• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.1028-1035
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• 2007

this study, forced vibration analysis was performed on the composite main wing structure of a small scale WIG craft which is equipped two-stroke pusher type reciprocating engine. The structural vibration analysis based on the finite element method was performed using a commercial FEM code, MSC/NASTRAN. Excitations for the frequency response analysis were assumed as the H-mode(horizontal mode), the V-mode(vertical mode) and the X-mode(twisted mode) which are typical main vibration modes of engine. And excitations for the transient response analysis were assumed as the L-mode(longitudinal mode) with the oscillating propeller thrust which occurs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.289-297
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• 2011

The explicit finite element method is an essential tool for solving large problems with severe nonlinear characteristics, but its results can be difficult to interpret. In particular, it can be impossible to evaluate its acceleration responses because of severe discontinuity, extreme noise or aliasing. We suggest a new post-processing method for transient responses and their response spectra. We propose smoothing methods using a Gaussian kernel without in depth knowledge of the complex frequency characteristics; such methods are successfully used in the filtering of digital signals. This smoothing can be done by measuring the velocity results and monitoring the response spectra. Gaussian kernel smoothing gives a better smoothness and representation of the peak values than other approaches do. The floor response spectra can be derived using smoothed accelerations for the design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.77-85
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• 1988

A stochchastic analysis procedure of generating floor response spectra for proportionally damped linear systems subject to earthquake loading is presented. Theories of random vibration and mode acceleration method are used in the formulation of governing equations. The structure-oscillator interaction is not considered. It is assumed that the input motions and oscillator responses are stationary Gaussian processes with mean zero. The nonstationary characteristics of earthquake motion are incorporated in the peak factor which is based on Vanmarcke's theory. Floor response spectra for both resonance and non-resonance cases are calculated under the assumption that the peak factors for structure and oscillator are equal to that for ground response spectrum. The validity of this method is demonstrated by comparing the results obtained by proposed method with those by time history analyses. The results obtained by this method are conservative and accurate with tolerable precision. This method saves much computing time compared with time history analysis method.

• 지반과기술
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• v.7 no.3
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• pp.62-64
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• 2010

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.151-171
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• 1992

선체응답의 변화를 고찰, 계산 결과를 요약하였다. 이에 대한 계산은 유체 동력학적 해석을 이용하였으며 본 이론의 합리성을 아울러 지적하였다. 선체의 유연성을 증가시킴으로서 추격선두 굽힘 모멘트는 줄지만, 모멘컴 굽힘 모멘트는 일반적으로 증가함이 나타났다.

• Journal of the KSME
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• v.50 no.4
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• pp.42-45
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• 2010

초속 수 킬로미터에 달하는 탄자 충돌 해석과 같은 고속 충돌 문제는 매우 짧은 작용시간, 지배적인 과도 응답 상태, 관성효과의 중요성 등을 특징으로 들 수 있다. 이 글에서는 고속 충돌 해석을 위한 삼각형/사면체 요소를 적용한 operator-splitting 유한 요소 해석 기술에 대해 소개하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06d
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• pp.9-12
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• 1998

공기경계층을 갖는 유리평판에서 힘의 크기가 10N이고 상승시간이 약 280ns 인 경사 점하중이 인가된 경우에 대하여 진앙점에서 입자 변위와 입자 속도를 계산하였다. 이론적으로 계산된 수직성분이 입자속도가 PZT변환자에 입사한다고 가정하여 PZT 변환자의 과도 응답특성을 Mason 등가회로와 격자점을 이용하여 계산하였다. 유리모세관의 파과시에 방출괴는 과도탄성파를 이용하여 유리평판의 진앙점에서 PZT 변환기의 응답을 조사하였고, 이론과 비교한 결과 상당히 일치하였다. 이를 이용하여 음향방출 시스템인 발생원, 전파매질, 변환자 및 신호분석시스템을 수학적으로 모형화할 수 있는 기초를 마련하였다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.2
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• pp.177-190
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• 1996

구조물의 동적 응답 해석 문제에 대해서, 확률 유한요소법을 논의코자, 기조의 유한요소 해석법에 수반 변수법(adjoint variable approach)과 2차 섭동법(second order perturbation method)을 적용한다. 동적 민감도의 시간 응답을 고려하기 위해서 모든 시간에 대해서 갖는 구속 조건의 범함수 형태를 취하고, 시간 적분에 있어서 중첩법(fold superposition technique)에 근거를 둔 수치 해석이 훨씬 더 효과적임을 보인다. 본 논문의 확률 유한요소 해석법은 기존의 유한요소 해석법은 기존의 유한요소 코드에 맞추어 쉽게 적용할 수 있는 이점이 있음을 보이며, 이의 검정을 위해서, 2차원과 3차원 프레임 구조물에 대한 수치 해석을 하고 그 결과를 검토해 보았다.

• Journal of the Korean Society for Railway
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• v.17 no.2
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• pp.100-105
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• 2014

To design a submerged floating railway that is safe against underwater explosions, railway behavior must be investigated and clarified. In this paper, shock waves and impulse pressures generated by a charge away from the submerged floating railway are expressed using experimental formulas. The submerged floating railway tethered by mooring lines is modeled as a simply supported beam with elastic springs. Finite element analysis for the beam model subjected to impulse loading is conducted so that the response of the submerged floating railway can be investigated. For design purposes, a simplified analysis method combined with dynamic load factor is proposed for the same model. Maximum deformation and internal forces are calculated and compared with the time dependent analysis results. It is shown that the simplified analysis results show good agreement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.206-213
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• 2013

Transient response of a crack in a functionally graded piezoelectric material (FGPM) interface layer between two dissimilar homogeneous piezoelectric layers under anti-plane shear is analyzed using integral transform approaches. The properties of the FGPM layer vary continuously along the thickness. Laplace and Fourier transforms are used to reduce the problem to two sets of dual integral equations, which are then expressed to the Fredholm integral equations of the second kind. Numerical values on the dynamic energy release rate (DERR) are presented for the FGPM to show the effects on electric loading, gradient of the material properties, and thickness of the layers. Computed results yield following conclusions: (a) the DERR increases with the increase of the gradient of the material properties of the FGPM layer; (b) certain direction and magnitude of the electric impact loading impedes crack extension; (c) increase of the thickness of the FGPM layer and the homogeneous piezoelectric layer which has larger material properties than those of the crack plane are beneficial to increase of the resistance of transient fracture of the FGPM layer.