Method for measuring round-trip time of ultrasound in thin layered medium based on sound pressure reflection coefficient power spectrum
A technology of sound pressure reflection coefficient and round-trip time, applied to measuring devices, using ultrasonic/sonic/infrasonic waves, instruments, etc., can solve problems such as the inability to determine the round-trip time of ultrasound in thin layers
Active Publication Date: 2014-04-02
DALIAN UNIV OF TECH
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However, when the bandwidth of the ultrasonic echo signal cannot cover two adjacent minimum values in the amplitude spectrum of the sound pressure reflection coefficient of the thin layer, usually we cannot determine the round-trip time of the ultrasonic wave in the thin layer
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[0024] figure 1 After system connection and instrument calibration of the measuring device shown, firstly, with the help of ultrasonic flaw detector 1, an ultrasonic pulse water immersion probe 2 with a chip diameter of 11.4mm and a nominal frequency of 25MHz (center frequency 16MHz, frequency bandwidth (-6dB) 12~22MHz ) to the measured Al thin slice sample 3 (using a micrometer to measure the thickness is 433 μm, because its sound velocity is 6320m / s, according to t=2d / c, the round-trip time is 137ns) to transmit and receive ultrasonic waves (Al thin slice sample 3 As for the water tank 4), the observation and collection of the waveform data of the Al thin slice sample is completed by means of the DPO4032 digital oscilloscope 5. Then repeat the above process on the standard test block for ultrasonic flaw detection, collect the echo signal of the upper surface of a standard test block, figure 2 Shown is the echo signal of Al thin slice sample. Utilize computer 6 to carry ou...
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The invention provides a method for measuring round-trip time of ultrasound in a thin layered medium based on a sound pressure reflection coefficient power spectrum the technical field of ultrasonic nondestructive test and evaluation of materials. According to the method, a pulse ultrasonic water immersion echo acquisition system is adopted to acquire a aliasing signal consisting of a reflection echo signal of an interface composed of water and a thin layered upper surface and a reflection echo signal of an interface composed of water and a thin layered lower surface, as well as an upper surface echo signal of a standard test block; and then the acquired signals are respectively subjected to FFT (Fast Fourier Transform) and further processed to obtain a sound pressure reflection coefficient power spectrum; then the horizontal ordinate of delta pulse corresponding to each cosine component is read out from a magnitude spectrum in the power spectrum, and the horizontal ordinate is round-trip time of ultrasound in a thin layered medium each time. The method is used for solving the problem that round-trip time of ultrasound in a thin layered medium cannot be determined because the bandwidth of ultrasonic echo signals cannot cover two adjacent minimal values in the sound pressure reflection coefficient magnitude spectrum of the thin layered medium. Used devices are simple, operability is strong, the measurement accuracy is high and repeatability is good.
Description
technical field [0001] The invention relates to a method for measuring the round-trip time of ultrasound in a thin-layer medium based on the sound pressure reflection coefficient power spectrum. It belongs to the technical field of ultrasonic nondestructive testing and evaluation of materials. Background technique [0002] Ultrasonic technology is used to measure the thickness of thin-layer media, and the most important thing is to measure the round-trip time of ultrasound in thin-layer media. Due to the aliasing of the surface echo and the bottom echo signal of the thin layer, the traditional time-domain analysis method of the pulse-echo signal cannot determine the round-trip time. At present, the commonly used signal processing methods for measuring the round-trip time of ultrasound in thin layers are sound pressure reflection coefficient magnitude spectrum and phase spectrum, such as foreign scholar Haines NF et al. in the article "The application of broadband ultrasound...
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IPC IPC(8): G01B17/02
Inventor 林莉胡志雄陈军罗忠兵李喜孟
Owner DALIAN UNIV OF TECH