• Title/Summary/Keyword: Surface characteristic

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Improving the Residual Stress Characteristics of the Metal Surface by Nd:YAG Laser Shock Peening (Nd:YAG 레이저 충격 피닝에 의한 금속표면의 잔류응력 특성 개선)

  • Yang, Se-Young;Choi, Seong-Dae;Jun, Jea-Mok;Gong, Byeong-Chae
    • 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.

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Effect of Flow Rate on Erosion Corrosion Damage and Damage Mechanism of Al5083-H321 Aluminum Alloy in Seawater Environment (해수 환경에서 Al5083-H321 알루미늄 합금의 침식부식 손상에 미치는 유속의 영향과 손상 메카니즘)

  • Kim, Young-Bok;Kim, Seong-Jong
    • Corrosion Science and Technology
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    • v.19 no.3
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    • pp.115-121
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    • 2020

  • In this study, erosion tests and erosion-corrosion tests of Al5083-H321 aluminum alloy were conducted at various flow rates in seawater. The erosion tests were conducted at a flow rate of 0 to 20 m/s, and erosion-corrosion tests were performed by potentiodynamic polarization method at the same flow rate. Characteristic evaluation after the erosion test was conducted by surface analysis. Characteristic evaluation after the erosion-corrosion test was performed by Tafel extrapolation and surface analysis. The results of the surface analysis after the erosion test showed that surface damage tended to increase as the flow rate increased. In particular, intermetallic particles were separated due to the breakdown of the oxide film at 10 m/s or more. In the erosion-corrosion test, the corrosion current density increased as the flow rate increased. Additionally, the surface analysis showed that surface damage occurred in a vortex shape and the width of the surface damage tended to increase as the flow rate increased. Moreover, damage at 0 m/s, proceeded in a depth direction due to the growth of pitting corrosion, and the damaged area tended to increase due to acceleration of the intermetallic particle loss by the fluid impact.

  • https://doi.org/10.14773/cst.2020.19.3.115 인용 PDF KSCI

Characterization of the Surface Contribution to Fluorescence Correlation Spectroscopy Measurements

  • Chowdhury, Salina A.;Lim, Man-Ho
    • Bulletin of the Korean Chemical Society
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    • v.32 no.2
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    • pp.583-589
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    • 2011

  • Fluorescence correlation spectroscopy (FCS) is a sophisticated and an accurate analytical technique used to study the diffusion of molecules in a solution at the single-molecule level. FCS is strongly affected by many factors such as the stability of the excitation power, photochemical processes, mismatch between the refractive indices, and variations in the cover glass thickness. We have studied FCS near the surface of a cover glass by using rhodamine 123 as a fluorescent probe and have observed that the surface has a strong influence on the measurements. The temporal autocorrelation of FCS decays with two characteristic times when the confocal detection volume is positioned near the surface of the cover glass. As the position of the detection volume is moved away from the surface, the FCS autocorrelation becomes one-component decaying; the characteristic time of the decay is the same as the faster-decaying component in the FCS autocorrelation near the surface. This observation suggests that the faster component can be attributed to the free diffusion of the probe molecules in the solution, while the slow component has its origin from the interaction between the probe molecules and the surface. We have characterized the surface contribution to the FCS measurements near the surface by changing the position of the detection volume relative to the surface. The influence of the surface on the diffusion of the probe molecules was monitored by changing the chemical properties of the surface. The surface contribution to the temporal autocorrelation of the FCS strongly depends on the chemical nature of the surface. The hydrophobicity of the surface is a major factor determining the surface influence on the free diffusion of the probe molecules near the surface.

  • https://doi.org/10.5012/bkcs.2011.32.2.583 인용 PDF KSCI