• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.188-200
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• 2002

In this study, a pavement evaluation method is introduced by a case study of the measurement data obtained in Incheon International Airport. Based on the results obtained by both visual inspection and automobile inspection equipments, the pavement surface condition is evaluated and used for maintenance and rehabilitation strategy for pavement. In addition, the special attention was given to the back calculation and solution technique of E-modulus by FWD's deflection data in Pavement.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.2
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• pp.72-79
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• 2018

Purpose: The purpose of this study was to compare flexural strength and elastic modulus of several splinting materials dependent on water absorption. Materials and Methods: Three different materials; LightFix, G-FIX, G-aenial Universal Flo; were used in this study. Thirty rectangular bar specimens ($25{\times}2{\times}2mm$) of each materials were prepared. Fifteen specimens of each materials were stored in 100% relative humidity atmosphere, $37^{\circ}C$ for 24 hours. The other specimens were stored in distilled water, $37^{\circ}C$ for 30 days. Flexural strength and elastic modulus were calculated using Universal testing machine. One-way ANOVA and Scheffe's post hoc test at 95% level of significance were used on all test results. Results: In LightFix, flexural strength and elastic modulus were significantly decreased after aging. In G-FIX, there was no significant change in flexural strength and elastic modulus after aging. In G-aenial Universal Flo, flexural strength was significantly decreased, but elastic modulus did not change significantly. Statistical analysis reveals that flexural strength and elastic modulus increased in the order of LightFix, G-FIX, G-aenial Flo in both 24 hours and 30 days. Conclusion: It could be deduced from this study that flexural strength and elastic modulus of some resins could be changed when it aged in oral environment. Thus this should be considered when choosing a resin to perform a resin-bonded splint.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.115-128
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• 2001

본 논문에서는 반복하중이나 지진하중을 받는 지반-구조물 시스템의 설계에 필수적인 변수인 전단탄성계수와 감쇠비에 대한 연구를 국내에 존재하는 비점성토 지반에 대하여 수행하였다. 국내 퇴적토지반 및 풍화토지반에서 채취된 자연시료와 입도분포를 조정하여 제작한 시료를 포함하여 총 60개의 시료에 대하여 20kPa에서 500kPa의 구속응력 범위에서 공진주 시험을 수행하고, 이를 조립질 사질토, 실트 및 실트질 모래, 풍화토의 3개의 그룹으로 나누어 결과를 정리하였다. 저변형률 영역의 변형특성인 최대전단탄성계수와 최소감쇠비에 대하여 구속응력의 영향을 확인하였다. 최대전단탄성계수를 예측하는 경험식을 3개의 그룹별로 제안하였다. 최소감쇠비는 구속응력에 따른 분포영역을 제시하였다. 세립분이 적은 조립질 사질토의 경우, 비선형 변형특성이 구속응력의 영향을 뚜렷이 받고 있어 이를 주요한 변수로 고려하여 대표곡선과 분포영역을 제안하였다. 구속응력의 영향을 적게 받는 실트 및 실트질 모래와 풍화토는 구속응력에 관계없이 대표곡선과 분포영역을 제안하였다. 제안된 각 시료의 대표곡선과 기존의 Vucetic-Dobry와 Seed-Idriss가 제안한 곡선과 비교하였다. 본 논문의 연구결과는 국내지반의 비점성토 지반에 대한 지진해석이나 동하중을 받는 시스템의 해석시 유용하게 사용될 것으로 판단된다.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.1-12
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• 2000

단층에 근접한 지진동에 대하여 성능이 저하되는 단자유도계의 변위응답에 대하여 연구하였다 5% 의 감쇠비를 갖는 세단계의 성능저하시스템을 5개의 단층에 근접한 지진동에 대하여 해석하였다 해석결과로부터 성능저하시스템의 비탄성 변위응답은 비저하시스템에 비하여 큰 값을 나타냄을 알 수 있었다 또한 성능저하 특성이 증가할수록 변위응답은 커지는 경향이 있다 이러한 변위증폭은 구조물의 고유주기 강도와 성능저하특성에 영향을 받으며 짧은 주기영역에서는 큰 값을 나타내며 긴 주기영역에서는 변위증폭이 거의 발생하지 않는다 단층에 근접한 각각의 지진동에 대한 변위증폭의 최대값은 1초 보다 작은 주기영역에서 비저하시스템의 4배 정도이다 변위증폭계수의 평균값은 짧은 주기영역에서는 2의 값을 가지면 구조물의 고유주기가 길어질수록 1에 수렴해 감을 알 수 있었다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.806-813
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• 2016

To alleviate the vibration problem or to satisfy the required criteria for manifesting the guaranteed performance of precise equipment, various vibration isolation materials or apparatus, such as viscoelastic material, air and coil spring, have been developed and applied. Among them, a wire mesh material is regarded as one of the good candidate for reducing the vibration in terms of moderate material price, easy shape machining and long life cycle without the property deterioration induced by the aging or environmental effects. In this paper, prior to wire mesh isolator design, the static and dynamic elastic modulus of wire mesh materials are extracted from the experiment by the simple shaped cylindrical specimens and their characteristics for applying to vibration isolator design are examined. The simple shaped specimens were made as considering the design parameters of a wire mesh mount; i.e. the density, wire diameter and wire mesh slope, and the sensitivity analysis were also performed from a view point of the extracted elastic modulus.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.502-502
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• 2007

A catenary system should be designed to have an uniform elasticity over a span in order to maintain the lowest possible loss of contact between a pantograph and a contact wire. A elasticity uniformity of a catenary can be regarded as a important design factor used for predicting the current collection performance for a catenary. There are a couple of formulas to calculate the degree of elasticity uniformity of a catenary according to the literature survey. The effectiveness of these formulas is reviewed by performing catenary elasticity and loss of contact analysis for various different configurations of catenary systems using a beam element based FEM program. The results reveals that these formulas are not suitable to predict the current collection performance for a catenary. Therefore, a new formula based on the standard deviation of the elasticity over a span is proposed in this study. The analysis results show that the new formula for an elasticity uniformity of a catenary is very effective in predicting the current collection performance for a catenary.

• Journal of the KSME
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• v.31 no.4
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• pp.356-363
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• 1991

선형 탄성 유한요소 응력해석과 평균응력 효과를 고려한 저주기 피로실험으로부터 결정된 피로 특성, 그리고 국부변형률 방법을 종합하여 외경에 흠이 존재하는 자긴가공된 두꺼운 압력 용기의 피로수명이 평가되었다. 직사각형의 매우 날카로운 흠에서의 응력집중계수는 타원형 홈에서의 응력집중계수의 약 두배의 값이 얻어졌으며, 고강도 압력용기강인 ASTM A723의 저주기 피 로거동에 대한 평균응력 영향은 Morrow 및 SWT 파라메타를 이용하여 충분히 고려되었다. 균열발생이 예상되는 위험한 부분인 홈의 뿌리부분에서의 국부적인 응력, 변형률이 계산되었으며 예측된 피로수명은 실험적으로 얻어진 수명과 비교했을 때 2에서 4배의 오차를 보이면서 일치 하는 결과를 얻었다.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.73-80
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• 2008

An improved method to measure the dynamic viscoelastic properties of elastomers is proposed. The method is based on the analysis of forced oscillation of a cylindrical sample loaded with inertial mass. No special equipment or instrumentation other than the ordinary vibration measurement apparatus is required. Typical measurement of the viscoelastic properties of a silicone rubber $Silastic^{(R)}$ S2 were measured over the wide frequency range from 10 Hz to 3 kHz under the action of wide region of deformation from $10^{-4}%$ to 5%. It was shown that modulus of elasticity and loss tangent fall on the single curves when the ratio of load mass to sample mass changed from 1 to 20.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.4
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• pp.162-167
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• 2005

As the properties of porous materials during the drying process relate to the atomistic defects of heterogeneous materials such as dislocation, grain, grain boundary, pore, etc., the knowledge of nano-scale analysis is needed in order to accurately analyze the drying process for porous materials. In this study, the atomic behavior of porous materials Is statically predicted by using the molecular dynamics simulation and the nano-scale material properties are computed. The elastic modulus, thermal expansion coefficient, and volumetric heat capacity numerically found from the molecular dynamics simulation are compared with those of experiment and theory and proved the accuracy.

• Composites Research
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• v.28 no.5
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• pp.260-264
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• 2015

In this paper, molecular dynamics (MD) simulation was carried to predict thermo-mechanical behaviors for carbon nanotube (CNT) reinforced epoxy composites and to analyze the trends. Total of six models having the volume fractions of CNT from 0 to 25% in epoxy were constructed. To predict thermal behaviors, temperature was increased constantly from 300 to 600 K, and the glass transition temperature ($T_g$) and coefficient of thermal expansion (CTE) analyzed using the relationship between temperature and specific volume. The elastic moduli that represented to the mechanical behaviors were also predicted by constant strain. Additionally, the effects of functionalization of CNT on mechanical behaviors of composite were analyzed. Models were constructed to represent CNTs functionalized by nitrogen doping and COOH groops, and interfacial behaviors and elastic moduli were analyzed. Results showed that the agglomerations of CNTs in epoxy cause by perturbations of thermo-mechanical behaviors, and the functionalization of CNTs improved the interfacial response as well as mechanical properties.