On the Directivity of Acoustic Waves Generated by the Angle Beam Wedge Actuator in Thin-Walled Structures

The paper aims to develop improved acoustic-based structural health monitoring (SHM) and nondestructive evaluation (NDE) techniques, which provide the waves directivity emitted by the angle beam wedge actuators in thin-walled structures made of plastic materials and polymeric composites. Our investigation includes the dispersive analysis of the waves that can be excited in the studied plastic panel. Its results allowed to find two kinds of generated acoustic waves—anti-symmetric Lamb waves (A0) and shear horizontally polarized SH waves (SS0). The bounds of the chosen frequency range for the experimental and numerical studies were accepted as a compromise between the desire to obtain a high defect resolution by generating short waves, their adjustable directivity, and maximum propagation length. The finite element model for the transducer was built by using the results of an actuator structure experimental study. The frequency response functions for the actuator current and oscillation amplitude of the footprint surface demonstrated good agreement. The found eigenfrequencies of the actuator’s structure were used for the numerical and experimental study of the Lamb and SH wave generation and propagation in a thin-walled plastic panel. Our results convincingly demonstrated the satisfactory directivity of the actuated waves at their excitation on the frequencies that corresponded to the natural modes of the actuator oscillation. The authors assume that an efficient use of the proposed technique for other analyzed quasi-isotropic materials and applied actuators can be provided by preliminary research using a similar approach and methods presented in this article

Mathematical and laboratory modeling of resonant impact on the spike for the purpose of grain selection

Mathematical and computer finite element model in the ACELAN package of resonant impact on a spike was developed and a full-scale experiment was carried out. Two installations are considered, one based on a cantilever, the free end of which acts on the spike, and the second is a semi-passive round bimorph. Excitation of vibrations is carried out using an actuator based on piezoceramic elements. In the first installation, low-frequency vibrations of the stem with a spike are excited and the resonance frequency is determined at which only an spike with grain performs intense vibrations. The second installation is designed to excite high-frequency vibrations at which resonant movements of the grains themselves arise. The purpose of both installations is to separate the grain from the spike using resonance phenomena

Numerical simulation of the experiment on pulsed excitation of stack type piezoelectric generator

The numerical modeling results of the full-scale experiment with low-frequency pulse excitation of the stack-type piezoelectric generator (PEG) for the energy storage device are described. PEG is a multilayer axisymmetric piezoceramic package. The dependence of the output voltage on the active load rate under the harmonic and non-stationary mechanical action of the PEG is studied. A finite element device model is developed in ANSYS , and a simplified one-dimensional analytical model is analyzed. The experimental results-to-numerical calculation correlation has shown their good convergence which allows using the analyzed numerical models to optimize the PEG design at the given external action frequency and active resistance value of the external electric circuit. In addition, it is found that the frequency dependence of the output voltage of the axial-type PEG is of a complex nature depending both on the compressive pulse loading level and the piezoelectric modulus value of the PEG sensitive element, and on the electrical load resistance