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- Title
Design of a miniaturised ultrasonic guided wave inspection instrument for steel strand flaw detection.
- Authors
Feng Fluan; Liu Xiucheng; Wu Bin; Flan Qiang; Fie Cunfu
- Abstract
Longitudinal mode ultrasonic guided waves (UGWs) in prestressed seven wire steel strands have an inherent notch frequency property covering a frequency range of less than 100 kHz. If UGWs having such a frequency range are used to inspect the strand, the inspection instrument may fail to delect small defec b due to difficulties in predicting the notch frequency. lhereforef it is more appropriate to design a miniaturised instrument that can excite and receive UGWs covering a frequency range of tar more than WO kHz for on-site strand inspection applications, In this study, an FPGA-controlfed instrument is developed lo test its UGW detection performance. The boost circuit operates in a frequency range of 0.1-1.5 MHt to produce a parametric bunt of square waves with a low distortion content. The detected UGW signal is then filtered by a low-pass filter and amplified by a two-stage programmable qain pre-amplifier with a maximum amplification of 80 dB. The long range strand inspection results show that the proposed instrument provides a signal-to-noise ratio for the detected tlGW signal of 6.06 dR after the UGW has propagated for 96 m in the strand. The influence of a notch defect on the extent of mode conversion between the L(0,1) and F(1, 1) modes and the amplitude of the signal reflected from the notch are analysed based on the short-time Fourier transform (STFT) results from the detected UGW signals. The variation in the UGW signal spectrum that is induced by a notch with a cross-sectional area loss of 1.13% can be identified, indicating thehigh UGW detection performance of the developed instrument.
- Subjects
INDUSTRIAL applications of ultrasonic waves; STEEL strip -- Defects; DETECTORS; ENGINEERING inspection equipment; FOURIER transforms
- Publication
Insight: Non-Destructive Testing & Condition Monitoring, 2017, Vol 59, Issue 1, p17
- ISSN
1354-2575
- Publication type
Article
- DOI
10.1784/insi.2017.59.1.17