Kyung In Jang

Tribological Properties of a Magnetorheological (MR) Fluid in a Finishing Process

This article examines the tribological properties of a magnetorheological (MR) fluid in a finishing process. The MR fluid under investigation contains about 85 wt% of micro-sized carbonyl iron (CI) particles and about 15 wt% of water and surfactant(s) compound. A semi-empirical material removal model is proposed for the description of the tribological behavior of the MR fluid in the finishing process by considering both the solid- and fluid-like characteristics of the fluid in a magnetic field. Additionally, Archards theory and Amontons law of friction are applied to the model, which is completed by experimental efforts to identify the relationship between the effective friction coefficient and the ratio of the interfacial particle velocity to the imposed pressure on the workpiece surface. It turns out that the effective friction coefficient has a linear relationship with this ratio. The validity of the proposed model is supported through material removal rate measurements. It is also shown that the proposed model is substantially different from the conventional Preston equation in that the material removal rate is not only a function of the product of the applied normal pressure and relative velocity, but it also strongly depends on the square of the relative velocity.

Parameter optimization for finishing hard materials with magnetorheological fluid using the penalized multi-response Taguchi method

Abstract This paper presents a novel penalized multi-response Taguchi method that is used to determine the optimal conditions and parameters for a wheel-type magnetorheological (MR) finishing process that uses sintered iron-carbon nanotube (I-CNT) abrasives. The main goal of this study is to achieve the best compromise, within given boundary constraint conditions, between the maximum material removal rate and the minimum surface roughness. The proposed Taguchi method includes two main parameters, namely the weighting loss factor and the severity factor, that account, respectively, for the response weights and the constraint conditions and that control the optimality direction. The method is applied to the finishing of hard-disk slider surfaces made of Al2O3-TiC, and the effects of the weighting loss and severity factors, along with their significance and relative importance in optimizing the finishing process, are thoroughly examined.

A behavioral model of axisymmetrically configured magnetorheological fluid using Lekner summation

This study presents a new behavioral model for the magnetorheological (MR) fluid used in cylindrical rectilinear dampers. The model predicts variations in the magnetic energy density, shear stress, and viscoelastic behavior against an imposed strain along the axial direction under an axisymmetric magnetic field. Using the Lekner summation method, slow convergent magnetic interaction energy functions are transformed into rapidly convergent ones. The Maxwell constitutive model is coupled to the static model to take into account the viscoelastic behavior of the MR fluid.