Abstract
Line-focus-beam ultrasonic material property characterization system enables accurate measurements on the phase velocities of leaky surface acoustic waves(LSAW) or rayleigh-type leaky surface acoustic waves.But in view of the lens of the conventional acoustic microscopy is expensive and difficult to produce,new method of design and fabrication of two line-focus lens-less polyvinylidene fluoride(PVDF) transducers is presented for acoustic microscopy system utilizing a 40 ?m thick piezoelectric PVDF film to construct the active element.The transducers introduced here centre around 5 MHz and 11 MHz respectively.Different from high cost of equipments and measuring the oscillation period on an operation of tone-burst mode,an improved V(f,z) method based on tow-dimensional Fourier transform is developed for the broadband measurements.A defocusing system for measuring surface acoustic waves is established and a non-contact immersion experiment of a polished fused quartz is carried out.The LSAW velocity extracted by V(f,z) analytical technique is compared with the theoretical one and they both are in good agreement.
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