• Title/Summary/Keyword: Element dispersion

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Mode localization and veering of natural frequency loci in two circular plates coupled with a fluid

  • Jeong, Kyeong-Hoon
    • Structural Engineering and Mechanics
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    • v.22 no.6
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    • pp.719-739
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    • 2006
  • An analytical method for the free vibration of two circular plates coupled with an inviscid and compressible fluid is developed by the Rayleigh-Ritz method. The fluid is bounded by a rigid cylindrical vessel and two circular plates with an unequal thickness and diameter. It was found that the theoretical results could predict well the fluid-coupled natural frequencies with an excellent accuracy when compared with the finite element analysis results. As the fluid thickness increases or the plate thickness difference increases, an abrupt curve veering in the natural frequency loci of the neighboring modes and drastic changes in the corresponding mode shapes are observed. The mode localization frequently appears in the higher modes and in the wide gap between the plates because of a decrease in the fluid coupling owing to the fluid dispersion effect.

Vibration Analysis of a Coil Spring by Using Dynamic Stiffness Method (동강성법을 이용한 코일스프링의 진동 해석)

  • Lee, Jae-Hyung;Kim, Seong-Keol;Heo, Seung-Jin;Thompson, D.J.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1933-1938
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    • 2000
  • The partial differential equations for a coil spring derived from Timoshenko beam theory and Frenet formulae. Dynamic stiffness matrix of a coil spring composed of a circular wire is assembled by using dispersion relationship, waves and natural frequencies. Natural frequencies are obtained from maxima in the determinant of inverse of a dynamic stiffness matrix with appropriate boundary conditions. The results of the dynamic stiffness method are compared with those of transfer matrix method, finite element method and test.

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Modeling and Numerical Investigation of the Biomechanical Interaction for Human-Rifle System

  • Chae, Je-Wook;Lee, Young-Shin
    • Journal of Mechanical Science and Technology
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    • v.18 no.12
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    • pp.2069-2079
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    • 2004
  • This paper represents the description of a complex mathematical model of biomechanical interaction for human-rifle system during shooting. The model is developed by finite element method using bar elements. And three typical shooting positions, i.e. standing, kneeling and prone are used. Characteristics of interior/exterior ballistics and behaviors of human-rifle system are evaluated by this model, which takes into account the influence of environment, bullet, powder, barrel geometry parameters and anthropological parameters. The results of this study can be applied to anthropology, biomechanics, medical science, gait analysis, interior ballistics and exterior ballistics.

Dispersion-Correction Finite Element Model for Simulation of Tsunami Propagation over Slowly Varying Depth (완변수심상 지진해일 전파 모의를 위한 분산보정 유한요소모형)

  • Lim, Chae-Ho;Jeon, Young-Joon;Bae, Jae-Seok;Yoon, Sung-Bum
    • Proceedings of the Korea Water Resources Association Conference
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    • 2007.05a
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    • pp.576-580
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    • 2007
  • 수치기법이 복잡한 Boussinesq 방정식 대신 간단한 선형 Boussinesq 형태의 파동방정식을 지배방정식으로 사용하면서도 완변수심상 지진해일 전파시 요구되는 물리적 분산효과를 정도 높게 고려할 수 있는 분산보정 지진해일 전파 유한요소모형을 개발하였다. 수심이 변하는 지형에서의 분산보정능력을 검증하기 위해 수중 원형천퇴상을 전파하는 Gaussian 형상의 가상지진에 대해 수치모의를 수행하고, 그 결과를 선형 Boussinesq 방정식에 의해 계산된 수치해와 비교하였다. 그 결과 개발된 유한요소모형이 수심이 변하는 지형에서도 상당히 정확하다는 것이 입증되었다.

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Numerical Simulation and Forecasting of Mechanical Properties for Multi-Component Nonferrous Dispersion-hardened Powder Materials

  • Ryabicheva, Lyudmila;Usatyuk, Dmytro
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.998-999
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    • 2006
  • A new mathematical simulation technique for physico-mechanical properties of multi-component powder materials is proposed in this paper. The main advantage of the technique is that finite elements representing different components are placed into a common mesh and may exchange their properties. The output data are properties of material after sintering. The technique allows us to investigate the influence of each component of a material on the properties and distribution of properties inside the sample. The comparative analysis of materials with different compositions is based on simulation results that are well concordant with the results of the laboratory experiments.

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A Study of Failure Mechanism for Inclined Impact of PELE (PELE의 경사진 충격에 따른 파괴 메커니즘에 대한 연구)

  • Jo, Jong-Hyun;Lee, Young-Shin
    • Journal of the Korea Institute of Military Science and Technology
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    • v.15 no.5
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    • pp.712-719
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    • 2012
  • Penetrator with enhanced lateral effect(PELE) is a newconcept projectile, without dynamite and fuze. It consists of high-density jacket, closed at its rear end and filled with a low-density filling material. To study the explosion characteristics of PELE, by AUTODYN-3D code, the calculation models of projectile body and bullet target are established and the process of penetrating aluminum-2024 alloy target of PELE is simulated, and the scattering characteristics after penetrating aluminum-2024 alloy target of PELE are studied by different initial velocity. The explicit finite element analysis of PELE fragmentation was implemented with stochastic failure criterion in AUTODYN-3D code. As expansion of filling, the fragments were obtained velocities and dispersed laterally and further more enhancing the damage area largely. The number and shape of the PELE fragments were different depend on impact velocity and incidence angle of filling which fragment generated during penetration and lateral dispersion process.

Vibration Analysis of a Helical Spring under the pre-load (예하중을 받는 헬리컬 스프링의 진동 해석)

  • Lee, Jae-Hyung;Heo, Seung-Jin
    • Proceedings of the KSME Conference
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    • 2001.06b
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    • pp.355-360
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    • 2001
  • By using Frenet formulation and Timoshenko beam theory, the partial differential equations of motion are derived for a helical spring having a doubly symmetrical cross section subjected to the pre-load axially. These equations of motion are solved to give the dispersion relationship and dynamic stiffness matrix is assembled. Natural frequencies are obtained from the receptance of the system. The results of the dynamic stiffness method are compared with those of the transfer matrix method from published examples and finite element method.

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Approaches of the Computaional Mechanics on the Stress Wave Analysis (응력파동해석에 대한 전산역학적 접근방법)

  • 조윤호;정현규;김승호
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.04a
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    • pp.415-429
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    • 2002
  • Various modeling techniques for ultrasonic wave propagation and scattering problems in finite solid media are presented. Elastodynamic boundary value problems in inhomogeneous multi-layered plate-like structures are set up for modal analysis of guided wave propagation and numerically solved to obtain dispersion curves which show propagation characteristics of guided waves. As a powerful modeling tool to overcome such numerical difficulties in wave scattering problems as the geometrical complexity and mode conversion, the Boundary Element Method(BEM) is introduced and is combined with the normal mode expansion technique to develop the hybrid BEM, an efficient technique for modeling multi-mode conversion of guided wave scattering problems.

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Methodology of Tolerance Analysis of Deformable Assembly (변형을 고려한 공차분석 방법론)

  • Lee, Kwang-Soo
    • Journal of the Korean Society of Safety
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    • v.22 no.6
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    • pp.20-26
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    • 2007
  • The new integrated CAD-CAM systems induce an increasing demand for simulation tools, which are able to simulate industrial part assembly processes by welding, gluing, riveting or bolting(more generally by fastening). Concerning fastened flexible parts, there exist no efficient computational aid on tolerance and methodology available on the field. The first part briefly presents the approach method based on the finite element method for TADA(Tolerance Analysis of Deformable Assemblies). The second part compares the results obtained by simulation using the commercial FEM code with the measurements. The principal elements of dispersion have been identified and studied on an experimental basis in order to test the robustness of the TADA model. This has enabled us to verify the model's possibilities as regards industrial constraints such as the use of incompatible meshes or the use of triangular elements and so on.

Preparation of High-Efficient Oil-based Nanofluids and It's Application to the Transformer (고효율 나노절연유 제조 및 변압기에의 적용)

  • Yoo, Hyun-Sung;Choi, Cheol;Oh, Je-Myung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.31-32
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    • 2007
  • Oil-based nanofluids are prepared by dispersing spherical and fiber-shaped $Al_2O_3$ and AlN nanoparticles in transformer oil. Two hydrophobic surface modification processes are compared in this investigation. It is obvious that the combination of nanoparticle, surfactant and surface modification process is very important for the dispersity of nanofluids. For ($Al_2O_3$+AIN) particles with 1% volume fraction, the enhancement of thermal conductivity and convective heat transfer coefficient is nearly 11% and 30%, respectively, compared to pure transformer oil. The cooling effect of ($Al_2O_3$+AlN)-oil nanofluids on the heating element and oil itself is confirmed by a natural convection test using a prototype transformer.

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