Characterization and representation of mechanical waves generated in piezo-electric augmented beams

Abstract

Mechanical waves are induced in solids due to the system's coupling with an external excitation. Depending upon the nature of the resulting displacement and phase difference between the vibrating particles at a particular frequency, the mechanical waves can be classified as standing waves, traveling waves or a combination of the two. This study focuses on the identification of these different forms of mechanical waves and discusses methods that can be suitably used for their classification. The Hilbert and Fourier methods of classification were validated using experimental results and then compared against each other. The experimental and theoretical analysis of mechanical waves was conducted on a beam with free-free boundary conditions excited by piezoelectric elements.

Turbulent Boundary Layer over a Piezoelectrically Excited Traveling Wave Surface

“…Malladi and Avirovik [2] also used their model to study the effects of phase difference on the generated traveling waves. As was discussed in Dehez [65], traveling waves generated via twomode excitation are mixed with standing waves and are thus hybrid waves.…”

“…In addition, the two-mode excitation method is open-loop controlled and has minimal limitations on the achievable frequencies. However, previous studies have primarily used this method on one-dimensional beams [1,2,33,34]. Traveling waves have been excited on a two-dimensional surface [35], but this was done from a fundamental standpoint and was mainly as a proof of concept.…”

Motion of a Legged Bidirectional Miniature Piezoelectric Robot Based on Traveling Wave Generation

“…The electromechanical performance of piezoelectric layers on laminates was already well established by Lee and Moon's seminal work [20]. Later reports demonstrated the generation of linear traveling waves on a beam using external actuation forces [21,22], or with two piezoelectric patches on the same beam [23], by combining two vibration modes with appropriate amplitudes and phases. In the latter, the patches were symmetrically situated with respect to the center of the plate, where each of them was actuated with the same sinusoidal signal, but the phase was shifted.…”

“…The previous expression can be truncated to the modes nearest to, above, and below the actuation frequency. The time-dependent modal factor can be Fourier-transformed to the following expression for each of the patches with an actuation voltage Ve j (ωt+φ) in the complex domain [20,23]:…”

“…This approach resulted in three key variables that may be varied to improve the quality and amplitude of the TW: patch length, frequency of actuation, and phase shift between the sinusoidal signals on each of the patches. Malladi et al [23] reported the effect of the frequency of actuation and the phase shift. Here, we also considered the effect of the patch length on the two figures of merit mentioned before.…”