speed. Moreover, the photopolymer solidification phenomena for the relatively higher laser power and lower scanning speed was investigated, too. In this case, comparing to the case of lower laser power and higher scanning speed, the photopolymer absorbed large amount of irradiation energy of the laser beam. These results were compared with those obtained from a photopolymer solidification model. From these results, a new laser-scanning scheme was proposed according to the shape of the 3D model. Samples by each method were fabricated successfully.

Characteristics of Surface Hardening by Laser Power Control in Real Time of Spheroidal Graphite Cast Iron (실시간 출력 제어를 통한 구상흑연 주철의 레이저 표면경화 특성)

  • Kim, Jongdo;Song, Mookeun
    • Laser Solutions
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    • v.18 no.2
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    • pp.1-4
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    • 2015
  • This study is related to the surface hardening treatment to spheroidal graphite cast iron for die by using high power diode laser. Laser device used in this experiment is capable of real-time laser power control. This is because the infrared temperature sensor (two color pyrometer) attached to the optical system measures the surface temperature of specimen and adjusts the laser power in real time. The surface treatment was carried out with the change of heat treatment temperature at the beam travel speed 3 mm/sec. Hardened width and depth was measured and hardened zone was analyzed by micro vickers hardness test in order to research the optimum condition of heat treatment. The changes in microstructure of the hardened zone also was examined. As a result of hardness measurement and observations on microstructure of hardened zone, hardness increased over three times as compared with base metal because the martensite was formed on the matrix structure.

Effect of Parameters in Evaporative Removal Process by Absorption of a CW Laser (연속 레이저 흡수에 의한 증발제거 과정의 관련 인자 영향 고찰)

  • 김진윤;송태호
    • Journal of Biomedical Engineering Research
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    • v.16 no.1
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    • pp.67-76
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    • 1995
  • Explosive evaporative removal process of biological tissue by absorption of a CW laser has been simulated by using gelatin and a multimode Nd: YAG laser. Because the point of maximun temperature of laser-irradiated gelatin exists below the surface due to surface cooling, evaporation at the boiling temperature is made explosively from below the surface. The important parameters of this process are the conduction loss to laser power absorption (defined as the conduction-to-laser power parameter, Nk), the convection heat transfer at the surface to conduction loss (defined as Bi), dimensionless extinction coefficient (defined as BrJ, and dimensionless irradiation time (defined as Fo). Dependence of Fo on Nk and Bi has been observed by experiment, and the results have been compared with the numerical results obtained by solving a 2-dimensional conduction equation. Fo and explosion depth (from the surface to the point of maximun temperature) are increased when Nk and Bi are increased. To find out the minimum laser power for explosive evaporative removal process, steady state analysis has been also made. The limit of Nk to induce evaporative removal, which is proportional to the inverse of the laser power, has been obtained.

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