• Title/Summary/Keyword: Friction properties

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Development of Ventilator without Power using Air Flow (공기흐름을 이용한 무동력 환풍장치 개발)

  • Kim, Bum-Suk;Kwon, Taek-Joo;Jeong, Ji-Hyun
    • Journal of Power System Engineering
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    • v.20 no.2
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    • pp.26-31
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    • 2016
  • The studies on the efficient ventilator to reduce fire and save energy have been proceeded actively. The purpose of this paper is to design a ventilator used in residential wood stove. The ventilator consists of rotation and support part, and it is operated by natural wind without power. The shape of rotation part of the ventilator is like airfoil to reinforce pressure drop. We designed direction controller for the rotation part to track the direction of wind continuously. The rotation and support part have point-contact each other to minimize a friction. We verify the properties of the proposed ventilator though simulation and experiment. The results show the proposed ventilator can exhaust safely combustion gas of the stove more than other ventilator.

Prediction of Earings in the Deep Drawing Processes of a Cylindrical Cup (원통컵 디프드로잉 공정의 귀발생 예측)

  • 이승열;이승열;금영탁;정관수;박진무
    • Transactions of Materials Processing
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    • v.4 no.3
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    • pp.222-232
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    • 1995
  • The planar anisotripic FEM analysis for predicting earing profiles and draw-in amounts in the deep-drawing process is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-based unit vector and normal contact pressure. The consistent full set of governing relations, which is comprising euilbrium and geometric constraint equations, is appropriately linearized. Barlat's strain-rate potential is employed, whose in-plane anisotropic properties are taken into account with anisotropic coefficients and potential parameters. The linear triangular membrane elements are used for depicting the formed sheet. In the numerical simulations of deep drawing processes of a flat-top cylindrical cup for 2090-T3 aluminum alloy sheet show good agreement with experiments, although some discrepancies were observed in the directional trend of cup height and thickness strains.

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Some Remarks on the Experiment and Finite Element Analysis to Evaluate to Forming Limit of Sheet Metals (금속판재의 성형성 평가를 위한 실험 및 유한요소해석에 관한 고찰)

  • 곽인구;신용승;김형종;김헌영
    • Transactions of Materials Processing
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    • v.9 no.4
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    • pp.379-388
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    • 2000
  • This study aims to examine the influence of experimental and numerical factors on the results of the test and finite element simulation to evaluate the formability of sheet metals. The stretch-forming test with a hemispherical punch is carried out to obtain the limiting dome height (LDH) and forming limit diagram (FLD) for several kinds of aluminium and steel sheet. The results of the LDH and FLD tests are analysed to find any correlation with the uniaxial tensile properties. It proves that the size of the prescribed grid has great influence on the measured value of strain. The finite element analysis of the punch stretching process is also carried out and the result is compared with the experimental data. The influence of the numerical parameters such as friction coefficient, element size and anisotropy model on the simulation results tms out to be very considerable.

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Response of Spatially Developing Turbulent Boundary Layer to Spanwise Oscillating Electromagnetic Force (횡 방향 진동하는 전자기력에 대한 공간 발달하는 난류 경계층의 반응)

  • Lee, Joung-Ho;Sung, Hyung Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.11 s.242
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    • pp.1189-1198
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    • 2005
  • Direct numerical simulations were performed to investigate the physics of a spatially developing turbulent boundary layer flow subjected to spanwise oscillating electromagnetic forces in the near wall region. A fully implicit fractional step method was employed to simulate the flow. The mean flow properties and the Reynolds stresses were obtained to analyze the near-wall turbulent structure. It is found that skin friction and turbulent kinetic energy can be reduced by the electromagnetic forces. The decrease in production is responsible fur the reduction of turbulent kinetic energy. Instantaneous flow visualization techniques were used to observe the response of streamwise vortices and streak structures to spanwise oscillating forces. The near-wall vortical structures are affected by spanwise oscillating electromagnetic forces. Following the stopping of the electromagnetic force, the flow eventually relaxes back to a two-dimensional equilibrium boundary layer.

Wear characteristics of plasma sprayed yttria-stabilized zirconia coating as phase transformation (지르코니아 용사코팅의 상변화에 따른 마멸특성)

  • Park, Chan;Chae, Young-Hun;Kim, Seock-Sam
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2001.11a
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    • pp.322-330
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    • 2001
  • The plasma-sprayed 8%Y$_2$O$_3$-Zirconia coating was studied to know the relationship between phase transformation and wear properties after several heat treatment. Wear tests were carried out with ball on disk on 50N, 70N, 90N. The specimen in this study was cast iron and tests were performed on room temperature. The transformation of phase and residual stress was measured by x-ray diffraction method(XRD) and worn surface were observed by SEM.

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Bioinspired Nanoengineering of Multifunctional Superhydrophobic Surfaces

  • Choi, Chang-Hwan
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2015.11a
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    • pp.102-133
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    • 2015
  • Nature, such as plants, insects, and marine animals, uses micro/nano-textured surfaces in their components (e.g., leaves, wings, eyes, legs, and skins) for multiple purposes, such as water-repellency, anti-adhesiveness, and self-cleanness. Such multifunctional surface properties are attributed to three-dimensional surface structures with modulated surface wettability. Especially, hydrophobic surface structures create a composite interface with liquid by retaining air between the structures, minimizing the contact area with liquid. Such non-wetting surface property, so-called superhydrophobicity, can offer numerous application potentials, such as hydrodynamic drag reduction, anti-biofouling, anti-corrosion, anti-fogging, anti-frosting, and anti-icing. Over the last couple of decades, we have witnessed a significant advancement in the understanding of surface superhydrophobicity as well as the design, fabrication, and applications of superhydrophobic coatings/surfaces/materials. In this talk, the designs, fabrications, and applications of superhydrophobic surfaces for multifunctionalities will be presented, including hydrodynamic friction reduction, anti-biofouling, anti-corrosion, and anti-icing.

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Comparison of contacting and non-contacting methods in measuring the surface roughness of texture (섬유의 거칠기 측정에 있어서 비접촉식 방식과 접촉식 방식의 비교)

  • 박연규;강대임;송후근;권영하
    • Science of Emotion and Sensibility
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    • v.2 no.1
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    • pp.105-111
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    • 1999
  • In order to introduce the touch to engineering and industries, it must be preceded to dstablish a quantitative barometer of the feeling. for this purpose, we developed a tactile measuring system to measure physical properties of texture, such as surface roughness, friction coefficient and compliance. The tactile measuring system uses a LASER type displacement sensor, which is a non-contacting system, in measuring the surface roughness. By considering that human tactile system is a contacting mechanism, this non-contacting method needs to be modified. As a precedent research of that, we compared the contacting and non-contacting method in this paper. Surface roughness of ten cloths were measured by using the measuring system, then compared to the test results using the Kawabata evaluation system(KES), which uses a contacting method in measuring the surface roughness.

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Ti(CN) coating on aluminum alloy formed by MO-PACVD (Al 합금에 MO-PACVD법으로 증착시킨 Ti(CN) 코팅 층의 물성에 관한 연구)

  • ;;J. Woehle;K.-T. Rie
    • Journal of the Korean institute of surface engineering
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    • v.33 no.1
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    • pp.38-47
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    • 2000
  • A Ti(CN) layer was formed on aluminum alloy by using diethylamino titanium, hydrogen and nitrogen with the pulsed DC PACVD process. Effect of process parameters such as precursor evaporation temperature, duty ratio, frequency, voltage, $H_2$/$N_2$gas ratio on the properties of Ti(CN) layer were investigated. The layer thus obtained had high hardness and low friction coefficient. Detailed results on the hardness, surface morphology, XRD, WDS analysis, wear test and scratch test of this layer are presented.

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Tribological Performance of Laser Textured Translucent Duplex α/β-Sialon Composite Ceramics

  • Joshi, Bhupendra;Tripathi, Khagendra;Gyawali, Gobinda;Lee, Soo Wohn
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2014.11a
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    • pp.180-181
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    • 2014
  • Optically translucent Sialon ceramics was fabricated by hot pressed sintering method. The Sialon ceramics was laser textured and their tribological performance was observed. Starved lubrication method was applied on Sialon ceramics with different dimple spacing under a load of 10N and at room temperature. The material having high dimple spacing ($200{\mu}m$) shows low coefficient of friction. The material shows mild wear and therefore, wear rate of steel ball (meeting partner) was observed to measure wear rate. Different phases Sialon ceramics were analyzed by XRD patterns. Moreover, the mechanical properties of the Sialon ceramics were observed.

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Wear and friction properties of alumina-zriconia-fluoride composites by laser surface texturing (알루미나 지르코니아 플로라이드 복합체의 레이저 표면 텍스처링에 대한 마찰 마모 특성)

  • Jeong, Sang-Hun;Kim, Seong-Ho;Lee, Sol-Bin;Jo, Seong-Hun;Kim, Tae-Ho;Lee, Su-Wan
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2014.11a
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    • pp.298-298
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    • 2014
  • 표면 텍스처링 기술은 서로 접촉되는 표면 형태에 발생하는 마찰을 줄이는 기술이다. 이 기술은 자동차와 같은 기계장치에서 마찰을 줄여 보다 좋은 에너지 효율을 얻을 수 있어 효과가 기대되는 기술이다. 본 연구는 고체윤활제($CaF_2$ or $BaF_2$)와 alumina, zriconia를 이용하여 자기 윤활 세라믹 복합체를 만들고 그 위에 표면 텍스처링 후, 윤활 상태에서의 마찰특성을 알아보았다.

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