• Journal of the Korean Society for Nondestructive Testing
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• 제18권1호
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• pp.42-45
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• 1998

원유 또는 가스 생산을 위해 해상에 설치되는 플랜트 해양설비는 크게 jacket과 module로 나눌 수 있다. Jacket은 module을 지지하기 위한 구조물로써 jacket 본체와 pile로 구성되어 있으며, 미국용접학회(AWS)의 규정에 의해 대부분의 맞대기 완전용접 이음부(full penetration butt welds)에 대해 100% 방사선투과검사를 실시하게 되어 있다. 그러나 지금까지 방사선투과검사를 실시해 온 경험으로 미루어 볼 때 방사성에 대한 안전성, 생산공정의 영향(검사지연) 등 방사선투과검사는 많은 문제점을 가지고 있었다. 이에 대한 문제점을 해소하고, 국내의 비파괴검사 기술 향상을 위해 자동 초음파탐상 system을 개발, 방사선투과검사를 자동 초음파탐상검사로 대체하여 적용한 사례를 간략하게 기술하였다. 또한, 적용 확대를 위해 개방중인 system을 소개하고 아울러 자동 초음파탐상기술에 대한 앞으로의 방향을 제시하였다.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권4호
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• pp.486-490
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• 2013

A defect which is axially oriented with small size is hard to detect in conventional system. CMFL(Cricumferential Magnetic Flus Leakage) type PIG(Pipelines Inspection Gauge) in the NDT(Nondestructive Testing), is operated to detect this defect called axially oriented cracks in the pipe. It is necessary to decompose the size and shapes of cracks for the manintenance of underground pipelines. This article is focused on the decomposing method of the size and shape of the axially oriented cracks by using inspection signal data for defect.

• Journal of the Korean Society for Nondestructive Testing
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• 제32권6호
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• pp.678-685
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• 2012

The objective of this study is to monitor the health status of harbor caissons which have potential foundation damage. To obtain the objective, the following approaches are performed. Firstly, a structural damage monitoring(SDM) method is designed for interlocked multiple-caisson structures. The SDM method utilizes the change in modal strain energy to monitor the foundation damage in a target caisson unit. Secondly, a finite element model of a caisson system which consists of three caisson units is established to verify the feasibility of the proposed method. In the finite element simulation, the caisson units are constrained each other by shear-key connections. The health status of the caisson system against various levels of foundation damage is monitored by measuring relative modal displacements between the adjacent caissons.

• Journal of Power System Engineering
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• 제21권3호
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• pp.102-107
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• 2017

A tungsten inert gas (TIG) welding method was used for the bonding of stainless steel. TIG welding using inert gas (He or Ar gas) is a method to prevent oxidation and nitriding of materials and to combine non-ferrous metals. This method has the advantage of obtaining a smooth weld surface. In this study, the welding characteristics of 304 stainless steel welded by TIG welding method were analyzed by using nondestructive technique. Ultrasonic and Acoustic Emission (AE) was applied to evaluate the micro-damage of TIG welded 304 stainless steel. The velocity and damping coefficient of ultrasonic wave showed a slight difference in HAZ, which is the welding part of stainless steel. The AE parameters of average frequency, rise time and event were analyzed for the dynamic behavior of stainless steel during loading. Optimal AE parameters for evaluating the degree of damage to the specimen have been derived. Fractograph and metal structures of 304 stainless steel using SEM and optical microscope were discussed.

• Journal of the Korean Society for Nondestructive Testing
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• 제16권1호
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• pp.46-51
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• 1996

원자로는 압력용기 및 내부 구조물로 구분되어 있다. 내부 구조물들의 경련 열화 현상에 따라 결함이 많이 발생하여 이에 대한 초음파검사가 요구되고 있다. 따라서 원자로 내부 구조물에 대한 초음파검사 현황 및 각각 구조물들의 검사 원리를 기술하였다. 특히 원자로 내부 구조물 중 CRDM, core baffle bolt, core barrel bolt, CRGT-support pin 및 fuel alignment pin에 대한 유럽 및 독일을 중심으로 한 검사 현황 및 검사방법을 간략하게 기술하였다. 이 기술에 대한 지침안(guideline)이 독일, 프랑스, 일본을 중심으로 하여 마련되고 있다.

• Journal of the Korean Society for Nondestructive Testing
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• 제30권6호
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• pp.521-526
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• 2010

Gas transmission pipelines are often inspected and monitored using the magnetic flux leakage method. An inspection vehicle known as a "pig" is launched into the pipeline and conveyed along the pipe by the pressure of natural gas. The pig contains a magnetizer, an array of sensors and a microprocessor-based data acquisition system for logging data. This paper describes magnetic flux leakage (MFL) signal processing used for detecting mechanical damages during an in-line inspection. The overall approach employs noise removal and clustering technique. The proposed method is computationally efficient and can easily be implemented. Results are presented and verified by field tests from an application of the signal processing.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제56권5호
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• pp.876-883
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• 2007

The magnetic flux leakage(MFL) type nondestructive testing(NDT) method is widely used to detect corrosion, defects and mechanical deformation of the underground gas pipelines. The object pipeline is magnetically saturated by the magnetic system with permanent magnet and yokes. Hall sensors detect the leakage fields in the region of the defect. The defects are sometimes occurred in group. The accuracy of the detecting signals in this defect cluster become lowered because of the complexity of the defect cluster. In this paper, the effects of the multi -defects are analyzed. The detecting signals are computed by 3-dimensional finite element method and compared with real measurement. The results say that, rather than the size of the defects, the effects of the relative position of the multi-defects are very important on the detecting signals.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2218-2223
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• 2014

A crack which is axially oriented with small size is hard to detect in conventional system. CMFL(Circumferential Magnetic Flux Leakage) type PIG(Pipelines Inspection Gauge) in the NDT(Nondestructive Testing), is operated to detect this defect called axially oriented cracks in the pipe. It is necessary to decompose the size and shapes of cracks for the maintenance of underground pipelines. This article is mainly focused on the decomposing method of the size and shape of the axially oriented cracks by using inspection signal data for defect.

• Structural Monitoring and Maintenance
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• 제1권2호
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• pp.197-211
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• 2014

An investigation of tunnel linings is performed at two tunnels in the US using complimentary noncontact techniques: air-coupled ground penetrating radar (GPR), and a vehicle-mounted scanning system (SPACETEC) that combines laser, visual, and infrared thermography scanning methods. This paper shows that a combination of such techniques can maximize inspection coverage in a comprehensive and efficient manner. Since ground-truth is typically not available in public tunnel field evaluations, the noncontact techniques used are compared with two reliable in-depth contact nondestructive testing methods: ground-coupled GPR and ultrasonic tomography. The noncontact techniques are used to identify and locate the reinforcement mesh, structural steel ribs, internal layer interfaces, shallow delamination, and tile debonding. It is shown that this combination of methods can be used synergistically to provide tunnel owners with a comprehensive and efficient approach for monitoring tunnel lining conditions.

• Smart Structures and Systems
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• 제22권2호
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• pp.193-200
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• 2018

From the viewpoint of engineering applications, the prediction of the failure of bogies plays an important role in preventing the occurrence of fatigue. Fatigue is a complex phenomenon affected by many uncertainties (such as load, environment, geometrical and material properties, and so on). The key to predict fatigue damage accurately is how to quantify these uncertainties. A Bayesian model is used to account for the uncertainty of various sources when predicting fatigue damage of structural components. In spite of improvements in the design of fatigue-sensitive structures, periodic non-destructive inspections are required for components. With the help of modern nondestructive inspection techniques, the fatigue flaws can be detected for bogie structures, and fatigue reliability can be updated by using Bayesian theorem with inspection data. A practical fatigue analysis of welded bogies is utilized to testify the effectiveness of the proposed methods.