다이폴 모델에 의한 스캔형 자기카메라 영상의 정해석

황지성(Jiseong Hwang),이진이(Jinyi Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

It is important to estimate the distribution of intensity of a magnetic field for application of magnetic method to industrial nondestructive evaluation. Magnetic camera provides the distribution of a quantitative magnetic field with homogeneous lift-off and same spatial resolution. And it is possible to interpret the distribution of the magnetic field when the dipole model is introduced. This study introduces the numerical and experimental considering of the quantitative evaluation of several size and shapes of the cracks using the magnetic field images of the magnetic camera.

Nondestructive Evaluation Using the Dipole Model and the Scan Type Magnetic Camera

Jiseong Hwang(황지성),Jinyi Lee(이진이) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11

It is important to estimate the distribution of intensity of a magnetic field for application of magnetic method to industrial nondestructive evaluation. Magnetic camera provides the distribution of a quantitative magnetic field with homogeneous lift-off and same spatial resolution. And it is possible to interpret the distribution of the magnetic field when the dipole model is introduced. This study introduces the numerical and experimental considering of the quantitative nondestructive evaluation of several size and shapes of the cracks using the magnetic field images of the scan type magnetic camera, which is used to overcome spatial limitation due to the sensor size. Furthermore, the effectiveness of the study and possibility of inverse analysis are discussed.

결함주변 자기량 변화를 이용한 자기쌍극자 모델의 개선

황지성(Jiseong Hwang),전종우(Jongwoo Jun),이진이(Jinyi Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

Nondestructive testing using a magnetic field is useful for detect a crack on the ferromagnetic material. The magnetic field distribution has to be obtained for evaluate a crack direction, size and shape quantitatively. Also, the crack could be evaluated by using inverse problem analysis. Conversely, an analysis method using a dipole model has analyzed the magnetic field distribution around a crack with higher speed than finite element method (FEM). Therefore a dipole model simulation could propose the useful information which is used for the inverse problem analysis. However the magnetic charge per unit area, m and the permeability, μ have been treated as constants up to now. Correspondingly, the analyzed results were different with the experimental results at a lot of cases. This paper proposes the improved dipole model simulation method, which is assumed that m is given more weight at the edge line of crack. The propriety of the improved method is verified by comparing with magnetic camera experiment results.

초고속 자기카메라에 의한 고속철도차륜 표면의 자기영상

황지성(Jiseong Hwang),이진이(Jinyi Lee),권석진(Sukjin Kwon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

Wheels are essential important parts of an express train supporting the weight of the high-speed train. Also, the 1000 wheels of each train have to be tested within 1 hour due to the limited available time for testing and repair in the maintenance factory. Correspondingly, a new and unique NOT system able to (a) detect cracks within a short time and (b) provide a high crack-detection ability irrespective of the state of materials is essential. In this paper, we propose a scan-type magnetic camera to satisfy this need. We use a linearly integrated, Hall sensor arrays (LIHaS) as a magnetic sensor to achieve high-speed testing. We use a small, yoke-type magnetizer as the magnetic source of a magnetic camera to achieve high crack-detection ability. Examining the cracks on a wheel model specimen with 30㎞/h speed allows us to verify the proposed method.

영상처리에 의한 자기카메라의 결함검출능 향상에 관한 연구

이진이(Jinyi Lee),황지성(Jiseong Hwang) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

The quantitative magnetic field around crack and its processed results could be obtained by using magnetic camera, and the crack could be inspected and evaluated quantitatively. In addition, the magnetic camera has to uphold with large lift-off to protect sensors from weak environment such as high temperature and mechanical vibration. However, the sensor sensitivity would be decreased when the lift-off was increased. Correspondingly, the improved techniques such as introducing a magnetic lens, increasing a S/N ratio, improving the ground method, developing an exclusive AD converter, and using a low-pass-filter, for increasing sensitivity of magnetic camera and probability of crack detection, have been studied. However, the unspecified noise from the signal lines could not be excluded exactly, and could be confused noise with small crack. This paper proposes a magnetic field image processing algorithm which could minimize or ignore the unspecified noise.

고속철도 차륜 비파괴검사를 위한 신호처리부의 개선

이진이(Jinyi Lee),황지성(Jiseong Hwang),권석진(Sukjin Kwon) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

A novel nondestructive testing (NDT) system, which is able to detect a crack with high speed and high spatial resolution, is urgently required for inspecting small cracks on express train wheels. This paper proposes an improved signal processing circuit of a scan-type magnetic camera, which uses the multiple amplifying circuits and the crack indicating pulse output system. The LIHaS is arrayed in parallel, and the Hall voltages from each sensor in the scanning direction are obtained and amplified. High-speed NDT can be achieved by using the exclusive analog-digital converter and micro-processor because the ∂ V<SUB>H</SUB>/∂ x value, which provides the most important crack information, can be obtained by buffering and calculating. The effectiveness of the novel method was verified by examine using cracks on the wheel specimen model.

홀센서를 이용한 상자성체의 비파괴검사

전종우(Jongwoo Jun),황지성(Jiseong Hwang),이진이(Jinyi Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

The cracks on the paramagnetic materials such as aluminum alloy and stainless steel, which arc used in the aircraft and the nuclear plants. could not be detected by using a static magnetic source. This paper proposes a magnetic source of scan type magnetic camera for detect a crack on the paramagnetic material by using the induced sheet type current. The sheet type AC current could be induced by using a primary coil and core. And the copper film, which includes a sheet type current, is positioned on the specimen. The eddy currents are induced around a crack on the specimen because the secondary sheet type current could be induced on the specimen surface, The signal process electrical circuits, which synchronize a Hall sensor output with an eddy current frequency, are developed and discussed. Also the propriety is verified by detect the cracks, which arc introduced on the aluminum alloy.

자기쌍극자 모델을 이용한 수치해석 소프트웨어의 개발

이진이(Jiuyi Lee),이세훈(Sehoon Lee),황지성(Jiseong Hwang),전종우(Jongwoo Jun) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This paper reports a development of numerical analysis software, which could analyze magnetic field around cracks by using an improved dipole model. The preprocessor includes crack forming software, and the magnetic charge per unit area, m could be distributed on the crack section area. Also lift-off, measurement area and sensor interval, magnetization direction could be considered in the preprocessor. Also, postprocessor provides the results presenting functions, such as natural magnetic field distribution and ∂B/∂x, ∂B/∂y. Also, the physical characteristics of magnetic optical sensor and Hall sensor are included in the postprocessor, and the magnetic field distribution could be changed optical intensity and electrical signal distribution. The experiment results, which are obtained by using magnetic camera and the magnetic optical nondestructive inspection system on the crack, are compared with analysis results by using dipole model analysis software.

비파괴검사용 자기카메라의 자원 및 자기렌즈의 3차원 시뮬레이션

황지성,이진이,최세호 한국비파괴검사학회 2004 학술대회 논문집 Vol.- No.-

It is important to estimate the distribution of intensity of a magnetic field for application of magnetic method to industrial nondestructive evaluation. Magnetic camera provides the distribution of a quantitative magnetic field with homogeneous lift-off and same spatial resolution, Leakage magnetic flux near the crack on the specimen could be amplified by magnetic fluid. This study introduces the 3-dimensional simulations consideration of the magnetic resource and the effects of lens for concentrating of magnetic flux.