• Proceedings of the KSME Conference
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• 2001.06a
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• pp.322-327
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• 2001

The internal leaks of RCS pressure boundary valves may cause thermal fatigue crack because of the TASCS in RCS branch line. After experienced unisolable piping failures in several PWR plants, many studies have peformed to understand these phenomena and various methods were applied to ensure the structural integrity of piping. In this paper, the cause of unisolable piping failures and the alternatives to prevent recurrence of failure were reviewed. Also, the severity of piping failure including susceptibility of valve leaks was evaluated for the Westinghouse 2-loop plant. The length of turbulent penetration on RHR inlet piping was measured and, thermal fluid analysis and fatigue analysis was performed for this piping. As a means of ensuring the structural integrity, temperature monitoring and specialized UT and other alternatives were compared for the further application.

• Journal of the Korea Furniture Society
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• v.13 no.1
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• pp.27-37
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• 2002

This study was investigated with the surface properties such as physical and accelerated tests of wood-based floorings. In physical test, hardness and abrasion resistance values of laminate floorings were higher than those of others. The center line average surface roughness($R_a$) of imported laminate flooring was highest value($1.34{\mu}m$) and that of imported solid wood flooring was lowest value($0.62{\mu}m$). In cold resistance and moist heat resistance, no defects were found on the surface of all flooring (crack, blistering, peeling, and gloss loss etc.) after testing. Wet-cold-dry cycle test showed that plywood flooring appeared some cracks. In accelerated weathering test, color difference increased with increasing Xenon arc light irradiation

• Journal of the speleological society of Korea
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• no.5
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• pp.37-52
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• 1997

In Japan, on the volcanic line from Mt.Fuji to Hachijou Isl. in Pacific, we can see the many fissure erupted craters. The fissure eruption hasn't always left the rift caves. Recently I am investigated this era and recognized the rift caves. at Mt. Fuji 4. Miyake Isl. 3, Hachijou Isl. 3. The time of fissure eruption in Miyake Isl. make the long crack and gush the lava flow. But. we can see the rift caves only in the caldera. In the rift caves, we can see the thin coated lava on the scoria wall of the cavity and not only the side ways to extend by gasic pressure, on the surface of the earth. It is tow type rift caves. 1) The gas run to the side direction and built the cavities and after blowout the ground. 2) The gas built the cavity and then blowout the earth. I think that the thick scoria layers the most important factor and indispensable condition to built the rift caves.

• 한국기계연구소 소보
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• s.19
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• pp.43-52
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• 1989

Material damage of Unifiner Change Heater: Tube used for nearly 20 years was evaluated and Mechanical tests such as tensile tests and creep-rupture tests were conducted to predict the residual life. After the investigation, any major damage or degradation was not found except the welded zone. Microstructural observation showed that most of delta-ferrite was transformed. to sigma-phase and consequently, the ductility was very much reduced. A KLA(Knife-Line Attack) crack with 60mm in length and 2.8mm in depth was found just near the welded zone, which is believed to be caused by intergranular corrosion. Creep-rupture tests, which are very essential to predict the residual life, showed that both used base and weld metals have similar results with the reference data.

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.29-38
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• 2001

The purpose of this paper is to evaluate the structural integrity of a reactor pressure vessel subjected to the pressurized thermal shock(PTS) during the transient events, such as main steam line break(MSLB) and small break loss of coolant accident(SBLOCA). For postulated surface or subsurface cracks, variation curves of stress intensity factor are obtained by using the three different methods, including ASME section XI code anlysis, the finite element alternating method and the finite element method. From the stress intensity factor curves, the maximum allowable nil-ductility transition temperatures(RT/NDT/) are determined by the tangent criterion and the maximum criterion for various crack configurations and two initial transient events. As a result of the analysis, it is noted that axial cracks have smaller maximum allowable RT$_{NDT}$ values than same-sized circumferential cracks for both the transient events in the case of the tangent criterion. Axial cracks have smaller RT$_{NDT}$ values than same-sized circumferential cracks for MSLB and circumferential cracks have smaller values than axial cracks for SBLOCA in the case of the maximum criterion.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.420-425
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• 2004

Lee and Kang measured side-necking deformation near a crack-tip for CT specimen using Stereoscopic Digital Speckle Photography and Digital Image Correlation. In this work the same technique was applied to SENB specimen. We happened to find that the deformation shape of the side-necking is similar to the one of plastic region estimated by McClictock using slip line theory. Based on volume constancy of plastic deformation as well as this finding, it is expected that a linear relationship holds between the volume of plastic deformation region and the one of side-necking upon the lateral surface of a specimen. To prove the idea, a preliminary study has been performed using 3-D finite element method on a model with modified boundary layer formulation. As the result, it is shown that the idea works well with acceptable error.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.31-34
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• 2006

A new continuum damage theory (CDT) has been proposed by Lee et al. (1996) based on the SEEP. The CDT has the apparent advantage over the other related theories because the complete constitutive law can be readily derived by simply replacing the virgin elastic stiffness with the effective orthotropic elastic stiffness obtained by using the proposed continuum damage theory. In this paper, the CDT is evaluated by the numerical experiment comparing the mode shapes and natural frequencies of a square plate containing a small line-through crack with those of the same plate with a damaged site replaced with the effective orthotropic elastic stiffness computed by using the CDT.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.100-101
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• 2017

LEFC(Light Emotion Friendly Conceret) was developed in Korea with demands of esthentic requirements in line with the recent developmental trend of concrete technology. The LEFC is made by inserting transparent transparent rods, and this forms a heterogeneous structure in the concrete matrix causing the LEFC substrate to crack due low adhesion between the rod and the cement. In this study, as a way to strengthen the bonding to the rod inserted in the LEFC, high strength vinylon fibers of varying mixture ratios were applied and physical properties were tested accordingly. To study the effect of different spacing of the bars on the LEFC, physical property testing was conducted on respective specimens with two different diameters (5mm, 10mm) inserted in different intervals of spacing (10mm, 15mm, and 20mm).

• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.7-11
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• 2010

Difficulties associated with full-scale pipe tests are rather obvious. That is, it is not only difficult to perform them but also very expensive and it requires lots of experience. And the process of the fracture test for the pipe specimen is very difficult and complicated. Because the pipe specimen, the test jig and the test equipment are very large and heavy, it requires lots of costs and times. In this study, to easily perform the fracture toughness test for a pipe specimen, load line displacement data was obtained using the image processing method.

• Tunnel and Underground Space
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• v.6 no.3
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• pp.239-244
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• 1996

Cracks have influence on the physical and mechanical and, more importantly, on the engineering properties of the rock. Physical properties including the volumetric deformation coefficient, electrical resistivity, seismic wave velocity, and the mechanical properties such as the elastic constants and strength of rock are affected significantly by the presence of cracks of various sizes. An experimental program was undertaken to investigate the effect of a finite line crack on the diffraction of the plane compressional wave. Horizontal and vertical components of displacement and acceleration curve were obtained using a single-source and multi-receivers system. A theoretical model from numerical analysis implementing the finite element method was compared with the measured data.