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Title |
Application of Amplitude Demodulation to Acquire High-sampling Data of Total Flux Leakage for Tendon Nondestructive Estimation
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Authors |
이주형(Joo-Hyung Lee) ; 곽임종(Imjong Kwahk) ; 조창빈(Changbin Joh) ; 최지영(Ji-Young Choi) ; 박광연(Kwang-Yeun Park) |
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DOI |
https://doi.org/10.11112/jksmi.2023.27.2.17 |
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Keywords |
Total flux leakage; 솔레노이드 센서; 신호후처리; 진폭복조; 프리스트레스 콘크리트; 외부텐던; 단면감소; 비파괴검사 Total flux leakage; Solenoid sensor; Post-signal-process; Amplitude demodulation; Prestressed concrete; External tendon; Section loss; Non-destructive evaluation |
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Abstract |
A post-processing technique for the measurement signal of a solenoid-type sensor is introduced. The solenoid-type sensor nondestructivelyevaluates an external tendon of prestressed concrete using the total flux leakage (TFL) method. The TFL solenoid sensor consists of primary and secondarycoils. AC electricity, with the shape of a sinusoidal function, is input in the primary coil. The signal proportional to the differential of the input is inducedin the secondary coil. Because the amplitude of the induced signal is proportional to the cross-sectional area of the tendon, sectional loss of the tendoncaused by ruptures or corrosion can be identified by the induced signal. Therefore, it is important to extract amplitude information from the measurementsignal of the TFL sensor. Previously, the amplitude was extracted using local maxima, which is the simplest way to obtain amplitude information. However, because the sampling rate is dramatically decreased by amplitude extraction using the local maxima, the previous method places manyrestrictions on the direction of TFL sensor development, such as applying additional signal processing and/or artificial intelligence. Meanwhile, theproposed method uses amplitude demodulation to obtain the signal amplitude from the TFL sensor, and the sampling rate of the amplitude informationis same to the raw TFL sensor data. The proposed method using amplitude demodulation provides ample freedom for development by eliminatingrestrictions on the first coil input frequency of the TFL sensor and the speed of applying the sensor to external tension. It also maintains a highmeasurement sampling rate, providing advantages for utilizing additional signal processing or artificial intelligence. The proposed method was validatedthrough experiments, and the advantages were verified through comparison with the previous method. For example, in this study the amplitudesextracted by amplitude demodulation provided a sampling rate 100 times greater than those of the previous method. There may be differences dependingon the given situation and specific equipment settings; however, in most cases, extracting amplitude information using amplitude demodulation yieldsmore satisfactory results than previous methods.
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