• Title/Summary/Keyword: Roll Force Model

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Analysis of rear suspension using airspring (공기스프링 현가장치 성능해석)

  • Tak, tae-oh;Kim, kum-Chul
    • Journal of Industrial Technology
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    • v.19
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    • pp.31-42
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    • 1999
  • This paper presents a method for evaluating the performance of a leaf spring suspension and an air spring suspension systems for trucks in terms of ride and handling. Leaf springs, which generally have non-linear progressive force-deflection characteristics, are modeled using beam and contact elements. The leaf spring analysis model shows good correlation with experimental results. Each component of an air spring suspension system, which is a single leaf, air spring, height control valve, compressor and linkages, is modeled appropriately. Non-linear characteristics of air spring are accounted for using the measured data, and pressure and volume relations for height control system is also considered. The wheel rate of the air suspension is taken lower but roll stiffness is taken higher than those of leaf springs to improve ride and handling performance, which is verified through driving simulations.

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On the Unstable Behavior of Roll Moment due to the Manoeuvering of a Ship (조종운동이 유발하는 횡경사모우멘트의 불안정거동에 관한 연구)

  • 윤점동;손경호
    • Journal of the Korean Institute of Navigation
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    • v.4 no.1
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    • pp.51-61
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    • 1980
  • In order to evaluate rolling characteristics of high speed container carrier the author developed yaw-sway-rudder coupled rool equation, which is likely to be 5th order differential equation. The free rolling time history with particular reference to automatic steering, was computed upon the base of the yaw-sway-rudder coupled roll equation. The computed result explained effects of $C_1$ and $C_2$ on rolling behaviors and furthermore the effect of $C_2$ proved to be very effective where $C_1$ and $C_2$ are yaw gin constant and yaw-rate gain constant of auto-pilot respectively. Computation was carried out using Matsumoto's data of hydrodynamic force derivatives of 5 meter long container model.

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Experimental study on the influence of Reynolds number and roll angle on train aerodynamics

  • Huang, Zhixiang;Li, Wenhui;Liu, Tanghong;Chen, Li
    • Wind and Structures
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    • v.35 no.2
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    • pp.83-92
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    • 2022
  • When the rolling stocks run on the curve, the external rail has to be lifted to a certain level to balance the centrifugal force acting on the train body. Under such a situation, passengers may feel uncomfortable, and the slanted vehicle has the potential overturning risks at high speed. This paper conducted a wind tunnel test in an annular wind tunnel with φ=3.2 m based on a 1/20th scaled high-speed train (HST) model. The sensitivity of Reynolds effects ranging from Re = 0.37×106 to Re = 1.45×106 was tested based on the incoming wind from U=30 m/s to U=113 m/s. The wind speed covers the range from incompressible to compressible. The impact of roll angle ranging from γ=0° to γ=4° on train aerodynamics was tested. In addition, the boundary layer development was also analyzed under different wind speeds. The results indicate that drag and lift aerodynamic coefficients gradually stabilized and converged over U=70 m/s, which could be regeared as the self-similarity region. Similarly, the thickness of the boundary layer on the floor gradually decreased with the wind speed increase, and little changed over U=80 m/s. The rolling moment of the head and tail cars increased with the roll angle from γ=0° to γ=4°. However, the potential overturning risks of the head car are higher than the tail car with the increase of the roll angle. This study is significant in providing a reference for the overturning assessment of HST.

Prediction of Three-Dimensional Strip Profile for 6-High Mill in Thin-Strip Rolling (6 단 압연기의 극박 압연공정에서 3 차원 판 형상 예측)

  • Lee, Sang-Ho;Song, Gil-Ho;Lee, Sung-Jin;Kim, Byung-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.8
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    • pp.855-861
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    • 2011
  • We predict the rolled-strip profile for a 6-high mill using thin rolling theory and a numerical model. In the numerical model, we calculate the distributions of the contact pressures between the rolls and the rolling pressure between the strip and the work roll in the transverse direction using the geometric structure of the 6-high mill and the boundary conditions. We determine the distribution of the rolling pressure in the rolling direction via a thin-foil rolling model using Fleck's theory. We calculate the three-dimensional elastic deformation of the work roll using the pressures of the width and rolling directions. We then obtain the three-dimensional strip profile via the elastic deformation of the work roll during the rolling process. The profile is verified by a thin cold-rolling test and FE simulation.

Performance Evaluation of 6WD Military Vehicle Featuring MR Damper (MR 댐퍼를 적용한 6WD 군용차량의 성능평가)

  • Ha, Sung-Boon;Choi, Seung-Bok;Rhee, Eun-Jun;Kang, Pil-Soon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.11a
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    • pp.460-465
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    • 2008
  • This paper proposes a new type of MR (magentorheological) fluid based suspension system and applies it to military vehicle for vibration control. The suspension system consists of gas spring and MR damper. The nonlinear behavior of spring characteristics is evaluated with respect to the wheel travel and damping force model due to viscosity and yield stress of MR fluid is derived. Subsequently, a military vehicle of 6WD is adopted for the integration of the MR suspension system and its nonlinear dynamic model is establishes by considering vertical, pitch and roll motion. Then, a sky-hook controller associated with semi-active actuating condition is designed to reduce the vibration. In order to demonstrate the effectiveness of the proposed MR suspension system, computer simulation is undertaken showing vibration control performance such as roll angle and pitch angle evaluated under bump and random road profiles.

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Performance Evaluation of 6WD Military Vehicle Featuring MR Damper (MR댐퍼를 적용한 6WD 군용차량의 성능평가)

  • Ha, Sung-Hoon;Choi, Seung-Bok;Rhee, Eun-Jun;Kang, Pil-Soon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.1
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    • pp.17-23
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    • 2009
  • This paper proposes a new type of MR(magnetorheological) fluid based suspension system and applies it to military vehicle for vibration control. The suspension system consists of gas spring and MR damper. The nonlinear behavior of spring characteristics is evaluated with respect to the wheel travel and damping force model due to viscosity and yield stress of MR fluid is derived. Subsequently, a military vehicle of 6WD is adopted for the integration of the MR suspension system and its nonlinear dynamic model is established by considering vertical, pitch and roll motion. Then, a sky-hook controller associated with semi-active actuating condition is designed to reduce the imposed vibration. In order to demonstrate the effectiveness of the proposed MR suspension system, computer simulation is undertaken showing vibration control performance such as roll angle and pitch angle evaluated under bump and random road profiles.

Measurement of Dynamic Stability Derivatives of Tailless Lamda-shape UAV using Forced Oscillation Method (강제진동 기법을 이용한 무미익 비행체의 동안정 미계수 측정)

  • Yang, Kwangjin;Chung, Hyoungseog;Cho, Donghyun;An, Eunhye;Ko, Joonsoo;Hong, JinSung;Kim, Yongduk;Lee, MyungSup;Hur, Gi-Bong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.44 no.7
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    • pp.552-561
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    • 2016
  • In this experimental study, the dynamic stability derivatives of a tailless lambda-shape UAV are estimated from time history data of aerodynamic moments measured from the internal balance while the test model is forced to oscillate at given frequencies and amplitudes. A 3-axis forced oscillation apparatus is designed to induce decoupled roll, yaw, pitch oscillations respectively. The results show that the roll damping derivatives remain stable at the entire range of angle of attack tested, whereas the pitch damping derivatives become unstable beyond $15^{\circ}$ angle of attack. The amplitude and frequency have little impact on roll damping derivatives while the smaller amplitude and frequency of oscillation improves the pitch stability. The yaw damping derivative values are fairly small as expected for a tailless configuration. The results indicate that the proposed methodology and test apparatus area valid for estimating the dynamic stability derivatives of a tailless UAV.

Development of Rollgap Simulator and Its Application to Draft Schedule Adjustment (롤갭 시뮬레이터의 개발과 패스스케쥴 개선)

  • Ahn Jaehwan;Lee Youngho;Lee In-Woo
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.08a
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    • pp.163-172
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    • 2004
  • A fast, accurate model for calculating roll gap variables are critical to the implementation of computer based automation systems for cold rolling mills. Based on the work of Fleck and Johnson, rollgap simulator with non-circular arc model was developed using the influence function. This developed model is capable of predicting values of force, torque and slip which can be applied over the wide range of rolling conditions including cold rolling/DR/temper mill with high execution speed. Friction coefficient was obtained as a function of operation conditions through analyzing measured data. After combination of rollgap simulator with production strategy, draft schedule for No.3 RCM (Reversible Cold Rolling Mill) in Incheon works of Dongbu Steel was developed. This draft schedule will be installed in the setup computer of No.3 RCM replacing old Hitachi model.

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Study on the Viscous Roll Damping around Circular Cylinder Using Forced Oscillations (강제동요를 이용한 원형실린더 점성 롤댐핑 연구)

  • Yang, Seung-Ho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.2
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    • pp.71-76
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    • 2017
  • The roll damping problem in the design of ships and offshore structures remains a challenge to many researchers due to the fluid viscosity and nonlinearity of the phenomenon itself. In this paper, the study on viscous roll damping of a circular cylinder was carried out using forced oscillations. The roll moment generated by forced oscillation using a torque sensor was measured for each forced oscillation period and compared with the empirical formula. Although the magnitude of the measured torque from the shear force was relatively small, the results were qualitatively similar to those obtained from the empirical formula, and showed good agreement with the quantitative results in some oscillation periods. In addition, the flow around the circular cylinder wall was observed closely through the PIV measurements. Owing to the fluid viscosity, a boundary layer was formed near the wall of the circular cylinder, and a minute wave was generated by periodical forced oscillations at the free surface through the PIV measurement. In this study, the suitability of the empirical formula for the roll moment caused by viscous roll damping was verified by model tests. The wave making phenomenon due to the fluid viscosity around the wall of a circular cylinder was testified by PIV measurements.

Modeling and stable startup strategy for strip-caster

  • Lee, Dukman;Lee, Jin S.;Kim, Y.H.;Lee, D.S.
    • 제어로봇시스템학회:학술대회논문집
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    • 1996.10a
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    • pp.319-323
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    • 1996
  • A new steel-making process, strip-casting, is introduced. The strip-casting is a new technique making the thin steel strip from the molten steel directly without resorting to repetitive reheating and hot-rolling required in a conventional steel-making method. This paper derives the mathematical model of strip caster, proposes a control strategy for stable startup operation and a fuzzy decision making rule for automatic control mode change in strip-casting process.

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