• Title/Summary/Keyword: Roller Profile

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Elastohydrodynamic Lubrication of a Profiled Cylindrical Roller (II) (프로파일링을 한 원통형 로울러의 탄성유체윤활 (II))

  • 박태조;김경웅
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.1975-1981
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    • 1991
  • A new numerical solution of the elastohydrodynamic lubrication(EHL) problem of an axially profiled cylindrical roller is presented. A finite difference method and the Newton-Raphson method are used to solve the nonlinear system equations. A non-uniform grid system is adopted to reduce the number of grid points and to obtain accurate solution. For two different types of profiles which have similar elastostatic pressure distribution, the EHL results show large differences. Especially the difference in film shape is larger than in pressure distribution. Therefore, the magnitude of the minimum film thickness should be a major criteria to design the axial profile of the roller. Variations of the minimum film thickness with dimensionless parameters show considerably different behavior from those of infinite solution and show a good agreement with the experimental data in literatures. Present numerical scheme can be used generally in the analysis of three-dimensional EHL problem.

FSI(Fluid-Structure Interaction) Analysis for Harmonious Operation of High-Speed Printing Machine

  • Kim, Jin-Ho;Lee, Jae-Woo;Park, Soo-Hyung;Byun, Do-Young;Byun, Yung-Hwan;Lee, Chang-Jin
    • International Journal of Aeronautical and Space Sciences
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    • v.9 no.1
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    • pp.137-146
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    • 2008
  • Proper amount of entrained air and nip force should be also considered to minimize ballooning phenomenon since tight contact between a roller and web is required. In this paper, various web materials, PET(Polyester) and OPP(Oriented Poly Propylene) have been selected and investigated to satisfy high-speed printing requirement. Several web speeds, web tensions, and temperature conditions are imposed on each web materials and the pressure and gap profiles as well as nip force have been calculated. Increase of both the winding roller radius and the incoming wrap angle is considered under proper taper tension at 500 m/min of rewinding roller. By solving coupled Reynolds equation and web deflection equation simultaneously, the fluid-structure interaction process has been developed and is applied to the rewinding roller to investigate the ballooning phenomenon which causes guiding problems in high-speed printing performance conditions. By adjusting the linear taper tension, stress distribution between rewinding webs can be remarkably reduced and stable pressure and gap profile with ignorable ballooning phenomenon have been found.

A Study on Curvature Determination Approach of Disk Cams Using relative Accelerations of Followers (종동절의 상대가속도를 이용한 원반 캠의 곡률반경 결정법에 관한 연구)

  • Shin, Joong-Ho;Kang, Dong-Woo;Kim, Jong-Soo;Kim, Dae-Won
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.8
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    • pp.113-119
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    • 2000
  • There are two major factors which affect the cam design : the pressure angle and the radius of curvature, Cam shape will have an instantaneous radius of curvature at every point. Even though the design constraint of the pressure angle has been satisfied the follower may still not complete the desired contact motion. If the radius of the follower roller is larger than the concave(negative) radius on the cam it occurs the gap between the cam and the follower roller at the contact point. And also if the curvature of the pitch curve of the cam is too sharp the cam profile may be undercut. This paper proposes a new approach which uses the relative velocity of the follower roller parallel to the tangent line at the contact point on the cam surface for determining the pressure angle and the relative acceeration for determining the radius of curvature.

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Stability Evaluation of the Railway Bogie According to the Tread Inclination of Wheel Profile Using Scale Model (축소모델을 이용한 차륜답면형상 답면구배에 따른 안정성 평가)

  • Hur, Hyun-Moo;You, Won-Hee;Kim, Nam-Po;Park, Tae-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.10
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    • pp.1099-1107
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    • 2009
  • Numerical simulation and experimental study to evaluate the critical speed of the railway bogie according to the tread inclination of wheel profile were conducted using 1/5 scale model. It has been shown that the results of the critical speed analysis for the scale bogie model is very close to the test results using scale bogie model and the critical speed is decreased in proportion to the increase of equivalent conicity of wheel profile. Results of this study show that the scale model could be applied to research area relating to vehicle stability as an alternative to overcome the experimental problems caused by full scale test on the roller rig.

A Study on the Factors Influencing the Non-Linear Stability of Railway Vehicles (철도차량의 비선형 안정성에 영향을 미치는 인자 연구)

  • Chung, Woo-Jin;Shin, Jeong-Ryol
    • Proceedings of the KSME Conference
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    • 2001.06b
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    • pp.513-518
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    • 2001
  • This research has been performed to estimate the hunting motion hysteresis of railway passenger cars. An old and a new car with almost same structure are chosen as analysis models. To solve effectively a set of simultaneous equations of motion strongly coupled with creep relations, shooting algorithm in which the nonlinear relations are regarded as a two-point boundary value problem is adopted. The bifurcation theory is applied to the dynamic analysis to distinguish differences between linear and nonlinear critical speeds by variation of parameters. It is found that there are some factors and their operation area to make nonlinear critical speed respond to them more sensitivity than linear critical speed. Full-scale roller rig tests are carried out for the validation of the numerical results. Finally, it is concluded that the wear of wheel profile and the stiffness discontinuities of wheelset suspension caused by deterioration have to be considered in the analysis to predict hysteresis of critical speed precisely.

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A Study on the Characteristics of Daylight Distributions by Different Sky Conditions and Controlled Roller Shade Heights (천공종류 및 롤러쉐이드의 제어된 높이에 따른 주광분포 특성에 관한 연구)

  • Park, Byoung-Chul;Lim, Ji-Sun;Kim, Yu-Sin;Lee, Jeong-Ho;Choi, An-Seop
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.23 no.2
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    • pp.18-26
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    • 2009
  • Daylight responsive dimming systems are one of lighting control systems which are to control artificial lightings using available daylight for energy savings. This system is not popular because useful daylight is usually blocked by uncontrolled passive shading systems in buildings. It is necessary to integrate daylight responsive dimming systems and automata! roller shading systems. In this research, mock-up test is performed to analyze the daylight distributions in three different rooms for integrated systems. Roller shades are installed in two rooms. One is fully downed and the other is controlled by sun profile angle. The other room has no shading system as a reference room.

Contact Fatigue Life for CRG System (CRG 시스템의 접촉 피로수명)

  • Nam, Hyoung-Chul;Kim, Chang-Hyun;Kwon, Soon-Man
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.11
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    • pp.1391-1397
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    • 2012
  • A cam ring gear (CRG) system based on a hypotrochoid curve consists of a pinion with roller teeth and its conjugated internal CRG. In this study, we investigated contact forces, contact stresses, and load stress factors to predict the surface pitting life using an exact CRG profile by introducing the profile modification coefficient. The results show that the pitting life can be extended significantly by increasing the profile modification coefficient without any other change of parameters in the CRG system.

Analysis of the Pressure Distribution for Press Shoe considering Partially Changed Curvature of Bearing Surface

  • Park, Sang-Shin;Park, Young-Ha;Lee, Young-Ze;Han, Man-Cheol
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.123-124
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    • 2002
  • A press shoe is an element of a machine for squeezing water from wood pulp in the field of manufacturing paper. This is used to compress the pulp enveloped by felt sheet with a large roller. The squeezing force is made by hydraulic pressure. The press shoe has a mechanism similar to a partial hydrostatic bearing. The pressure profile between press shoe and roller affects their squeezing ability, and partial peak pressure can tear the wet pulp. The curvature of the surface of press shoe varies to reduce the peak pressure and increase the mean pressure simultaneously. Therefore, the prediction of pressure distribution considering partially changed curvature of hydrostatic bearing is very important for designing the press shoe. In this study, the difference formulation of Reynolds' equation for partial hydrostatic bearing is by direct numerical method and a computer program to calculate the pressure distribution is developed. We investigate the effect of partially changed curvature of bearing surface on the pressure distribution. Other design parameter for hydrostatic bearing such as depth of pocket and relative velocity are also studied.

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Analysis of the Pressure Distribution for Press Shoe considering Partially Changed Curvature of Bearing Surface

  • Park, Sang-Shin;Park, Young-Ha;Lee, Young-Ze;Han, Man-Cheol
    • KSTLE International Journal
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    • v.3 no.2
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    • pp.90-94
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    • 2002
  • A press shoe is an element of a machine for squeezing water from wood pulp in the field of manufacturing paper. This is used to compress the pulp enveloped by felt sheet with a large roller. The squeezing farce is made by hydraulic pressure. The press shoe has a mechanism similar to a partial hydrostatic bearing. The pressure profile between press shoe and roller affects their squeezing ability, and partial peak pressure can tear the wet pulp. The curvature of the surface of press shoe varies to reduce the peak pressure and increase the mean pressure simultaneously, Therefore, the prediction of pressure distribution considering partially changed curvature of hydrostatic bearing is very important far designing the press shoe. In this study, the difference formulation of Reynolds equation far partial hydrostatic bearing is derived by direct numerical method and a computer program to calculate the pressure distribution is developed. We investigate the effect of partially changed curvature of bearing surface on the pressure distribution. Other design parameter far hydrostatic bearing such as depth of pocket and relative velocity are also studied.