摘要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.
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.
MAO Jie;LI Ming-Xuan;WANG Xiao-Min. Thickness Determination for a Two-Layered Composite of a Film and a Plate by Low-Frequency Ultrasound[J]. 中国物理快报, 2007, 24(3): 755-758.
MAO Jie, LI Ming-Xuan, WANG Xiao-Min. Thickness Determination for a Two-Layered Composite of a Film and a Plate by Low-Frequency Ultrasound. Chin. Phys. Lett., 2007, 24(3): 755-758.
[1] Haines N F, Bell J C and Mclntyre P J 1978 J. Acoust. Soc.Am. 64 1645 [2] Kinra V K and Iyer V R 1995 Ultrasonics 33 111 [3] Kinra V K and Iyer V R 1995 Ultrasonics 33 95 [4] Kinra V K and Zhu C 1993 J. Acoust. Soc. Am. 93 2454 [5] Lavrentyev A I and Rokhlin S I 2001 Ultrasonics 39 211 [6] Lavrentyev A I and Rokhlin S I 1997 J. Acoust. Soc. Am. 1023467 [7] Mao J, Wang X M, Lian G X and Li M X 2005 Acta Acustica30 149 (in Chinese) [8] Li M X, Wang X M and Mao J 2004 Chin. Phys. Lett. 21 766
2007, Vol. 24 
