• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.617-624
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• 2002

An equation of J-integral for a penny-shaped crack at the end of the fiber embedded in rubber matrix is proposed. The values of J-integral for the specimens with various crack and specimen radius are obtained by FEA(Finite Element Analysis). The dimensional analysis is applied to derive an equation of J-integral as a nonlinear elastic energy release rate. The geometry and deformation calibration function in an equation of J can be expressed in a separated form. The geometry calibration function characterizing the effects of cord and specimen size is expressed in a polynomial form of fourth order. The deformation calibration function characterizes the effect of the overall level of strain. As approaching the infinitesimal strain, the value of the deformation calibration function approaches the results of LEFM(Linear Elastic Fracture Mechanics).

• Structural Engineering and Mechanics
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• v.82 no.3
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• pp.313-323
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• 2022

Steel laminated elastomeric bearings are commonly used in bridge structures to control displacements and rotations and transfer forces from the superstructure to the substructure. Proper knowledge of design, fabrication and erection procedures is important to ensure stability and adequate structural performance during the lifetime of the bridge. Difference in elevations sometimes leads to large size gaps between the bearing and the girder which makes the grout thickness that is commonly used for leveling deviate beyond standards. This paper investigates the structural response of High Strength Fiber Reinforced Cementitious (HSFRC) thin plinths that are used to close gaps between bearing pads and precast girders. An experimental program was developed for this purpose where HSFRC plinths of different size were cast and tested under vertical loads that simulate bridge loading in service. The structural performance of the plinths was closely monitored during testing, mainly crack propagation, vertical reaction and displacement. Analytically, the HSFRC plinth was analyzed using the beam on elastic foundation theory as the supporting elastomeric bearing pads are highly compressible. Closed form solutions were derived for induced displacement and forces and comparisons were made between analytical and experimental results. Finally, recommendations were made to facilitate the practical use of HSFRC plinths in bridge construction based on its enhanced load carrying capacity in shear and flexure.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.246-250
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• 2001

In resin transfer molding (RTM), resin is forced to flow through the fiber perform of inhomogeneous permeability. This inhomogeneity is responsible for the mismatch of resin velocity within and between the fiber tows. The capillary pressure of the fiber tows exacerbates the spatial variation of the resin velocity. The resulting microscopic perturbations of resin velocity at the flow front allow numerous air voids to form. In this study, a mathematical model was developed to predict the formation and migration of micro-voids during resin transfer molding. A transport equation was employed to account for the migration of voids between fiber tows. Incorporating the proposed model into a resin flow simulator, the volumetric content of micro-voids in the preform could be obtained during the simulation of resin impregnation.

• Journal of Nutrition and Health
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• v.26 no.9
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• pp.1085-1097
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• 1993

Recently, as korean eating habits have been westernized, the incidence of large intestinal disease, which has been recognized as western diseases until now, has been increasing. This study was conducted to find the association of fiber intake and large bowel function. This was a cross-sectional survey, the data were obtained by self-administering questionnaire and study population was adults aged more than 18 years old in Seoul(N=1200). The response rate was 81.8%. The results were summarized as followed: 1) The factors associated with bowel function was sex, habits of defecation such as regularity and frequencies of defecation, fecal form, gastrointestinal diseases, psychological scores, self-assessment of physical status, exercise and alcohol drinking. 2) The association between the amount of fiber intake and bowel function was significant. This association was still significant, when the confounders such as disease of upper digestive system and alcohol drinking were controlled.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.76-79
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• 1999

The purpose of this study is to investigate the spalling properties of high-performance concrete with the kinds of aggregates and polypropylene(below PP) fiber contents. According to the experimental results, concrete contained no PP fiber take place in the form of the surface spalling and the failure of specimens after fire test regardless of the kinds of aggregates. Concrete contained more than 0.05% of PP fiber with the kinds of aggregates does not take place the spalling. Concrete using basalt has better performance in spalling resistance that concrete using granite and limestone. It is found that residual compressive strength has 50~60% of their original strength. Although specimens after exposed at high temperature are cured at water for 28days, they do not recover their original strength.

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.13-16
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• 1998

Poly(vinyl alcohol) (PVA) gels are easily formed via physical pathway. Most PVA solutions including PVA/water solution are well known to form thermally reversible gels at low temperature but these gels showed poor mechanical properties. In order to overcome this weak point, transparent crosslinked PVA hydrogels were prepared by electron beam irradiation or by chemical process with crosslinking agents or additives. (omitted)

• Smart Structures and Systems
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• v.18 no.5
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• pp.911-930
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• 2016

The main purpose of this paper is to study the effects of initial stress, gravity, anisotropy and porosity on the propagation of shear wave (SH-waves) in a fiber-reinforced layer placed over a porous media. The frequency equations in a closed form have been derived for SH-waves by applying suitable boundary conditions. The frequency equations have been expanded and approximated up to $2^{nd}$ order of Whittaker's function. It has been observed that the SH-wave velocity decreases as width of fiber-reinforced layer increases. However, with the increase of initial stress, gravity parameter and porosity, the phase velocity increases. The results obtained are in perfect agreement with the standard results investigated by other relevant researchers.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.192-195
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• 2003

UV curing technology becomes important in various sectors of applications due to the high efficiency, environmental protection and saving energy. Above all, It is necessary to consider the formulation of glass fiber sizes in some detail to achieve this study since they are governed by the products to be made and their performance in the composites made form them. The effect of glass fiber sizes against UV curing system was investigated by the method of changing size formulation. Nanosil 700 was used in order to increase curing efficiency. Yellow effect was not observed at the 1% fiber sizer content.

• Journal of Sericultural and Entomological Science
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• v.40 no.2
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• pp.163-168
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• 1998

Hydrolysis rate and activation energy of Antheraea pernyi silk fiber treated with HCI were examined. Thermal decomposition temperature and surface morphology were also investigated by using differential scanning calorimeter and scanning electron microscope. As the concentration of hydrochloric acid and the treatment temperature increased, the hydrolysis occurred more rapidly. The activation energy of Antheraea pernyi, 74.0 kJ/mol, was higher than that of Bombyx mori, 58.1 kJ/mol. As the concentration of hydrochloric acid increases, the activation energy of Antheraea pernyi decreased from 74.0 kJ/mol to 62.0 kJ/mol. The shape of acid-resistance fraction of Antheraea pernyi became more distroyed and was transformed from fiber to powdered form with an increase of hydrolysis rate. The thermal decomposition temperature of Antheraea pernyi was 360.8$^{\circ}C$ until the hydrolysis rate was 81.8 wt%, but ti decreased to 347.0$^{\circ}C$ when the hydrolysis rate was 93.8 wt%.

• Journal of the Optical Society of Korea
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• v.3 no.2
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• pp.74-79
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• 1999

We present a simple design rule for a passive temperature-compensating optical package. We also present experimentally that a package fabricated by using the design rule compensates the temperature dependence of the resonant wavelength of an optical long period fiber grating by varying the strain inside the fiber, The package fabricated in this work consists of two pieced of brass tube, 10 mm long, and a piece of nylon rod, 45.4 mm long. It is shown that the package can compensate the temperature-induce wavelength shifts of the long period grating to a range of 6.8 pm/$^{\circ}C$, compared with 0..48 nm/$^{\circ}C$ for an uncompensated grating. The reduced strength of the fiber caused by exposure to ultraviolet limits the performance of the package to the range operating temperature form -3 $^{\circ}C$ to 7$0^{\circ}C$.