• Title/Summary/Keyword: surface damage

Search Result 2,303, Processing Time 0.032 seconds

Effect of Applied Current Density on the Corrosion Damage of Steel with Accelerated Electrochemical Test (전기화학적 가속 부식 평가법에서 강재의 부식 손상에 미치는 인가전류밀도의 영향)

  • Lee, Jung-Hyung;Park, Il-Cho;Park, Jae-Cheul;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
    • /
    • v.49 no.5
    • /
    • pp.423-430
    • /
    • 2016
  • In this study, we investigated the corrosion damage characteristics of steel for offshore wind turbine tower substructure using an accelerated electrochemical test. The galvanostatic corrosion test method was employed with a conventional 3 electrode cell in natural sea water, and the steel specimen was served as a working electrode to induce corrosion in an accelerated manner. Surface and cross-sectional image of the damaged area were obtained by optical microscope and scanning electron microscope. The weight of the specimens was measured to determine the gravimetric change before and after corrosion test. The result revealed that the steel tended to suffer uniform corrosion rather than localized corrosion due to active dissolution reaction under the constant current regime. With increasing galvanostatic current density, the damage depth and surface roughness of surface was increased, showing approximately 25 times difference in damage depth between the lowest current density ($1mA/cm^2$) and the highest current density ($200mA/cm^2$). The gravimetric observation showed that the weight loss was proportionally increased with increment of current density that has 75 times different according by experimental conditions. Consequently, uniform corrosion of the steel specimen was conveniently induced by the electrochemically accelerated corrosion technique, and it was possible to control the extent of the corrosion damage by varying the current density.

Evaluation on Surface Scaling and Frost Resistance for concrete Deteriorated due to Cyclic Freezing and Thawing with Inherent Chloride

  • Kim, Gyu Yong;Cho, Bong Suk;Lee, Seung Hoon;Kim, Moo Han
    • Corrosion Science and Technology
    • /
    • v.6 no.4
    • /
    • pp.177-185
    • /
    • 2007
  • The purpose of this study is to evaluate freezing-thawing and surface scaling resistance in order to examine the frost durability of concrete in a chloride-inherent environment. The mixing design for this study is as follows: 3 water binder ratios of 0.37, 0.42, and 0.47; 2-ingredient type concrete (50% OPC concrete and 50% ground granulated blast-furnace slag), and 3-ingredient type concrete (50% OPC concrete, 15% fly ash, and 35% ground granulated blast-furnace slag). As found in this study, the decrease of durability was much more noticeable in combined deterioration through both salt damage and frost damage than in a single deterioration through either ofthese; when using blast-furnace slag in freezing-thawing seawater, the frost durability and surface deterioration resistance was evaluated as higher than when using OPC concrete. BF 50% concrete, especially, rather than BFS35%+FA15%, had a notable effect on resistance to chloride penetration and freezing/expansion. It has been confirmed that surface deterioration can be evaluated through a quantitative analysis of scaling, calculated from concrete's underwater weight and surface-dry weight as affected by the freezing-thawing of seawater.

Investigation on Electrolytic Corrosion Characteristics with the Variation of Current Density of 5083-H321 Aluminum Alloy in Seawater (5083-H321 알루미늄 합금의 해수 내 전류밀도의 변화에 따른 전식 특성 연구)

  • Kim, Young-Bok;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
    • /
    • v.52 no.1
    • /
    • pp.23-29
    • /
    • 2019
  • Electrolytic corrosion of the ship's hull can be occurred due to stray current during welding work using shore power and electrical leakage using shore power supply. The electrolytic corrosion characteristics were investigated for Al5083-H321 through potentiodynamic polarization and galvanostatic corrosion test in natural seawater. Experiments of electrolytic corrosion were tested at various current densities ranging from $0.01mA/cm^2$ to $10mA/cm^2$ for 30 minutes, and at various applied time ranging from 60 to 240 minutes. Evaluation of electrolytic corrosion was carried out by Tafel extrapolation, weight loss, surface analysis after the experiment. In the electrolytic corrosion characteristics of Al5083-H321 as the current density increased, the surface damage tended to proportionally increase. In the current density of $0.01mA/cm^2$ for a applied long time, the damage tended to grow on the surface. In the case of $10mA/cm^2$ current density for a applied long time, the damage progressed to the depth direction of the surface, and the amount of weight loss per hour increased to 4 mg/hr.

PCD 공구에 의한 Graphite/Epoxy 복합재료 가공시 발생하는 표면조도의 특성 연구

  • 왕덕현
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 1992.10a
    • /
    • pp.101-105
    • /
    • 1992
  • Machined graphite/epoxy composite surfaces were studied by using SEM(Scanning Electron Microscopy). surface profilometry and its analysis to determine suitable surface describing parameters for machined unidirectional and laminate composite surface. The surface roughness and profile are found to be highly dependent on the fiber layup direction and the measurement direction. Machined unidirectional and 0.deg. 45 .deg. 90 .deg. plies in laminate composite surface profiles are found to be Gaussian in the direction of machining. Since there exist bare fibers without matrix smearing in 0 .deg. ply, higher surface roughness values were found in this orientation. It was possible to machine 90 .deg. and -45 .deg. plies due to the adjacent plies, which were holding those plies. It was found that the microgeometrical variations in terms of roughness parameters Ra without Dy (maximum Damage Depth) region and Dy are better descriptors of the machined laminate composite surface than commonly used roughness parameters Ra and Ra. The characteristics of surface profiles in laminate composite are well represented in CHD (Cumulative Height Distribution) plot and PPD (Percentage Probability Density) plot. Also, the power spectral density function is shown to be capable of identifying the wavelength distribution of the machining damage.

Evaluation on cavitation damage in sea water with shot peening stand-off distance for ALBC3 alloy (ALBC3 합금의 쇼트피닝 분사거리에 따른 해수 내 캐비테이션 손상 평가)

  • Han, Min-Su;Jang, Seok-Ki;Kim, Jong-Sin;Kim, Seong-Jong
    • Corrosion Science and Technology
    • /
    • v.12 no.5
    • /
    • pp.239-244
    • /
    • 2013
  • Marine equipment exposed to harsh environments requires not only excellent corrosion resistance but also improvement of physical characteristics against natural material degradation. With growing interests in ocean energy resources, the higher reliability for marine equipment has become more important in terms of material characteristics. ALBC3 alloy represents excellent corrosion resistance and is widely used in corrosive environments. However, cavitation damage occurs frequently due to its poor durability in high flow rate of marine environment. In this research, shot peening technology was employed as a surface modification with shot peening stand-off distance to mitigate cavitation damage. The effects of shot peening on extent of cavitation damage and weight loss were evaluated for both shot peened and non-peened specimens. The results revealed that the application of shot peeing decreased cavitation damage for all experimental conditions in comparison with the non-peened specimens. The optimum stand-off distance was determined to be 10 cm, since more than 35 % of cavitation damage reduction was observed.

Effect of Burn out Print Finishing on Cellulose Fiber Damage (섬유소계 직물의 탄화날염가공이 섬유손성에 미치는 영향)

  • 신정숙;송석규
    • Journal of the Korean Society of Clothing and Textiles
    • /
    • v.25 no.1
    • /
    • pp.124-131
    • /
    • 2001
  • To find out the effect of burn out print finishing for better quality of fabric, examined processing which could make less damages on the fiber because the biggest problem is remained fibers damage after burn out print finishing. Fiber damage examined to the condition of finishing material NaHSO$_4$and H$_2$SO$_4$, 3~10min., 100~13$0^{\circ}C$, glycerin. The fiber damages evaluated the break strength and the surface condition by SEM. Among satin, pile fabric which remained fiber is silk, warp knitted fabric which remained fiber is polyester, the fibers damage level were warp knitted fabric$0^{\circ}C$, glycerin and for 6 minutes by NaHSO$_4$. When carbonized by 20%. 50% and 70% to express textile design, carbonizing rate was not effect on the fiber damage very much. There was almost no damages with glycerine, and almost no damages during 3~6minutes fixation time, 10$0^{\circ}C$ steaming heat fixation by NaHSO$_4$and H$_2$SO$_4$. Without glycerine, there were damage by hydrolysis on polyesters surface and the fiver was broken by fixation time.

  • PDF

Assessment of Low Velocity Impact Damage of Filament Wound Composite Vessels with Surface Protective Materials (필라멘트 와인딩 복합재 압력용기의 저속충격손상 평가에 관한 연구)

  • Lee, Jang-Ho;Kang, Ki-Weon
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.11 no.8
    • /
    • pp.2741-2749
    • /
    • 2010
  • This paper presents the impact damage behavior of filament wound composite vessels and the effect of surface protective materials on their impact resistance. Using an instrumented impact testing machine, a series of impact tests was performed on the base panels and the protected panels (panels with surface protective materials of rubber, kevlar/epoxy or glass/epoxy laminates) that were cut from the full scale vessel. And the impact damage parameters were used to identify the effect of protective materials on the damage resistance of composite vessels. Damage resistance of the composite vessels was considerably affected by the protective materials regardless of the shape of the indenters. Among the protective materials, glass/epoxy laminates was the most effective mean for improving the damage resistance of composite vessels.

Rolling Contact Fatigue Analysis According to Defect Size on Rail (레일의 표면결함크기에 따른 구름접촉수명평가)

  • Seo, Jung-Won;Kwon, Seong-Tae;Lee, Dong-Heong;Kwon, Seok-Jin
    • Proceedings of the KSR Conference
    • /
    • 2011.10a
    • /
    • pp.637-642
    • /
    • 2011
  • Rails are subjected to damage from rolling contact fatigue, which leads to defects such as cracks. Rolling contact fatigue damages on the surface of rail such as head check, squats are one of growing problems. Another form of rail surface damage, known as "Ballast imprint" has become apparent. This form of damage is associated with ballast particles becoming trapped between the wheel and the surface of rail. These defects are still one of the key reasons for rail maintenance and replacement. In this study, we have investigated whether the ballast imprint is an initiator of head check type cracks and effect of defect size using Finite element analysis. The FE analysis were used to investigate stresses and strains in subsurface of defects according to variation of defect size. Based on loading cycles obtained from FE analysis, fatigue analysis for each point was carried out.

  • PDF

Comparative Analysis of Mortality in Species of Trees after Surface Forest Fire (지표화 산불피해지의 수종별 임목 고사율 비교분석)

  • Lee, Si-Young;An, Sang-Hyun
    • Journal of the Korean Society of Hazard Mitigation
    • /
    • v.9 no.2
    • /
    • pp.39-43
    • /
    • 2009
  • we studied and analyzed a tree mortality of 7 species(Pinus koraiensis etc) in surface forest fire area. In this results, the order of tree mortality was Cryptomeria japonica>Pinus koraiensis>Pinus densiflora>Pinus thunbergii>Larix leptolepis>Pinus rigida>Quercus. More damaged crown was higher tree mortality and more d.b.h was less tree mortality. Especially, oak trees in which a damage rate of crown was less 30% almost survived.

Important Parameters Related With Fault for Site Investigation of HLW Geological Disposal

  • Jin, Kwangmin;Kihm, You Hong;Seo, Dong-Ik;Kim, Young-Seog
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
    • /
    • v.19 no.4
    • /
    • pp.533-546
    • /
    • 2021
  • Large earthquakes with (MW > ~ 6) result in ground shaking, surface ruptures, and permanent deformation with displacement. The earthquakes would damage important facilities and infrastructure such as large industrial establishments, nuclear power plants, and waste disposal sites. In particular, earthquake ruptures associated with large earthquakes can affect geological and engineered barriers such as deep geological repositories that are used for storing hazardous radioactive wastes. Earthquake-driven faults and surface ruptures exhibit various fault zone structural characteristics such as direction of earthquake propagation and rupture and asymmetric displacement patterns. Therefore, estimating the respect distances and hazardous areas has been challenging. We propose that considering multiple parameters, such as fault types, distribution, scale, activity, linkage patterns, damage zones, and respect distances, enable accurate identification of the sites for deep geological repositories and important facilities. This information would enable earthquake hazard assessment and lower earthquake-resulted hazards in potential earthquake-prone areas.