• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.2
• /
• pp.191-206
• /
• 2007

The general theoretical solutions for the wavespeed and damping derived in Part 1 of this work, are incorporated into the computer code. In this paper the code is used in a parametric study of the influence of excitation frequency and variations in material properties on propagation velocity and damping. Compressional wave velocity for waves of the first kind is shown to vary as a function of the frequency-permeability product, with a zone where wavespeed transitions from a lower bound value to a higher bound value with increasing values of the product. Damping is seen to be a maximum where the rate of change in wavespeed is greatest. Waves of the second kind also show a transition in wavespeed from near zero at low values of the frequency-permeability product to an upper bound value at higher values of the product.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1992.06a
• /
• pp.96-99
• /
• 1992

섬유강화 복합재료의 동탄성계수와 감쇠특성을 규명하기 위하여 랜덤하게 분포된 무한 실린더 형상의 산란체를 가진 매질내에서, 조화운동을 하는 압축 및 SV탄성파의 전파에 관하여 연구하였다. 단일 실린더에 대한 산란계수로부터 La의 준결정근사법을 이용하여 다중산란에 관한 이론을 유도하였고, 매질내에서의 파동전파 특성을 내포하는 분산관계식을 얻었다. 수치적으로 분산관계식의 해를 구함으로써 2 차원 유효체적강성, 횡방향 유효전단강성 및 각 파동의 전파에 따른 감쇠계수를 주파수와 체적비의 함수로서 제시하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.8
• /
• pp.793-799
• /
• 2015

In this research, we study the propagation of longitudinal and transverse waves through a metal rod including a liquid layer using computational and experimental analyses. The propagation characteristics of longitudinal and transverse waves obtained by the computational and experimental analyses were consistent with the wave propagation theory for both cases, that is, the homogeneous metal rod and the metal rod including a liquid layer. The fluid-structure interaction modeling technique developed for the computational wave propagation analysis in this research can be applied to the more complex structures including solid-liquid interfaces.

• Bulletin of the Korean Space Science Society
• /
• 2009.10a
• /
• pp.39.1-39.1
• /
• 2009

중성입자가 함께 존재하는 불균일한 플라즈마 내로 입사하는 전파들은 플라즈마의 전자 밀도와 전자-중성입자 충돌에 의해 영향을 받게 된다. 특히 전자들의 운동이 중요한 높은 주파수 파동들은 상위 혼합 공명(Upper Hybrid Resonance)과 주변 자기장 현상에 의한 파동 모드 변환(mode conversion)으로 전파의 성질이 변하게 된다. 그리고 전자-중성입자에 의한 충돌은 에너지의 감쇄 등의 영향을 미치게 된다. 이러한 조건을 모두 고려한 유체 수치 모델을 이용하여 지구의 전리층이나 약한 자기권을 가지고 있는 행성 대기와 같이 플라즈마와 중성입자가 섞여있는 매질에서의 전자기파 파동의 특성을 조사하였다. 주파수, 중성대기 밀도 및 입사 각도에 따라 파동의 공명 흡수량과 감쇄량을 각각 알아본다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.311-314
• /
• 2007

The experimental method of measuring dynamic properties of structures was presented. The method is based on the flexural wave propagation characteristics. Using the method, change in structural dynamic properties due to damage is measured. The crack has much more significant impact on the strain energy than the inertial effects. From this, the sensitivity of the dynamic stiffness on the crack location is estimated by calculating the strain energy. When the wave propagates, the strain and kinetic energies shows cyclic changed over space. The crack that occurred at locations where the wave energy is in the form of the potential energy affected most significantly the wave propagation characteristics. The effects of crack location on the wave propagation were used to determine the crack location.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• v.y2005m4
• /
• pp.183-188
• /
• 2005

This study targets to investigate thermal wave transfer in a droplet strongly coupled with acoustic pressure and its effects on combustion response. The one-dimensional vaporization model uses SRK equation of state and flash calculation method to obtain more accurate thermophysical properties and compute vapor-liquid equilibrium. Calculations of an n-pentane droplet exposed into a perturbing nitrogen gas is carried out in terms of different ambient gas pressures and wave frequencies. The thermal wave is transferred more effectively at lower frequencies, which results in the decrease in the amplitude of the response.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.23 no.6
• /
• pp.512-519
• /
• 2013

It is important to understand the vibrating behavior of plate structures for its many engineering applications. In this study, the vibration characteristics of strip plates that have finite width and infinite length are investigated theoretically and numerically. The waveguide finite element(WFE) approach, which is an effective tool for studying waveguide structures, is used in this study. The WFE method requires only a cross-sectional finite element model, and uses theoretical harmonic solutions to assess wave propagation along the longitudinal direction. First, WFE results for a simple strip plate are compared with the theoretical results(i.e., dispersion diagrams and point mobilities) to validate the numerical model. Then, in the numerical analysis, different numbers of longitudinal stiffeners are included in the plate model to investigate the effects of stiffeners in terms of the dispersion curves and mobilities. Finally, the dispersion curves of a stiffened double plate are obtained to examine the characteristics of its wave propagation.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.32 no.4
• /
• pp.257-263
• /
• 2019

Multilayered structures include lamination by relatively thick plies and thin interlayers. For efficient peridynamic analysis of dynamic fracturing multilayered structures, the interlayer is modeled using ghost peridynamic particles while the ply is formulated via real peridynamics. With the nonlocal ghost interlayer, one may keep the discretization resolution low for the ply. In this study, the characteristics of dynamic wave propagation through the nonlocal ghost interlayer in peridynamic analysis are investigated. It is observed that the interlayer not only binds adjacent plies, but also significantly influences energy transfer between plies, and thereby their deformation and motion. In addition, near a surface or boundary, peridynamic particles do not have a full nonlocal neighborhoods. This causes the effective material properties near the surface to be different from those in the bulk. Surface correction based on neighborhood volumes is employed. The impact of surface correction on wave propagation in multilayered structures is investigated.

• Journal of Ocean Engineering and Technology
• /
• v.7 no.2
• /
• pp.44-56
• /
• 1993

The purpose of this paper is to analyze the impact response behaviors of glass/epoxy laminated composite plates subjected to the transversely impact of a steel ball. For this purpose, dynamic finite element analysis based on the higher-order shear defomation plate theory is used to compute the contact forces, rebound velocity of a steel ball, and dynamic strain response histories. And low-velocity and high-velocity impact experiments were conducted to compare the results and compute the wave propagation velocities. The results obtained from impact experiments are in good agreement with those of dynamic finite element analysis. Also the wave propagation velocities obtained from high-velocity impact experiments and wave propagation theory agree well, and wave velocities were higher in the smaller radius of steel ball.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.2
• /
• pp.95-103
• /
• 2007

An analytical closed-form solution for wave propagation velocity and damping in saturated porous media is presented in this paper The fully coupled field model with compressible solid Brains and pore water were used to derive this solution. An engineering approach for the analysis of fully saturated porous media was adopted and closed-form solutions for one dimensional wave propagation in a homogeneous domain were derived. The solution is highly versatile in that it considers compression of the solid grains, compression of the pore water, deformation of the porous skeleton, and spatial damping and can be used to compute wavespeeds of first and second kind and damping coefficients in various geologic materials. This solution provides a means of analyzing the influence of material property variations on wavespeed and attenuation. In Part 2 of this work the theoretical solution is incorporated into the numerical code and the code is used in a parametric study on wave propagation velocity and damping.