• Title/Summary/Keyword: surface roughness model

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Mixed Lubrication Analysis of Parallel Thrust Bearing by Surface Topography (표면거칠기를 고려한 평행 스러스트 베어링의 혼합윤활 해석)

  • 이동길;임윤철
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2000.06a
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    • pp.134-141
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    • 2000
  • The real area of contacts, average film thickness, mean real pressure, and mean hydrodynamic pressure are investigated numerically in this study, especially for the parallel thrust bearing. Model surface is generated numerically with given autocorrelation function and some surface profile parameters. Then the average Reynolds equation contained flow factors and contact factor is applied to predict the effects of surface roughness in mixed lubrication regimes. In this equation, flow factors are defined as correction terms to smooth out high frequency surface roughness and contact factor is introduced to relieve from obtaining the average film thickness. Therefore the computation time to obtain h can be reduced.

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A noncontact optical roughness measurement technique of ground surface by light scattering (광산란을 이용한 연삭표면의 비접촉식 광학적 조도측정기술)

  • 임동열;김승우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.6
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    • pp.1303-1311
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    • 1988
  • Described is method for development of an optical roughness measurement sensor for in-subequality assurance in the precision grinding. Main approach is made based upon the Brckmann's light scattering theory, in which general solutions of the optical scattering behaviour are given under many simplifying assumptions on the model of the surfaces illuminated. For the ground surface, the assumptions are verified through computer simulation and experimental work in order to examine the validity of Beckmann's theory on predicting the optical responses according to the roughness variation. As a result, an optical monitoring strategy is derived which can evaluate the roughness value of the ground surface by statistically detecting the pattern of intensity distribution of the scattered light. Finally, the strategy is proven by comparing with the results using the stylus method.

Correlation of Texture and Sensory Analysis on Film Surfaces for Implementing Emotional Design (감성디자인 구현을 위한 플라스틱 필름 표면의 거칠기와 감각 특성의 상관관계 도출)

  • Do Yeop Kim;Yong Ju Lee;Minjung Joo;Ha Kyoung Yu;Hyung Jin Kim
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.30 no.2
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    • pp.149-160
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    • 2024
  • One of the main functions of packaging is promoting the products. Competitive markets demand that products appeal more to consumers in many perspectives. Other than its original purpose, which is protection, packaging has been tasked with implementing the emotional appeal of a product through unique shapes, textures, and visual designs. Understanding emotional appeals to consumer is a potential marketing strategy so that research have been done about techniques to visualize the design and print the specific textures. Especially, paper-like films are known as eco-friendly or emotional design and they are able to protect the products from oxygen or water vapor better than papers. In this study, paper-like films, which is printed with inks to have rougher surfaces, are analysed in terms of roughness, friction, imaging and sensory evaluation of subjective softness from consumers. Also, the prediction model was established with the correlation of the measured results and sensory panel test (SPT) of consumer preferences by touch. The results showed that the prediction of subjective texture preference was contributed by 63.9% for surface roughness and 36.1% for friction profile parameters. It confirmed that surface roughness characteristics should be prioritized to improve tactile preference for paper-like films.

Turbulent Flow and Heat Transfer in an Annular Passage with Repeated-Ribbed Roughness on Both Walls (양측벽면에 반복돌출형 거칠기가 있는 이중관통로내의 난류운동과 열전달)

  • 안수환;이윤표
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.5
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    • pp.26-36
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    • 1996
  • The fully developed turbulent momentum and heat transfer induced by the square-ribbed roughness elements on both the inner and outer wall surfaces in concentric annuli are studied analytically based on a modified turbulence model. The analytical results of the fuid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity positions and friction factors, and etc. shown in Fig.1. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Reynolds number, Nusselt bumber and Prand시 number. The study demonstrates that certain artificial roughness elements may be used to enhance heat transfer rates with advantage from the overall efficiency point of view by investigating turbulent flows and heat transfer in Fig.1.

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Fully Developed Turbulent Flow and Heat Transfer in Concentric Annuli with Square-Ribbed Roughness (사각형 거칠기가 있는 동심 이중관내의 완전히 발달된 난류유동과 열전달)

  • 안수환;김경천;이윤표
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.4
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    • pp.1072-1080
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    • 1994
  • The fully developed turbulent momentum and heat transfer induced by the square-ribed roughness elements on the outer wall surface in concentric annuli are studied analytically based on a modified turbulence model. The analytical results of the fluid flow are verified by experiment. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Reynolds number, Nusselt number and Prandtl number. The study demonstrates that certain artificial roughness elements may be used to enhance heat transfer rates with advantages from the overall efficiency point of view.

Mathematical Friction Model for Sheet Metal Forming Analysis (박판성형 해석용 수학적 마찰 모델)

  • Keum Y. T.;Song M. J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.05a
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    • pp.182-185
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    • 2004
  • Based on the experimental observation, the mathematical friction model, which is an essential information for analyzing the forming process of sheet metal, is developed considering lubricant viscosity, surface roughness and hardness, punch corner radius, and punch speed. By comparing the punch load found by FEM with a proposed friction model with experimental measurement when the coated and uncoated steel sheets are formed in 2-D geometry in dry and lubricant conditions, the validity and accuracy of the developed friction model are demonstrated.

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An Experimental Study on the Variation of Vertical Dispersion within Boundary Layer with Surface Roughness (대기 경계층 연직방향 확산의 지면 거칠기에 따른 변화에 관한 실험적 연구)

  • 박옥현;윤창옥
    • Journal of Korean Society for Atmospheric Environment
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    • v.16 no.3
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    • pp.237-246
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    • 2000
  • An experimental study has been carried out using a rotating water channel in order to investigate the effect of surface roughness on the vertical dispersion of plume within boundary layer. Dispersion measurements of tracers released from two sources with different height at neutral conditions over various rough terrain ranging from rural to urban have been performed. Various values of roughness length were simulated by combining of 4 stream velocities and 3 roughness element conditions. Dispersion measurements have also been made for rough terrain where high buildings are locally concentrated. Values of σz increase with roughness and this tendency appears to apply both cases of with and without locally concentrated high buildings. The comparisons of the Bowne's nomogram on σ2 vs x relationship and the measurements of σ2 with roughness show good accordance in σ2 distribution at stability D class over rural, suburban and urban terrain. For constant roughness length the σ2 values of plumes from lower source height are smaller than those of plumes from higher source at short downwind distance, but this relationship becomes reverse as distance increases. Crossing appears to be made before about 2km. The value of constant I in McMullen's equation σ2=exp [I+J(In x) + K(In x)2] appears to increase with roughness length, however, the relationships between other constants and roughness have been confirmed. The values of σ2 for various downwind distances, estimated by using an equation which is employed in ISC (Industrial Source Complex) dispersion model for areas where high buildings are locally assembled, are in accordance with measurements from water channel experiments.

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PREDICTION OF AERODYNAMIC PERFORMANCE LOSS OF A WIND TURBINE BLADE SECTION DUE TO CONTAMINANT ACCUMULATION (외부 오염물 증착에 의한 풍력 터빈 날개 단면의 공력 성능 저하 예측)

  • Yang, T.H.;Choi, J.H.;Yu, D.O.;Kwon, O.J.
    • Journal of computational fluids engineering
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    • v.18 no.1
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    • pp.91-97
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    • 2013
  • In the present study, the effects of contaminant accumulation and surface roughness on the aerodynamic performance of wind turbine blade sections were numerically investigated by using a flow solver based on unstructured meshes. The turbulent flow over the rough surface was modeled by a modified κω SST turbulence model. The calculations were made for the NREL S809 airfoil with varying contaminant sizes and positions at several angles of attack. It was found that as the contaminant size increases, the degradation of the airfoil performance becomes more significant, and this trend is further amplified near the stall condition. When the contaminant is located at the upper surface near the leading edge, the loss in the aerodynamic performance of the blade section becomes more critical. It was also found that the surface roughness leads to a significant reduction of lift, in addition to increased drag.

A Numerical Study on Dispersion of Inert Particles in a Rough Single Fracture (거친 균열 암반에서의 용질 입자 확산에 대한 수치적 연구)

  • Jeong, Woochang
    • Journal of the Korean GEO-environmental Society
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    • v.7 no.5
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    • pp.79-87
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    • 2006
  • This paper presents the numerical model developed to simulate the solute transport in rough and smooth single fractures. The roughness of these fractures is represented by using the fractal surface method. In this study, the 3D transport model, which is based on the random walk technique, is used to simulate the dispersion process of a solute which is represented by numerical particles. As the simulation results, it can be observed that the dispersion of solute in the fracture is significantly affected by the fracture roughness and particle size.

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A Study on the Cutting Force Simulation for Ball-end Milling Operation (볼-엔드 밀링가공시 절삭력의 시뮬레이션에 관한 연구)

  • 홍민성;김종민
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.12 no.6
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    • pp.84-91
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    • 2003
  • In metal cutting operation, it is very important that predict cutting force and work surface. Vibration is an unstable cutting phenomenon which is due to the interaction of the dynamics of the chip removal process and the structural dynamics of machine tool. When vibration on, it reduces tool life, results in poor surface roughness and low productivity of the machining process. In this study, the experiments were conducted in machining center without cutting fluid to investigate the phenomenon of vibration. In the experiments, accelerometers were set up at the tail stock and tool holder and signals were picked up. Surface roughness profiles are generated under the ideal condition and the occurrence of vibration based on the surface shaping simulation model.