Autoregression spectrum analysis method for improving ultrasonic testing time resolution
A time-resolution, ultrasonic detection technology, applied in the direction of using ultrasonic/sonic/infrasonic waves, measuring devices, instruments, etc., can solve the problems of wide application limitations, the production cost of hardware circuits of the measurement system, and the increase in the production cost of high-frequency ultrasonic probes.
Active Publication Date: 2015-06-03
BEIJING UNIV OF TECH
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However, the production cost of the hardware circuit of the measurement system and the production cost of the high-frequency ultrasonic probe will be greatly increased, so its wide application is greatly limited.
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[0038] 1) For the convenience of operation and implementation, the water layer is used as the liquid layer for experimental measurement. The thickness of the steel specimen is 10 mm. The feeler gauge is placed between the upper and lower steel specimens to construct a 350 μm thick water layer. The sampling frequency is set to 100MHz, and the above-mentioned thin-layer liquid thickness measurement system is used to excite and collect the ultrasonic echo signal y(t);
[0039] 2) Under the condition of not changing the measurement parameters, the water film thickness is set to zero, and the upper surface echo of the lower steel test block is collected. The signal is used as the reference signal h(t) in the Wiener filtering process;
[0040] 3) Wiener filtering is performed on the ultrasonic echo signal y(t), and inverse Fourier transform is performed on y(t) and h(t) respectively to obtain H(ω) and Y(ω), and formula 1 is used to calculate water The impulse response E(ω) of the m...
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The invention relates to an autoregression spectrum analysis method for improving ultrasonic testing time resolution. The method comprises that ultrasonic echo signals y(t) are collected specific to to-be-tested liquid; under the condition that testing parameters are not changed, the thickness of the to-be-tested liquid is set to be zero, the ultrasonic echo signals are collected and are used as reference signals h(t) in a Wiener filtering process; the ultrasonic echo signals y(t) are subjected to Wiener filtering, an impulse response frequency spectrum E(w) of the end face of a liquid layer is obtained; an autoregression model order K is chosen, the autoregression coefficient under the order is calculated with an R-W method; frequency spectrum reconstruction is carried out by choosing a frequency attenuation window with a certain width; a reconstructed frequency spectrum is subjected to inverse Fourier transform so that a time-domain signal x(t) is obtained, according to the wave crest position and the wave trough position of the time-domain signal x(t), the position of echo on the upper surface and the lower surface of the liquid layer, and accordingly the transmission time of sound wave in the liquid layer is determined, and the thickness of the liquid layer can be calculated by combining the transmission time with the transmission speed of the sound wave in the liquid layer.
Description
technical field [0001] The invention relates to an autoregressive spectrum analysis method for improving the time resolution of ultrasonic detection signals. Background technique [0002] As one of the five conventional nondestructive testing techniques, ultrasonic technology can be used to measure the thickness of dielectric layers. Based on the propagation time and velocity of ultrasonic waves in the medium, the conventional ultrasonic reflection echo technology can realize the measurement of the thickness of large-scale medium layers. However, when the thickness of the dielectric layer is small, the ultrasonic reflection echoes on the upper and lower surfaces of the dielectric layer will be superimposed, and it is difficult to directly obtain the propagation time of the ultrasonic wave through the interface on both sides of the liquid layer from the time-domain waveform, so it is impossible to directly use the conventional ultrasonic echo The wave time difference method ...
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IPC IPC(8): G01B17/02
Inventor 焦敬品侯松马庆增肖凯何存富吴斌
Owner BEIJING UNIV OF TECH