• Corrosion Science and Technology
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• v.11 no.4
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• pp.129-134
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• 2012

UT(Ultrasonic Test), one of the non-destructive tests, is the most common thickness measurement method for evaluating the wear rate in NPPs(Nuclear Power Plants). UT is used widely because it is easy and safe for use. However some amount of error inevitably occurs in attempting to measure the thickness. The error, that could make the thickness data thicker or thinner, may affect estimation of wear rate in pipes. NPPs are composed of a lot of pipes and components. Some of them are tested to check the current status during RFO(Re-Fueling Outage). Reliability analysis of UT is essential for evaluating pipe wear rate and establishing the long-term management plan in NPPs. This paper reviewed the cause of error occurrence and presented the UT data reliability analysis method. Also, this paper shows the application result of reliability analysis to the UT data acquired in NPPs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.2
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• pp.137-146
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• 2001

The non-destructive tests are widely used to predict the strength of existing structures. The purpose of the present study is to propose the prediction equations for strength evaluation of concrete structures. The present study focuses on the rebound method and ultrasonic pulse velocity method for quartzite aggregate concrete. The major test variables include the water-cement ratio and curing methods. The water-cement ratio are 0.4, 0.5, 0.6, 0.7, respectively and the curing method covers ail-dry condition and standard curing condition. The prediction equations for strength of concrete are proposed from the present test data.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1712-1714
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• 2001

This paper deals with the development and application of an inner corrosion detector for the ACSR(Aluminum Conductor Steel Reinforced) power lines. The detector runs on an ACSR power line and inspects the inner corrosion of the conductor using the technology of the nondestructive eddy current test. It is consists of an ECT sensor, signal processing units, a RF transmitter/receiver, and etc.. The experimental result through field tests shows the detector can efficiently find both the zinc and aluminum loss of ACSR power lines.

• International Journal of Safety
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• v.7 no.1
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• pp.10-14
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• 2008

For evaluating the radiation degradation of cross-linked polyethylene (XLPE) cable insulation due to the irradiated oxidation, XLPE was irradiated with ${\gamma}$-ray. For each irradiated samples, TGA, DSC, FT-IR, and tensile tests were carried out. Regarding radiation degradation, oxidative process was predominant. TGA, DSC and FT-IR can be useful tools for evaluating the radiation degradation due to the irradiated oxidation because these analyses need only small amount of samples. The results of TGA, DSC and FTIR analyses showed the similar tendency for irradiated degradation. They can be useful tools for evaluating the oxidation of insulating material by non-destructive testing.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1084-1089
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• 2009

This paper presents the example of landslide triggered by the failure of earth retaining wall. Close examinations such as visual inspections and non-destructive testings revealed that the earth retaining wall does not have enough strength to resist active earth pressure and ground water pressure. This fact is proved to be a direct initiation of landslide. Numerical studies including slope stability analyses and seepage analyses were performed with material properties obtained by geophysical explorations and laboratory tests. The results of numerical studies show that the overturning of the earth retaining wall affects the slope stability, leading to landslide consequently.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.91-98
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• 2002

Prediction for the compressive strength of concrete by non-destructive tests(NDT) has a tendency to show different outcomes according to various aggregates. The purpose of this study is to develop estimation equation by rebound number, ultrasonic velocity and combined method at concrete structures which used granite as coarse aggregates. The test variable is water/cement ratio(41.1%, 48.6%, 67.6%), curing method(moisture condition, dry condition) and age(7, 14, 28, 56). According to the test variable, new equation was suggested, and compared with the existing equations.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.1-4
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• 2001

A new non-destructive fatigue prediction model of the composite laminates is developed. The natural frequencies of fatigue-damaged laminates under extensional loading are related to the fatigue lift of the laminates by establishing the equivalent flexural stiffness reduction as a function of the elastic properties of sublaminates. The flexural stiffness is derived by relating the $90^{\circ}$-ply elastic modulus reduction, and using the laminate plate theory to the degraded elastic modulus and the intact elastic modulus of other laminate. The natural frequency reduction model, in which the dominant fatigue mode can be identified from the sensitivity scale factors of sublaminate elastic properties, provides natural frequency vs. fatigue cycle curves for the composite laminates. Vibration tests were also conducted on $[\textrm{90}_{2}\textrm{0}_{2}]_s$ carbon/epoxy laminates to verify the natural frequency reduction model. Correlations between the predictions of the model and experimental results are good.

• Computers and Concrete
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• v.15 no.5
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• pp.795-805
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• 2015

In this study, dynamic modulus of elasticity of self-consolidating rubberized concrete is evaluated by using results of ultrasonic pulse velocity and resonance frequency tests. Additionally, correlation between dynamic modulus of elasticity and compressive strength results is compared. For evaluating the dynamic modulus of elasticity of self-consolidating rubberized concrete, prismatic specimens having $100{\times}100{\times}500$ mm dimensions are prepared. Dynamic modulus of elasticity values obtained by non-destructive measurements techniques are well agreed with those given in the literature.

• Structural Engineering and Mechanics
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• v.30 no.4
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• pp.481-500
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• 2008

In this paper, a model updating technique in dynamics is used to identify elastic properties for pultruded GFRP-Glass Fiber Reinforced Plastic framed structural systems used in civil construction. Traditional identification techniques for composite materials may be expensive, while this alternative approach allows to identify several properties simultaneously, with very good precision. Furthermore, the procedure of a non-destructive type has a relatively simple implementation. Properties describing the mechanical behavior for beam and shell finite element modeling are identified. The used formulation is based on the minimization of eigensolution residuals. Important points concerning model updating procedures have been observed, such as the particular vibrational behavior of the test structure, the modeling strategies and the optimal placement of the sensors in the experimental procedure. Results obtained by experimental tests show the efficiency of the proposed procedure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1509-1521
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• 2013

Social demand for the stability of structures lead to the development of the technology to accomplish it. The non-destructive seismic technique, which is able to assess structural integrity of infrastructures, belongs to this category. Seismic technique is focused on the measurement of seismic velocity propagating through the material, and has to utilize sensors coupled to material surface, which does not allow the testing to be performed on the fly. In this paper, a general vocal microphone, which works as a non-contact sensor, was adopted to facilitate seismic testing with mobility and efficiency improved. The target of using microphones was oriented toward quality assessment of compacted subgrade, stiffness evaluation and health monitoring of concrete structures. Experimental parametric study and field applications were performed to investigate reliability and efficiency of microphones. Finally, the optimal test configuration of microphones was suggested for resonance tests and surface-wave tests.