• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.21-26
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• 2003

The reel-lay method of submarine pipelines a continuous string of pipe coiled onto a reel. Assembly of this pipe that is string is accomplished onshore by welding, and nondestructive testing is carried out prior to coiling the pipe. The total length of pipes on the reel depends on the reel and pipe diameters. Pipeline installation is accomplished by uncoiling, straightening the pipe, and laying out the pipe string onto the seabed as the barge moves forward. Installation associated with coiling and uncoiling is related to the bending moment and strain relationship of the pipeline, A highgrade pipe material is required when the reel-lay method is used. This paper is concerned with the highly plastic bending moment of the pipeline, including the effect of ovality. Moment calculation in the pipe is accomplished by the numerical method, including the variable ovalities during the plastic bending of the pipe string. The new calculation method of the high plastic bending moment was applied to the reel-lay method.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.475-478
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• 2006

In electrical impedance tomography (EIT) an array of electrodes is attached on the boundary of an object and small alternating currents are injected through these electrodes, and then the resulting voltages are measured. An estimation for the cross-sectional resistivity distribution in the object is obtained by using these current and voltage data in a nondestructive manner. In this paper, the electrical impedance imaging of two-phase flows undergoing rapid transient is considered with a special emphasis on the effect of the current pattern on the image reconstruction. The trigonometric current pattern, which is commonly used in the conventional static electrical impedance imaging, shows poor performance in case of the dynamic imaging considered in this work. Extensive numerical experiments are conducted with various kinds of current patterns and their effects on the image reconstruction performance are examined.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.129-136
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• 2001

The remaining life estimation for the aged components in power plants as well as chemical plants are very important beacuse mechanical properties of the components are degraded with time of service exposure in high temperature. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, nondestructive techniques are needed to estimate the degradation. In this study, test materials with 4 different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C$. And the DC potential drop method and destructive methods such as tensile, $K_{IC}$ and hardness tests were used in order to evaluate the degradation of 1Cr-1Mo-0.25V steels. The objective of this study is to investigate the possibility of the application of DCPD method to estimate the material degradation, and to analyse the relationship between the electrical resistivity and the degree of material degradation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.301-306
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• 2003

Spot welding is frequently used for industrial purpose, such as automobile and aerospace industries and household appliances due to its high performance. In these day, robotization and systemization of welding process made it possible to produce more precise or smaller electric parts. And when it comes to welding of steel sheet, the size of nugget must be getting smaller. Therefore, welding conditions are limited to avoid defects, such as deformation, damage, weakening of joining area. In this research, the measurement of the nugget size by the nondestructive inspection has been conducted. As a result, the right estimation of the nugget size and void defects, the detection of corona bond near joining area, the selection of the optimum ultrasonic mode, and set up for ultrasonic inspection are studied. From the trustworthy solutions of nugget size estimated by results of measurement, the optimum inspection conditions depending upon the width of welding parts are determined as well.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.415-423
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• 2001

In is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing(NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interface crack length in the adhesively bonded joints of double-cantilever beam(DCB). The optimum condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated. The experimental values are in good agreement with the computed results by boundary element method(BEM) and Riplings equation.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.103-106
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• 2000

Nondestructive tests are useful method in rapidly evaluating the condition of existing concrete structures. An objective of this work is to investigate the factors influencing the longitudinal wave velocity-strength relationship, such as w/c ratio, curing temperature, curing condition. Test results show that a change in the w/c ratio ranging from 0.46 to 0.88 and in the curing temperature from 1$0^{\circ}C$ to 3$0^{\circ}C$ did not alter the velocity-strength relationship. however, curing methods had significant effects on the velocity-strength relationship. Therefore, the estimation of compressive strength until 28 day can be accomplished by only a nonlinear equation with consideration of curing condition.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.97-102
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• 2000

It is well recognized that the ultrasonic methods is one of the most common and reliable nondestructive testing(NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam(DCB). The optimum condition of transmission coefficients in the adhesively bonded joints and it's experimental accuracy by the ultrasonic method have been investigated. The experimental values are in good agreement with the computed results by boundary element method(BEM) and Ripling's equation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.49-53
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• 2004

Thin spot welding is frequently used for industrial purpose, such as automobile and aerospace industries and household appliances due to its high performance. In these days, the systemization of welding process made it possible to produce more precise or smaller electric parts. And when it comes to welding of steel sheets, the size of nugget must be getting smaller. Therefore, welding conditions are limited to avoid defects, such as deformation, damage and weakening of joining area. In this research, thin spot welding establishes the welding conditions, and then the measurement of the nugget size by the nondestructive inspection has been conducted. As a result, the right estimation of the nugget size, the detection of corona bond near joining area, the selection of the optimum ultrasonic mode, and setup for ultrasonic inspection are studied. From the trustworthy solutions of the nugget size estimated by results of measurement, the optimum inspection conditions depending upon the width of welding parts are determined as well.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.288-290
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• 2005

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive continuous indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.65-66
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• 2018

As a result of this study, it was possible to derive the compressive strength curves of ordinary to ultra high strength concrete using the hammer type non - destructive testing equipment. In order to obtain reliable results, it is necessary to construct additional data. In addition, if reliability is ensured through construction site evaluation, it is considered that the application is possible on construction site.