• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.5
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• pp.341-348
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• 2015

Active infrared thermography methods have been known to possess good fault detection capabilities for the detection of defects in materials compared to the conventional passive thermal infrared imaging techniques. However, the reliability of the technique has been under scrutiny. This paper proposes the lock-in thermography technique for the detection and estimation of artificial subsurface defect size and depth with uncertainty measurement.

• Composites Research
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• v.26 no.3
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• pp.195-200
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• 2013

This study aims to detecting and analyzing the defects of damaged carbon fiber reinforced composites after impacts, particularly focusing on barely visible impact damages. The impact test was progressed by a drop-weight machine and applied to introduce simulated damages on laminated composites used in aircrafts. Various nondestructive testing (NDT) techniques were applied to identify the defects on the specimens with different levels of impact energies. Based on the measurements data, the levels of the barely visible impacts, and the applicability and effectiveness of the detection methods were discussed. Generally, the results demonstrated that their inner damages contained bigger footprints than those on the surfaces. However, when the damage energy was low, it was found that the inner damage size could be smaller than those appeared on the surfaces.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.813-815
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• 2011

This study inspects the fault of the vehicle forming assembly and the assembly state of components at high speed and high degree of precision. This study also proposes the general inspection system capable of adapting to a number of products. The inspection program is composed of the fault inspection algorithm to examine the surface of the object and the state of the assembly and the high speed procession algorithm for the real time examination. The fault inspection algorithm is processed largely by a method using average of pixel in ROI and a method dividing the area and checking the presence of the object. Lastly, we verified the efficiency of the sysytem through the evaluation of its accuracy and processing time.

• Journal of the Korean Magnetics Society
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• v.26 no.1
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• pp.24-30
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• 2016

MFL (Magnetic flux leakage) type nondestructive testing has been used for inspection of underground gas pipelines to find metal defects by detecting magnetic leakage signal. Because the underground gas pipeline is exposed by environment such as high pressure with great humidity, external defects are easily formed on the surface of pipelines and they are being grouped respectively. These adjacent defects cause the signal distortion of leakage flux so that it is hard to estimate the shape information of defects. In this paper, we performed to study of the signal distortion and compensating method for multiple defects in MFL type nondestructive testing system by using 3D FEM simulation. This paper proposes the basic algorithm of defect signal analysis on multiple defects on the surface of 30 inch diameter pipeline.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.3
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• pp.246-252
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• 2004

Electronic speckle pattern interferometry (ESPI) for quantitative evaluation of delaminations inside of a composite material plate is described. Delaminations caused by the impact on composite materials are difficult to detect visual inspection and ultrasonic testing due to non-homeogenous structure. This paper proposes the quantitative evaluation technique of the defects made in the composite plates by impact load. Artificial defects are introduced inside of the composite plate for the development of a reliable ESPI inspection technique. Real defects produced by impact tester are inspected and compared with the results of visual inspection which shows a good agreement within 5% error.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.369-372
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• 2010

평판 디스플레이(flat panel display)의 크기가 커짐에 따라 다양한 기판을 이용한 제조 방법이 개발되고 있다. 디스플레이 제조 공정 중 기판의 결함을 찾아서 분류하는 검사 시스템은 최종 제품의 품질을 결정하는 매우 중요한 부분이다. 본 연구는 머신비전 기술을 이용하여 불투명하고 반사율이 높은 기판 표면의 결함을 찾아내고, 이 결함을 스크래치(scratch), 흑결함(dark defect), 백결함(white defect)으로 분류하는 장치를 구현하는데 목적이 있다. 이를 구현하기 위해 본 논문에서는 정밀 스테이지(stage)와 라인 카메라(line CCD camera)을 이용한 광학계를 활용하여 검사 시스템을 구현하였다. 구축된 시스템을 이용하여 취득한 이미지를 12 개의 영역으로 등분하여 각각의 국부 영역에 대한 문턱값 연산(thresholding)을 적용함으로써 조명의 불균일을 의한 검출 에러율을 획기적으로 낮추었다. 간단한 컴퓨터비전 알고리듬의 채용으로도 검사 시스템의 구현이 가능함을 보였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.451-456
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• 2000

The development of an integrated technology including fabrication of corrosion defect specimens and their practical use is needed to enhance the reliability of eddy current test for nuclear steam generator tubing. In this paper, the necessity and importance are presented from the viewpoint of the structural integrity, simulation specimens for real defects, and experiences from the destructive examination of pulled tubes. The models for several corrosion defects we also briefly introduced, with the scheme for their practical use.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.4
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• pp.20-30
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• 2001

This study represents the Nondestructive Test about impact damage of composite materials made by different lay-up patterns and degrees. For this study, they were examined by the drop test on composite materials of two type lap-up patterns with fabric and unidirectional prepreg and examined nondestructive test of those. Nondestructive methods were X-ray test with $ZnI_2$ penetrant and Ultrasonic C-scan. The defect detectability of X-ray and Ultrasonic test was compared according to defect species. And the amounts of damage on impacted zone wert compared according to impact energy on two type test specimens. At results, Ultrasonic test was more effective to detect delamination and Penetrant X-ray test was more effective to detect matrix crack and fiber fracture. There were some differences in defect shapes and grades according to lay-up patterns and degrees, and the trend appeared that matrix crack, delamination, fiber fracture occured and increasing defects sizes according to increasing impact energy.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.3
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• pp.195-201
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• 2016

Eddy current testing (ECT) is commonly applied for the inspection of automated production lines of metallic products, because it has a high inspection speed and a reasonable price. When ECT is applied for the inspection of a metallic object having an uneven target surface, such as the spline gear of a spline shaft, it is difficult to distinguish between the original signal obtained from the sensor and the signal generated by a defect because of the relatively large surface signals having similar frequency distributions. To facilitate the detection of defect signals from the spline gear, implementation of high-order filters is essential, so that the fault signals can be distinguished from the surrounding noise signals, and simultaneously, the pass-band of the filter can be adjusted according to the status of each production line and the object to be inspected. We will examine the infinite impulse filters (IIR filters) available for implementing an advanced filter for ECT, and attempt to detect the flaw signals through optimization of system design parameters for detecting the signals at the system level.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.805-807
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• 2011

In this paper, we propose a method to inspect defects of injection molded automotive parts. In order to inspect them, we developed and used a line detection algorithm and a defect analysis algorithm. The line detection algorithm defines center point of a laser line and the inspection algorithm determines the defects of automotive parts using pattern data of inspected objects and the data results from the line detection algorithm. We evaluated the accuracy and the processing time of inspection and they showed good performance.