• Title/Summary/Keyword: Roll-coefficient

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A Study on the Roll Damping of Two-Dimensional Cylinders (2차원 주상체의 횡요감쇠에 대한 연구)

  • Yuck Rae H.;Lee Dong H.;Choi Hang S.;Jin Young M.;Bang Chang S.
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.197-200
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    • 2002
  • In this paper, roll damping coefficients for a non-conventional cross section, which is herein named as 'step' model, are investigated numerically and experimentally. Experiments are extensively carried out to estimate the roll damping coefficients. Numerical estimations are also made with the help of numerical codes. For convenience, the roll damping is divided into wave-making component and viscous component. The wave-making component is determined using a potential code and the viscous component using a viscous flow code, in which the fluid domain is taken as unbounded. In order to validate the present approach, a typical cross section with bilge is considered and our results are compared with published data. The comparison shows a good agreement qualitatively. For the step model, numerical results are compared well with experimental data besides some quantitative discrepancies at a certain range of frequency. It is thought that the discrepancy might be caused by the ignorance of the free surface in viscous computations. It is found in the case of the step model that not only the viscous component but also the wave component increases considerably compared to the section with bilge.

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Development of Ceramic Roll Materials for Food Grinding Processing and Evaluation of Mechanical Behavior (식품분쇄용 세라믹 롤 재료 개발과 기계적 특성평가)

  • 강위수
    • Journal of Biosystems Engineering
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    • v.26 no.1
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    • pp.47-56
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    • 2001
  • In order to prevent the possibility of mixing of metal powder during food grinding processing with the metal roll mill this study was conducted to develope the materials of ceramics roll as a substitute of gray cast iron mill. Since the ceramics is brittle material and can be broken easily by a crack, it was needed to develope engineering ceramics roll materials with high elastic modulus and fracture toughness. Adding 0∼50 wt% Al$_2$O$_3$as densification additives to porcelain body material and forming the ceramics an different condition, mechanical properties were evaluated. The material structure’s densification process was analyzed by SEM and XRD. The evaluation of the mechanical properties of ceramics roll materials were compared and analyzed by non-destructive test using Young’s modulus and destructive test using 3-point bending strength and fracture toughness. The results showed several correlative results. Porcelain body material with 40 wt% Al$_2$O$_3$content heated at 1,200$\^{C}$ for 5h was high bulk density of 2.77, Young’s modulus of 118.4Gpa, 3-point bending strength of 137 MPa and fracture toughness of 2.88 MPa$.$m$\^$$\sfrac{1}{2}$/ . After analyzing the relationship between non-destructive test and destructive test, the coefficient of determination was more than 0.9. Therefore, the evaluation of non-destructive test by ultrasonic was turned out to be feasible in evaluating the mechanical properties of ceramics.

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A Study on the Ink Transfer Using the Roughness and Substrate Energy of Substrate in Roll to Roll Printing Systems (롤투롤 인쇄 시스템에서의 기판 소재의 거칠기와 표면에너지를 이용한 잉크 전이에 대한 연구)

  • Shin, Kee-Hyun;Kim, Ho-Joon
    • Journal of the Semiconductor & Display Technology
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    • v.9 no.2
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    • pp.103-109
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    • 2010
  • An ink transfer is modeled and experimentally verified using roll-to-roll electric direct gravure printing process. The ink transfer model based on the physical mechanism for the maximum ink transfer rate is proposed, and experimented by the electric printing machine in FDRC for the relations of the maximum ink transfer rates to the printing pressure, the operating speed, the operating tension, the surface roughness of substrates, and the contact angle between substrate and silver ink. The free ink split coefficient and immobilized ink under the maximum ink transfer rate are calculated by the physical parameter in a printing process and contact angle between substrates and ink. Numerical simulations and experimental studies were carried out to verify performances of the proposed ink transfer model. Results showed that the proposed ink transfer model was effective for the prediction of the amount of transferred ink to the substrate in a direct gravure printing systems.

Development of Tube End-forming Process using Roll Die (롤다이를 이용한 튜브 축관공정 개발)

  • Kim, Yeong-Hwan
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.4
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    • pp.121-126
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    • 2011
  • An accumulator placed on the refrigerant cycle pipe lines is a part to relax fluctuations of pressure within the pipe lines and stabilize refrigerants flowed into pipe. The accumulator has been mainly manufactured by the process of tube spinning using CNC(Computer Numerical Control) lathe. However, this process has the defects which are low productivity per hour and high cost. For that reason, tube end-forming using roll die is actively being developed, recently. The purpose of this study is to develope the tube end-forming process using roll die in order to manufacture the accumulator for the refrigeration pipe lines. First, the process design of tube end-forming was performed based on specification of product, and then was verified with FE analysis. Also, the effects of friction coefficient and revolution speed of roll die on forming load were investigated. The analytical results were applied in the final process design of tube end-forming. Finally, tube end-forming test was carried out to verify the validity of the FE analysis and the process design.

Development of High Precision Forward Slip Model By Using Roll Torque in Hot Strip Finishing Mill (압연롤 토크를 이용한 열연박판 마무리압연 선진율 예측 정밀도 개선연구)

  • 문영훈;김영환
    • Transactions of Materials Processing
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    • v.8 no.6
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    • pp.583-590
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    • 1999
  • New forward slip model has been developed for the precise prediction of rolling speed in the hot strip finishing mill. Besides those influential factors such as neutral point, work roll diameter, friction coefficient, bite angle and the thickness at each side of entry and delivery of the rolls, roll torque was specifically taken into account in this study. To consider the effect of width change on forward slip, calibration factors obtained from rolling torque has been added to new prediction model and refining method has also been developed to reduce the speed unbalance between adjacent stands. The application of the new model showed a good agreement in rolling speeds between the predictions and the actual measurements, and the standard deviation of prediction error has also been significantly reduced.

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A Numerical Study on Pontoon Type Floating Breakwaters in Oblique Waves

  • Kim, Do-Young
    • International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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    • v.3 no.1
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    • pp.23-28
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    • 2000
  • A numerical investigation was made to examine characteristics of rectangular pontoon type floating breakwaters in oblique waves. Sway and heave wave exciting forces, roll moment acting on the floating breakwater and three motion reponses decrease as the incident wave angle increases for the most of the wave ranges. There exists a minimum wave transmission coefficient which is a function of wave frequency. In short wave range wave transmission coefficient increases as the incident wave angle increases. In long wave range, however, wave transmission coefficient decreases as the wave incident angle increases.

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Numerical Approach to Optimize Piercing Punch and Die Shape in Hub Clutch Product (허브클러치 제품의 피어싱 펀치 및 금형 형상 최적화를 위한 수치접근법)

  • Gu, Bon-Joon;Hong, Seok-Moo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.9
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    • pp.517-524
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    • 2019
  • The overdrive hub clutch is attached to a 6-speed automatic transmission to reduce fuel consumption by using the additional power of the engine. This paper proposes a means to minimize the load and roll-over ratio on the punch during the piercing process for the overdrive hub clutch product. Die clearance, shear angle, and friction coefficient, which can affect the load and roll-over ratio of the punch during processing, were set as the design variables. Sensitivity analysis was also conducted to determine the influence of each design variable on the punch load and roll-over ratio. As a result, shear angle, friction coefficient and die clearance were found to be sensitive to load and roll-over ratio. The punch load and roll-over ratio were set as the objective function and the equation of each design variable and objective function was derives using the Response Surface Method. Finally, the optimal value of the design variables was derived using the Response Surface Method. Application of this model to finite element analysis resulted in 22.14% improvement in the roll-over ratio of the punch load and material.

Control Scheme Using Forward Slip for a Multi-stand Hot Strip Rolling Mill

  • Moon, Young-Hoon;Jo, I-Seok;Chester J. Van Tyne
    • Journal of Mechanical Science and Technology
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    • v.18 no.6
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    • pp.972-978
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    • 2004
  • Forward slip is an important parameter often used in rolling-speed control models for tandem hot strip rolling mills. In a hot strip mill, on-line measurement of strip speed is inherently very difficult. Therefore, for the set-up of the finishing mill, a forward slip model is used to calculate the strip speed from roll circumferential velocity at each mill stand. Due to its complexity, most previous researches have used semi-empirical methods in determining values for the forward slip. Although these investigations may be useful in process design and control, they do not have a theoretical basis. In the present study, a better forward slip model has been developed, which provides for a better set-up and more precise control of the mill. Factors such as neutral point, friction coefficient, width spread, shape of deformation zone in the roll bite are incorporated into the model. Implementation of the new forward slip model for the control of a 7-stand hot strip tandem rolling mill shows significant improvement in roll speed set-up accuracy.

On the Motion Characteristics of Small Trawler under Operation (소형 트롤 어선의 예망중 동요특성)

  • Lee, Chun-Ki;Kang, Il-Kwon;Kim, Jeong-Chang
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.40 no.1
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    • pp.65-72
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    • 2004
  • This paper deals with an experimental study on the dynamical characteristics of ship motion during trawling job on the real sea. The experiments were carried out on the small stern trawler, and roll and pitch motion of the ship according to the wave directions were simultaneously recorded by P/C in the same sea conditions. From these data, the statistical properties and power spectra were obtained, and then the analysis of ship motion in trwal job was made. As a result, it was found that the pitch motions in trwal job were displayed low amplitudes on the whole, but the rolling motions were displayed high amplitudes relatively, and very high value on the beam and quartering sea especially. Also, the trial ship has a high extinction coefficient in the roll motion, compared with the rule of stability, but when wave height takes 2.5m over, it can induce the safety of ship to scare occasionally. Therefore, a usefull countermeasure for the safety of ship has to be made adequately.

Measurements of film thickness and temperature distribution in EHL point contact at high roll/slip ratios (높은 구름/미끄럼 비를 갖는 점 접촉 EHL 하에서의 온도분포와 유막 두께 분포의 측정)

  • Kim, Sung-Gi;Yagi, Kazuyuki;Nakahara, Tsunamitsu;Kyougoku, Keizi;Kim, Kyung-Woong
    • Proceedings of the KSME Conference
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    • 2001.06c
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    • pp.293-298
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    • 2001
  • In this paper, film thickness and temperature distribution are measured in EHL point contact at high roll/slip ratios. Infrared temperature mapping with two band pass filters, proposed by Ausherman (1976), is used to measure temperature distribution. And the optical interferometric method with two filters (red and green filters) is used to measure film thickness. Result of experiment showed that temperature rising at film and ball surface occurred very dramatically in Dimple zone. As slip velocity, roll/slip ratio and load increased, size of Dimple and temperature rising became more large. In addition, position and shape of Dimple were changed by roll/slip ratios, and increasing of Dimple size decreased traction coefficient. In short, it is appointed that the Dimple phenomenon be developed by the effect of viscosity wedge.

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