Humans are sensitive to air-borne sound as well as to mechanical vibrations propagating in solids in the frequency range below 20 kHz. Therefore, the development of multifunctional filters for both vibration reduction and sound insulation within the frequency range of human sensitivity is a research topic of primary interest. In this paper, a high-contrast biphasic mechanical metamaterial, composed of periodic elastic solid cells with air-filled voids, is presented.
View Article and Find Full Text PDFIEEE Trans Ultrason Ferroelectr Freq Control
December 2019
This article presents improvements to ultrasonic imaging of solid platelike structures using the minimum-variance distortionless response (MVDR) beamforming processor. The primary application of this work is in the nondestructive testing (NDT) of platelike components that are widely used in aerospace, marine, and civil structures. The study proposes a new set of weights, or MVDR replica vectors, that are based on the physics of the propagating Lamb modes, including the symmetric mode S0, the antisymmetric mode A0, and the shear horizontal mode SH0.
View Article and Find Full Text PDFThis paper investigates the interaction of different shear- and Rayleigh-Lamb-guided waves in plates with a discontinuity such as a notch or an internal void. The problem was solved numerically using a finite element model and by exploiting an analytical solution obtainable for the double sharp changes of the cross-section that served as a reference. We aimed to elucidate the relation between the size and shape of the discontinuity and the reflection and transmission coefficients of the scattered field.
View Article and Find Full Text PDFThe measurement of stress in a structure presents considerable interest in many fields of engineering. In this paper, the diagnostic potential of nonlinear elastic guided waves in a prestressed plate is investigated. To do so, an analytical model is formulated accounting for different aspects involved in the phenomenon.
View Article and Find Full Text PDFThis study investigates the scattering of guided waves from a discontinuity exploiting the principle of reciprocity in elastodynamics, written in a form that applies to waveguides. The coefficients of reflection and transmission for an arbitrary mode can be derived as long as the principle of reciprocity is satisfied at the discontinuity. Two elastodynamic states are related by the reciprocity.
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