• 제목/요약/키워드: free-formed surface

검색결과 223건 처리시간 0.032초

용융아연 도금공정에서의 SNOUT 내부 유동장 해석 ( I ) (Velocity Field Measurement of Flow Inside SNOUT of Zinc Plating Process ( I ))

  • 신대식;최제호;이상준
    • 대한기계학회논문집B
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    • 제23권10호
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    • pp.1265-1273
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    • 1999
  • PIV(Particle Image Velocimetry) velocity field measurements inside the snout of a1/10 scale model of the Zn plating process were carried out at the strip speed $V_s=1.5m/s$. Aluminum powder particles ($1{\mu}m$) and atomized olive oil ($3{\mu}m$) were used as seeding particles to simulate the molten Zinc flow and deoxidization gas flow, respectively. A pulsed Nd:Yag laser and a $2K{\times}2K$ high-resolution CCD camera were synchronized for the PIV velocity field measurement. From flow visualization study, it is found that the liquid flow in the Zn pot is dominantly governed by the uprising flow caused by the rotating sink roll, with its effect on the steel strip inside the snout largely diminished by installing of the snout. The deoxidization gas flow in front of the strip inside the snout can be characterized by a large-scale vortex rotating clockwise direction formed by the moving strip. In the rear side of the strip, a counter-clockwise vortex is formed and some of the flow entrained by the moving strip impinges on the free surface of molten zinc. The liquid flow in front of the strip is governed by the flow entering the snout, caused by the spinning sink roll. Just below the free surface a counter-clockwise vortex is formed near the snout wall. The moving strip affects dominantly the flow behind the strip inside the snout, and large amount of the liquid flow follows the moving strip toward the sink roll. The thickness of the flow following the strip is very thin in the front side due to the uprising flow, however thick boundary layer is formed in the rear side of the strip. Its thickness is increased as moving downstream toward the sink roll. Inside the snout, the deoxidization gas flow above the free surface is much faster than the liquid flow in the zinc pot. Due to the larger influx of the flow following the moving strip in the rear side of the strip, higher percentage of imperfection can be anticipated on the rear surface of the strip.

시안화아연욕을 사랑한 아연 전착층의 조직특성 (Microstructure of Zinc electrodeposit in Cyanide Solution)

  • 예길촌;조은형
    • 한국표면공학회지
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    • 제17권2호
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    • pp.41-58
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    • 1984
  • Zinc was electrodeposited from cyanide solutions at temperature from 20$^{\circ}C\;to\;40^{\circ}C$ in the range of current density from 0.5 to 8A/$dm^2$. The preferred orientation changed from (10.3)+(11.0) to (11.0) texture with increasing cathode overpotential in the additive free solution, while the (11.0) preferred orientation developed at lower overpotentials (800-1270 mV) and the (11.0)+(10.0) preferred orientation was formed at higher overpotential (1300-1400mV) in the solution with brightner. Mossy type of morphology developed mostly in the additive free deposits and the microstructure of the cross section of the above deposits changed from columar structure to granular structure with increasing overpotential. The surface appearance of the deposits with additive having (11.0) texture was the smooth deposit of very small crystallite, while that of the deposits having (11.0)+(10.0) texture was fine crystalline deposit. The microstructure of the cross section of them was the fine field oriented type of structure.

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고온 노출 니켈기 초내열합금 터빈 블레이드의 Cr/Ti/Al 성분이 고온 산화에 미치는 영향 (Effect of Cr/Ti/Al Elements on High Temperature Oxidation Behavior of a Ni-Based Superalloy with Thermal Exposure)

  • 최병학;한성희;김대현;안종기;이재현;최광수
    • 한국재료학회지
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    • 제33권2호
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    • pp.77-86
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    • 2023
  • High-temperature oxidation of a Ni-based superalloy was analyzed with samples taken from gas turbine blades, where the samples were heat-treated and thermally exposed. The effect of Cr/Ti/Al elements in the alloy on high temperature oxidation was investigated using an optical microscope, SEM/EDS, and TEM. A high-Cr/high-Ti oxide layer was formed on the blade surface under the heat-treated state considered to be the initial stage of high-temperature oxidation. In addition, a PFZ (γ' precipitate free zone) accompanied by Cr carbide of Cr23C6 and high Cr-Co phase as a kind of TCP precipitation was formed under the surface layer. Pits of several ㎛ depth containing high-Al content oxide was observed at the boundary between the oxide layer and PFZ. However, high temperature oxidation formed on the thermally exposed blade surface consisted of the following steps: ① Ti-oxide formation in the center of the oxide layer, ② Cr-oxide formation surrounding the inner oxide layer, and ③ Al-oxide formation in the pits directly under the Cr oxide layer. It is estimated that the Cr content of Ni-based superalloys improves the oxidation resistance of the alloy by forming dense oxide layer, but produced the σ or µ phase of TCP precipitation with the high-Cr component resulting in material brittleness.

정밀가공을 위한 CAD/CAM/CAT 일괄처리시스템 (CAD/CAM/CAT Turmaround System for Precision Machining)

  • 안중용;김승철;정성종
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 1993년도 추계학술대회 논문집
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    • pp.417-422
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    • 1993
  • In order to minimize turnaround of machining in FMS lines, CAD/CAM/CAT integrated system called MascCAM was developed. Developing enhanced CAM and inspection modules in the MascCAM environment, 2D came, 2 $^{1}$2/ D prismatic parts and 3D free-formed surfaces were able to be automatically designed, manufactured and inspected on the machine tools by using AutoCAM and Z-map. Introducing Z-map technique, the MascCAM was able to be interfaceed with and CAD system. Developed QPPGT module generates a quick and fool-proof inspection work to users. A vertical and a horizontal machining center equipped with FANUC OMC were used for experiments. Performance of the system was confirmed by a large amount of experiments.

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접촉감지프로브를 이용한 자유곡면의 삼차원형상 자동측정 (Automatic Measurement of 3-Dimensional Profile of Free-Formed Surfaces by Using Touch-Trigger Probes)

  • 송창규
    • 대한기계학회논문집
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    • 제17권2호
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    • pp.407-415
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    • 1993
  • This report presents an automatic measurement method of 3-dimensional profiles of free-formed surfaces, by using a touch a touch-trigger contact probe along with a conventional coordinate measuring machine. The method proceeds in three steps; The surface profile under consideration is traced by the probe in an automatic manner, and then its measured data is compensated by considering the actual probe radius. Finally the compensated data is rearranged in the form suitable for the further processings of CAD/CAM applications. Some experimental results are discussed to verify the validity of the method suggested in this study.

고온 부식환경에 대한 Fe-Cr-X 합금의 열역학적 반응경로에 관한 연구 (A Study of Thermodynamical Reaction Path in Fe-Cr-X Alloys at High Temperature Corrosion Environments)

  • 이병우;김우열
    • 수산해양기술연구
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    • 제32권4호
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    • pp.411-420
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    • 1996
  • The structure of the scale formed on the surface of Fe - Cr - X alloys exposed to 1143K high sulfidation($Ps_2$ = 1.11$\times$$10^-7$ atm, $Po_2$ = 3.11$\times$$10^-20$ atm) or sulfidation/oxidation(($Ps_2$= 1.06$\times$$10^-7$ atm, ($Po_2$ = 3.11$\times$$10^-18$ atm) environment has been observed and analysed using XRD, SEM/EDS. To investigate the possibility of protective film formed on the surface of the alloys, Aluminium, Nickel were selected as alloying elements. Thermodynamic phase stability diagram was used to predict the reaction path of scale formed on Fe - Cr - X alloys. Parabolic rate constant($K_p$) value with 6wt% Al in Fe - 25Cr alloy decreased significantly compared with the Fe - 25Cr alloy without 6wt% Al. Since thin layer of defect free sulfide film, (Al, Cr)Sx, was formed at the alloy/scale interface. Fe - rich sulfide scale at outer layer and Cr - rich sulfide scale containing porosity at inner layer of Fe - 25Cr alloy have been observed. The reaction path for these scales could be predicted by the thermodynamic stability diagram.

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2차원 Coanda 노즐 제트 의 특성 에 관한 실험적 연구 (Experimental Study of the Characteristics of 2-Dimensional Coanda Nozzle Jet)

  • 이동호;정명균;김응태
    • 대한기계학회논문집
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    • 제6권3호
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    • pp.222-231
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    • 1982
  • A single free jet formed by the interaction of two curved wall jets on a Cylinder surface is defined as "the Coanda nozzle jet" in this study. In order to investigate the characteristics of Coanda nozzle jet, an experimental analysis was carried out; measurements of the static pressure distribution on the cylinder surface, the mean velocity profile, the turbulence intensity, and the Reynolds shear stress by using x-type hot-wire probe.ire probe.

무연 솔더가 적용된 자동차 전장부품 접합부의 열적.기계적 신뢰성 평가 (Thermo-Mechanical Reliability of Lead-Free Surface Mount Assemblies for Auto-Mobile Application)

  • 하상수;김종웅;채종혁;문원철;홍태환;유충식;문정훈;정승부
    • Journal of Welding and Joining
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    • 제24권6호
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    • pp.21-27
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    • 2006
  • This study was focused on the evaluation of the thermo-mechanical board-level reliability of Pb-bearing and Pb-free surface mount assemblies. The composition of Pb-bearing solder was a typical Sn-37Pb and that of Pb-free solder used in this study was a representative Sn-3.0Ag-0.5Cu in mass %. Thermal shock test was chosen for the reliability evaluation of the solder joints. Typical $Cu_6Sn_5$ intermetallic compound (IMC) layer was formed between both solders and Cu lead frame at the as-reflowed state, while a layer of $Cu_3Sn$ was additionally formed between the $Cu_6Sn_5$ and Cu lead frame during the thermal shock testing. Thickness of the IMC layers increased with increasing thermal shock cycles, and this is very similar result with that of isothermal aging study of solder joints. Shear test of the multi layer ceramic capacitor(MLCC) joints was also performed to investigate the degradation of mechanical bonding strength of solder joints during the thermal shock testing. Failure mode of the joints after shear testing revealed that the degradation was mainly due to the excessive growth of the IMC layers during the thermal shock testing.

고순도 지르코니아 분말의 합성 및 그 특성 (조립방법에 따른 성형 및 소결 특성) (The Synthesis of High-purity Zirconia Powders and Its Properties (Compaction and Sintering Behaviro as a Function of Granulation Methods))

  • 김환;이종국;김주영;황규홍
    • 한국세라믹학회지
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    • 제25권4호
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    • pp.357-363
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    • 1988
  • Ccompaction and sintering behavior of highly pure PSZ powders were investigated by laying the stress on the granulation processes. The particle size of coprecipitated PSZ powder was so fine that the agglomeration was severely formed during drying and calcing step and by this agglomeration differential sinering was occurred. The methanol dispersion of precipitates was the good method of avoiding severe agglomeration formed during drying process because of small surface tension than water. But perfect deagglomeraton was not possible due to high surface area of powders. So homogenization by granulation was needed, and among the method spray granulation was the most desirable to obtain homogeneous compacts and subsequent flaw-free ceramics.

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화력발전소에서 생성된 크링커에 대한 연구 (Studies on the clinker formed in thermal power plants)

  • 박현주;남창현;윤여찬;이태원
    • 한국연소학회지
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    • 제8권2호
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    • pp.34-40
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    • 2003
  • Analyses for concentration, surface phenomena, and crystal structure were performed to identify the causes of clinker formation in three type of pulverized coal fired boilers. Some clinkers had partially molten surface and more CaO and $Fe_2O_3$ as compared with fly ash, and the major crystalline phases identified in the clinker were mullite and quartz. Clinkers were formed in high temperature zone of the boiler according to the identification of mullite by XRD. Free $SiO_2$ in sand combined with K, Na and Ca in limestone served as a fluxing agent to form clinkers in a circulating bed boiler.

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