High-speed angular-scan pulse-echo ultrasonic propagation imager for in situ non-destructive evaluation

Syed H. Abbas,Jung-Ryul Lee 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.2

This study examines a non-contact laser scanning-based ultrasound system, called an angular scan pulse-echo ultrasonic propagation imager (A-PE-UPI), that uses coincided laser beams for ultrasonic sensing and generation. A laser Doppler vibrometer is used for sensing, while a diode pumped solid state (DPSS) Q-switched laser is used for generation of thermoelastic waves. A high-speed raster scanning of up to 10-kHz is achieved using a galvano-motorized mirror scanner that allows for coincided sensing and for the generation beam to perform two-dimensional scanning without causing any harm to the surface under inspection. This process allows for the visualization of longitudinal wave propagation through-the-thickness. A pulse-echo ultrasonic wave propagation imaging algorithm (PE-UWPI) is used for on-the-fly damage visualization of the structure. The presented system is very effective for high-speed, localized, non-contact, and non-destructive inspection of aerospace structures. The system is tested on an aluminum honeycomb sandwich with disbonds and a carbon fiber-reinforced plastic (CFRP) honeycomb sandwich with a layer overlap. Inspection is performed at a 10-kHz scanning speed that takes 16 seconds to scan a 100 ⨯ 100 mm2 area with a scan interval of 0.25 mm. Finally, a comparison is presented between angular-scanning and a linear-scanning-based pulse-echo UPI system. The results show that the proposed system can successfully visualize defects in the inspected specimens. This study examines a non-contact laser scanning-based ultrasound system, called an angular scan pulse-echo ultrasonic propagation imager (A-PE-UPI), that uses coincided laser beams for ultrasonic sensing and generation. A laser Doppler vibrometer is used for sensing, while a diode pumped solid state (DPSS) Q-switched laser is used for generation of thermoelastic waves. A high-speed raster scanning of up to 10-kHz is achieved using a galvano-motorized mirror scanner that allows for coincided sensing and for the generation beam to perform two-dimensional scanning without causing any harm to the surface under inspection. This process allows for the visualization of longitudinal wave propagation through-the-thickness. A pulse-echo ultrasonic wave propagation imaging algorithm (PE-UWPI) is used for on-the-fly damage visualization of the structure. The presented system is very effective for high-speed, localized, non-contact, and non-destructive inspection of aerospace structures. The system is tested on an aluminum honeycomb sandwich with disbonds and a carbon fiber-reinforced plastic (CFRP) honeycomb sandwich with a layer overlap. Inspection is performed at a 10-kHz scanning speed that takes 16 seconds to scan a 100 ⨯ 100 mm2 area with a scan interval of 0.25 mm. Finally, a comparison is presented between angular-scanning and a linear-scanning-based pulse-echo UPI system. The results show that the proposed system cThis study examines a non-contact laser scanning-based ultrasound system, called an angular scan pulse-echo ultrasonic propagation imager (A-PE-UPI), that uses coincided laser beams for ultrasonic sensing and generation. A laser Doppler vibrometer is used for sensing, while a diode pumped solid state (DPSS) Q-switched laser is used for generation of thermoelastic waves. A high-speed raster scanning of up to 10-kHz is achieved using a galvano-motorized mirror scanner that allows for coincided sensing and for the generation beam to perform two-dimensional scanning without causing any harm to the surface under inspection. This process allows for the visualization of longitudinal wave propagation through-the-thickness. A pulse-echo ultrasonic wave propagation imaging algorithm (PE-UWPI) is used for on-the-fly damage visualization of the structure. The presented system is very effective for high-speed, localized, non-contact, and non-destructive inspection of aerospace structures. The system is tested on an aluminum honeycomb sandwich with disbonds and a carbon fiber-reinforced plastic (CFRP) honeycomb sandwich with a layer overlap. Inspection is performed at a 10-kHz scanning speed that takes 16 seconds to scan a 100 ⨯ 100 mm2 area with a scan interval of 0.25 mm. Finally, a comparison is presented between angular-scanning and a linear-scanning-based pulse-echo UPI system. The results show that the proposed system can successfully visualize defects in the inspected specimens.an successfully visualize defects in the inspected specimens.

초음파 펄스에코 신호의 3차원 처리

송문호,손상락,조정호,성제중,안형근,장순재 한국비파괴검사학회 2003 한국비파괴검사학회지 Vol.23 No.5

비파괴 시험을 위한 3차원 구조의 초음파 영상에는 다양한 결함을 명백하게 보여줄 수 있을 만큼 상세하고 쉽게 알아볼 수 있는 정보가 제공되어야 한다. 수년 동안 원자력 발전소에서 사용된 금속관에 발견되는 소규모의 균열은 전형적인 결함들인데, 이러한 밀리미터 이하의 균열이나 결함은 최종 3차원 영상에서 묘사되어야만 의미있는 검사가 될 것이다. 향상된 선명도와 그에 따른 결함의 발견 과정의 한 단계로써, 펄스에코(pulse-echo) 초음파를 사용한 3차원 영상제작 기술을 제안한다. 이 기술은 필요한 스캐닝과 펄스에코 데이터의 처리과정을 통한 검사로 3차원 물체의 3차원 영상을 생성하는데, 2차원 위너필터(Wiener filter)에 의해 초음파 빔을 선명하게 하는 기술을 포함한다. 제안하는 위너필터는 빔의 전달에서 펄스에코 데이터를 초음파 빔 방향의 수직방향에 따라 필터링한다. 이 3차윈 처리과정은 결함의 선명성을 증진시키고 사용자에게 3차윈 구조물의 좌우 회전 및 축 회전과 같은 조작 능력을 제공한다. 이러한 조작 능력은 3차원에서 다양한 결함들의 크기와 위치의 분명한 묘사를 가능하게 한다. Infrasonic imaging of 3-D structures for nondestructive evaluation must provide readily recognizable images with enough details to clearly show various flaws that may or may not be present. Typical flaws that need to be detected are miniature cracks, for instance, in metal pipes having aged over years of operation in nuclear power plants; and these sub-millimeter cracks or flaws must be depicted in the final 3-D image for a meaningful evaluation. As a step towards improving conspicuity and thus detection of flaws, we propose a pulse-echo ultrasonic imaging technique to generate various 3-D views of the 3-D object under evaluation through strategic scanning and processing of the pulse-echo data. We employ a 2-D Wiener filter that filters the pulse-echo data along the plane orthogonal to the beam propagation so that ultrasonic beams can be sharpened. This three-dimensional processing and display coupled with 3-D manipulation capabilities by which users are able to pan and rotate the 3-D structure improve conspicuity of flaws. Providing such manipulation operations allow a clear depiction of the size and the location of various flaws in 3-D.

비선형 고체의 응력자유 경계로부터 반사된 위상배열 집속 빔의 2차 고조파 거동

정현조 한국비파괴검사학회 2019 한국비파괴검사학회지 Vol.39 No.1

응력자유 경계면을 갖는 고체에서의 비선형 고조파 발생에서 응력자유 경계는 2차 고조파 발생을 파괴적으로 변화시키므로 펄스-에코법은 실제로 사용될 수 없었다. 집속 빔은 종종 펄스-에코 모드에서 유체의 비선형 및 생체 역학적 이미징에 사용되었다. 본 논문에서는 선형 위상배열 탐촉자의 집속 빔을 이용하여 펄스-에코 모드에서 응력자유 경계면을 갖는 비선형 고체에서 2차 고조파의 생성을 크게 개선할 수 있음을 보였다. 응력자유 및 강체 경계에 집속된 후에 반사되는 기본파 및 2차 고조파의 빔 음장을 계산하였고 그 속성을 수신 평균 음장을 통하여 관찰하였다. 경계면으로부터 반사된 후에 얻게 되는 두 개의 2차 고조파 성분, 즉 최초 전파 과정에서 발생한 후 반사된 2차 고조파와 반사된 기본파의 역방향 전파 과정에서 새롭게 생성된 2차 고조파, 사이의 위상차를 분석하였으며, 시뮬레이션 결과에서 관찰되는 2차 고조파의 생성을 이 두 성분의 위상차를 이용하여 설명하였다. In nonlinear acoustic harmonic generation in solids with stress-free boundaries, such a boundary is known to destructively change the second harmonic generation, and the pulse-echo method was not practically applicable. Focused beams have often been used for fluid nonlinearity and biomechanical imaging in pulse-echo test setups. This paper considers the focused beam fields of linear phased array transducers to ensure that pulse-echo harmonic generation can be applied to solids with stress-free boundaries. The fundamental and second harmonic beam fields that are focused at and reflected from the stress-free and rigid boundaries are calculated and their properties are investigated in terms of the received average fields. The phase difference between the two second harmonic components after reflection from the boundary, i.e., the reflected and newly generated second harmonics, is emphasized. The phase difference is used to explain the improved and accumulated second harmonic observed in the simulation results.

High-speed angular-scan pulse-echo ultrasonic propagation imager for in situ non-destructive evaluation

Abbas, Syed H.,Lee, Jung-Ryul Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.22 No.2

This study examines a non-contact laser scanning-based ultrasound system, called an angular scan pulse-echo ultrasonic propagation imager (A-PE-UPI), that uses coincided laser beams for ultrasonic sensing and generation. A laser Doppler vibrometer is used for sensing, while a diode pumped solid state (DPSS) Q-switched laser is used for generation of thermoelastic waves. A high-speed raster scanning of up to 10-kHz is achieved using a galvano-motorized mirror scanner that allows for coincided sensing and for the generation beam to perform two-dimensional scanning without causing any harm to the surface under inspection. This process allows for the visualization of longitudinal wave propagation through-the-thickness. A pulse-echo ultrasonic wave propagation imaging algorithm (PE-UWPI) is used for on-the-fly damage visualization of the structure. The presented system is very effective for high-speed, localized, non-contact, and non-destructive inspection of aerospace structures. The system is tested on an aluminum honeycomb sandwich with disbonds and a carbon fiber-reinforced plastic (CFRP) honeycomb sandwich with a layer overlap. Inspection is performed at a 10-kHz scanning speed that takes 16 seconds to scan a $100{\times}100mm^2$ area with a scan interval of 0.25 mm. Finally, a comparison is presented between angular-scanning and a linear-scanning-based pulse-echo UPI system. The results show that the proposed system can successfully visualize defects in the inspected specimens.

환경특성에 따른 집박쥐의 반향정위(Echolocation) 시그널 분석

정철운 ( Chul Un Chung ),한상훈 ( Sang Hoon Han ),김성철 ( Sung Chul Kim ),이정일 ( Chong Il Lee ) 한국환경생태학회 2009 한국환경생태학회지 Vol.23 No.6

환경특성에 따른 집박쥐(Pipistrellus abramus)의 반향정위 변화를 분석하기 위하여 2009년 4월부터 8월까지 경상북도 경주시 천북면 일원의 주간 휴식장소를 대상으로 실시하였다. 환경특성 유형은 일몰 후 출현순간, 출현 후 이동, 논 경작지, 산림 가장자리, 개방공간, 주택단지 등 6개 유형으로 구분하여 비교하였다. 분석결과 환경특성에 따른 차이 및 서식지간 이동과 먹이포획을 위한 비행 사이에서는 차이가 있는 것으로 나타났다. 외부 환경으로의 출현 순간에서는 짧은 시간의 FM 시그널만 확인되었으며, 개방 공간에서는 긴 시간의 CF 시그널 형태의 음을 이용하는 것으로 나타났다. 그 외 환경특성에서는 펄스의 형태적인 차이는 있었지만 FM과 CF 시그널을 혼합하여 이용하는 것으로 확인되었다. 먹이포획을 위한 비행과 서식지간 이동을 위한 비행에서는 펄스의 지속시간을 제외한 펄스 간격, 최고 진동수, 개시부와 종결부 진동수에서는 두 가지 비행패턴 사이에서 유의적인 차이가 확인되었다. 출현순간을 제외하고 서식지간 이동을 위한 비행시에는 곤충의 반향을 감지하여 곤충의 탐색에 적합한 협대역의 FM 시그널과 긴 펄스 지속시간을 가지는 형태를 보였으며, 먹이포획을 위한 비행에서는 폭넓은 탐색과 정확한 위치파악을 위한 광대역의 FM 시그널과 짧은 시간의 펄스 지속시간을 갖는 것으로 확인되었다. This study was conducted to analyze the changes in the echolocation of Pipistrellus abramus according to environmental characteristics. The survey was conducted in the day-roosting site of P. abramus located in Gyeongju City (North Gyeongsang Province) from April to August, 2009. The environmental characteristics during the research were classified in six categories: the emergence time after sunset moving time from day roost to feeding areas; rice fields; forest edges; open spaces; and residential areas. Analysis results showed that there are differences in environmental characteristics and also differences between the moving time to the habitat and the moving time to capture preys. At the emergence time from day roost, Pipistrellus abramus used a FM signal with a short pulse-duration. In open spaces, however, they used a CF signal with a long pulse-duration. In different environmental situations, they used both FM and CF signals, although the types of pulse which they used were different. Except pulse-duration, there were significant differences in pulse-interval, peak-frequency, starting-frequency and ending-frequency between the movement among habitats and the movement to capture preys. Except the emergence time from day-roost, they showed a narrow band FM signal and a long pulse-duration that are suitable to search for insects by sensing echoes of insects when they moved among their habitats. When they were out to capture their preys, they showed a broad band FM signal and a short pulse-duration which enabled them to widely search and accurately locate their preys.

전영역 펄스-에코 초음파전파영상화 시스템의 CN-235의 도색된 샌드위치 조종면 In-situ 비파괴평가 기술

홍승찬 ( Seung-chan Hong ),이정률 ( Jung-ryul Lee ),박종운 ( Jongwoon Park ) 한국복합재료학회 2016 Composites research Vol.29 No.5

본 연구에서는 전영역 초음파전파영상화 시스템이라 불리는 새로운 초음파전파영상화 장치를 소개한다. 본 시스템은 비파괴적으로 구조를 2 축 선형 이동 스테이지 기반으로 검사한다. 일치된 초음파 센싱과 가진 레이저 빔이 구조를 스캔하며 동시에 펄스-에코 모드 레이저 초음파를 수집한다. 이 과정은 스캔영역만큼 큰 두께 방향의 전영역 초음파를 생성하는 것을 가능하도록 한다. 본 시스템을 사용하여 실제로 운용 중인 알루미늄 허니콤구조 기반의 CN-235의 도색된 샌드위치 조종면를 검사 및 평가하고 구조 검사 결과로써 전영역 초음파전파 영상을 소개하였으며 기존 초음파 탐상 기법의 결과와 비교하여 성능 및 민감도를 검증하였다. In this paper, a novel ultrasonic propagation imaging system, called a full-field pulse-echo ultrasonic propagation imaging (FF PE UPI) system is introduced. The system nondestructively inspected targets with two-axis translation stage. The coincident laser beams for ultrasonic sensing and generation are scanned and pulse-echo mode laser ultrasounds are captured. This procedure makes it possible to generate full-field ultrasound in through-thethickness direction as large as the scan area. Structural inspection results in the form of full-field ultrasonic wave propagation videos are introduced, which are painted sandwich control surfaces. In addition, the inspection results of FF PE UPI system are compared with conventional ultrasonic testing methods such as waterjet and portable C-scan.

다중 반사파 중첩 자료의 상호상관을 이용한 엔지니어링 플라스틱 코어의 초음파속도 측정

이상규 ( Sang Kyu Lee ),이태종 ( Tae Jong Lee ),김형찬 ( Hyoung Chan Kim ) 한국지구물리·물리탐사학회 2013 지구물리와 물리탐사 Vol.16 No.3

여러 가지 초음파 속도 측정법 중 비교적 정확하고 다양한 목적에 활용될 수 있다고 알려진 반사파 중첩법(pulse-echo-overlap method)에 의해 초음파의 전파시간을 자동으로 측정할 수 있는 시스템을 구축하고, 엔지니어링 플라스틱 시험편에 대한 초음파 속도를 초동발췌법(first arrival picking method)과 비교하였다. 다섯 가지 종류의 엔지니어링 플라스틱 코어에 대해 반사파 중첩법과 초동발췌법에 의해 초음파 속도를 측정한 결과, 반사파 중첩법은 초동발췌법보다 최소4배로 긴 다중반사파 자료가 필요하므로 매질의 감쇠특성에 의해 측정가능한 시험편의 길이에 제약이 있다. 또한 측정되는 속도는 초동발췌법에 의한 속도보다 낮게 측정되는 경향을 보였으며, 수신된 파형을 분석한 결과, 이는 전파거리가 길어짐에 따른 매질의 감쇠 및 분산특성에 의한 영향으로 해석되었다. 상호상관을 이용하여 제1반사파가 제2반사파 및 제3반사파와 가장 잘 중첩되는 시간을 실시간으로 자동으로 발췌하도록 프로그램하여 실험자에 의한 측정 편차가 개입될가능성을 배제함으로써 반복성과 재현성을 높였다. 또한, 실험의 조건이 변하지 않는 경우는 중합수를 늘림으로서 무작위잡음에 의한 측정오차를 줄일 수 있으며, 실험 조건이 변하는 경우는 속도변화 모니터링에도 활용이 가능하다. An automated ultrasonic velocity measurement system adopting pulse-echo-overlap (PEO) method has been constructed, which is known to be a precise and versatile method. It has been applied to velocity measurements for 5kinds of engineering plastic cores and compared to first arrival picking (FAP) method. Because it needs multiple reflected waves and waves travel at least 4 times longer than FAP, PEO has basic restriction on sample length measurable. Velocities measured by PEO showed slightly lower than that by FAP, which comes from damping and diffusive characteristics of the samples as the wave travels longer distance in PEO. PEO, however, can measure velocities automatically by cross-correlating the first echo to the second or third echo, so that it can exclude the operator-oriented errors. Once measurable, PEO shows essentially higher repeatability and reproducibility than FAP. PEO system can diminish random noises by stacking multiple measurements. If it changes the experimental conditions such as temperature, saturation and so forth, the automated PEO system in this study can be applied to monitoring the velocity changes with respect to the parameter changes.

Corrosion visualization under organic coating using laser ultrasonic propagation imaging

Jung-Ryul Lee,An Seob Shin,Jin Hwan Park,Hee-Soo Lee,Yunshil Choi 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.2

Protective coatings are most widely used anticorrosive structures for steel structures. The corrosion under the coating damages the host material, but this damage is completely hidden. Therefore, a field-applicable under-coating-corrosion visualization method has been desired for a long time. Laser ultrasonic technology has been studied in various fields as an in situ nondestructive inspection method. In this study, a comparative analysis was carried out between a guided-wave ultrasonic propagation imager (UPI) and pulse-echo UPI, which have the potential to be used in the field of under-coating-corrosion management. Both guided-wave UPI and pulse-echo UPI were able to successfully visualize the corrosion. Regarding the field application, the guided-wave UPI performing Q-switch laser scanning and piezoelectric sensing by magnetic attachment exhibited advantages owing to the larger distance and incident angle in the laser measurement than those of the pulse-echo UPI. Regarding the corrosion visualization methods, the combination of adjacent wave subtraction and variable time window amplitude mapping (VTWAM) provided acceptable results for the guided-wave UPI, while VTWAM was sufficient for the pule-echo UPI. In addition, the capability of multiple sensing in a single channel of the guided-wave UPI could improve the field applicability as well as the relatively smaller size of the system. Thus, we propose a guided-wave UPI as a tool for undercoating- corrosion management.

FEM 시뮬레이션을 이용한 FZP 집속 빔 생성에 관한 연구

신효정(Hyojeong Shin),조성종(Sungjong Cho),정현조(Hyunjo Jeong),최성호(Sungho Choi) 한국비파괴검사학회 2020 한국비파괴검사학회지 Vol.40 No.2

고체 재료의 비선형 파라미터 측정에서 펄스-에코법으로 단일 평면형 탐촉자를 사용하는 경우 응력 자유 경계면에서 반사 전, 후에 생성된 제2고조파는 위상 차에 의해 서로 상쇄되어 측정이 어렵다. 그러나, 집속 빔을 이용하면 제2고조파의 진폭을 증가 시킬 수 있음이 이전의 연구에서 보고된 바 있다. 본 논문에서는 펄스-에코 모드에서 비선형 파라미터 측정을 위해 고체 시편 내부에 집속 빔을 생성하기 위한 연구를 수행하였다. 프레넬 존 플레이트 원리를 이용해 평면을 갖는 고체 시편에 집속 빔을 생성하고 이를 비선형 파라미터 측정에 적용하기 위하여 이론해석 및 시뮬레이션을 수행하였다. 해석 결과에 따르면 고체 시편 내부에 집속 빔 생성이 가능함을 확인할 수 있었다. 또 집속 위치, 수신 방법 등을 고려하고, 집속 빔의 음장, 수신 신호 파형 등의 분석을 실시하였으며, 이러한 결과로부터 고체의 비선형 파라미터 측정에 집속 빔을 이용할 수 있을 것으로 판단된다. When nonlinear parameters of solid samples are measured in the pulse-echo mode using a single planar transducer, destructive second harmonic waves are generated before and after the stress-free reflection boundary owing to their phase differences, which make the nonlinear parameters difficult to measured. Previous studies have reported that the second harmonic wave amplitude can be increased using a focused beam. To measure nonlinear parameters in the pulse-echo setup, simulation studies focused beam generations in solid specimens were performed. The behavior of a focused beam generated by the Fresnel zone plate principle was investigated through theoretical analysis and finite element simulation. The simulation results showed that the focusing beam could be generated inside the solid sample. The focus position and reception method were also considered to examine the waveform behavior, It was found that the focused beam method can be utilized for nonlinear parameter measurements of solids in the pulse-echo method.

Pulsed (Field) Gradient Spin Echo (PGSE) NMR에 의한 ADS/OTAC 혼합 수용액에서의 콜로이드 희합체의 자가 확산 계수

김홍운 ( Hong Un Kim ),임경희 ( Kyung Hee Lim ),김은희 ( Eun Hee Kim ),정재준 ( Chae Joon Cheong ) 한국유화학회 2002 한국응용과학기술학회지 Vol.19 No.4

N/A Transesterfication of vegetable oils and methanol with alkaline catalyst was carried out to produce biodiesel fuel by continuou process. The process consists of two static mixers, one tubular reactor and two coolers and gave 95∼99% of methyl ester yield from soybean oil and rapeseed oil. Experimental variables were the molar ration of methanol to vegetable oil, alkaline catalyst contents, flow rates, mixer element number. The optimum ranges of operating variables were as follows reaction temperature of 70℃, 1:6 of molar ratio of methanol to oil, 0.4%(w/w) sodium hydroxide based on oil, static mixer elements number of 24 and 4 min. residence time.