Study on thickness measurement of elastic plates by high-overtone bulk acoustic resonances

Using a high-overtone bulk acoustic resonance of multi-layered elastic structure excited by a piezoelectric patch,a method for evaluating the elastic plate thickness is presented.According to the relations between the frequencies of high-overtone resonances and the thickness changes of the elastic plates,the theory and numerical calculations of the method are given.The calculated results demonstrate the parallel resonance frequencies and the spacing of the parallel resonance frequencies(SPRF) are relative to thickness deviations of the elastic plates.The parallel resonance frequencies linearly vary with the thickness deviations,and there is a periodical jumping phenomenon as the deviations increase. By investigating the tendency of the jumping,one can improve the measurement accuracy of the thickness of the elastic plates.Additionally,the feasibility of the measurement method has been verified by comparing a numerical calculation example and an experimental measurement.