| Original Articles |
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Thickness Determination for a Two-Layered Composite of a Film and a Plate by Low-Frequency Ultrasound |
| MAO Jie;LI Ming-Xuan;WANG Xiao-Min |
| Institute of Acoustics, Chinese Academy of Sciences, Beijing 100080 |
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| Cite this article: |
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MAO Jie, LI Ming-Xuan, WANG Xiao-Min 2007 Chin. Phys. Lett. 24 755-758 |
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Abstract We present an ultrasonic method for determining the thickness of a composite consisting of a soft thin film attached to a hard plate substrate, by resonance spectra in the low frequency region. The interrogating waves can be incident only to the two-layered composite from the substrate side. The reflection spectra are obtained by FFT analysis of the compressive pulsed echoes from the composite, and the thicknesses of the film and the substrate are simultaneously inversed by the simulated annealing method from the resonant frequencies knowing other acoustical parameters in prior. The sensitivity of the method to individual thickness, its convergence and stability against experimental noises are studied. Experiment with interrogating wavelength 4 times larger than the film thickness in a sample of a polymer film (0.054mm) on an aluminium plate (6.24mm) verifies the validity of the method. The average relative errors in the measurement of the thicknesses of the film and the substrate are found to be -4.1% and -0.62%, respectively.
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| Keywords:
43.35.+d
43.60.+d
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Received: 18 September 2006
Published: 08 February 2007
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| PACS: |
43.35.+d
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(Ultrasonics, quantum acoustics, and physical effects of sound)
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43.60.+d
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(Acoustic signal processing)
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[8] Li M X, Wang X M and Mao J 2004 Chin. Phys. Lett. 21 766 |
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