Method for measuring acoustic impedance and acoustic attenuation of thin layer based on sound pressure reflection coefficient power spectrum
A sound pressure reflection coefficient and power spectrum technology, which is applied to the analysis of solids using sound waves/ultrasonic waves/infrasonic waves, can solve problems such as ultrasonic non-destructive measurement methods for measuring thin-layer acoustic impedance that have not yet been seen.
Active Publication Date: 2013-10-30
DALIAN UNIV OF TECH
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[0003] So far, there is no practical ultrasonic non-destructive measurement method that can be directly used to measure the acoustic impedance of thin layers under any parameters of unknown thin layers
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[0027] figure 1 After system connection and instrument calibration of the measuring device shown, first use the ultrasonic flaw detector 1 and use the ultrasonic pulse water immersion probe 2 with a nominal frequency of 2MHz (center frequency 2.1MHz, frequency bandwidth (-6dB) 1.30~2.83MHz) Measure resin glass sheet sample 3 (the sound velocity of resin glass is 2730m / s (the value is provided by the American Nondestructive Testing Manual). The density ρ measured by the Archimedes method is 1.18g / cm 3 , according to the acoustic impedance calculation formula Z=ρc, the acoustic impedance of the resin glass sheet sample is 3.139×10 6 rayl) to transmit and receive ultrasonic waves (resin glass thin layer sample 3 is placed in the water tank 4), with the help of DPO4032 digital oscilloscope 5 to complete waveform observation and waveform signal acquisition. figure 2 Shown are the ultrasonic echo signal diagrams of the Plexiglas sheet sample 3 and the standard sample. Utilize the...
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Abstract
The invention discloses a method for measuring the acoustic impedance and acoustic attenuation of a thin layer based on a sound pressure reflection coefficient power spectrum, belonging to the technical field of ultrasonic nondestructive testing and evaluating of materials. The method comprises the steps of: acquiring aliasing signals formed by interface reflection echoes from water and an upper surface of the thin layer as well as from the water and a lower surface of the thin layer by using a pulsed ultrasound water logging echo system, acquiring an upper surface echo signal of a standard test block, performing FFT (Fast Fourier Transform) on the two signals respectively, and performing further processing to obtain the sound pressure reflection coefficient power spectrum; and then, performing low-pass filtering and band-pass filtering on the power spectrum to solve relevant coefficients in a power spectrum expression, and substituting the coefficients into an equation to solve the acoustic impedance and the acoustic attenuation of the thin layer. The method disclosed by the invention can be used for solving the acoustic impedance and the acoustic attenuation at the same time under the condition that any parameters of the thin layer are unknown, and the defect that part of parameters of the thin layer need to be known to obtain other parameters in the prior art is overcome.
Description
technical field [0001] The invention relates to a method for measuring thin-layer acoustic impedance based on the sound pressure reflection coefficient power spectrum, which belongs to the technical field of ultrasonic nondestructive testing and evaluation of materials. Background technique [0002] At present, for bulk materials, the main method of acoustic impedance measurement is to measure its density and sound velocity and obtain it through Z=ρc. However, due to the aliasing of thin-layer time-domain waveforms, it is difficult to directly obtain the accurate value of thin-layer sound velocity. method is not suitable for thin layers. In recent years, relevant scholars have obtained the acoustic parameters of thin layers by spectrum analysis method. For example, in "Ultrasonic nondestructive evaluation of thin (sub-wavelength) coatings", American scholar Kinra proposed a method for measuring four parameters of thin layer sound velocity, acoustic impedance, sound attenuat...
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IPC IPC(8): G01N29/09G01N29/11
Inventor 林莉胡志雄陈军罗忠兵李喜孟
Owner DALIAN UNIV OF TECH