• Composites Research
• /
• v.23 no.4
• /
• pp.1-6
• /
• 2010

The dynamicresponse of biomimetic composites mimicking nacre under low velocity impact is investigated. The composites have hierarchical structures with a staggered pattern consisting of a protein and a mineral. To analyze the impact response of the composites, the finite element method is used. The effects of the hierarchical structures of the compositeson the dynamic response are examined. It is shown that the maximum stress, displacement and contact force in the composite subjected to low velocity impact decrease as the level of structural hierarchy increases.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.5
• /
• pp.601-610
• /
• 1986

The acoustic intensity in the very near field of a vibrating surface reveals information about the location of sound sources and sinks. A system model of tennis racket was developed from simultaneous measurement of excitation force, surface vibration and the near field sound pressure. The characteristics of structural dynamics were obtained by standard experimental modal analysis techniques while the sound radiation characteristics were determined by estimating the acoustic intensity. In this paper, the information about vibration behviour was obtained by acoustic intensity method and some, experiments for verification were carried out. Close correlation was found between experimentally determined acoustic intensity and vibration mode patterns of the tennis racket.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.4 no.2
• /
• pp.83-98
• /
• 2000

자오방향 및 주변방향으로 피르스트레스트 하중이 작용된 축대칭 쉘 구조물을 기하학적으로 축대칭인 구조물의 특성을 최대한으로 이용할 수 있도록 회전 링요소로 모델화하였다 보강링 요소의 모델은 축대칭 쉘요소를 이용하였으며 본체 구조물과 절점에서 부착되있는 것으로 가정하여 이의 편심을 고려하였다 유체-구조물의 상호관계는 접촉면에서 구조물의 가속도에 비례한 부가질량으로 표현하였으며 부가질량은 유체를 비점성 비압축 및 비회전을 가정하여 유한요소법에 의해 구하였다 이에 대한 수치해석을 통하여 고유진동해석 및 지진하중을 주하중으로 한 동적해석을 실시하였다 프로그램을 통하여 해석한 결과를 프리스트레스 하중 하에서 고유진동수에 대한 정해와 비교한 결과 20개의 요소로 모델링한 경우에서도 정해와 근접한 해를 얻을 수 있었다 또한 내부유체가 있는 경우와 링보강을 한 경우에 대한 고유진동수를 문헌과 비교한 결과 근접한 해를 얻을 수 있었다.

• Membrane Journal
• /
• v.4 no.2
• /
• pp.85-95
• /
• 1994

This papr studies the dynamic effects of polyelectrolyte in the multilayered membrane. It is found that electrophoretic convection in the fluid phase can be used to accelerate the speed of the polyelectrolyte. The model in the membrane separation is studied via interactions between fluid and solid phases. The spectra evaluation using the operator theoretic method is performed for the parametric studies of the physical properties in the membrane process. The findings of this paper shoould be useful in guiding the design of separation devices. This paper shows one example for macroscopic study the theoretical review paper of membrane transport.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.11
• /
• pp.158-164
• /
• 2000

In this study a computer program is developed for analyzing the elasto-plastic dynamic behaviors of the plate subjected to line-loading by a low-velocity impactor. The equilibrium equation associated with the Hertzian contact law is formulated to evaluate the transient dynamic behaviour of the impacted plate. Compared with an elastic analysis, the effects of material plasticity are presented. Consequently, in the case of elasto-plastic analysys, impulse decreases, displacements increase and contact time duration is longer than the elastic case for same finite element model. And the time variation of the impacting load is not significant due to the plasticity except at the beginning of impact duration, and the induced stresses of the plate are more realistic.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.11
• /
• pp.1111-1117
• /
• 2008

During the dynamic analysis of a system, the Coulomb friction law is emploved to calculate the friction force. Since the static friction coefficient is only employed during the zero relative velocity, it is impractical to employ the coefficient during the dynamic analysis. To calculate the static friction force, therefore, some friction models have been developed. In this study, the integration stability and the accuracy of the models are investigated with some numerical examples. The effect of time step size during the numerical integration is also investigated. The numerical study shows that the friction model employed for most commercial codes is not as good as the one proposed in this study.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.10a
• /
• pp.195-198
• /
• 2003

정밀 수치해석으로 구한 태핑음 데이터를 기준으로 하여 복합재료 구조물 내의 층간분리 손상의 존재 여부를 판단하는 비파괴 검사법을 제안하였다. 태핑음의 수치 모사를 위해 동적 접촉 알고리듬을 이용한 유한요소법과 경계요소법을 이용하였다. 태핑음 수치해석 과정에 대한 정식화를 수행하고 실제 구조물의 태핑음과 비교하여 수치해석 기법의 타당성을 밝혔다. 웨이브릿 페킷 변환에 근거한 특성 추출법을 이용하여 태핑음으로부터 손상 판단을 위한 특성을 추출하고 손상 판단의 지표가 되는 특성 지수를 정의하였다. 복합재료 구조물에 대한 층간분리 손상 검출과정을 시연함으로써 제시된 태핑음 검사법의 타당성을 밝혔다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2002.09a
• /
• pp.179-182
• /
• 2002

Geosynthetics are widely used in landfill for filtration, drainage, separation and so on. For many landfill failure cases, interfaces of geosynthetics can be potential failure surfaces. Therefore, it is very Important to estimate the interface properties of geosynthetics. In this study, shaking table tests were peformed between smooth geomembrane and geotextile. From the test results, it was found that there is a limited acceleration that can be transmitted from smooth geomembrane to geotextile. And the influence of normal stress and frequencies of excitation were discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2001.04a
• /
• pp.489-494
• /
• 2001

This paper deals with a dynamic modeling of artillery system loaded by gun charge explosion during firing condition. Geometric and elastic gun data are used to modify a projectile interaction model. The maximum impact force on gun barrel was 15,000 N and the gun barrel moved about 1.3 m. A cannon bal] was presented to travel in the flexible gun, the traveling distance was about 23,000 m, and the angular velocity was about 10rad/sec. The artillery dynamic system using the multi-body dynamics enables us to obtain the data for the fatigue analysis.

• Journal of the Korean Society of Visualization
• /
• v.22 no.1
• /
• pp.28-33
• /
• 2024

We visualized the rupturing of liquid films flowing over a disk rotating with large angular velocity. A setup of high speed imaging for liquid flows on dark and reflective surfaces are suggested. From the result, rivulet structures are revealed to be strongly governed by three-dimensional surface structures developed in the film flow. Additionally, unique flow structures including the rivulet sliding and internal meandering are investigated. Generation mechanism of such structures are discussed in terms of the dynamic contact angle theory.