• Title/Summary/Keyword: Air-coupled 트랜스듀서

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Identification of Guided-Wave Modes in Pipings of Power Plants by using Air-coupled Transducer (Air-coupled 트런스듀서를 이용한 발전설비 배관에서의 유도초음파 모드 규명)

  • Park, Ik-Keun;Kim, Hyun-Mook;Kim, Yong-Kwon;Song, Won-Joon;Cho, Yong-Sang;Jhang, Kyung-Young;Cho, Youn-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.4
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    • pp.341-347
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    • 2004
  • In order to inspect the piping effectively, one of the important components in the facility of power plants, the ultrasonic guided wave was generated by a tomb transducer and was received in a non-contact fashion by using an air-coupled transducer. The guided wave modes that ran be generated by the comb transducer in piping are predicted from the theoretical dispersion curves and the element spacing of a comb transducer. Moreover, to receive the specific modes, the receiving angle of the air-coupled transducer is calculated from Snell's law between the phase velocities of guided waves and the sound velocity of air. The guided wave modes obtained in experiments are identified from the result of time-frequency analysis such as wavelet transform and two-dimensional fast Fourier transform.

Detection of Laser excited Lamb-wave using Air-coupled Transducer and Identification of Propagation Mode using Wavelet Transform (공기-결합 트랜스듀서를 이용한 레이저 여기 램파의 검출과 웨이브렛 변환을 이용한 전파모드 규명)

  • Kim, Hyun-Mook;Kim, Hong-Jun;Jhang, Kyung-Young;Lee, Jun-Hyun
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.851-856
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    • 2003
  • This paper proposes a single-mode Lamb-wave generation and detection system using a pulsed laser as a generator and an air-coupled transducer combined with the wavelet transform analysis, as the detector. The laser source with arrayed linear slits was used to generate Lamb-wave which is able to control the wavelength of Lamb-wave to be generated by changing the slits separation. An ari-coupled transducer was used to receive Lamb-wave, which can selectably receive a single mode of leaky Lamb wave by changing the oblique angle of transducer, since the leaky Lamb-wave has unique leaky-angle according to the mode. Also, the received signal was processed by wavelet transform for the analysis in domain of time-frequency. The theoretical dipersion curve and the experimetal result was compared to show good agreement.

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Non-Contact Ultrasonic Testing of Aircraft Joints using Laser Generated Lamb Wave (레이저 여기 램파를 이용한 항공기 판재 접합부의 비접촉식 초음파 검사)

  • Jhang, Kyoung-Young;Kim, Hong-Joon;Ceringlia, Donatella;Djordjevic, Boro
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.2
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    • pp.163-168
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    • 2001
  • Due to aging, adhesively bonded and riveted aircraft lap joints can contain distends, cracks around rivet holes, fatigue induced flaws, and corrosion. It is required for the safety of aircraft to inspect these defects through the whole region of mint in rapid speed. Bond quality or adhesively bonded and riveted aluminum lap splice joints is investigated using non-contact remote ultrasonic nondestructive evaluation (NDE). Non-contact ultrasonic tests are performed using laser generation and air-coupled transducer detection. A Q-switched Nd:YAG laser and a periodic transmission mask are used to generate a selected Lamb mode. The Lamb wave is generated on one side of the lap splice joint, propagates along the plate, interacts with the joint and is detected on the other side by a micromachined air-coupled capacitance transducer. Analysis of recorded signals allows to evaluate the condition of the bond.

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Evaluation of Internal Defect of Composite Laminates Using A Novel Hybrid Laser Generation/Air-Coupled Detection Ultrasonic System (레이저 발생 초음파와 공기 정합 수신 탐촉자를 이용한 복합재료 적층판의 내부 박리 결함 평가)

  • Lee, Joon-Hyun;Lee, Seung-Joon;Byun, Joon-Hyung
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.1
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    • pp.46-53
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    • 2008
  • Ultrasonic C-scan technique is one of very popular techniques being used for detection of flaws in polymer matrix composite(PMC). However, the application of this technique is very limited for evaluation of defects in PMC fabricated by the automated fiber placement process. The purpose of this study is to develop a novel ultrasonic hybrid system based on nondestructive and non-contact ultrasonic techniques for evaluation of delamination in carbon/epoxy and carbon/PPS composite laminates. It was shown that the newly developed ultrasonic hybrid system based on dual air-coupled pitch-catch technique with ultrasonic scattering reflection concept could provide excellent image with higher resolution of delamination in PMC compared with the conventional pitch-catch method. It is expected that this ultrasonic hybrid technique can be applied for on-line inspection of flaws in PMC during the fabrication process.

A Study of Non-contacting Ultrasonic Technique for Evaluation of Fiber Reinforced Composite Materials (섬유강화 복합재료의 비접촉식 초음파 평가 기법 연구)

  • Choi Sang-Woo;Seo Kyeong-Cheol;Lee Joon-Hyun;Byun Joon-Hyun
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.10a
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    • pp.268-271
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    • 2004
  • Non-contact technique should be developed for receiving ultrasonic wave for on-line monitoring of processing defects of fiber reinforced composites, since couplant must be applied on composite materials when conventional ultrasonic testing technique was used. Restriction of conventional ultrasonic testing technique was proven by transmitting and receiving ultrasonic wave on CFRP in various direction of wave propagation with various incident angle of ultrasonic beam. Air-coupled transducer and laser interferometer were applied for non-contacting reception of ultrasonic wave in fiber reinforced composite materials. Air-coupled transducer has optimal sensitivity and frequency band of 300kHz has homogeneous characteristics on direction of wave propagation.

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