• Geomechanics and Engineering
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• 제16권1호
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• pp.85-95
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• 2018

Water affects the mechanical properties of coal and stress wave propagation. To comprehensively investigate the effect of water content on the properties of coal, laboratory tests including X-Ray Diffraction (XRD) analysis, P-wave test, S-wave test, static and dynamic compression test with different water contents were conducted. The compressive strength, elastic modulus and failure strain and their mechanism of coal specimen under coupled static-dynamic load with the increased water content were observed. Meanwhile, energy transmission and dissipation characteristics of a stress wave in coal specimens with different water contents under dynamic load and its relation with the failure features, such as fragmentation and fractal dimension, of coal was analyzed. Furthermore, the dynamic interpretation of water infusion to prevent coal burst based on water infusion model of coal seam roadway was provided.

• 한국소음진동공학회논문집
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• 제13권12호
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• pp.918-922
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• 2003

Elastomers are extensively used in various machine design application, mainly for vibration/shock/noise control devices. However. there are still a lot of difficulties in designing the elastomeric components applied in complex shapes and under pre-deformed states. One of the most Influential factors related to mechanical properties of elastomers are pre- and dynamic strains. Consequently, a large number of experiments have to be conducted to identify dynamic properties of elastomers considering their combined effects. In this paper, we present an efficient experimental method to identify mechanical properties of elastomers considering effects of pre- and dynamic strains. This method is capable of predicting the dynamic characteristics of elastomers under arbitrary strain states from reduced experimental data.

• 대한기계학회논문집A
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• 제36권12호
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• pp.1635-1642
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• 2012

어셈블리 시스템의 동적거동을 예측하기 위해서는 그 시스템의 체결에 사용된 조인트의 동특성을 정확히 아는 것이 중요하다. 그러나 이들 체결부의 동특성은 매우 큰 산포로 인하여 해석 또는 실험적인 방법으로 동특성을 동정하기 까다로우며, 때로는 불가능 한 경우도 있다. 체결부 동특성 동정 관련 선행 연구사례는 대부분이 실험과 해석을 연계한 방법이며, 그 대상은 볼트조인트에 국한되어 있다. 본 연구에서는 힌지조인트를 대상으로 체결부의 동특성을 동정하는 간단한 방법을 제시한다. 본 연구에서 제시하는 방법의 타당성을 입증하기 위해두 개의 빔이 힌지조인트에 연결된 체결구조물을 제작하여 주파수-응답 실험을 실시하고 그 결과를 제시된 방법의 결과와 비교/검증한다. 그리고 본 연구에서 제안하는 방법을 실제 자동차에 사용되고 있는 글로브박스(Glove Box)의 힌지조인트에 적용해 보았다.

• Elastomers and Composites
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• 제45권1호
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• pp.44-50
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• 2010

기계적 혼련법으로 butadiene rubber(BR)과 대표적인 결정성고무인 chloroprene rubber(CR) 블렌드 혼련물을 제조하여, 이들의 가교 거동, 기계적 성질, 내오존성 및 동적 기계적 성질 등을 검토하였다. 내오존시험에 있어서 50 wt% CR 고무의 첨가에 의하여 크게 개선됨을 확인할 수 있었다. Rheovibron에 의한 동적 계적 특성 측정의 결과로부터 BR/CR 블렌드는 두 개의 전이를 보였으며 $tan{\delta}$ 피이크의 위치는 CR 고무의 함량이 증가함에 따라 고온 쪽으로 이동함을 확인할 수 있었다. 한편 CR 고무량이 증가할수록 최적 가황시간이 증가하는 경향을 보였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.220-221
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• 2007

Recently, imprint lithography have received significant attention due to an alternative technology for photolithography on high performance microelectronic devices. In this work, we investigated thermal stabilities and dynamic mechanical properties of dielectric materials for thermal imprint lithography. Curing behaviours, thermal stabilities, and dynamic mechanical properties of the dielectric materials cured with various curing agent and spherical filler were studied using dynamic differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), rheometer and universal test machine(UTM).

• 대한기계학회논문집A
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• 제26권7호
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• pp.1416-1425
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• 2002

In this study, the effects of combined environmental factors on mechanical and thermal analysis properties of graphite/epoxy composites were evaluated by the use of an accelerated aging test. Environmental factors such as temperature, moisture. and ultraviolet were considered. A xenon-arc lamp was utilized for ultraviolet light. and exposure times of up to 3000 hours were applied. Several types of specimens - tensile. bending, and shear specimens those are transverse to the fiber direction, and bending specimens those are parallel to the tiber direction - were used to investigate the effects of environmental factors on mechanical properties of the composites. Also, glass transition temperature, storage shear modulus, loss shear modulus, and tan ${\delta}$ were measured as a function of exposure times through a dynamic mechanical analyzer. In addition. a suitable testing method for determining the effect of environmental factors on mechanical properties is suggested by comparing the results from using two different types of strain measuring sensors. Finally, composite surfaces exposed to environmental factors were examined using a scanning electron microscope.

• Computers and Concrete
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• 제20권2호
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• pp.229-246
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• 2017

The dynamic bending response of single walled carbon nanotube reinforced composite (SWCNTRC) plates subjected to hygro-thermo-mechanical loading are investigated in this paper. The mechanical load is considered as wind pressure for dynamic bending responses of SWCNTRC plate. The dynamic version of the High Order shear deformation Theory (HSDT) for a composite plate with Matrix and SWCNTRC plate is first formulated. Distribution of fibers through the thickness of the SWCNTRC plate could be uniform or functionally graded (FG). The dynamic displacement response is predicted by using Nemarck integration method. The effective material properties of SWCNTRC are estimated by using micromechanics based modeling approach. The effect of different environmental condition, volume fraction of SWCNT, Width-to-thickness ratio, wind pressure, different SWCNTRC-FG plates, boundary condition, E1/E2 ratio, different temperature on dynamic displacement response is investigated. The dynamic displacement response is compared with the available literature and it shows good agreement.

• Elastomers and Composites
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• 제52권4호
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• pp.326-331
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• 2017

Two kinds of polyurethane elastomers were prepared and their acoustical properties underwater investigated. Their dynamic mechanical properties were measured using a dynamic mechanical analyzer. The sound speed and echo reduction in the 1-50 kHz frequency range were calculated from the data obtained using the analyzer. The sound speed, transmission and attenuation cofficient in 300-800 kHz were measured in a water-filled tank. Impedance tube experiments were performed to determine the reflective coefficient and echo reduction in the 3-8 kHz range. The polyurethane elastomer containing a hollow glass sphere showed a lower reflective coefficient and a higher echo reduction than the polyurethane elastomer without a filler.

• Elastomers and Composites
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• 제51권3호
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• pp.218-225
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• 2016

In order to examine correlation between silane coupling agent and activator which affects the physical properties of silica filled natural rubber compound, such as heat buildup, rebound property, dynamic mechanical and morphological properties were measured. With incorporation of silane coupling agent, $tan{\delta}$ at $0^{\circ}C$ was increased and at $60^{\circ}C$ was decreased, which resulted in improving of wet grip and rolling resistance. When silane coupling agent which is corresponding to 8~10% of silica was used, most favorable heat build up and $tan{\delta}$ was obtained. And also when activator was used, dispersibility of silica was improved as a result of reduction of reaggregation of silica.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.208-214
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• 2008

The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids (the Lennard-Jones fluid, water and aqueous sodium-chloride solution) confined between two plates that are separated by 1.086 nm; included in the equilibrium properties are the density distribution and the static structure, and the diffusivity in the dynamic property. Three kinds of fluids considered in this study are. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.