Guided Waves Propagating in a Bi-Layer System Consisting of a Piezoelectric Plate and a Dielectric Fluid Layer
This study employs a theoretical modeling and an experimental measurement for investigating the dispersion behavior of guided waves propagating in a bi-layer system consisting of a piezoelectric plate and a dielectric fluid layer. The theoretical model is based on a recursive asymptotic stiffness matrix method (RASM) with the fluid layer modeled as an equivalent elastic body. A laser ultrasound technique is used to measure the dispersion relations of the bi-layer system. Behaviors of mode couplings between guided modes propagating in the piezoelectric plate and those in fluid layer are characterized in the modeling and measurements. Dispersion behaviors of guided modes propagating in the bi-layer system are discussed for varying fluid thicknesses. For all of the investigated cases, the theoretical modeled dispersion spectra agree well with the measurements.
Available from: Pascal Laugier
- "They depend on the thicknesses, the mass densities, the plate elastic coefficients C ij and the fluid longitudinal velocity c f . However, for simplicity, following Simonetti (2004) and Wu and Yang (2011), the bilayer waveguide is assumed in a first approximation to behave mainly like two decoupled waveguides. It implies that a measured guided mode wavenumber k exp corresponds to either a plate k p or a fluid wavenumber k f . "
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ABSTRACT: Human soft tissue is an important factor that influences the assessment of human long bones using quantitative ultrasound techniques. To investigate such influence, a series of soft tissue-bone phantoms (a bone-mimicking plate coated with a layer of water, glycerol or silicon rubber) were ultrasonically investigated using a probe with multi-emitter and multi-receiver arrays in an axial transmission configuration. A singular value decomposition signal processing technique was applied to extract the frequency-dependent wavenumbers of several guided modes. The results indicate that the presence of a soft tissue-mimicking layer introduces additional guided modes predicted by a fluid waveguide model. The modes propagating in the bone-mimicking plate covered by the soft-tissue phantom are only slightly modified compared to their counterparts in the free bone-mimicking plate, and they are still predicted by an elastic transverse isotropic two-dimensional waveguide. Altogether these observations suggest that the soft tissue-bone phantoms can be modeled as two independent waveguides. Even in the presence of the overlying soft tissue-mimicking layer, the modes propagating in the bone-mimicking plate can still be extracted and identified. These results suggest that our approach can be applied for the purpose of the characterization of the material and structural properties of cortical bone.
Physics in Medicine and Biology 04/2012; 57(10):3025-37. DOI:10.1088/0031-9155/57/10/3025 · 2.76 Impact Factor
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IEEE transactions on ultrasonics, ferroelectrics, and frequency control 11/2012; 59(11):2580-3. DOI:10.1109/TUFFC.2012.2492 · 1.51 Impact Factor
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