• Journal of Korea Foundry Society
• /
• v.14 no.3
• /
• pp.267-273
• /
• 1994

The structure of austempered ductile cast iron, called ADI, consists of graphite, retained austenite, and bainite. The bainite component of them is considered a useful structure for exriting materials for roll of rolling mill. Therefore, the ADI can be considered applicable to material for rolling contact element. The diverse tests, such as rolling contact friction test, impact test, and X-ray reflection test, were carried out to investigate the possibility of it`s application. The result of this study showed that the expected fact was confirmed. The specimen showed that the best performance had the structure of the low bainite containing the stable retained austenite of about 20%.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1996.10a
• /
• pp.150-156
• /
• 1996

The cold rolling of metal sheets leads to the formation of an inhomogeneous microstructure and texture. The type and sharpness of texture through the thickness and the degree of inhomogeneity depend on the friction between rolls the rolled material and the geometry of the rolling gap. In order to follow the effect of friction, two kinds of stecimens were prepared by applying with and without lubrication during the cold rolling. Although the deformed microstructure of the specimens rolled without lubrication was much inhomogenous than that of the specimens rolled with lubrication, the effect of lubrication on the cold rolling texture was not found. the recrystallization behavior was strongly dependent on the deformation process. Thus, the retardation of the recrystallization was observed in the specimens rolled without lubrication.

• Journal of the Korean Society of Safety
• /
• v.26 no.3
• /
• pp.1-7
• /
• 2011

Fatigue damage on the train wheel surface was estimated by considering the effect of friction coefficient of rolling on the contact surface between the wheel and rail during operation. From FEM analys, the maximum Tresca stress was 550.7 MPa at a depth of 2.07 mm under the maximum contact pressure ($P_{max}$ = 894.3 MPa) between wheel and rail. The maximum stress continued to increase along with the increase in the frictional coefficient. The fatigue initiation lifetime of the wheel by the rolling contact was predicted using the Smith-Watson-Topper (SWT) equation and the maximum principal strain equation (${\varepsilon}$-N).

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.5
• /
• pp.423-429
• /
• 2015

Linear motion (LM) ball guides have good accuracy and high efficiency. They are widely applied for precision machinery such as machine tools, semiconductor fabrication machines and robots. However, friction force incurs heat between the balls and grooves. Thermal expansion due to the heat deteriorates stiffness and accuracy of the LM ball guides. For accurate estimation of stiffness and accuracy during the linear motion, friction models of LM ball guides are required. To formulate accurate frictional models of LM ball guides according to load and preload conditions, rolling and viscous frictional analyses have been performed in this paper. Contact loads between balls and grooves are derived from Hertzian contact analysis. Contact angle variation is incorporated for the precision modeling. Viscous friction model is formulated from the shear stress of lubricant and the contact area between balls and grooves. Experiments confirm validity of the developed friction model for various external load and feedrate conditions.

• Proceedings of the KSR Conference
• /
• 2000.11a
• /
• pp.219-225
• /
• 2000

This study is to develop a Fe-based disc brake lining with sponge structure for rolling stock of 150km/h train and to concept design with 3 groove type for brake disc reducing hot hair-crack and certainly friction coefficient. The developing brake lining would be to presumption of saving 300 million won during one year

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.6 s.171
• /
• pp.159-167
• /
• 2005

This work focuses on the effects of crack free friction on Mode II stress intensity factors, $K_{II}$, for a vertical surface crack in a two-dimensional finite element model of TiN/steel subject to rolling contact. Results indicate that maximum $K_{II}$ values, which occur when the load is adjacent to the crack, may be significantly reduced in the presence of crack face friction. The reduction is more significant for thick coatings than for thin. Crack extension and increased layer thickness result in increased $K_{II}$ values. The effect of crack face friction on compressive $K_I$ values appears negligible. Comparative results are presented for $MoS_2/steel$ and diamond-like carbon(DLC)/Ti systems.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.08a
• /
• pp.19-24
• /
• 2004

Symmetrical and asymmetrical rolling was performed in AA 1050 sheets. Asymmetrical rolling was carried out by using different roll velocities of upper and lower rolls. The effect of the reduction per rolling pass on the formation of textures and microstructures during symmetrical and asymmetrical rolling was studied. In order to intensify the shear deformation, symmetrical and asymmetrical rolling was carried out without lubrication. The strain states associated with rolling were investigated by simulations with the finite element method (FEM). A fairly homogeneous residual shear strain throughout the sheet thickness was observed after asymmetrical rolling. Symmetrical rolling with a high friction gave rise to a strong net shear strain gradient in the sheet thickness.

• Transactions of Materials Processing
• /
• v.15 no.7 s.88
• /
• pp.479-484
• /
• 2006

The evolution of strain states and textures during rolling with various conditions was investigated by finite element method (FEM) simulations and measurements of rolling textures. Symmetrical rolling with a high friction gives rise to a strong variation of shear strains in rolled sample leading to the formation of texture gradients throughout the thickness layers. A small variation of shear strains during rolling with a well lubrication condition leads to the formation of a fairly homogeneous rolling texture throughout the sheet thickness. During asymmetrical rolling, a proper control of rolling parameters provides the evolution of a fairly homogeneous shear texture throughout the whole sheet thickness.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.39-39
• /
• 2000

In this paper, a decoupler of tandem cold rolling mill is designed. Before designing the decoupler, this paper improved conventional linear model by considering friction and yield stress of rolling strip. In a stand, the decoupler let an output be controlled by an input. And even if states of other stands should be changed, current stand takes no interference from those changes. In addition, with the same method, a feedforward controller is designed for an input strip thickness error. Finally, performance of controllers above is shown with nonlinear simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.330-331
• /
• 2007

The effect of frictional rolling and subsequent heat treatment was studied on the evolution of texture of AA 3003 Aluminum alloy. With frictional rolling without lubrication it is possible to obtain a larger friction between roll and sample which lead to the formation of uniform rolling texture in the whole thickness layers.