• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.517-522
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• 2000

In the past few years, the nondestructive inspection technology has greatly developed due to the increased necessity to gain a complete understanding of the bridge behavior. Especially, the deformations of bridges contain a lot of informations about its health state. By measuring these deformations it is possible to analyze the loading and aging behavior of the structure. However, the current methods (such as LVDT, dial gage, optical displacement tranceducer, etc) are often of changeable application on site and have the limitations of installation. In this paper, the classical beam theory was reviewed and the deflections of structure are estimated using measured strain which is easy to acquire. The applicability of this algorithm is verified by a preliminary steel beam test and two types of concrete beam tests. Also fiber optic sensors as well as resistive strain gages were installed in the concrete beams to establish the applicability of fiber optic sensors in the field of civil engineering.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.739-744
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• 2000

Concrete structures generally have cracks, so for the safety and durability of structures, studies to detect cracks using nondestructive tests have been treated in great deal. In order to assure the reliability of concrete structure, microscopic fracture behavior and internal damage progress of concrete under the loading should be fully understood. The purpose of this study predicts location of initial crack and measures direction of crack propagation for on-line monitoring before the crack really grows in structures by using two-dimensional Acoustic Emission(AE) source location based on rectangular method with three-point bending test. This will allow efficient maintenance of concrete structure through monitoring of internal cracking based on AE method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1285-1287
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• 1998

Vibration measurements to monitor the condition of machinery and machine elements offers several advantages over traditional methods of nondestructive evaluation. RIST(Research Institute of Industrial Science & Technology) has established a calibration system for accelerometers that measures within a frequency range from 2Hz to 6,300Hz and a temperature range from $-40^{\circ}C$ to $180^{\circ}C$. The calibration procedures are based on the principle of the comparison method. To monitor vibration signals of machinery and machine elements, annular shear type piezoelectric accelerometers employing solid state microelectronics were fabricated. The voltage sensitivity and resonant frequency of fabricated accelerometers was 83mV/g, 23kHz, respectively. This paper discusses the method of fabrication of annular shear type piezoelectric accelerometers and the results of field tests in POSCO(Pohang Iron & Steel Co. LTD.).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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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.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.379-381
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• 1995

Many generating stations in korea are 25 years or more old, and are nearing the end of their planned life. Financial conditions and Site, Environment problems have made approval for construction of new stations increasingly difficult, and extending the life of an existing older plant may be a palatable alternative. Therefore, To determine whether generator rewinds are necessary to achieve an extended life, and Methods are required to estimate the proable remaining life of existing winding, here, We are going to estimate insolation condition through Nondestructive diagonostic test and Aging history tests of generator Stator winding and winding conditions through deterioration characteristics due to Heat cycle.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.132-137
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• 2008

A failure analysis of ammonia converter which suffered hydrogen attack in two years since its initial operating time was presented. It is constructed from 2.25 Cr.1 Mo steel. Analysis showed that the failure on closing seam weld joint was due to local improper post weld heat treatment (PWHT). Improper PWHT can introduce high residual stresses in thick-walled pressure vessel. High residual stress level in weld joint is very prone to hydrogen attack for any components which are operating in hydrogen gas environment. The repair procedures based on the principle to decrease the residual stress then proposed. The repair was controlled very carefully by applying several nondestructive tests in the each stage of repair. To assure the successful of the proposed repair, after one year since repair time, high temperature ultrasonic and TOFD methods were applied on-stream to this equipment in order to evaluate its post repair condition. The two methods showed good results on the repaired area.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.420-422
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• 2003

Aging and failure of motor insulation depend on the stresses imposed on it. The insulation life time depends on the severity of the stresses. The electrical aging by transient surge is very important to traction motor in EMU(electric multiple unit). This paper Presents the insulation characteristics of stator coil by transient surge from inverter. There are several nondestructive tests available for checking the condition of motor insulation, the probable extent of aging,. and the rate of which aging is taking pace. So the insulation characteristics of stator coil were each analyzed by measurement of leakage current, dielectric loss($tan{\delta}$), capacitance, polarization index(PI) and partial discharge. The method of diagnosis is able to analyze the aging condition and Predict the life of the traction motor in EMU.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.269-276
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• 2004

Deterioration analysis was performed on carbody and bogies of a shunting locomotive, which has been used for shunting works in steel making processes. In this investigation, various types of technical evaluation methods for the locomotive were employed to assess the current deterioration status. Corrosion test and nondestructive evaluation (NDE) techniques were employed to demonstrate the wear status of the carbody and bogie parts in the locomotive. Since the locomotive has been working under corrosive environment, the corrosion tests with x-ray analysis for exterior part of the locomotive were conducted to examine the evolution of corrosion reaction, and NDE techniques such as ultrasonic testing, magnetic particle testing, and x-ray radiography, were conducted on the carbody and bogies to inspect any possible inherent and/or in-service flaws. In this paper, the degree of deterioration in a shunting locomotive has been presented based on the analysis results.