• Title/Summary/Keyword: Surface Charging

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The Analysis of Surface Degradation Mechanism on PRP(epoxy/glass fiber) by Corona Charging Properties (코로나 대전 특성을 이용한 FRP의 표면 열화메커니즘의 해석)

  • Lee, Baek-Su;Im, Gyeong-Beom;Jeong, Ui-Nam;Park, Jong-Gwan;Lee, Deok-Chul
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.5
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    • pp.373-378
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    • 1999
  • In order to analyse the degradation mechanism of polymer materials for outdoor condition, FRP laminate was exposed to high temperature and ultraviolet rays. Then, thedegradation process was evaluated by comparing contact angle, surface potential decay, and polarity effect respectively. Especially, the analysis of surface degradation phenomena by corona charging method showed the exact correlation with the result of chemical properties. Therefore we can confirm that the application of corona charging method on the identification of degradation process is very useful. If this method is usedin degradation studies on the polymer surface, it will be more effective on the surface analysis of polymer insulators. With corona charging method and chemical spectrum analysis, it was possible concretely to define degradation process on the polymer surface exposed at the situation of different environmental conditions.

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Filtration Efficiency of Electrically Charged Air Filters by a Corona Method

  • Murtadlo, Zainul Alim Ali;Joe, Yun-Haeng;Park, Seok-Hoon;Park, Hyun-Seol
    • Particle and aerosol research
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    • v.15 no.1
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    • pp.15-25
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    • 2019
  • The influences of corona charging parameters on collection efficiency and surface potential of air filters were investigated. A polypropylene filter medium was electrically charged using a corona charger, and the resulting surface potential and filtration efficiency against neutralized KCl particles were measured. The filter media was charged under different conditions of applied voltage, voltage polarity, charging time, and distance between electrodes. In addition, we considered charging both sides of the filter as well as charging one side of the filter. As a result, electrical force obtained by charged fiber affected filtration efficiency when the apply voltage strength was higher than 7 kV. Negatively charged filter had higher filtration efficiency than positively charged filter while the surface potential of the negatively charged filter was slightly lower than those of positively charged filter. Moreover, the filtration efficiency increased as the charging time of filter fiber increased and the distance between electrodes decreased. The filtration efficiency was more sensitive to changes of charging time than to those of electrode distance, and the efficiency of both sides charged filter was higher than that of single side charged filter.

The Effect of Hydrogen on the Variation of Properties at the Surface Layers of 590 MPa DP Steels Charged with Hydrogen (수소장입시킨 590 MPa DP강의 표면층 물성변화에 관한 수소의 영향)

  • Choi, Jong-Un;Park, Jae-Woo;Kang, Kae-Myung
    • Journal of the Korean institute of surface engineering
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    • v.46 no.3
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    • pp.126-132
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    • 2013
  • It was investigated that the effects of hydrogen charging on the properties of 590 MPa Dual Phase(DP) steels at the surface layers. The hydrogen-charging time was changed from 5 to 50 hours and current densities from 100, 150, and 200 $mA/cm^2$, respectively. It was found that the hydrogen content in the specimen was increased with as the charging time and the current density. The microvickers hardness of the subsurface zone was increased from 215.3 HV to 239.5 HV due to the increase in current density and charging time. The comparison of the absorbed energies tested by a small-punch (SP) test showed that the absorbed energy of the specimen was greatly reduced from 436 to 283 $kgf-mm^2$ because of hydrogen embrittlement. It was confirmed that bulb aspects of fracture surface became more brittle with increasing hydrogen content.

Application of Nondestructive Technique on Hydrogen Charging Times of Stainless Steel 304L (스테인리스 304L강의 수소장입시간에 대한 비파괴기법 적용)

  • Lee, Jin-Kyung;Hwang, Seung-Kuk;Lee, Sang-Pill;Bae, Dong-Su;Son, Young-Seok
    • Journal of Power System Engineering
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    • v.19 no.5
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    • pp.60-66
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    • 2015
  • Embrittlement of material by hydrogen charging should be cleared for safety of storage vessel of hydrogen and components deal with hydrogen. A stainless steel is generally used as materials for hydrogen transportation and storage, and it has a big advantage of corrosion resistance due to nickel component in material. In this study, microscopic damage behavior of stainless steel according to the hydrogen charging time using nondestructive evaluation was studied. The surface of stainless steel became more brittle as the hydrogen charging time increased. The parameters of nondestructive evaluation were also changed with the embrittlement of stainless steel surface by hydrogen charging. Ultrasonic test, which is the most generalized nondestructive technique, was applied to evaluate the relationship between the ultrasonic wave and mechanical properties of stainless steel by hydrogen charging. The attenuation coefficient of ultrasonic wave was increased with hydrogen charging time because of surface embrittlement of stainless steel. In addition, acoustic emission test was also used to study the dynamic behavior of stainless steel experienced hydrogen charging. AE event at the hydrogen charged specimen was obviously decreased at the plastic zone of stress-strain curves, while the number of event for the specimen of hydrogen free was dramatically generated when compared with the specimens underwent hydrogen charging.

Effect of Lateral Diffusion on Hydrogen Permeation Measurement in Thick Steel Specimens

  • Traidia, A.;El-Sherik, A.M.;Attar, H.;Enezi, A.
    • Corrosion Science and Technology
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    • v.16 no.4
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    • pp.201-208
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    • 2017
  • A finite element analysis is proposed to study the effect of specimen dimensions on lateral diffusion of hydrogen during hydrogen permeation flux measurements. The error of measurement on thick specimens because of 1D diffusion approximation may be as much as 70%. A critical condition for accurate measurements is to designate the area of hydrogen monitoring/exit surface smaller than the area of hydrogen charging/entry surface. For thin to medium thickness specimens (ratio of thickness to specimen radius of 5:10 and below), the charging surface should be maximized and the monitoring surface should be minimized. In case of relatively thick specimens (ratio of thickness to specimen radius above of 5:10), use of a hydrogen-diffusion barrier on the specimen boundaries is recommended. It would completely eliminate lateral losses of hydrogen, but cannot eliminate the deviation towards 2D diffusion near the side edges. In such a case, the charging surface should be maximized and the monitoring surface should be as closer in dimension as the charging surface. A regression analysis was carried out and an analytical relationship between the maximum measurement error and the specimen dimensions is proposed.

The Change of Microstructures According to the Charging Amounts of Hydrogen in High Strength DP Steels and TRIP Steel (고강도 DP강과 TRIP강의 표면 수소 주입량에 따른 수소취성평가)

  • Lee, Chul-Chi;Park, Jae-Woo;Kang, Kae-Myung
    • Journal of the Korean institute of surface engineering
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    • v.45 no.3
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    • pp.130-135
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    • 2012
  • Hydrogen charging was electrochemically conducted at high strength DP steels and TRIP steel with varying charging time. The penetration depths and the mechanical properties with charging conditions were investigated through the distribution of micro-hardness and the microstructural observation of the subsurface zone. The micro-Vickers hardness was measured to evaluate the hydrogen embrittlement of subsurface zone in addition to the microscope investigation. It was shown that the hydrogen amounts decreased in DP steels and TRIP steel with increasing hydrogen charging time. As shown by micro-Vickers hardness test and small punch test results, micro-Vickers hardness and SP energy for DP steels and TRIP steel decreased with increasing hydrogen charging time, for constant value of charging current density. SEM investigation results for the hydrogen contained samples showed that the major fracture behavior was brittle fracture which results in dimples on fractured surface and the size of dimples were decreased with increasing hydrogen charging time. These results indicate that hydrogen embrittlement is the major cause for the fracture of high strength steels and also micro-Vickers hardness test and small punch test is a valuable test method for hydrogen embrittlement of high strength sheet steels.

Study on UV degradation in Polymeric Insulating Materials for Use in Outdoor Insulators by Corona-Charging (코로나 대전을 통한 옥외용 고분자 절연재료의 자외선 열화특성 연구)

  • Youn, Bok-Hee;An, Jong-Sik;Lee, Sang-Yong;Huh, Chang-Su
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.05c
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    • pp.106-109
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    • 2001
  • In this paper, we have investigated the degradation of shed materials of outdoor insulators by UV-radiation by using corona-charging and XPS analysis. The accumulated charges on polymeric surface having intrinsic hydrophobic property have a negative impact on retaining its hydrophobicity. Therefore, shorter decay times of surface charges are preferred. The surface voltage decay on UV-treated silicone rubber and EPDM show a different decay trend with UV treated time. From the XPS analysis, the oxidized groups of silica-like structure in silicone rubber increase with UV treatment time. For EPDM, the oxidized carbon groups of C=O, O=C-O increase as elapse of UV radiation time. These oxidized surface for each material have different electrostatic characteristics, so deposited charges may be expected to have different impacts on their surface hydrophobicity. The degradation mechanism based on our results is discussed.

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Study on the Fine Particle Charging Characteristics with the Electrohydrodynamic Atomization (전기 수력학적 방법을 이용한 미세 입자의 하전 특성에 관한연구)

  • 안진홍;김광영;윤진욱;안강호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.4
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    • pp.289-294
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    • 2001
  • A well defined electro-spraying and electro-static precipitator(ESP) experiment is carried out to investigate the charging characteristics of the submicron particles and the monodisperse particles. The basic idea is that the highly charged electro-sprayed droplets will be produced into the gas when the Coulombic repulsive force on the surface is higher than the surface tension of the spraying liquid. During this process many highly charged smaller droplets or ions, if the droplets are completely dried out, will be produced in the space. These charged species will be attached ion the particles and then eventually charge the particles. These charged particles will be easily collected with ESP. The experimental results show that the atomizer generated particles with geometric mean diameter (GMD) of 62nm are charged more than 90% even at the mean face velocity of 2.5m/s at the charging zone.

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An Analysis of Small Punch Test Conducted with the High Strength Dual Phase Sheet Steels Charged with Hydrogen (수소주입된 고강도 DP 박강판의 소형펀치시험결과 분석)

  • Choi, Young-Cheul;Park, Jae-Woo;Kang, Kae-Myung
    • Journal of the Korean institute of surface engineering
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    • v.46 no.5
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    • pp.229-233
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    • 2013
  • The small punch(SP) tests that can be applied to high strength sheet steel in automobile were carried out to evaluate the behavior of hydrogen embrittlement of DP sheet steels. In order to charge hydrogen at DP sheet steels, DP sheet steels were treated by the electrochemical hydrogen charging method under the charging conditions of current densities of 100, 150 and 200 $mA/cm^2$ for charging times of 5, 10, 25 and 50 hrs. Respectively, After hydrogen charging with experimental conditions, SP tests were performed. From the SP results, the correlations between the variation of bulb diameters and bulb heights with the hydrogen charging conditions were analysed. It was shown that the variation of bulb diameters were not significant with the hydrogen embrittlement due to the amounts of hydrogen charging. On the other hand, the bulb heights were observed to decrease with increasing hydrogen contents. It was thought that these results of the variation of bulb shapes after SP tests would be estimated as the index of evaluation of hydrogen embrittlement.

Micro-Hardnesses and Microstructural Characteristics of Surface Layer of 590MPa DP Steels According to Hydrogen Charging (수소주입에 따른 590 MPa급 DP강 표면층의 미소경도와 조직특성)

  • Kang, Kae-Myung;Park, Jae-Woo
    • Korean Journal of Materials Research
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    • v.20 no.11
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    • pp.581-585
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    • 2010
  • High strength sheet steels for automobile are seriously compromised by hydrogen embrittlement. This issue has been continuously studied, but the field of interest, which lies between microstructural characteristics and hydrogen behavior with hydrogen charging, has not yet been thoroughly investigated. This study was done to investigate the behavior of hydrogen according to the hydrogen volume fraction on 590MPa grade DP steels, which are developed under hydrogen charging conditions as high strength sheet steels for automobiles. The penetration depths and the mechanical properties, according to charging conditions, were investigated through the distribution of micro-hardness and the microstructural observation of the subsurface zone. It was found that the amount of hydrogen trapping in 590MPa DP steels was related to the austenite volume fraction. It was confirmed that the distribution of micro-hardnesses according to the depth of the subsurface zone under the free surface showed the relationship of the depth of the hydrogen saturation between the charging conditions.