• Structural Engineering and Mechanics
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• v.63 no.2
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• pp.137-146
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• 2017

The size-dependent behavior of single walled carbon nanotubes (SWCNT) embedded in the elastic medium and subjected to the initial axial force is investigated using the mixed finite element method. The SWCNT is assumed to be Euler-Bernoulli beam incorporating nonlocal theory developed by Eringen. The mixed finite element model shows its great advantage of dealing with nonlocal behavior of SWCNT subjected to a concentrated load owing to the existence of two coefficients ${\alpha}_1$ and ${\alpha}_2$. This is the first numerical approach to deal with a puzzling fact of nonlocal theory with concentrated load. Numerical examples are performed to show the accuracy and efficiency of the present method. In addition, parametric study is carefully carried out to point out the influences of nonlocal effect, the elastic medium, and the initial axial force on the behavior of the carbon nanotubes.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.2
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• pp.139-143
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• 2017

Finite element analysis was performed for a split-type CFRP bicycle frame, which was designed to apply a compression molding process with carbon fiber prepreg for a conventional bicycle. An epoxy adhesive material for joining the frames was selected by the extent of stress at joint interfaces. The split-type bicycle frame was then formed and its weak parts examined by the boundary conditions according to reliability tests. The results verified the reliability of the bicycle frame after modification of these weak parts. The finished product was manufactured by using this developed split-type bicycle frame.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.478-482
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• 2010

A series of molecular dynamic (MD), finite element (FE) and ab initio simulations are carried out to establish suitable modeling schemes for the continuum-based analysis of aluminum matrix nanocomposites reinforced with carbon nanotubes (CNTs). From a comparison of the MD with FE models and inferences based on bond structures and electron distributions, we propose that the effective thickness of a CNT wall for its continuum representation should be related to the graphitic inter-planar spacing of 3.4${\AA}$. We also show that shell element representation of a CNT structure in the FE models properly simulated the carbon-carbon covalent bonding and long-range interactions in terms of the load-displacement behaviors. Estimation of the effective interfacial elastic properties by ab initio simulations showed that the in-plane interfacial bond strength is negligibly weaker than the normal counterpart due to the nature of the weak secondary bonding at the CNT-Al interface. Therefore, we suggest that a third-phase solid element representation of the CNT-Al interface in nanocomposites is not physically meaningful and that spring or bar element representation of the weak interfacial bonding would be more appropriate as in the cases of polymer matrix counterparts. The possibility of treating the interface as a simply contacted phase boundary is also discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.45-48
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• 2008

Periodic lattice structures such as the large space lattice structures and carbon nanotubes may take the extension-transverse shear-bending coupled vibrations, which can be well represented by the extended Timoshenko beam theory. In this paper, the spectrally formulated finite element model (simply, spectral element model) has been developed for extended Timoshenko beams and applied to some typical periodic lattice structures such as the armchair carbon nanotube, the periodic plane truss, and the periodic space lattice beam.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1403-1406
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• 2008

Periodic lattice structures such as the large space lattice structures and carbon nanotubes may take the extension-transverse shear-bending coupled vibrations, which can be well represented by the extended Timoshenko beam theory. In this paper, the spectrally formulated finite element model (simply, spectral element model) has been developed for extended Timoshenko beams and applied to some typical periodic lattice structures such as the armchair carbon nanotube, the periodic plane truss, and the periodic space lattice beam.

• Korean Journal of Digital Imaging in Medicine
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• v.12 no.2
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• pp.145-150
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• 2010

Thick films of carbon fiber were prepared by a heating element of plan shape made in Darin co., We have investigated surface morphology of the specimen depending on heat-treatment temperatures. Scanning electron microscope(SEM) image of carbon fiber thick films of the specimen heat treated shows a grain growth at $1200^{\circ}C$ and becomes a poly-crystallization at $1350^{\circ}C$. The variation of resistivity at the thermally annealed specimen above $600^{\circ}C$ depends on type of the substrates. It may be due to a variation of film thickness and a difference of interfacial phenomena. A heating element of features was affected significantly by skin blood and quantity of heat of the body physiological function. After radiation of farinfrared for plate heating element, the function of biometric physiological is considered of skin blood flow and calorie which greatly affects on individuals. Electromagnetic wave was not influence on the body.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.3043-3051
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• 2013

As abnormal climate phenomena frequently happen due to the after-effect of the global warming, all nations suggest climate change response policies in many different fields to prevent global warming by reducing greenhouse gas. Especially, these days, the realization that the greenhouse gas from city buildings should be decreased is growing, and it is because that buildings are accounted for a quarter of national greenhouse gas emission and it is more than half the percentage of emissions within the city. Accordingly, Korean government sees the need to take an initiating role to fulfill low-carbon green policies and promotion strategies in the public sector, and wants to facilitate greenhouse gas reduction in the private sector as well. In this background, this study tries to examine the low-carbon planning element in public buildings and figure out the amount of carbon reduction and economic analysis centering Cheongju city as case study. Lastly, we propose some suggestion for low-carbon and greening of public buildings.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.65-71
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• 2019

The development of adsorbed natural gas (ANG) has emerged as one of potential solutions. It is desirable to reduce the weight of vessel by applying light-weighed a composite carbon fiber in order to response to a egulation of $CO_2$ emission. Through understanding of a composite carbon fiber, and material characteristic of a composite carbon fiber is required in order for better application of a reduction of weight and an analysis of material characteristic. Herein, this study suggest the composite carbon fiber vessel applied to the characteristic of carbon fiber, and it decides the preliminary shape based on the test of material characteristic for ANG vessel applied to a composite carbon fiber, and its basic shape calculate through on the netting theory. Moreover, the detail shape design is analyzed by a finite element analysis, and in the stage of detail sahp design and analysis of stress was performed on the typical shape using a finite element analysis, and the result of preliminary design was verified.

• Journal of Power System Engineering
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• v.3 no.3
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• pp.76-82
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• 1999

This study presents a methodology to predict the hardenability of quenched carbon steels. The equation of transient heat conduction is analyzed to formulate a cooling curve by a finite element method which incorperates coupled effects of temperature on physical properties, the metallic structures and also the latent heat by phase transformation. The volume traction of martensite and pearlite are the structural analysis for hardenability analysis. In order to demonstrate the feasibility of adopting a full quench model respectively. This procedure could be used as the database for optimal condition of heat treatment processes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.111-118
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• 2002

In this paper, FEM analysis is performed in order to estimate the behavior of RC columns retrofitted with Carbon Fiber Sheet(CFS). Two node truss element and four node isometric plate bond element are used for modeling the CFS and the adhesion between concrete and CFS, respectively. Five specimens with different quantity of CFS are analyzed and compared with experimental results. From the comparison, analytical results show a good agreement with the test results. Therefore, it is advisable to use the FEM used in this paper to predict the behavior of columns with CFS.