• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.371-376
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• 2004

It is well known that a specific experimental method such as the Split Hopkinson Pressure Bar (SHPB) technique is the simplest experimental technique to determine the dynamic material properties under the impact compressive loading conditions with strain-rate of the order of $10^3/s{\sim}10^4/s$. This type of experimental procedure has been widely used with proper modification on the test setups to determine the varying dynamic response of materials for the dynamic boundary conditions such as tensile and fracture as well. In this paper, dynamic compressive deformation behaviors of an Ethylene Copolymer materials widely used for the isolation of vibration from varying structures under dynamic loading are estimated using the SHPB technique.

• 한국정밀공학회지
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• 제21권6호
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• pp.122-130
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• 2004

It is well known that a specific experimental method, the Split Hopkinson Pressure Bar (SHPB) technique is a best experimental technique to determine the dynamic material properties under the impact compressive loading conditions with strain-rate of the order of 10$^3$/s∼10$^4$/s. This type of experimental procedure has been widely used with proper modification on the test setups to determine the varying dynamic response of materials for the dynamic boundary conditions such as tensile and fracture as well. In this paper, dynamic compressive deformation behaviors of a rubber and an Ethylene Copolymer materials widely used for the isolation of vibration from varying structures under dynamic loading are estimated using a Split Hopkinson Pressure Bar technique.

• Computers and Concrete
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• 제16권4호
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• pp.643-667
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• 2015

3-dimentional precast recycled aggregate concrete (RAC) finite element models were developed by means of the platform OpenSees to implement sophisticated nonlinear model subjected to seismic loads. Efforts were devoted to the dynamic responses (including dynamic characteristics, acceleration amplifications, displacements, story drifts) and capacity curve. In addition, this study extended the prediction on dynamic response of precast RAC model by parametric study of material properties that represent the replacement percentage of recycled coarse aggregate (RCA). Principles and assumptions that represent characteristics of precast structure and influence of the interface between head of column and cast-in-place (CIP) joint on the stiffness of the joints was put forward and validated by test results. The comparison between simulated and tested results of the precast RAC frame shows a good correlation with most of the relative errors about 25% in general. Therefore, the adopted assumptions and the platform OpenSees are a viable approach to simulate the dynamic response of precast frames made of RAC.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.349-352
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• 2002

In this paper, dynamic properties of fiber reinforced soils were investigated at shearing strains between $10^{-4}%\;and\;10^{-1}%$ using resonant column test. Resonant column test has been widely used as a primary laboratory testing technique in investigating dynamic soil properties expressed in term of shear modulus and material damping. At strains above elastic threshold, the variations of shear modulus(G) and damping ratio(D) were investigated. Based on test results, the small strain shear modulus($G_{max}$) and damping ratio($D_{min}$) were determined and the effects of confinement on $G_{max}$ and $D_{min}$ were characterized.

• Coupled systems mechanics
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• 제4권1호
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• pp.19-36
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• 2015

Modelling and analysis of a brick masonry building involves uncertainties like modelling assumptions and properties of local material. Therefore, it is necessary to perform a calibration to evaluate the dynamic properties of the structure. The response of the finite element model is improved by predicting the parameter by performing linear dynamic analysis on experimental data by comparing the acceleration. Further, a nonlinear dynamic analysis was also performed comparing the roof acceleration and damage pattern of the structure obtained analytically with the test findings. The roof accelerations obtained analytically were in good agreement with experimental roof accelerations. The damage patterns observed analytically after every shock were almost similar to that of experimental observations. Damage pattern with amplification in roof acceleration exhibit the potentiality of earthquake resistant measures in brick masonry models.

• Advanced Composite Materials
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• 제16권4호
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• pp.315-334
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• 2007

In the present study, chopped henequen natural fibers without and with surface modification by electron beam (E-beam) treatment were incorporated into a polypropylene matrix. Prior to composite fabrication, a bundle of raw henequen fibers were treated at various E-beam intensities from 10 kGy to 500 kGy. The effect of E-beam intensity on the interfacial, mechanical and thermal properties of randomly oriented henequen/polypropylene composites with the fiber contents of 40 vol% was investigated focusing on the interfacial shear strength, flexural and tensile properties, dynamic mechanical properties, thermal stability, and fracture behavior. Each characteristic of the material strongly depended on the E-beam intensity irradiated, showing an increasing or decreasing effect. The present study demonstrates that henequen fiber surfaces can be modified successfully with an appropriate dosage of electron beam and use of a low E-beam intensity of 10 kGy results in the improvement of the interfacial properties, flexural properties, tensile properties, dynamic mechanical properties and thermal stability of henequen/polypropylene composites.

• Structural Engineering and Mechanics
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• 제11권3호
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• pp.273-286
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• 2001

Viscoelastic (VE) dampers have shown to be capable of providing structures with considerable additional damping to reduce the dynamic response of structures. However, the VE material appears to be sensitive to the variations in ambient temperature and vibration frequency. To minimize these effects, a new VE material has been developed. This new material shows less sensitivity to variations in vibration frequency and temperature. However, it is highly dependent on the shear strain. Experimental studies on the seismic behavior of a 2/5 scale five-story steel frame with these new VE dampers have been carried out. Test results show that the structural response can be effectively reduced due to the added stiffness and damping provided by the new type of VE dampers under both mild and strong earthquake ground motions. In addition, analytical studies have been carried out to describe the strain-dependent behavior of the VE damper. The dynamic properties and hysteresis behavior of the dampers can be simulated by a simple bilinear model based on the equivalent dissipated energy principle proposed in this study.

• 오토저널
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• 제11권1호
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• pp.44-50
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• 1989

본 논문에서는 모우드 해석법(Modal Analysis Method)을 이용하여 종래 재료에 비해 우 수한 기계적 성질을 갖는 복합재료에 대하여 동특성을 규명하고자 하였다. 재료로는 알루미늄 판(AL PLATE)과 탄소섬유강화 복합적층판(CFRP)을 비교하였으며, 그 결과 전체적인 진동레 벨이 AL PLATE 보다 CFRP PLATE가 낮았고 섬유방향이 고정단고 직각인 경우보다 평행인 경우가 낮음을 알았다. 또한 AL PLATE와 유사한 진동형을 나타내는 CFRP PLATE의 고유 진동모우드가 저주파수쪽으로 이동함을 알 수 있었다.

• 대한기계학회논문집
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• 제12권4호
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• pp.675-681
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• 1988

본 연구에서는 표면감쇠처리되지 않은 구조물의 모우드특성을 아는 경우에 표 면감쇠처리에 의해서 결정되는 새로운 오무드변수를 계산하는 한 방법을 제시하고자 한다.즉, 실험적으로 측정된 점탄성물질의 동특성으로부터 표면감쇠처리되기 전의 모우드를 이용하여 표면감쇠처리된 구조물의 모우드감쇠와 고유진동수 및 주파수응답 함수를 계산한다. 이 과정을 Fig.1에 보여진, 표면감쇠처리된 네 개의 보와 하나의 집중질량으로 구성된 부정정계 구조물에 적용 서술하고자 한다.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.419-431
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• 2004

The dynamic response of a cracked functionally graded piezoelectric material (FGPM) under transient anti-plane shear mechanical and in-plane electrical loads is investigated in the present paper. It is assumed that the electroelastic material properties of the FGPM vary smoothly in the form of an exponential function along the thickness of the strip. The analysis is conducted on the basis of the unified (or natural) crack boundary condition which is related to the ellipsoidal crack parameters. By using the Laplace and Fourier transforms, the problem is reduced to the solutions of Fredholm integral equations of the second kind. Numerical results for the stress intensity factor and crack sliding displacement are presented to show the influences of the elliptic crack parameters, the electric field, FGPM gradation, crack length, and electromechanical coupling coefficient.