• Proceedings of the KSME Conference
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• 2001.06e
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• pp.185-190
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• 2001

Rotating disks are used in various machines such as floppy disks, hard disk, turbines and circular sawblades. The problems of vibrations of rotating disks are important in improving these machines. Many investigators have dealt with these problem. Specially, vibrations of a rotating flexible disk taking into account the effect of air is difficult problem in simulation. The governing equation of a rotating flexible disk coupled to the surrounding fluid is investigated by a simple mathematical model. And several important parameters concerned with the stability of a rotating flexible disk are defined. Coupling strength between air and rotating flexible disk is proportional to square of disk radius directly and square root of the all of bending rigidity, disk density and thickness inversely. Lift-to-damping coefficient has relation to the onset of disk flutter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.344-349
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• 2012

This paper presents a new small-sized damper featuring magneto-rheological (MR) fluid which can be applied to vibration control system. The proposed MR damper consists of cylinder, piston, a couple of bearings, oil-seals and magnetic circuit which has two coils. In this damper, approximately 5cc of MR fluid is used. The damping force of the MR damper is designed to be followed by linear shear-mode Bingham-plastic model. In order to verify the performance of the MR damper, an experimental apparatus is established. In the experimental test, the damping force of the MR damper is measured with respect to time, displacement and velocity. In addition, the time response of MR damper is measured when 1A of step current is applied. Finally, The proposed small MR damper is applied to vibration control. In this process, a simple 1-DOF system is modeled and controlled using PID controller.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.11
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• pp.1121-1127
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• 2012

This paper presents a new small-sized damper featuring magneto-rheological(MR) fluid which can be applied to vibration control system. The proposed MR damper consists of cylinder, piston, a couple of bearings, oil-seals and magnetic circuit which has two coils. In this damper, approximately 5cc of MR fluid is used. The damping force of the MR damper is designed to be followed by linear shear-mode Bingham-plastic model. In order to verify the performance of the MR damper, an experimental apparatus is established. In the experimental test, the damping force of the MR damper is measured with respect to time, displacement and velocity. In addition, the time response of MR damper is measured when 1A of step current is applied. Finally, the proposed small MR damper is applied to vibration control. In this process, a simple 1-DOF system is modeled and controlled using PID controller.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.6 no.1
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• pp.64-69
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• 2006

Due to the inherent nonlinear nature of Electro-rheological (ER) fluid dampers, one of the challenging aspects for utilizing these devices to achieve high system performance is the development of accurate models and control algorithms that can take advantage of their unique characteristics. In this paper, the nonlinear damping force model is made to identify the properties of the ER damper using higher order spectrum. The higher order spectral analysis is used to investigate the nonlinear frequency coupling phenomena with the damping force signal according to the sinusoidal excitation of the damper. Also, this paper presents an inverse model of the ER damper, i.e., the model can predict the required voltage so that the ER damper can produce the desired force for the requirement of vibration control of vehicle suspension systems. The inverse model is constructed by using a multi-layer perceptron neural network. A quarter-car suspension model is considered in this paper for analysis and simulation. Simulation results show that the proposed inverse model of ER damper can obtain control voltage of ER damper for required damping force.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.691-700
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• 2000

This paper presents a novel type of a semiactive damper featuring an electro-rheological(ER) fluid. Unlike conventional cylindrical ER damper, the proposed one has controllable orifices by the intensity of electric fields (We call it orifice type). The dynamic model of the orifice type ER damper is formulated by incorporating field-dependent Bingham properties of an arabic gum-based ER fluid. Design parameters such as electrode gap are subsequently determined on the basis of the dynamic model. After manufacturing the orifice type ER damper, field-dependent damping forces and damping force controllability are empirically evaluated. In the evaluation procedure, conventional cylindrical ER damper is adopted and its performance characteristics are compared with those of the orifice type ER damper. In addition, the proposed one is installed with a full-car model and its vibration control performance associated with a skyhook controller is investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1298-1302
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• 2000

Electrorheological(HER) and magnetorheologica(MR) fluids have a unique ability to increase the dynamic yield stress of the fluid substantially when electric or magnetic field is applied. ER and MR fluid-based dampers are typically analyzed using Bingham-plastic shear flow analysis under Quasi-steady fully developed flow conditions. An alternative perspective, supported by measurements reported in the literature, is to allow for post-yield shear thinning and shear thickening. To model these, the constant post-yield plastic viscosity in Bingham model can be replaced with a power-law model dependent on shear strain rate that is known as the Herschel-Bulkley fluid model. The objective of this paper is to predict the damping forces analytically in a typical ER bypass damper for variable electric field, or yield stress using Herschel-Bulkley analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.69-77
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• 1995

This paper presents performance investigation of a continuously variable ER(Electro-Rheological) damper for passenger vehicles. A dynamic model of the damper is formulated by incorporating electric field-dependent Bingham properties of the ER fluid. The Bingham properties are experimentally obtained through Couette type electroviscous measurement with respect to two different particle concentrations. The governing equation of the hydraulic model treating three components of fluid resistances;electrode duct flow, check valve flow and piston gap flow, is achieved via the bond graph method. A prototype ER damper is then designed and manufactured on the basis of parameter analysis. The damping forces of the system are experimentally evaluated by changing the intensity of the electric field, the particle concentration and the electrode gap.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.5
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• pp.156-168
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• 2022

The design and construction are carried out to improve the structural stability of caisson breakwaters by installing new caissons on the front or rear of old caissons. The wave forces acting on caisson are excessively calculated by the resonance of fluid existing between the old caisson and the new caisson in the numerical analysis using potential flow. In this study, we used the damping zone option in ANSYS AQWA program to analyze the wave forces acting on individual caissons according to the interaction effects between the incident wave and the caisson. By applying the damping zone option to the fluid in which resonance occurs, the wave forces acting on individual caissons were calculated by the change of damping factor. In addition, the wave force characteristics acting on individual caissons were analyzed for the different distances between caissons in the frequency domain analysis.

• Tribology and Lubricants
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• v.17 no.2
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• pp.97-108
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• 2001

This paper describes the development of performance analysis technique for a leaf-type gas lubricated fail bearing. Stiffness coefficient and frictional damping due to the slip between all contacts of leaves are evaluated for various leaf structures. The fluid film thickness and pressure distribution are computed but it is not considered the elastic deformation by film pressure. The analysis results include the effects that the curvature radius and the length of leaf and the friction coefficient have on the static and dynamic characteristics of the foil bearings.

• Computers and Concrete
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• v.24 no.5
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• pp.445-452
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• 2019

In this paper, dynamic stress, strain and deflection analysis of concrete pipes conveying nanoparticles-water under the seismic load are studied. The pipe is buried in the soil which is modeled by spring and damper elements. The Navier-Stokes equation is used for obtaining the force induced by the fluid and the mixture rule is utilized for considering the effect of nanoparticles. Based on refined two variables shear deformation theory of shells, the pipe is simulated and the equations of motion are derived based on energy method. The Galerkin and Newmark methods are utilized for calculating the dynamic stress, strain and deflection of the concrete pipe. The influences of internal fluid, nanoparticles volume percent, soil medium and damping of it as well as length to diameter ratio of the pipe are shown on the dynamic stress, strain and displacement of the pipe. The results show that with enhancing the nanoparticles volume percent, the dynamic stress, strain and deflection decrease.