• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.496-500
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• 2004

A new, commercially available polishing process called magnetorheological finishing is used to polish and figure precision optics. To understand and model this process correctly it is important to determine the mechanical properties of the fluid under the influence of the magnetic field. Magnetorheological (MR) fluids are commonly modeled as Bingham fluids, so one of the essential properties to measure is the yield stress. Since MR fluids are inherently anisotropic, the yield stress will depend on the mutual orientation of the magnetic field and the direction of deformation. The relative orientation of the field and deformation in polishing does not coincide with common rheological setups, so a new rheometer has been designed and tested. This new magnetorheometer design has been shown to give correct stresses during calibration experiments using Newtonian fluids with a known viscosity. The measured stress has also been shown to have a magnitude consistent with published finite element approximations for magnetic fluids. The design of the instrument was complicated because of the requirements imposed upon the magnetic field, and the difficulty in satisfying the no slip boundary condition. Our results show the importance of having a homogeneous field in the test region during measurements. The solutions to these problems and discussion of the measurements on nonmagnetic and magnetic fluids are given.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.350-355
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• 2005

This paper presents a new approach for hysteresis modeling of a magnetorheological (MR) fluid. The field-dependent hysteresis of MR fluid is investigated using the Preisach model. The commercial MR Product (MRF-132LD, Lord Corporation) is employed. Its field-dependent shear stress is then obtained using a rheometer (MCR 300, Physica). In order to show the applicability of the Preisach model to the MR fluid, two significant Properties; the minor loop property and the wiping-out property are experimentally examined. Subsequently, the Preisach model for the MR fluid is identified using experimental first order descending (FOD) curves in discrete manner. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one. In addition, the hysteresis model proposed in this work is compared to Bingham model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제16권1호
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• pp.3-11
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• 2006

This paper presents a new approach for hysteresis modeling of a magnetorheological (MR) fluid. The field-dependent hysteresis of MR fluid is investigated using the Preisach model. The commercial MR product (MRF-132LD, Lord Corporation) is employed. Its field-dependent shear stress is then obtained using a rheometer (MCR 300, Physica). In order to show the applicability of the Preisach model to the MR fluid, two significant properties; the minor loop property and the wiping-out. property are experimentally examined. Subsequently, the Preisach model for the MR fluid is identified using experimental first order descending (FOD) curves in discrete manner. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one. In addition, the hysteresis model proposed in this work is compared to Bingham model.

• Tunnel and Underground Space
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• 제30권3호
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• pp.193-213
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• 2020

A mathematical model to simulate more realistically the penetration of compacted bentonite buffer installed in the deposition hole into the discontinuity in the excavation damaged zone formed at the inner wall of the deposition hole in the geological repository for spent fuel is developed. In this model, the penetration of compacted bentonite is assumed to be the flow of Bingham fluid through the parallel planar rock fracture. The penetration of compacted bentonite is analyzed using the developed model. The results show that the maximum penetration depth of compacted bentonite into the rock fracture is proportioned to the swelling pressure of saturated compacted bentonite and the aperture of rock fracture. However, it is in inverse proportion to the yield strength of compacted bentonite. The viscosity of compacted bentonite dominates the penetration rate of compacted bentonite, but has no influence to the maximum penetration depth.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.595-600
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• 2007

This paper presents a new jetting dispenser driven by a piezoelectric actuator at high operating frequency to provide very small dispensing dot size of adhesive in modern semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the structured system is derived by considering behavior of each component such as piezostack and dispensing needle. In the fluid modeling, a lumped parameter method is applied to model the adhesive whose rheological property is expressed by Bingham model. The governing equations are then derived by integrating the structural model with the fluid model. Based on the proposed model, dispensing performances such as dispensing amount are investigated with respect to various input trajectories.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제18권4호
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• pp.432-438
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• 2008

This paper presents a new jetting dispenser driven by a piezoelectric actuator at high operating frequency to provide very small dispensing dot size of adhesive in modern semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the structured system is derived by considering behavior of each component such as piezostack and dispensing needle. In the fluid modeling, a lumped parameter method is applied to model the adhesive whose rheological property is expressed by Bingham model. The governing equations are then derived by integrating the structural model with the fluid model. Based on the proposed model, dispensing performances such as dispensing amount are investigated with respect to various input trajectories.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.109-114
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• 2001

This paper presents field-dependent dynamic characteristics of a shock damper featuring an electro-rheological(ER) damper. A cylindrical type of the shock damper is designed and manufactured on the basis of the field-dependent Bingham model. The damping force is then measured with respect to the piston velocity at various electric fields. The measured damping force is incorporated with the 1DOF shock system to analyze the shock isolation performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.489-494
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• 2002

This paper presents hydraulic model which can capture the hysteric damping force behavior of ER damper. A flow mode rue ER damper is manufactured, and its field-dependent damping forces are measured. Newly proposed hydraulic model which derived from physical hydro-mechanical parameters of ER damper are conventional Bingham model are investigated to represent the field-dependent damping force characteristics of ER damper. After principal parameters of two models are estimated from the measured damping forces data, the force vs velocity hysteresis cycles are then reconstructed. The results show that the proposed hydraulic model can capture the hysteresis behavior of ER damper accurately.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.323-330
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• 2004

The purpose of this paper is to experimentally identify the finite element (FE) model of a building structure with magnetorheological (MR) fluid damper. Using FE model based system identification (FEBSI) technique, The model of MR damper having nonlinear characteristics is expressed with equivalent linear properties such as mass, stiffness, and damping. Bingham model is used for MR damper modeling. The equivalent stiffness and damping matrices of MR damper are predicted by applying an equivalent linearization technique, and those values are compared with the experimentally obtained ones.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 1995년도 추계학술대회 논문집
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• pp.60-63
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• 1995

The behavior of the work materials in the chip-tool interface in extremely high strain rates and temperatures is more that of viscous liquids than that of normal solid metals. In these circumstances the principles of fluid mechanics can be invoked to describe the metal flow in the neighborhood of the cutting edge. In the present paper an Eulerian finite element model is presented that simulates metal flow in the vicinity of the cutting edge when machining a low carbon steel with carbide cutting tool. The work material is assumed to obey visco-plastic (Bingham solid) constitutive law and Von Mises criterion. Heat generation is included in the model, assuming adiabatic conditions within each element. the mechanical and thermal properties of the work material are accepted to vary with the temperature. The model is based on the virtual work-stream function formulation, emphasis is given on analyzing the formation of the stagnant metal zone ahead of the cutting edge. The model predicts flow field characteristics such as material velocity effective stress and strain-rate distributions as well as built-up layer configuration