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.

Edge Effect Investigation of DP980 Steel Sheet in Multiple Laser Scanning Process

Yajing Zhang,Wenbin Dong,Yinhu Qiao,Chunyu Zhang 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.3

Due to free spring back, laser forming is an effective non-contact forming technique for hard forming materials. A desired shape is obtained by residual plastic strain which is induced by thermal stresses depending on multiple laser scanning. In this study, the combination of experimental and numerical analysis is employed to investigate the temperature distribution and bending angle of the dual phase (DP980) high strength steel sheet. The edge effect of six cases of laser scanning process involving 1, 2, 3, 4, 5 and 10-time laser scanning are investigated by analyzing their bending angle relative variations and transverse plastic strains. It is found that the edge effect at the middle part of laser scanning line reduces with the increasing number of laser scanning cycles. It is attributed to the fact that the relative variation of the residual plastic strain reduces with the increase of laser scanning cycles. To efficiently reduce the edge effect of DP980 steel sheet, a locally repeated scanning strategy is proposed. The numerical simulation results indicate that the edge effect reduces significantly in the 10-time laser scanning process and the average bending angle simultaneously increases around 20% under the new laser scanning strategy.

Microstructure, Stress and Optical Properties of CdTe Thin Films Laser-annealed by Using an 808-nm Diode Laser: Effect of the Laser Scanning Velocity

김남훈,박찬일,이현용 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.2

A continuous wave 808-nm diode laser was used for the laser annealing process of CdTe thin films at various laser scanning velocities by using a galvanometric mirror. The grains in the laserannealed CdTe thin films grew along the C (111), H (110) and C (311) planes. The lattice constants of the CdTe thin films reached a minimum at a laser annealing velocity of 167 mm/s due to the disintegration of some large grain. The optical band gap energy of the CdTe thin films was inversely proportional to the lattice constant, showing 1.439 eV and 1.474 eV for the CdTe thin films laserannealed with laser scanning velocities of 667 mm/s and 167 mm/s, respectively. The absorbance of the CdTe thin films showed an improved value of 2.80 in the visible spectral region after laser annealing at a laser scanning velocity of 167 mm/s with the appropriate mixture of scattering and transparent grains in CdTe thin films although the crystallinity had deteriorated and showed the small recrystallized grains under this condition.

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.

A novel one-body dual laser profile based vibration compensation in 3D scanning

Lim, Yongseok,Choi, Woong,Park, Yongju,Oh, Sangwook,Kim, Younghun,Park, Jongsun Elsevier 2018 MEASUREMENT -LONDON- Vol.130 No.-

<P><B>Abstract</B></P> <P>Recently, the 3D laser profile scanner has often been used for the precise measurement of 3D surface information (object surface) such as height, area, and slope. However, a difficulty encountered with the conventional laser scanning method is that it cannot compensate for the errors resulting from vibration, so the scanned object should be measured in a fixed (immobile) state. In this paper, we propose a novel dual laser profile method and its error compensation algorithm to compensate for vertical vibration, even with a moving object. In order to remove errors caused by vibration, the proposed system projects two laser profiles onto the surface, such that the projected position overlaps the one with the previous position. With the overlapped position, the height difference between the measured objects is used to calculate the vibration errors. To generate two laser profiles simultaneously, we present a novel approach for generating two laser profiles from one laser-emitting source (a one-body dual line laser using a triangular structured blazed grating reflector). By exploiting the one-body dual line laser and error compensation algorithm, the proposed 3D laser profile scanner system achieves an error reduction of about 96.3% in the root mean square error (RMSE), compared to the conventional approach.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Overlapping two laser profiles with time difference allows vibration compensation. </LI> <LI> One laser source generates two precise laser profiles using grating structure. </LI> <LI> Global compensation algorithm corrects error from superimposing two laser profiles. </LI> </UL> </P>

The Scanning Laser Source Technique for Detection of Surface-Breaking and Subsurface Defect

Sohn, Young-Hoon,Krishnaswamy, Sridhar The Korean Society for Nondestructive Testing 2007 한국비파괴검사학회지 Vol.27 No.3

The scanning laser source (SLS) technique is a promising new laser ultrasonic tool for the detection of small surface-breaking defects. The SLS approach is based on monitoring the changes in laser-generated ultrasound as a laser source is scanned over a defect. Changes in amplitude and frequency content are observed for ultrasound generated by the laser over uniform and defective areas. The SLS technique uses a point or a short line-focused high-power laser beam which is swept across the test specimen surface and passes over surface-breaking or subsurface flaws. The ultrasonic signal that arrives at the Rayleigh wave speed is monitored as the SLS is scanned. It is found that the amplitude and frequency of the measured ultrasonic signal have specific variations when the laser source approaches, passes over and moves behind the defect. In this paper, the setup for SLS experiments with full B-scan capability is described and SLS signatures from small surface-breaking and subsurface flaws are discussed using a point or short line focused laser source.

3D Laser Scanning을 활용한 화재 손상 부위의 보수·보강 물량 산출 방식 개선에 관한 연구

정희재,함남혁,이병도,박광민,김재준 한국BIM학회 2019 KIBIM Magazine Vol.9 No.1

Recently, there is an increase in fire incidents in building structures. Due to this, the importance of fire-damaged buildings’ safety diagnosis and evaluation after fire is growing. However, the existing fire-damaged safety diagnosis and evaluation methods are personnel-oriented, so the diagnostic results are intervened by investigators’ subjectivity and unquantified. Thus, improper repair and reinforcement can result in secondary damage accidents and economic losses. In order to overcome these limitations, this study proposes using 3D laser scanning technology. The case analysis of fire-damaged building structures was conducted to verify the effectiveness of accuracy and manpowering by comparing the existing method and the proposed method. The proposed method using 3D laser scanning technology to obtain point cloud data of fire-damaged field. The point cloud data and BIM model is combined to inspect the fire-damaged area and depth. From inspection, quantified repair and reinforcement quantity take-off can be acquired. Also, the proposed method saves half of the manpowering within same time period compared to the existing method. Therefore, it seems that using 3D laser scanning technology in fire-damaged safety diagnosis and evaluation will improve in accuracy and saving time and manpowering.

3D 스캐닝 임베디드 시스템 설계

홍선학,조경순 (사)디지털산업정보학회 2017 디지털산업정보학회논문지 Vol.13 No.4

It is the approach of embedded system design that finds 3D scanning technology to analyze a real object or environment to collect data on its shape and appearance. 3D laser scanning developed during the last half of 20th century in an attempt to accurately recreate the surfaces of various objects. 1960s, early scanners used lights, cameras, and projectors to carry out the scanning in the lacks of performance which encountered many difficulties with shiny, mirroring, or transparent objects. The 3D scanning technology has leveled-up with helpful of embedded software platform research and design. In this paper, First we designed the hardware of laser/camera setup and turntable moving part which is the base of object. Second, we introduced the process of scanning 3D data with software and analyzed the resulting scanned image on the web server. Last, we made the 3D scanning embedded device with 3D printing model and experimented the 3D scanning performance with Raspberry Pi.

Er:YAG 레이저로 처리한 상아질에 대한단일 단계 접착시스템의 결합

이명구 ( Myung Goo Lee ),조영곤 ( Young Gon Cho ) 조선대학교 치의학연구원 2013 Oral Biology Research (Oral Biol Res) Vol.37 No.1

The purpose of this study was to evaluate the influence of Er:YAG laser irradiation on the microshear bond strength (μSBS) of three single-step adhesive systems to dentin. Materials and Methods: The occlusal dentin surfaces of 30 extracted teeth were exposed. Samples were divided into six groups according to laser irradiation of dentin surface and type of single-step adhesive system (LP group: Adper Prompt L-Pop (3M ESPE Dental Products), LP-L group: Er:YAG laser (KEY Laser 3, KaVo)+Adper Prompt L-Pop, GB group: G-Bond (GC Corporation), GB-L group: Er:YAG laser+G-Bond, AB group: ALL-Bond SE (Bisco Inc.), AB-L group: Er:YAG laser+ALL-Bond SE). The bonded specimens were subjected to μSBS test, and the resin-dentin interfaces were observed under field emission scanning electron microscope. Results: There were no significant differences among the μSBS of LP, GB, and AB groups, whereas the μSBS of the LP-L and AB-L groups were significantly higher than that of the GB-L group (p<0.05). More adhesive failures were seen in the laser-irradiated groups than in the non-irradiated groups. All other groups, except the GB-L group, showed close adaptation at the interface of dentin and composite resin. Conclusion: Use of Er:YAG laser irradiation can reduce the bonding strength of composite resin to dentin depending on the type of single-step adhesive system.

DED 공정변수에 따른 SUS316L 적층 레일의 경도 특성 연구

김무선(Moo-Sun Kim) 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.10

본 연구에서는 적층공정 기술인 DED(directed energy deposition) 공정기술을 철도 레일에 적용하여 금속 적층을 진행하였을 때 적층면과 레일에서 발생하는 경도 특성의 변화를 시험 분석하였다. 레일은 열차의 반복되는 주행 하중에 의해 마모 및 표면결함이 자주 발생하는 철도 주요 인프라이며, 레일 표면을 복원하기 위해 마모면 상부에 금속 적층을 진행하는 방식의 유지보수방법을 고려할 수 있다. DED 공정기술은 레이저를 이용하여 얇은 융착 레이어를 반복하여 적층하는 방식의 열사이클로 인해 고유의 물성 변화 특징을 가진다. 본 연구에서는 DED 공정의 주요 변수 변화에 따라 발생하는 경도 특성 변화를 살펴보았다. 시편 제작은 레일 상부 절삭 후 DED 공정기술로 일정 높이만큼 적층 진행하였다. 적층 소재는 SUS316L을 적용하였으며 공정조건 변수는 레이저 출력 크기와 레이저 스캔 스피드를 다양화하여 시편을 제작하였다. 제작된 시편을 대상으로 레일 단면의 경도값(HV)을 적층 표면부터 레일목까지 순차적으로 측정하였다. 경도특성 분석 결과, 레이저 출력이 높을수록 적층면의 경도값은 낮아졌으며 레이저 스캔 속도가 높을수록 상대적으로 높은 경도값을 보였다. 레이저 출력과 레이저 스캔 속도가 연관된 에너지 밀도로 설명하면 결국 에너지 밀도가 높을 수록 경도값은 낮아짐을 의미한다. 이는 적층공정시 레이저에 의한 에너지 밀도가 높을수록 냉각속도가 느려지면서 이와 관련된 미세조직 특성의 변화로 인해 최종적인 경도 특성이 달라지는 것으로 판단된다. In this study, DED (directed energy deposition) process technology, one of the additive manufacturing process technologies, was applied to rails to analyze the hardness characteristics in the deposited area on a rail surface. A rail is the main infrastructure of a railway where wear and defects on the surface frequently occur due to the cycle of running loads of trains. To repair the rail surface, a maintenance method of metal deposition on the top of the worn surface can be considered. DED process technology has unique physical properties due to the thermal cycle of repeatedly stacking thin fused layers by using a laser. This study examined the changes in hardness characteristics according to the changes of key parameter values in DED process technology. Specimens were manufactured by cutting the upper part of a rail and depositing metal to a certain height using DED process technology. SUS316L was applied as the deposition material, and specimens were produced with varying laser power and laser scanning speed as DED process variables. The hardness value (HV) on the rail cross section of the manufactured specimen was measured sequentially from the deposition surface to the rail neck. As a result of the hardness characteristic analysis, the higher the laser power, the lower the hardness value of the deposition surface was, the higher the laser scanning speed was, and the higher the hardness value was. In terms of the energy density, which is related to the laser power and laser scanning speed, the higher the energy density, the lower the hardness value was. It is estimated that the cooling rate is slower in the fusion process due to the higher energy density of the laser affecting the microstructure characteristics in the deposited metal and change the final hardness characteristics.