• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.721-724
• /
• 2005

With the advantages of large vibration energy dissipation of structures, the granular materials are used as vibration and acoustic treatments. In this case of vibro acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured. Using the Rayleigh-Ritz method, the effects of damping materials on the dynamic characteristics of beams were investigated. The results suggested that the acoustic structure Interaction between the frame and the structure enhances the dissipation of the vibration energy significantly. The same methods were applied also to vibration control of sandwich panels. By filling the cavities of honeycomb cores using unconsolidated granular materials, its sound transmission toss was improved significantly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.89-94
• /
• 2006

In this paper, the effects of the system parameters on the high cycle fatigue life based on structural dynamic analysis of a turbine blade are investigated. Conventional studies have forcused on the fatigue life of turbine blades with specific system parameters. However, each parameter has statistical deviation because of inhomogeneity of material property, tolerance, and operating conditions. Therefore a methodology that estimates the effects of system parameter on the fatigue lift deviation is demonstrated.

• Journal of computational fluids engineering
• /
• v.12 no.3
• /
• pp.41-46
• /
• 2007

Dynamic behavior of immiscible gas bubble attached to the wall in channel flow plays very important role in many engineering applications. Special attention has been paid to micro direct methanol fuel cell(${\mu}$DMFC) where surface tension becomes dominant factor with minor gravitational effect due to its reduced size. Therefore, displacement of $CO_2$ bubble generating on a cathode side in ${\mu}$DMFC can be very difficult and efficient removal of $CO_2$ bubbles will affect the overall machine performance considerably. We have focused our efforts on studying the dynamic behavior of immiscible bubble attached to the one side of the wall on 2D rectangular channel subject to external shear flow. We used Level Contour Reconstruction Method(LCRM) which is the simplified version of front tracking method to track the bubble interface motion. Effects of Reynolds number, Weber number, advancing/receding contact angle and property ratio on bubble detachment characteristic has been numerically identified.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.10
• /
• pp.88-95
• /
• 2006

Cold gas dynamic spray is a relatively new coating process by which coatings can be produced without significant heating during the process. Cold-spray uses supersonic gas flow to carry metallic powders to the substrate. Its low process temperature can minimize thermal stress and also reduce the deformation of the substrate. Most researches on cold-spray have focused on micro scale coating, but in this study macro scale deposition was conducted. Properties of aluminum layer by cold-spray deposition such as coefficient of thermal expansion (CTE), modulus of elasticity. hardness, and electric conductivity were measured. The results showed that properties of aluminum layer by cold-spray deposition were different from properties of pure aluminum and aluminum alloy.

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

• Smart Structures and Systems
• /
• v.13 no.1
• /
• pp.25-39
• /
• 2014

The axisymmetric dynamic instability of polar orthotropic sandwich annular plate combined with electrorheological (ER) fluid core layer and constraining layer are studied in this paper. And, the ER core layer and constraining layer are used to improve the stability of the annular plate system. The boundaries of instability regions for the polar orthotropic sandwich annular plate system are obtained by discrete layer annular finite element and the harmonic balance method. The rheological property of an electrorheological material, such as viscosity, plasticity, and elasticity can be controlled by applying different electric field strength. Thus, the damping characteristics of the sandwich system are more effective when the electric field is applied on the sandwich structure. Additionally, variations of the instability regions for the polar orthotropic sandwich annular plate with different applying electric field strength, thickness of ER layer and some designed parameters are investigated and discussed in this study.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1871-1876
• /
• 2005

In this paper, We present a new nonlinear adaptive control law using a disturbance accommodating control (DAC) observer for a Japanese automatic landing flight experiment vehicle called ALFLEX. A future spaceplane must have ability to deal with greater fluctuations in the stability and control derivatives of flight dynamics, because its flight region is much wider than that of conventional aircraft. In our previous studies, digital adaptive flight control systems have been developed based on a linear-parameter-varying (LPV) model depending on dynamic pressure, and obtained good simulation results. However, under previous control laws, it is difficult to accommodate uncertainties represented by disturbance and nonlinearity, and to design a stable flight control system. Therefore, in this study, we attempted to design a nonlinear adaptive control law using the DAC Observer and inverse dynamic methods. A good tracking property of the obtained system was confirmed in numerical simulation.

• Proceedings of the KIEE Conference
• /
• 1999.07c
• /
• pp.1057-1059
• /
• 1999

A procedure to develop dynamic equivalent systems of the KEPCO power system in the year 2010 was proposed, and 3 different equivalent systems in which the number of generators are 39, 30, and 19 were developed in this paper. The static and dynamic property of the reduced systems was verified by the comparison of time-domain simulation for the original system and the reduced systems.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.96-100
• /
• 2003

In the tensile loading of sheet metals made from polycrystalline aluminum alloys, a single deformation band appears inclined to the elongation axis in the early stage of plastic deformation, and symmetric double bands are observed in the later stage. This character of the localized deformation bands has been analyzed by a perturbation method. Macroscopic slip modes composed of slip planes and slip directions were assumed to describe the tensile and shear strains. Along time integration path, the value of the perturbation growth parameter was checked to find at which angle to the elongation axis the localized deformation bands are generated. It was shown that the mode of the localized deformation is related to asymmetry of material property.

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