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

Abstract

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.

On the Directivity of Lamb Waves Generated by Wedge PZT Actuator in Thin CFRP Panel

“…In order to develop the finite-element model of the full system's dynamics that should be quantitatively comparable with the response of a real-world experimental system, the electrical and mechanical subsystems properties of the modeled actuator need to be as close as possible to the properties of the used Olympus actuator. Identification technique of its structure and the electro-mechanical properties were presented in our paper [41]. The sources, which have been used to adequately build the transducer's structure and replicate its dynamics in FE model, were the technical notes about the ultrasonic principles important to wedge transducer application and design, including the scheme and main requirements to the active element, backing, matching layers and the sound path presented by Olympus Co. ® [48], the outer dimensions of the used actuator (see Figure 3), the frequency response functions for the electric current through PZT active plate, and out-of-plane displacement amplitude on the actuator's footprint (see Figure 4a,b), which have been determined experimentally.…”

“…This paper is aimed to reveal the possibility of generating directed acoustic waves by the angle-beam wedge actuator in thin-walled structures made of highly anisotropic material. As objects of our study we used the orthotropic CFRP panel and the angle-beam wedge actuator Olympus V414-SB-ABWS (Waltham, MA, USA), which has been modeled and experimentally investigated in our works [41]. By using experimentally verified frequency response functions for the displacement amplitudes and the electric current consumption of the actuator, the testing frequencies were selected.…”

“…The linear and angular outer dimensions of the used wedge actuator[41].Materials 2020, 13, x FOR PEER REVIEW 9 of 23…”

On the Directivity of Lamb Waves Generated by Wedge PZT Actuator in Thin CFRP Panel

“…In order to develop the finite-element model of the full system's dynamics that should be quantitatively comparable with the response of a real-world experimental system, the electrical and mechanical subsystems properties of the modeled actuator need to be as close as possible to the properties of the used Olympus actuator. Identification technique of its structure and the electro-mechanical properties were presented in our paper [41]. The sources, which have been used to adequately build the transducer's structure and replicate its dynamics in FE model, were the technical notes about the ultrasonic principles important to wedge transducer application and design, including the scheme and main requirements to the active element, backing, matching layers and the sound path presented by Olympus Co. ® [48], the outer dimensions of the used actuator (see Figure 3), the frequency response functions for the electric current through PZT active plate, and out-of-plane displacement amplitude on the actuator's footprint Materials 2020, 13, 907 9 of 22 (see Figure 4a,b), which have been determined experimentally.…”

“…This paper is aimed to reveal the possibility of generating directed acoustic waves by the angle-beam wedge actuator in thin-walled structures made of highly anisotropic material. As objects of our study we used the orthotropic CFRP panel and the angle-beam wedge actuator Olympus Materials 2020, 13, 907 6 of 22 V414-SB-ABWS (Waltham, MA, USA), which has been modeled and experimentally investigated in our works [41]. By using experimentally verified frequency response functions for the displacement amplitudes and the electric current consumption of the actuator, the testing frequencies were selected.…”