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.

Nondestructive Evaluation for Mechanical Degradation of Ultrasuper-Critical Heat-Resistance Steel by Reversible Permeability

SeongBin Ahn(안성빈),JaeJin Kim(김재진),DongMin Seo(서동민),ChungSeok Kim(김정석) 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.6

Nondestructive evaluation for mechanical degradation of ultrasuper-critical (USC) heat-resistance steel, which is attractive to the next generation of power plants is studied by magnetic reversible permeability. The interrelationship between reversible permeability and high-temperature mechanical degradation has been investigated by precise measurement of permeability nondestructively. Also, the effects of microstructural variation on reversible permeability are discussed. Isothermal aging was observed to coarsen the tempered carbides (Cr23C6), generated the intermetallic phases (Fe₂W), and grow rapidly during aging. The dislocation density also decreases steeply within lath interior. The peak to peak interval (PPI) of reversible permeability profile decreased drastically during the initial 500 h aging period, and was thereafter observed to decrease only slightly. The variation in PPI is closely related to the decrease in the number of pinning sites and the degradation in tensile strength.

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 for Remanent Life of 1Cr-0.5Mo Steel by Reversible Permeability

Kwon-sang Ryu,Yun Hee Lee,Jong Seo Park,Bong Baek 한국자기학회 2012 Journal of Magnetics Vol.17 No.3

Peak interval for reversible permeability is presented for nondestructively evaluating the remanent life of 1Cr-0.5Mo steel. The method to measure the peak interval of reversible permeability is based on the value of reversible permeability is the same as the differential value of the hysteresis loop. The measurement principle is based on the first harmonics voltage induced in a sensing coil using a lock-in amplifier tuned to a frequency of the exciting voltage. Results obtained for the peak interval of reversible permeability and Rockwell hardness on the aged samples decrease as aging time and the Larson-Miller parameter increase. We could estimate the remanent life of 1Cr-0.5Mo steel by using the relationship between the peak interval of reversible permeability and the Larson-Miller parameter, nondestructively.

Magnetic dipole model in an eddy current flow detection for a Nondestructive evaluation

Han, S.G.,Kim, J.Y.,Kang, J.H. The Korean Superconductivity Society 1999 Progress in superconductivity Vol.1 No.1

A SQUID magnetometer or a SQUID gradiometer can be used to measure the field or gradient distribution respectively. We describe the magnetic dipole model of the eddy current for the nondestructive evaluation. Such a theoretical calculation of the magnetic dipole field produced by a deep flaw in matalic materials can be used for aerospace and transportation fields.

충격반향기법을 이용한 깊은 기초의 건전도 평가(수치해석)

김동수,박연홍 한국지반공학회 1999 한국지반공학회논문집 Vol.15 No.2

근래에 들어 구조물의 대형화에 따라 현장타설 말뚝을 하부 구조물로서 광범위하게 적용하고 있다. 그러나 현장타설 말뚝에 결함이 생기면 상부 하중에 대한 지지력 저하와 함께 침하량이 증가하게 되어 상부 구조물에 치명적인 손실을 초래할 수 있다. 따라서 비파괴시험 기법에 의한 콘크리트 말뚝의 효과적인 건전도 평가기법 개발이 중요하게 대두되고 있다. 본 연구에서는 수치해석을 통하여 콘크리트 말뚝의 건전도 평가에 이용되는 충격반향기법의 적용성을 검토하였다. 3차원 축대칭 유한요소법을 이용하여 건전한 말뚝과 현장타설 말뚝의 전형적인 결함인 병목, 공동, 불량 콘크리트를 포함하는 말뚝, 그리고 지반 및 암반위에 놓인 말뚝에 관한 해석을 수행하였다. 해석결과 현장타설 말뚝에 적용되는 충격반향기법의 적용성 평가에 있어서 유한요소법이 효과적임을 알 수 있었다. These days we broadly apply drilled shafts for deep foundations to build infrastructures. The defects of the deep foundations cause the decrease of their support load capacity and the increase of settlement, and the subsequent damage of the super-structures. In consequence, non-destructive testings techniques of concrete piles are important for their integrity evaluation. To improve understanding and reliable application of the impact echo method for the integrity evaluation of the drilled concrete piles, numerical studies of the impact response of concrete piles by using axi-symmetric three-dimensional finite element method are peformed for (a) sound piles: (b) piles containing necks, voids and layers of low-quality concrete: and (c) piles in soil and/or above rock. The results of these studies show that the finite element method is effective for evaluating the impact response of drilled concrete piles.

A Review: Mechanical and Interfacial Properties of Composites after Diverse Types of Aging Using Micromechanical Evaluation

신평수,Jong-Hyun Kim,Ha-Seung Park,백영민,이상일,K. Lawrence DeVries,박종만 한국섬유공학회 2020 Fibers and polymers Vol.21 No.2

Composites has been an area of active research for the past several decades due to their lightweight and good mechanical properties. However, the aging of fiber reinforced composites is a major issue due to exposure of thermal, waterand ultraviolet conditions. Continuous damage could bring about mechanical property degradation and damage at the interface. This is a comprehensive review on of aging effects in water, heat, ultraviolet etc. on composites and the changes in chemical, mechanical and interfacial properties, evaluated by nondestructive and micro-mechanic evaluations. It focuses particularly on composites with superior chemical, mechanical and interfacial properties, as well as good high resistance to aging, as these are considered to be important Structural materials. Types of composites and aging effects of aged composite by exposure to water, heat and ultraviolet radiation are explored. Based on these nondestructive and micro-mechanical evaluations methods are suggested to reduce the diverse ageing effects.

Multiple crack evaluation on concrete using a line laser thermography scanning system

Jang, Keunyoung,An, Yun-Kyu Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.22 No.2

This paper proposes a line laser thermography scanning (LLTS) system for multiple crack evaluation on a concrete structure, as the core technology for unmanned aerial vehicle-mounted crack inspection. The LLTS system consists of a line shape continuous-wave laser source, an infrared (IR) camera, a control computer and a scanning jig. The line laser generates thermal waves on a target concrete structure, and the IR camera simultaneously measures the corresponding thermal responses. By spatially scanning the LLTS system along a target concrete structure, multiple cracks even in a large scale concrete structure can be effectively visualized and evaluated. Since raw IR data obtained by scanning the LLTS system, however, includes timely- and spatially-varying IR images due to the limited field of view (FOV) of the LLTS system, a novel time-spatial-integrated (TSI) coordinate transform algorithm is developed for precise crack evaluation in a static condition. The proposed system has the following technical advantages: (1) the thermal wave propagation is effectively induced on a concrete structure with low thermal conductivity of approximately 0.8 W/m K; (2) the limited FOV issues can be solved by the TSI coordinate transform; and (3) multiple cracks are able to be visualized and evaluated by normalizing the responses based on phase mapping and spatial derivative processes. The proposed LLTS system is experimentally validated using a concrete specimen with various cracks. The experimental results reveal that the LLTS system successfully visualizes and evaluates multiple cracks without false alarms.

Multiple crack evaluation on concrete using a line laser thermography scanning system

Keunyoung Jang,Yun-Kyu An 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.2

This paper proposes a line laser thermography scanning (LLTS) system for multiple crack evaluation on a concrete structure, as the core technology for unmanned aerial vehicle-mounted crack inspection. The LLTS system consists of a line shape continuous-wave laser source, an infrared (IR) camera, a control computer and a scanning jig. The line laser generates thermal waves on a target concrete structure, and the IR camera simultaneously measures the corresponding thermal responses. By spatially scanning the LLTS system along a target concrete structure, multiple cracks even in a large scale concrete structure can be effectively visualized and evaluated. Since raw IR data obtained by scanning the LLTS system, however, includes timely- and spatially-varying IR images due to the limited field of view (FOV) of the LLTS system, a novel time-spatial-integrated (TSI) coordinate transform algorithm is developed for precise crack evaluation in a static condition. The proposed system has the following technical advantages: (1) the thermal wave propagation is effectively induced on a concrete structure with low thermal conductivity of approximately 0.8 W/m K; (2) the limited FOV issues can be solved by the TSI coordinate transform; and (3) multiple cracks are able to be visualized and evaluated by normalizing the responses based on phase mapping and spatial derivative processes. The proposed LLTS system is experimentally validated using a concrete specimen with various cracks. The experimental results reveal that the LLTS system successfully visualizes and evaluates multiple cracks without false alarms.

Laser Lock-in Thermal Wave Imaging for Nondestructive Evaluation

An, Yun-Kyu,Sohn, Hoon,Kim, Ji Min The Korean Society for Nondestructive Testing 2013 한국비파괴검사학회지 Vol.33 No.4

This paper presents a new laser lock-in thermography (LLT) technique for nondestructive evaluation. LLT utilizes a modulated continuous wave laser beam as a heat source to obtain high fidelity thermal wave images even at the presence of background heat disturbances. The thermal waves propagating along the surface and through-the-thickness directions of a structure are visualized using newly developed laser lock-in amplitude and phase images, enhancing the detectability of surface and subsurface defects. The LLT technique is numerically investigated and experimentally validated using thermal images obtained from a steel specimen with low emissivity.