• 전기전자학회논문지
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• 제20권4호
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• pp.424-427
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• 2016

이 논문에서는 FRP(Fiber Reinforced Polymer)의 내부 결함이나 물리적 손상을 검출하기 위하여 SAR(Synthetic Aperture Radar)를 이용한 마이크로파 비파괴 검사법(Microwave Nondestructive Inspecting)을 제안한다. 전파가 다층 유전체인 FRP에 수직으로 입사되면 계면이나 횡축 균열과 같은 결함에 좋은 반응을 나타낸다. 이때 반사파로부터 계면 깊이나 결함 위치를 SAR 이미지 기법으로 결함을 형상화할 수 있다. 그 결과, SAR 시스템으로 FRP 복합 소재 내부 결함들의 종류, 크기나 위치를 효율적으로 진단할 수 있음을 확인하였다.

• 센서학회지
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• 제7권3호
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• pp.203-210
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• 1998

An experimental study of an eddy current nondestructive testing system to measure dimensions of cylindrical metallic rods, such as cross-sectional area or diameter, is presented. Impedance characteristics of a solenoid sensor, which are generally based on Maxwell's equations in electromagnetic field, are briefly discussed for inspecting geometrical parameters of the coil sensor and testing materials. A measurement system for detecting the diameter of the metallic rod is implemented. This instrument has capabilities for detecting the sensor output signals and estimating demensions of the testing material, continuously. As a result, it was shown that the eddy current sensor with an encircling coil could estimate the diameter of metallic rod. The implemented measurement system gives accurate information for inspecting the dimension of conducting rod with good sensitivity.

• 비파괴검사학회지
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• 제35권4호
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• pp.258-267
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• 2015

Eddy current testing is widely used for inspecting steam generator tubing in nuclear power plants (NPPs). The inspection technique for steam generator tubing in NPPs should be qualified in accordance with examination guidelines. When the components of a qualified system such as eddy current tester, probe, and data analysis program, are changed, the equivalency of the modified system to the originally qualified system must be verified. The eddy current tester is the most important part of an eddy current testing system because it excites and transmits alternating currents to the probe, receives coil impedance of the probe and generates signals for anomalies. The Korea Hydro & Nuclear Power Co., Ltd. (KHNP) developed an eddy current testing system with an eddy current tester and data acquisition-analysis program for inspecting the steam generator tubing in NPPs; this system can be used for an array probe and as a bobbin and rotating probes. The equivalency assessment for the currently developed system was carried out, and we describe the results in this paper.

• 비파괴검사학회지
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• 제18권1호
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• pp.27-32
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• 1998

비파괴검사를 이해하고 습득하기 위해 필수적인 실습 위주의 교육 환경을 대체할 수 있는 수단으로, 가상적인 실습 환경을 제공하는 지능형 교육 시스템을 설계하고, 이를 구현하였다. 용접부 및 다양한 제품을 검사하는데 필수적인 비파괴검사는 그 전문기술을 이해하기 위해 다양한 현장 경험을 필요로 할 뿐만 아니라, 기술지식의 지속적인 유지를 위해 반복적인 교육과 훈련을 필요로 한다. 이러한 문제를 해결하기 위해 개인용 컴퓨터를 이용하여 개별학습이 가능한 지능형 교육 시스템을 개발하였으며, 가상 실습 환경의 구축과 개별학습을 효율적으로 지원하기 위해 학습 결과를 자기진단 할 수 있는 평가 시스템의 연구가 필요하다.

• 비파괴검사학회지
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• 제26권3호
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• pp.198-205
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• 2006

The necessity of nondestructively inspecting austenitic steels, fiber-reinforced composites, and other inherently anisotropic materials has stimulated considerable interest in developing beam models for anisotropic media. The properties of slowness surface playa key role in the beam models based on the paraxial approximation. In this paper, we apply a modular multi-Gaussian beam (MMGB) model to study the effects of material anisotropy on ultrasonic beam profile. It is shown that the anisotropic effects of beam skew and excess beam divergence enter into the MMGB model through parameters defining the slope and curvature of the slowness surface. The overall beam profile is found when the quasilongitudinal(qL) beam propagates in the symmetry plane of transversely isotropic austenitic steels. Simulation results are presented to illustrate the effects of these parameters on ultrasonic beam diffraction and beam skew. The MMGB calculations are also checked by comparing the anisotropy factor and beam skew angle with other analytical solutions.

• 비파괴검사학회지
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• 제36권2호
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• pp.155-159
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• 2016

Eddy current testing (ECT) is an important nondestructive testing technology for the inspection of flaws in conductive materials. However, this widely used technology is not suitable for inspecting lamination when a conventional pancake coil is used because the eddy current (EC) generated by the pancake coil is parallel to the lamination and will not be perturbed. A new method using a rectangular coil placed vertical to the work piece is proposed for lamination detection. The vertical sections of the rectangular coil induce ECs that are vertical to the lamination and can be perturbed by the lamination. A parametric study of a rectangular coil by finite element analysis was performed in order to examine the capability of generating vertical EC.

• 센서학회지
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• 제26권1호
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• pp.39-43
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• 2017

Development of vision system as a nondestructive evaluation system can be very useful in screening the defective mechanical parts before they are assembled into the final product. Since the tens of thousands of the mechanical parts are used in an automobile carefully inspecting the quality of the mechanical parts is very important to maximize the performance of the automobile. To sort out the defective mechanical parts before they are assembled, auto parts fabrication companies employ various inspection systems. Nondestructive evaluation systems are getting rapidly popular among various inspection systems. In this study, we have developed a vision system to inspect the inside of the brake caliper, a part that is used to compose a brake which is the most important to the safety of the drivers and the passengers. In a brake caliper, a piston is pushed against the brake disk by oil pressure, causing a friction to damp the rotation of the wheel. Inside the caliper, a groove is positioned to adopt an oil seal to prevent the oil leaks. Inspecting the groove with our vision system, we could examine the existence of the contaminants which are normally the residual tiny pieces from the machining process. We used a high resolution GigE camera, 360 degree lens to look in the inside view of the caliper at once, and a special illumination system in this vision system. We used the edge detection technique to successfully detect the contaminants which were in the form of small metal chips. Labview graphical program was used to process the digital data from the camera and to display the vision and the statistics of the contaminants. We were very successful in detecting the contaminants from the various size calipers. We think we are ready to employ this vision system to the caliper production factories.

• 비파괴검사학회지
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• 제27권3호
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• pp.217-223
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• 2007

This paper introduces an active sensing node using radio-frequency (RF) telemetry. This device has brought the traditional impedance-based structural health monitoring (SHM) technique to a new paradigm. The RF active sensing node consists of a miniaturized impedance measuring device (AD5933), a microcontroller (ATmega128L), and a radio frequency (RF) transmitter (XBee). A macro-fiber composite (MFC) patch interrogates a host structure by using a self-sensing technique of the miniaturized impedance measuring device. All the process including structural interrogation, data acquisition, signal processing, and damage diagnostic is being performed at the sensor location by the microcontroller. The RF transmitter is used to communicate the current status of the host structure. The feasibility of the proposed SHM strategy is verified through an experimental study inspecting loose bolts in a bolt-jointed aluminum structure.

• 비파괴검사학회지
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• 제21권4호
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• pp.383-390
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• 2001

Long-range guided wave inspection is a new emerging technology for rapidly and globally inspecting a large area of a structure from a single test location. This paper describes a general overview of the guided wave properties and its application for long-range inspection of structures the principle and instrument system for a guided wave inspection technology called "magnetostrictive sensor (MsS)" that generates and detects guided waves electromagnetically in the material under testing, and examples of long-range guided wave inspection of structures that can be accomplished using the MsS.

• 비파괴검사학회지
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• 제27권6호
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• pp.483-500
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• 2007

Emerging sensor-based structural health monitoring (SHM) technology can play an important role in inspecting and securing the safety of aging civil infrastructure, a worldwide problem. However, implementation of SHM in civil infrastructure faces a significant challenge due to the lack of suitable sensors and reliable methods for interpreting sensor data. This paper reviews recent efforts and advances made in addressing this challenge, with example sensor hardware and software developed in the author's research center. It is proposed to integrate real-time continuous monitoring using on structure sensors for global structural integrity evaluation with targeted NDE inspection for local damage assessment.