Time and polarization resolved ultrasonic measurements using a lensless line-focus transducer

Abstract

We have developed a transducer which allows the benefits of Line-Focus Beam (LFB) acoustic minoscopy to be realized over large areas, using a conventional pulserreceiver. Experimental evidence is presented to show that the transducer is correctly modeled in detail by Green's function theory, and that all relevant wave speeds can also be predicted using a much simpler geometrical ray model. Data obtained by simply rotating the transducer a fixed distance above the specimen are presented using grey-scale plots which establish the ease with which anisotropy can be revealed.Finally, a grey scale plot of rotational-scan data recast in terms of velocity is shown to demonstrate the simultaneous detection of both surface and pseudo-surface waves in the same crystallographic orientation of a silicon specimen.

Corrosion evaluation of additive manufacture metal alloy by nondestructive line-focused transducer

“…As mentioned in the last chapter, the design of the transducer system mainly refers to the work of Yamanaka [16] and D. Xiang [18].…”

Cylindrical Rayleigh surface waves on a layer-coated cylinder measured by PVDF transducer and defocusing measurement method

“…The line-focused PVDF transducer, which was first developed by Hsu [20,21] in 1995, will be used for measuring cylindrical Rayleigh surface waves propagating on a layer-coated cylindrical sample. The transducer consists of a cylindrically curved PVDF film as the piezoelectric element for transmitting and receiving acoustic waves.…”

“…In this work, we will apply line-focused PVDF transducers and the defocusing measurement method [20,21] to determine the dispersion curve of cylindrical Rayleigh surface waves propagating on a single-layer-coated elastic cylinder. PVDF focusing transducers and the defocusing measurement method have been successfully used for measuring surface acoustic waves on isotropic/anisotropic solids [20][21][22][23] and layered materials [24], as well as measuring guided waves such as Lamb waves on plates [25][26][27].…”

“…PVDF focusing transducers and the defocusing measurement method have been successfully used for measuring surface acoustic waves on isotropic/anisotropic solids [20][21][22][23] and layered materials [24], as well as measuring guided waves such as Lamb waves on plates [25][26][27]. Its measuring principle is similar to acoustic microscopy and V(z) measurement [28] except that PVDF focusing transducers are working with a pulser/receiver to obtain reflected time-domain waveforms.…”

“…Its measuring principle is similar to acoustic microscopy and V(z) measurement [28] except that PVDF focusing transducers are working with a pulser/receiver to obtain reflected time-domain waveforms. Therefore, a waveform processing method, such as the V(f, z) waveform processing method [20], is needed to accurately determined the wave velocity over a relatively wide range of frequency. So far, the PVDF transducers have been used mainly on samples with flat and planar surfaces.…”