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김영완(Young-Wann Kim),박경조(Kyung-Jo Park) 한국소음진동공학회 2014 한국소음진동공학회 논문집 Vol.24 No.4
The sensor configuration of the magnetostrictive guided wave system can be described as a single continuous transducing element which makes it difficult to separate the individual modes from the reflected signal. In this work we develop the mode decomposition technique employing chirplet transform based on the maximum likelihood estimation, which is able to separate the individual modes from dispersive and multimodal waveform measured with the magnetostrictive sensor, and estimate the time-frequency centers and individual energies of the reflection, which would be used to locate and characterize defects. Simulation results on a carbon steel pipe are presented, which show the accurate mode separation and more discernible time-frequency representation could become enabled using the proposed technique.
김영완(Young-Wann Kim),정강(Kang Jung) 한국소음진동공학회 2016 한국소음진동공학회 논문집 Vol.26 No.7
In this study, the exact rigidity and the free vibration of trapezoidal corrugated plate are analyzed by being based on the Kirchhoffs plate theory and the Ritz method. The previous rigidity of corrugated plate analyzed by considering just a geometric characteristic, a basic assumption and an equivalent idea can cause large errors in practical behaviors. Accordingly, the exact rigidity supplemented by correction factors of the theoretical rigidity is needed. Therefore an analysis on the exact rigidity and the free vibration using the rigidity for the plate is performed in this paper.
김영완(Young-Wann Kim),정강(Kang Chung) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The theoretical method is developed to investigate the vibration characteristics of the combined cylindrical shells with an annular plate joined to the shell at any arbitrary axial position. The structural rotational coupling between shell and plate is simulated using the rotational artificial spring. For the translational coupling, the continuity conditions for the displacements of shell and plate are used. For the uncoupled annular plate, the transverse motion is considered and the in-plane motions are not. And the additional transverse and in-plane motions of the coupled annular plate by shell deformation are considered in analysis. Theoretical formulations are based on Love’s thin shell theory. The frequency equation of the combined shell with an annular plate is derived using the Rayleigh-Ritz approach. The effect of inner-to-outer radius ratio, axial position and thickness of annular plate on vibration characteristics of combined cylindrical shells is studied. To demonstrate the validity of present theoretical method, the finite element analysis is performed.
김영완(Kim, Young-wann) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.4
A theoretical method is presented to investigate the thermoelastic and dynamic response of functionally graded material (FGM) rectangular plates made up of metal and ceramic. The temperature is assumed to be constant in the plane of the plate and to vary in the thickness direction only. Material properties are assumed to be temperature-dependant, and vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The third order shear deformation theory (TSDT) to account for rotary inertia and transverse shear strains is adopted to formulate the theoretical model. The modal analysis technique is used to develop the analytic solutions of the dynamic problem. The effect of material compositions and temperature fields is examined. The present theoretical results are verified by comparing with those from finite element analysis by ANSYS.
김영완(Young-Wann Kim),박경조(Kyung-Jo Park) 한국소음진동공학회 2015 한국소음진동공학회 논문집 Vol.25 No.6
In this work we use the mode decomposition technique employing chirplet transform, which is able to separate the individual modes from dispersive and multimodal waveform measured with the magnetostrictive sensor. The mode decomposition technique is also used to estimate the time-frequency centers and individual energies of the reflection, which would be used to locate and characterize axial defects. The arrival times of the separated modes are calculated and the axial defect lengths can be evaluated by using the estimated arrival time. Results from an experiment on a carbon steel pipe are presented and it is shown that the accurate and quantitative defect characterization could become enabled using the proposed technique.
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김영완(Young-Wann Kim) 한국소음진동공학회 2023 한국소음진동공학회 논문집 Vol.33 No.2
This paper presents the transient response analysis conducted for sandwich plates subjected to blast load. These plates are made of two isotropic face sheets and a porous core composed of closed-cell foam. The core with functionally graded pore distribution through the thickness direction is uniformly reinforced using graphene nanoplatelets. Three different porosity distributions are considered, namely, two functionally graded symmetric types and a uniform type. In the analytical method of investigating the transient response of sandwich plates, Reddy’s third order shear deformation theory is employed. To verify the reliability of the presented analytical method, the transient responses are compared to those obtained using the ANSYS software. The influences of the weight fraction, geometry of the graphene nanoplatelet, porosity distribution and porosity coefficient on the transient response are examined using a few examples.