• Title, Summary, Keyword: variable viscosity

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The Lubrication Characteristics of the Vane Tip Under Pressure Boundary Condition of Oil Hydraulic Vane Pump

  • Cho Ihn-Sung;Oh Seok-Hyung;Song Kyu-Keun;Jung Jae-Youn
    • Journal of Mechanical Science and Technology
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    • v.20 no.10
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    • pp.1716-1721
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    • 2006
  • The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke's chart, which is an improvement over Johnson's chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigid-variable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.

A Case Study of a Six Sigma Project for Improving Gate Painting Quality (게이트 도장 품질 개선을 위한 6시그마 프로젝트 사례 연구)

  • Hong, Sung-Hoon;Choi, Ik-Jun
    • Journal of the Korean Society for Quality Management
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    • v.34 no.1
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    • pp.1-12
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    • 2006
  • This paper presents a six sigma project for improving gate painting quality in a medium-sized automotive part company. The project follows a disciplined process of five macro phases: Define, Measure, Analyze, Improve, and Control. A CTQ(critical to quality) is determined based on COPQ(cost of poor quality) analysis, and a process map is utilized for identifying process input variables. Three KPIV s(key process input variable) are selected; Painting Temperature, Painting Quantity, and Painting Viscosity, and DOE(design of experiments) is utilized for finding the optimal process conditions for three KPIVs. MINITAB software is used for data analyses and DOE. The sigma level of defects rate has improved from 2.93 to 3.66.

Analysis of the Dynamic Behavior and Lubrication Characteristics of the Piston-Cylinder System in Reciprocating Compressors (왕복동형 압축기 피스톤-실린더계의 동적 거동 및 윤활특성 해석)

  • 김태종
    • Tribology and Lubricants
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    • v.18 no.4
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    • pp.291-298
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    • 2002
  • In this study, a numerical analysis f3r the piston secondary dynamics and lubrication characteristics of small refrigeration reciprocating compressors is presented. In general, the length of cylinder in this class of compressors is shortened to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder wall is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the piston dynamics, the change in bearing length of the piston and all corresponding forces and moments are considered in order to determine the piston trajectory, velocity and acceleration at each step. A Newton-Raphson procedure was employed in solving the secondary dynamic equations of the piston. The developed computer program can be used to calculate the entire piston trajectory and the hydrodynamic forces and moments as functions of crank angle under compressor running conditions. The results explored the effects of the radial clearance, lubricant viscosity, and pin location on the stability of the piston, the oil leakage, and friction losses.

Analysis of the Effect of Screen Printing Variables on Thick Film Thickness (스크린인쇄조건에 따른 후막인쇄물의 잉크층 두께에 관한 분석)

  • Lim, Kyu-Jin;Yi, Arm;Shin, Jong-Soon
    • Journal of the Korean Printing Society
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    • v.20 no.2
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    • pp.19-30
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    • 2002
  • Four screen mesh counts of 100, 150, 200, and 305 threads per inch are chosen and a designed test figure is exposed on them for printing experiment to measure the ink deposit thickness. Among a number of variables, the ink viscosity, the screen gap and the squeegee pressure and speed are estimated with their effected thickness. These variables affect as much as around 50% compared with the theoretical ink volume listed by the mesh manufacturer and each variable has different influence on the thickness. The data and graphs have been analyzed for the thick film production.

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Performance of Squeeze Film Damper Using Magneto-Rheological Fluid (MR유체를 이용한 스퀴즈필름 댐퍼의 응답특성)

  • 안영공;양보석;신동춘;김동조
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.67-70
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    • 2002
  • This paper presents the property of the Squeeze Film Damper (SFD) using Magneto-Rheological fluid (MR fluid). The damping property of a SFD for a flexible rotor system varied according to vibration mode. MR fluid is known as a functional fluid with controllable apparent viscosity of the fluid by applied magnetic field strength. When the MR fluid is applied in the SFD, the SFD using MR fluid can effectively reduce vibrations of the flexible rotor in a wide range of rotating speed by control of the applied magnetic field strength. To investigate in detail the SFD using MR fluid, the SFD to support one mass was constructed and its performance was experimentally investigated in the present study. The damping property of the SFD using MR fluid has viscous damping by Newtonian fluid, but not Coulomb friction by Bingham fluid. Therefore, The system damped by the SFD can be considered as a linear system.

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A Modeling of a Variable-damping Mount Using Magneto-Rheological Fluid (ER유체를 이용한 이방성 스퀴즈필름 댐퍼의 응답특성에 관한 연구)

  • Ahn, Young-Kong;Yang, Bo-Suk;Morishita, Shin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.256-261
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    • 2000
  • Electro-Rheological(ER) fluid is applied to a controllable squeeze film damper(SFD) for stabilizing a flexible rotor system. ER fluid is a class of functional fluid whose yield stress varies according to the applied electric field strength, which is observed as viscosity variation of the fluid. In applying ER fluid to a SFD, a pair of rings of the damper can be used as electrodes. When the electrodes are divided into a horizontal pair and a vertical one, the SFD can produce damping force in each direction independently. A prototype of the directionally controllable SFD was constructed and its performance was experimentally and numerically investigated in the present work.

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Circulation Experiment of the Chinhae Bay using a Three-Dimensional Diagnostic Numercal Model (3차원 진단모델을 이용한 진해만의 수치유동실험)

  • 배삼완
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.33 no.4
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    • pp.360-369
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    • 1997
  • We calculated the residual current forced by buoyancy, wind stress, and tidal stress in the Chinhae Bay using a three-dimensional diagnostic model. The calculated current was also compared with the observation. The flow directs outward from the central area of the Bay in the upper layer, and also forms eddy-shape stucture in the upper and middle layers. The flow of bottom layer shows an opposite pattern compared to those of top and middle layers. The maximum speed was 6.05 em/see (September) and 3.49 cm/sec (November) in the upper layer, and 4.39 cm/sec on both month in the middle layer. The Kinetic energy of November (8.39xlO' W) was larger than that of September (1.24xlO 'W), mainly resulting from larger buoyancy effect in September. In spite of the roughness of the grid size(1 km) and wind date, the calculated flow shows eorrelation(r=0.71) with the observation. We expect that the correlation be increased by increased by adopting the fine grid and the variable coefficients of diffusion and viscosity.

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Numerical Study on Thermo-Hydro-Mechanical Coupling in Rock with Variable Properties by Temperature (암석의 온도의존성을 고려한 열-수리-역학적 상호작용의 수치해석적 연구)

  • 안형준;이희근
    • Tunnel and Underground Space
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    • v.7 no.1
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    • pp.13-19
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    • 1997
  • It is necessary to study on thermo-hydro-mechanical effect at rock mass performing project such as radiowaste disposal in deep rock mass. In this study, thermo-hydro-mechanical coupling analysis which is considered interaction and the variation of rock properties induced by temperature increase was performed for the circular shaft when appling temperature of 20$0^{\circ}C$ at the shaft wall. The shaft is diameter of 2 m and under hydrostatic stress of 5 MPa. In the cases, thermal expansion by temperature increase progress from the wall to outward and thermal expansion could induce tensile stress over the tensile strength of rock mass at the wall. When rock properties were given as a function of temperature, thermal expansion increased, tensile stress zone expanded. Lately, water flow is activated by increase of permeability and decrease of viscosity.

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Constrained rotary MR damper design and its application (자기 유변 유체를 이용한 각도 제한 회전 감쇠기 설계 및 응용)

  • 김상화;박영진
    • 제어로봇시스템학회:학술대회논문집
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    • pp.191-194
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    • 1997
  • Passive, semi-active and active dampers have been used to dissipate energy in mechanical systems. Semi-active dampers have higher performance than passive dampers and require lower power to operate than active dampers. Its damping characteristics can be changed appropriately for varying conditions. In this paper, we developed a semi-active damper based on Magnetorheological(MR) fluid. MR fluid has a variable damping characteristics proportional for the magnetic field intensity. It has several advantages such as high strength, low viscosity, robustness in impurities and wide temperature range of operational stability. We designed a constrained rotary MR damper base on valve mode which can dissipate more energy per unit volume. The system with Bingham characteristics is obtained and proved by the experiment.

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AERODYNAMIC SENSITIVITY ANALYSIS FOR NAVIER-STOKES EQUATIONS

  • Kim, Hyoung-Jin;Kim, Chongam;Rho, Oh-Hyun;Lee, Ki Dong
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.3 no.2
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    • pp.161-171
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    • 1999
  • Aerodynamic sensitivity analysis codes are developed via the hand-differentiation using a direct differentiation method and an adjoint method respectively from discrete two-dimensional compressible Navier-Stokes equations. Unlike previous other researches, Baldwin-Lomax algebraic turbulence model is also differentiated by hand to obtain design sensitivities with respect to design variables of interest in turbulent flows. Discrete direct sensitivity equations and adjoint equations are efficiently solved by the same time integration scheme adopted in the flow solver routine. The required memory for the adjoint sensitivity code is greatly reduced at the cost of the computational time by allowing the large banded flux jacobian matrix unassembled. Direct sensitivity code results are found to be exactly coincident with sensitivity derivatives obtained by the finite difference. Adjoint code results of a turbulent flow case show slight deviations from the exact results due to the limitation of the algebraic turbulence model in implementing the adjoint formulation. However, current adjoint sensitivity code yields much more accurate sensitivity derivatives than the adjoint code with the turbulence eddy viscosity being kept constant, which is a usual assumption for the prior researches.

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