• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.581-586
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff’s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.550-559
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• 2006

This paper presents designs and performance investigations of two bypass-type MR (magneto-rheological) shock dampers for high impulsive force systems, one of which is with single rod and the other with double rod. First of all, on the basis of the Bingham properties of the MR fluid and the magnetic field analysis of the magnetic circuit, the MR shock dampers are designed and manufactured. After experimental investigations on their magnetic field-dependent damping forces and responses characteristics, dynamic models of the proposed dampers are formulated and compared. Then, a simple 1 degree-of-freedom mass-drop system is constructed, and the effective and practical control algorithm is designed by considering dynamic characteristics of the shock control system. The shock control performances of the proposed MR shock dampers are verified through the comparison study of experiment results with simulation ones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.633-638
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• 2009

This paper presents an optimal design of a magnetorheological(MR) fan clutch based on finite element analysis and also presents torque control of engine cooling fan using a sliding mode control. The MR fan clutch is constrained in a specific volume and the optimization problem identifies the geometric dimension of the fan clutch that minimizes an objective function. The objective function for the optimization problem is determined based on the solution of the magnetic circuit of the initially designed clutch. Under consideration of spatial limitation, design parameters are optimally determined using finite element analysis. After describing the configuration of the MR fan clutch, the viscous torque and controllable torque are obtained on the basis of the Bingham model of MR fluid. Then, a sliding mode controller is designed to control the torque of the fan clutch according to engine room temperature and control performance is evaluated through computer simulation.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.73-82
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• 2008

Recently MR CDC damper has been applied to semi-active suspension control system gradually. Compared to former hydraulic CDC damper, it has rapid time response performance as well as simple internal structure and wide range of damping force. In order to develop control logic algorithm which enables to take maximum advantage of unique characteristics of MR CDC damper, it is inevitable to perform a thorough investigation into its nonlinear performance. In many previous researches, MR fluid model was either simply assumed as Bingham Plastic, or a phenomenological model based on experiment was established instead to predict damping performance of MR CDC damper. These experimental flow model which is not based on flow analysis but intentionally built to fit damping characteristics, may lead to totally different results in case of different configuration or structure of MR CDC damper. In this study, a generalized flow formula from mathematical flow model of MR fluid for annular orifice is derived to analyze and predict damping characteristics when current is excited at piston valve.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.39-56
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• 2009

Vibration is an undesirable phenomenon in a dynamic system like lightly damped aerospace structures and active vibration control has gradually been employed to suppress vibration. The objective of the current investigation is to introduce an active torsional magneto-rheological (MR) fluid based damper for vibration control of a typical nose landing gear. They offer the adaptability of active control devices without requiring the associated large power sources. A torsional damper is designed and developed based on Bingham plastic shear flow model. The numerical analysis is carried out to estimate the damping coefficient and damping force. The designed damper is fabricated and an experimental setup is also established to characterize the damper and these results are compared with the analytical results. A typical FE model of Nose landing gear is developed to study the effectiveness of the damper. Open loop response analysis has been carried out and response levels are monitored at the piston tip of a nose landing gear for various loading conditions without damper and with MR-damper as semi-active device. The closed-loop full state feedback control scheme by the pole-placement technique is also applied to control the landing gear instability of an aircraft.

• Geomechanics and Engineering
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• v.15 no.4
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• pp.973-986
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• 2018

The objective of this paper is to present abacuses obtained from a parametric study of deep-lined tunnels using a numerical finite element model. This numerical model was implemented in software GEOMEC91, which is a two-dimensional axisymmetric model that considers the progress of excavation and the placing of the lining through the activation and deactivation of elements. It is adopted a step of excavation constant (1/3 of radius), constant velocity and circular cross section along the tunnel axis. It is used for rock mass a viscoplastic constitutive law with von-Mises criterion of viscoplasticity without hardening whose deformation rate over time is given by the Bingham model. The lining uses a linear elastic constitutive law. In total are 1716 analysis presented in 60 abacuses that show the value of ultimate convergence ($U_{eq}$) due to tunneling speed. In addition, it is shown an example of the use of the abacuses to determine the ultimate convergence ($U_{eq}$) of the tunnel and pressure ($P_{eq}$) on the lining.

• Economic and Environmental Geology
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• v.14 no.1
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• pp.1-25
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• 1981

This paper is a literature review on the following subjects: 1) relationships between porphyry molybdenum and copper systems; 2) hydrothermal environments of molybdenite depositions; 3) genetic significance of molybdenite polyforms; and 4) trace element patterns in molybdenite useful as an exploration guide. The geologic similarities between porphyry molybdenum (e. g. Climax) and porphyry copper (e. g. Bingham) systems exist, and similar techniques can be applied for exploring deposits of either type. Several features suggest that tungsten and tin may form porphyry-like systems (i. e. lowgrade, large tonnage). The clustering of porphyry-like systems in geophysically distinctive batholithic provinces is well documented and provides larger targets for reconnaissance exploration. Geochemical studies suggest that uranium should often occur in close proximity to molybdenum ores in igneous as well as sedimentary environments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.4
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• pp.13-21
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• 2001

Electrorheological(ER) fluid is a kind of smart material with variable shear stress and dynamic viscosity under various electric field intensity. Electric field can control the damping characteristics of ER damper. The objective of this study is the analysis of the performance of ER damper and its application to shock absorber. Idealized nonlinear Bingham plastic shear flow model is used to predict the velocity profile between electrodes. Cylindrical dashpot ER damper with moving electrode is constructed and tested under various electric fields. The analytic and experimental results for damping force are compared and discussed. Drop test system using ER damper is prepared to identify transient vibration characteristics. The rebound is eased as the applied electric field increases. When semi-active control algorithm is applied, rebound phenomenon disappears and vibration energy level decays faster than the case of zero electric field.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1110-1118
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff' s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.6
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• pp.499-505
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• 2011

This paper presents optimal design of controllable magnetorheological suspension unit for a tracked vehicle. As a first step, a double-rod type MR suspension unit is designed on the basis of the Bingham model of commercially available MR fluid, and its damping characteristics are evaluated with respect to the intensity of the magnetic field. Subsequently, the governing equation of motion of the MR suspension system featuring the MR valve is established. Then, the optimization problem to find optimal geometric dimensions of the MR supension unit is formulated by considering an objective function which is related to damping torque and control energy. The first order optimization method intergrated with a commercial finite element method(FEM) software is adopted to obtain optimal solution of the system. The performance characteristics of the optimized MR susepnsion unit is then evaluated and compared with initial one.