• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.222-227
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• 2002

MR(Magneto-rheological) fluid is smart fluid that can change its characteristics then magnetic fields are applied. Recently, many researches have been performed on this MR fluid for the application in a vareity of areas including automobile shock absorbers. This paper describes the design procedure of a MR damper and the analysis results of its dynamic characteristics. MR fluid in the magnetic field shows initial yield shear stress and increasing resistive viscosity with final saturation thereafter. Herschel-Bulkley model is used to simulate the flow characteristics of MR fluid and magnetic analysis is used to identify the magnetic property of the MR fluid in the orifice of the damper. The dynamic characteristics of the damper was predicted and compared with the experimental results for typical sinusoidal excitations.

• Journal of the Korean Mathematical Society
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• v.36 no.1
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• pp.193-207
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• 1999

Let ${\gamma}$ : Ilongrightarrow R2 be a sufficiently smooth curve and $\sigma$${\gamma}$ be the affine arclength measure supported on ${\gamma}$. In this paper, we study the Lp - improving properties of the convolution operators T$\sigma$${\gamma}$ associated with $\sigma$${\gamma}$ for various curves ${\gamma}$. Optimal results are obtained for all finite type plane curves and homogeneous curves (possibly blowing up at the origin). As an attempt to extend this result to infinitely flat curves we give and example of a family of flat curves whose affine arclength measure has same Lp-improvement property. All of these results will be based on uniform estimates of damping oscillatory integrals.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.4
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• pp.76-83
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• 2001

In this study, the static and dynamic characteristics of turning process was modelled and the analytic realization of regen-erative chatter mechanism was discussed. In this regard, we have discussed on the comparative assessment of recursive times series modeling algorithms that can represent the machining process and detect the abnormal machining behaviors in precision turning operation. In this study, simulation and experimental work were performed to show the malfunction behaviors. For this purpose, new Recursive Extended Instrument Variable Method(REIVM) was adopted for the on-line system identification and monitoring of a machining process. Also, we can apply REIVE algorithms in real process for the detection of chatter frequency and dynamic property and analyze the stability lobe of the system by changing a parameter of cutting dynamics in regenerative chatter mechanics, if it is stable or unstable, Also, The stability lobe of chatter was analysed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.288-291
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• 2001

Vehicle evaluation is performed on the proving ground, and durability test and dynamic test cost lots of money and time. Doing replace real vehicle experiment with similar experiment environment, it will take us much more useful advantages. Suspension simulator is required the robust and high-reliability and used widely. But it's natural of high-leveled control technique to manage to be fitted fluid system's property and complex that is for the lack of self-damping, nonlinearity, compressibility. In designing and evaluating simulator, it is important to understand the capability of kinematic and static performances. In this paper, an kinematic modeling and analysis has been presented using ADAMS to design that can reproduce longitudinal, lateral, and vertical force.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.199-209
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• 2001

Modal analysis method (MAM) is introduced for the fully coupled structural dynamic problems. In this paper, the beam with active constrained layered damping (ACLD) treatment is considered as a representative problem. The ACLD beam consists of a viscoelastic layer that is sandwiched between the base beam structure and an active piezoelectric layer. The exact damped natural modes are spectrally formulated from a set of fully coupled dynamic equations of motion. The orthogonality property of the exact damped natural modes is then derived in a closed form to complete the modal analysis method. The accuracy of the present MAM is evaluated through some illustrative examples: the dynamic characteristics obtained by the present MAM are compared with the results by spectral element method (SEM) and finite element method (FEM). It is numerically proved that MAM solutions become identical to the accurate SEM solutions as the number of exact natural used in MAM is increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.969-974
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• 2003

A simple and cost-effective method for the electrostatic suspension of thin plates like silicon wafers is proposed which is based on a switched voltage control scheme. It operates according to a relay feedback control and deploys only a single high-voltage power supply that can deliver a dc voltage of positive and/or negative polarity. This method possesses the unique feature that no high-voltage amplifiers are needed which leads to a remarkable system simplification relative to conventional methods. It is shown that despite the inherent limit cycle property of the relay feedback based control, an excellent performance in vibration suppression is attained due to the presence of a relatively large squeeze film damping origination from the air between the electrodes and levitated object. Using this scheme, a 4-inch silicon wafer was levitated stably with airgap variation decreasing down to 1 $\mu\textrm{m}$ at an airgap of 100 $\mu\textrm{m}$

• Smart Structures and Systems
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• v.8 no.5
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• pp.487-499
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• 2011

The parametric resonance problems of axisymmetric sandwich annular plate with an electrorheological (ER) fluid core and constraining layer are investigated. The annular plate is covered an electrorheological fluid core layer and a constraining layer to improve the stability of the system. The discrete layer annular finite element and the harmonic balance method are adopted to calculate the boundary of instability regions for the sandwich annular plate system. Besides, the rheological property of an electrorheological material, such as viscosity, plasticity, and elasticity can be changed when applying an electric field. When the electric field is applied on the sandwich structure, the damping of the sandwich system is more effective. Thus, variations of the instability regions for the sandwich annular plate with different applying electric fields, thickness of ER layer, and some designed parameters are presented and discussed in this study. The ER fluid core is found to have a significant effect on the location of the boundaries of the instability regions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.948-951
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• 2004

This paper introduces the two recently developed checking techniques far missed eigenvalues of nonproportionally damped system. The first technique is based on the argument principle. On the other hand, the second one is based on Rombouts' algorithm and Gleyse's theorem, which has been known as the effective and well-proven method. In the paper, the main features of the two techniques are explained and their effectiveness is also investigated by considering a numerical example.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.3
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• pp.7-13
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• 1998

This paper presents a new concept of a commercial vehicle seat suspension system. The proposed suspension system features an ER(electro-rheological)damper which can produce continuously tunable damping forces by control elecric fields. A dynamic model of the ER damper is first achieved by incorporating Bingham property of the ER fluid, followed by the formulation of governing equations of motion for the suspension system The effectiveness of the proposed ER seat suspension system is evaluated by investigating vibration with respect to sinusoidal inputs.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.76-83
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• 1993

The vibration characteristics of radial tire are studied. In order to obtain theoretical natural frequency and mode shape, the plane vibration of a tire is modeled to that of circular beam. By using the Tielking method based on Hamilton's principle, theoretical results are determined by considering tension force due to tire inflation pressure, rotational velocity and tangential, radial stiffness. Modal parameters varying the inflation pressure are determined experimentally by using the transfer function method. Results show that material property and wear are parameter for shifting of natural frequency and damping.