Experimental validation of axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency

The axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency capability have been proposed by adjusting the external electric resistance and the ratio of piezoelectric layer numbers between the actuator part and the sensor part, which have promising potential in designing the novel cymbal transducer for underwater sound projector and ultrasonic radiator applications. In the previous studies, the multilayer models were established to guide the design of the transducers with arbitrary layer number, and analyzed the dynamic characteristics theoretically. In this work, an experimental study is performed to validate the theoretical models and predictions. Piezoelectric rings with multiple concentric annular electrodes are designed to characterize the multilayer piezoelectric composite cylindrical transducers. The top surface of the piezoelectric rings is divided into two separate parts. One part is covered by multiple concentric annular electrodes, corresponding to the piezoelectric layers, and the other part is uncovered, corresponding to the elastic layers. Four prototypes are fabricated and each consists of four concentric annular electrodes. The impedance spectra are measured by the impedance analyzer to obtain the resonance and anti-resonance frequencies. Effects of two adjusting methods on the dynamic characteristics are evaluated experimentally. The experimental results basically coincide with the theoretical ones. This comprehensive experimental work assures the feasibility of using axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequencies and confirms the benefit of the developed theoretical models for guiding the fabrication and optimization of this type of transducers.

New ultrasonic technology of performance restoration of burner devices of gas pumping units

The analysis of the problem of pollution removal from hard-to-reach areas (cavities, closed openings and channels) on complicated-shaped parts of products of power mechanical and aggregate engineering is performed. The chemical composition of pollution on the example of the burner devices is studied. It is determined, that the large amount of deposits on weight consists of oxides of iron and the alloying metals. It is shown, that the most effective method of performance restoration of channels and openings is ultrasonic cleaning. However, this method has restrictions on impact on the hidden (shadow) zones owing to attenuation in cavitation processes. The cleaning method, according to which the combined impact is applied to the cleaned surfaces of the general cavitation and local contact vibration effect of the ultrasonic radiator, leading to high-frequency deformations and tension in deposits of organic and inorganic pollution and to their intensive peeling, is suggested. The technological modes of ultrasonic cleaning are defined experimentally. It is determined, that application of the suggested method allows significantly reduce the time of cleaning of channels and openings with removal to 97-98% of pollution at the brought ultrasonic power in 1 kW in comparison with the existing schemes of the general cavitation cleaning.