• Journal of Mechanical Science and Technology
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• v.16 no.4
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• pp.492-500
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• 2002

This paper presents a study of the effect of varying the roll gap of oval pass in round-oval-round pass sequence on the interracial slip of workpiece, entrance and exit velocities, stresses and roll load that the workpiece experiences during rolling, by applying analytical method, finite element simulation and verification through hot bar rolling tests. The results have shown that the roll gap variation of oval pass affects the interfacial slip of workpiece along the groove contact and the specific roll pressure. The optimum conditions in terms of minimum interfacial slip and minimum specific roll pressure, which might influence the maximum groove life, is obtained when the subsequent round pass is completely filled.

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1543-1549
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• 2012

This study focuses on the state space model and the design of a state observer for the slip dynamics between rolls in STS cold cluster mills. First, a mathematical model of the roll slip is given as a nonlinear differential equation. Then, by using a Taylor series expansion, it is linearized as a state space model. Next, by using Gopinath's algorithm, a minimal-order state observer based on the state space model is designed to estimate the angular speed of all idle rolls except for an actuated roll that is measureable. Finally, a computer simulation is used to validate that the proposed state space model very well describes slip dynamics between, and moreover, the state observer very well estimates the angular speed of the idle roll.

• 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.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.274-278
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• 1992

냉간압연기술의 발달로 냉간압연기도 매우 다양하게 발달되었으며 냉간압연의 원자재인 열간압연재의 종류도 다양하다. 최근 열간압연가공시 회수율이 높은 연속주조재(Continuous casting strip)인 CC 재가 종전의 가공과정이 복잡하며 불량율이 높은 Ingot주조재(Ingot casting strip)인 IC 재 보다 생산비율이 점차 증대되어 냉간압연재료의 주종을 차지하고있다. CC재는 냉간압연가공시 IC재에 비해 Work roll 조도저하가 현저하게 크기 때문에 슬립(Slip)과 채팅(Charttering) 현상 등이 발생하여 압연가공성이 불안정 하게 되어 Work roll과 판표면에 손상이 생기게 되고, 압연가공시 Roll 사고 등의 문제가 발생하므로 Roll 마멸의 정도를 파악하여 Roll을 효과적으로 관리하므로써 Work roll과 판표면의 슬립현상 및 채터 링현상 등을 방지할 수 있다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.121-124
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• 2001

On-line prediction model which calculate roll force, roll power and forward slip of continuous hot strip rolling was built based on the results of plane strait rigid-viscoplastic finite element process model. Using the integrated FE process model, a series of finite element simulation was conducted over the process variables, and the influence of various process conditions on non-dimensional parameters was inspected. The prediction accuracy of the proposed on-line model under front and back tension is examined through comparison with predictions from a finite element process model over the various process conditions. In addition, we examined the validity of the on-line prediction model through comparison with roll force of experiment in hot rolling.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1296-1302
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• 2002

A mathematical model for cold rolling and temper rolling process of thin steel strip has been developed using the influence function method. By solving the equations describing roll gap phenomena in a unique procedure and considering more influence factors, the model offers significant improvements in accuracy, robustness and generality of the solution for the thin strip cold and temper rolling conditions. The relationship between the shape of the roll profile and the roll force is also discussed. Calculation results show that any change increasing the roll force may result in or enlarge the central flat region in the deformation zone. Applied to the temper rolling process, the model can well predict not only the rolling load but also the large forward slip. Therefore, the measured forward slip, together with the measured roll force, was used to calibrate the model. The model was installed in tile setup computer of a temper rolling mill to make parallel setup calculations. The calculation results show good agreement with the measured data and the validity and precision of the model are proven.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1868-1873
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• 2011

In this paper, a theoretical formulation of a simplified wheel-set model for collision-induced derailments was evaluated by numerical simulations for the wheel-climb derailment and wheel-lift derailment types. The derailment types were classified into the wheel-climb derailment and the wheel-lift derailment according to the friction force direction of the wheel-flange. The wheel-climb derailment type was classified into Climb-up, Climb/Roll-over, and Roll-over-C, and wheel-lift derailment type was classified into Slip-up, Slip/Roll-over and Roll-over-L. To verify the theoretical equations derived for the wheel-climb derailment and the wheel-lift derailment, dynamic simulations using RecurDyn of Functionbay and Ls-Dyna of LSTC were performed and compared for some examples. The derailment predictions of the suggested theoretical formulation were in good agreement with those of the numerical simulations. The direction of the frictional force between the wheel-flange and the rail can be well predicted using the suggested derailment formulation at a initial derailment.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.131-137
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• 2014

The SUV has a risk of rollover because of the highness of center of mass. In this paper the roll-behavior of a SUV in turning motion is analyzed. Dynamic model of the vehicle on the slope is developed and simulation is carried out using the software ADAMS/Car. The results show that the relational expression between the ground force acting on the tire and the roll motion is well established. It is also identified that the driving state of the vehicle becomes unstable at the lower or upper position of the slope.