• Title/Summary/Keyword: Beam spot

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Shape and Chemical Composition of Laser Surface Alloyed Layer under Moving Laser Source (공정변수에 따른 레이저표면합금층의 형상 및 성분변화에 관한 연구)

  • 최정영;이창희
    • Laser Solutions
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    • v.2 no.2
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    • pp.8-17
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    • 1999
  • This study includes a basic feature of laser surface alloying for enhancing the surface properties of materials. Effects of laser processing parameters such as beam power, beam size, scanning speed on the shape and composition of alloyed layer was simulated in case of moving beam conditions (2-dimensional numerical methods). Simulated results were compared with experiments, in which the plasma coating of 80% Ni + 20% Cr deposited on the SS41 substrate was remelted with CO2 laser with Gaussian energy distribution. Simulation and experiments revealed that the shape (dimension)and composition of laser alloyed layer were strongly dependent upon the process parameters, especially interaction time (travel speed) as compared to beam diameter, beam power and absorptivity. The shape and composition of alloyed layervaried more or less exponentially with parameters.

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Electron Beam Behaviors by the Electrostatic Lens in Triode Field Emission Gun (3극 전계방출 전자총의 정전기 렌즈에 의한 전자빔 거동)

  • Kim, Chung-Soo;Kim, Dong-Hwan;Park, Man-Jin;Jang, Dong-Young;Han, Dong-Chul
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.6
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    • pp.163-167
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    • 2007
  • A field emission electron gun including 3 electrodes including one cathode and two anodes is very important for high resolution electron microscope. To have functions to control the initially-emitted electron beam, two anodes act as an electrostatic lens according to equipotential lines by adjusting the spot size, intensity, and working distance. To verify the action of the electron beam by the electrostatic lens by changing several parameters such as electrode shape, displacement and applied voltage to the electrodes, the two lenses were design and simulated and then their performances were analyzed with angular beam intensity(distribution), electrical optic axis variation and their stability.

Research on rib-to-diaphragm welded connection by means of hot spot stress approach

  • Wang, Binhua;Lu, Pengmin;Shao, Yuhong
    • Steel and Composite Structures
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    • v.18 no.1
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    • pp.135-148
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    • 2015
  • The cutout hole locating at the place of rib-to-diaphragm welded connection is adopted to minimize the restraint, which is caused by the floor-beam web to rib rotation at the support due to the unsymmetrical loads in orthotropic deck. In practice, an inevitable problem is that there is a large number of welding joint's cracks formed at the edge of cutout hole. In this study, a comparative experiment is carried out with two types of cutout hole, the circular arc transition and the vertical transition. The fatigue life estimation of specimens is investigated with the application of the structural hot spot stress approach by finite element analyses. The results are compared with the ones of the fatigue tests which are carried out on these full-scale specimens. Factors affecting the stress range are also studied.

a Study on Heat Source Equations for the Prediction of Weld Shape in Laser Micro-welding (미세 레이저 용접에서 용융부 형상예측을 위한 열원의 방정식에 관한 연구)

  • 장원석;나석주
    • Journal of Welding and Joining
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    • v.18 no.4
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    • pp.76-81
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    • 2000
  • In this research, various heat source equations that have been proposed in previous study were calculated and compared with new model in various laser parameters. This is to treat the problem of predicting, by numerical analysis, the thermo-mechanical behaviors of laser spot welding for thin stainless steel plates. A finite element code, ABAQUS is used for the heat transfer analysis with a three-dimensional plane assumption. Experimental studies if the laser spot welding have also bee conducted to validate the numerical models presented. The results suggest that temperature profiles and weld dimensions are varied according to the heat source of the laser beam. For this reason, it is essential to incorporate an accurate description of the heat source.

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Fiber Laser Welding in the Car Body Shop - Laser Seam Stepper versus Remote Laser Welding -

  • Kessler, Berthold
    • Journal of Welding and Joining
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    • v.31 no.4
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    • pp.17-22
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    • 2013
  • The excellent beam quality of high power fiber lasers are commonly used for remote welding applications in body job applications. The Welding speed and productivity is unmatched with any other welding technology including resistance spot welding or traditional laser welding. High tooling cost for clamping and bulky safety enclosures are obstacles which are limiting the use. With the newly developed Laser stitch welding gun we have an integrated clamping in the process tool and the laser welding is shielded in a way that no external enclosure is needed. Operation of this laser welding gun is comparable with resistance spot welding but 2-times faster. Laser stitch welding is faster than spot welding and slower than remote welding. It is a laser welding tool with all the laser benefits like welding of short flanges, weld ability of Ultra High Strength steel, 3 layers welding and Aluminium welding. Together with low energy consumption and minimum operation cost of IPG fiber laser it is a new and sharp tool for economic car body assembly.

A Scanning electron microscopic study of the dentinal tubule obliteration effect by the different irradiations of a pulsed Nd:YAG laser (Nd:YAG 레이저의 조사방법의 차이에 따른 상아세관 폐쇄효과에 관한 주사전자현미경적 연구)

  • Ko, Eun-Young;Kim, Song-Wook;Yum, Chang-Yup;Kim, Byoung-Ock;Han, Kyung-Yoon
    • Journal of Periodontal and Implant Science
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    • v.27 no.4
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    • pp.829-844
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    • 1997
  • Dentin hypersensitivity must be one of the most frequent postoperative complaints in periodontal patients. Obliterating the open dentinal tubules or decreasing the diameter of their orifices would, therefore, be an objective of treatment for hypersensitive teeth. The purpose of this study was to evaluate the effect of a pulsed Nd:YAG laser irradiation on obliteration of dentinal tubules and to determine any difference according to irradiation methods. The 45 posterior teeth that had been extracted due to periodontal disease were initially treated with tetracycline HCI(100 mg/ml, 4 min.) to remove the smear layer after root planing. The root surfaces were then irradiated by a pulsed Nd:YAG laser(EL.EN.EN060, Italy) by different laser beam spot size and different exposure condition: ${\cdot}$ group 1: irradiated group by small spot(beam diameter=1mm, lW, 2 sec) ${\cdot}$ group 2: irradiated group by large spot(beam diameter=10mm, 1W, 200 sec) ${\cdot}$ group 3: irradiated group by gradual increase of watt (from 0.3W to 1.0W), beam diameter=4mm ${\cdot}$ group 4: irradiated group by fixed watt(1.0 W), beam diameter=4mm ${\cdot}$ control group: no irradiation but root planing and tetracycline HCI conditioning only. Additionally, the specimens were retreated with tetracycline HCI(100mg/ml, 4min.) to evaluate the stability of obliteration effect by Nd:YAG laser. Specimens were examined under the scanning electron microscope(JEOL, JSM-840A, Japan). Photomicrographs were taken at ${\times}4,000$ magnification and were analyzed statistically. The results were as follows: l. Scanning electron micrographs of root surface treated by tetracycline HCI alone(control group) showed widened, funnel-shaped dentinal tubules, while those of the root surface irradiated by various methods showed partially or completely obliterated dentinal tubules and various surface alterations, eg, flat, multiple pitted, melted and resolidified surface at the same energy density. 2. There was no significant difference in the obliteration effect of dentinal tubules between group 1 and group 2, and between group 3 and group 4(p>0.05). 3. The obliteration effect of dentinal tubules by a Nd:YAG laser irradiation was relatively stable to tetracycline HCI. The results demonstrate that a pulsed Nd:YAG laser irradiation within 1.0W, regardless of irradiation methods, can obliterate dentinal tubules effectively.

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$CO_2$ Laser Beam Welding and Formability of Steel Plates with Different Thicknesses (이종두께 강판의 $CO_2$ 레이저 용접 및 성형성)

  • Suh, J.;Han, Y.H.;Kim, J.O.;Lee, Y.S.
    • Journal of Welding and Joining
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    • v.14 no.1
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    • pp.82-91
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    • 1996
  • The maximum butt-joint gap size in $CO_2$ laser beam welding of SAPH steel plates with different thicknesses and its bending formability were studied. In the range of the gap size$\geq$0.1mm, the optimal butt welding speed was faster than that of no gap (air gap) condition. This behaviour was independent on the difference of thickness at any combination. Also, the allowable gap size in steel plates with different thicknesses was larger than with same thicknesses. In the range of $T/T_0$(bead shape) $\geq$ 0.8, good bending formability was obtained at any combination of thickness. The formability was improved by reducing the hardness in weld bead using pre-heating process. Finally, FEM result of the laser beam welded underframe with different thicknesses was compared to that of the conventional spot welded underframe.

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Realization for Each Element for capturing image in Scanning Electron Microscopy (주사 전자 현미경에서 영상 획득에 필요한 구성 요소 구현)

  • Lim, Sun-Jong;Lee, Chan-Hong
    • Laser Solutions
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    • v.12 no.2
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    • pp.26-30
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    • 2009
  • Scanning Electron Microscopy (SEM) includes high voltage generator, electron gun, column, secondary electron detector, scan coil system and image grabber. Column includes electron lenses (condenser lens and objective lens). Condenser lens generates fringe field, makes focal length and control spot size. Focal length represents property of lens. Objective lens control focus. Most of the electrons emitted from the filament, are captured by the anode. The portion of the electron current that leaves the gun through the hole in the anode is called the beam current. Electron beam probe is called the focused beam on the specimen. Because of the lens and aperture, the probe current becomes smaller than the beam current. It generate various signals(backscattered electron, secondary electron) in an interaction with the specimen atoms. In this paper, we describe the result of research to develop the core elements for low-resolution SEM.

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EUVL Mask Defect Isolation and Repair using Focused Ion Beam (Focused Ion Beam을 이용한 EUVL Mask Defect Isolation 및 Repair)

  • 김석구;백운규;박재근
    • Journal of the Semiconductor & Display Technology
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    • v.3 no.2
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    • pp.5-9
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    • 2004
  • Microcircuit fabrication requires precise control of impurities in tiny regions of the silicon. These regions must be interconnected to create components and VLSI circuits. The patterns to define such regions are created by lithographic processes. In order to image features smaller than 70 nm, it is necessary to employ non-optical technology (or next generation lithography: NGL). One such NGL is extreme ultra-violet lithography (EUVL). EUVL transmits the pattern on the wafer surface after reflecting ultra-violet through mask pattern. If particles exist on the blank mask, it can't transmit the accurate pattern on the wafer and decrease the reflectivity. It is important to care the blank mask. We removed the particles on the wafer using focused ion beam (FIB). During removal, FIB beam caused damage the multi layer mask and it decreased the reflectivity. The relationship between particle removal and reflectivity is examined: i) transmission electron microscope (TEM) observation after particle removal, ii) reflectivity simulation. It is found that the image mode of FIB is more effective for particle removal than spot and bar mode.

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Application of ESPI to Measurement of Out-of-plane Displacement in a Spot Welded Canti-levered Plate

  • Baek, Tae-Hyun;Kim, Myung-Soo;Na, Eui-Gyun;Koh, Seung-Kee
    • International Journal of Precision Engineering and Manufacturing
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    • v.4 no.5
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    • pp.41-46
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    • 2003
  • Electronic Speckle Pattern Interferometry (ESPI) has been recently developed and widely used because it has the advantage of being able to measure surface deformations of engineering components and materials in industrial areas without contact. The speckle patterns formed with interference and scattering phenomena can measure not only the out-of-plane but also the in-plane deformations. Digital image equipment processes the information included in the speckle patterns and displays the consequent interferogram on a computer monitor. In this study, the experimental results of a canti-levered plate using ESPI were compared with those obtained from the simple beam theory. The ESPI results of the canti-levered plate, analyzed by 4-step phase shifting method, are close to the theoretical expectation. Similarly, out-of-plane displacements of a spot welded canti-levered plate were also measured by ESPI with 4-step phase shifting technique. The phase map of the spot welded canti-levered plate is quite different from that of the canti-levered plate without spot welding.