Analysis on coupled vibration of piezoelectric ceramic stack with two piezoelectric ceramic elements

Research on Inherent Frequency and Vibration Characteristics of Sandwich Piezoelectric Ceramic Transducer

Great progress has been made in the field of ultrasonic processing in recent years, and piezoelectric ceramic transducers have been widely used as drive sources. In this paper, a sandwich piezoelectric ceramic transducer is designed, and the vibration of each part of the transducer is analyzed by elastic mechanics and piezoelectric theory. According to its mechanical and electrical boundary conditions, the vibration model of the piezoelectric transducer was established. Based on the equivalent elastic modulus method for simplifying the pre-stressed bolts into a one-dimensional transducer vibration model, the relationship between the one-dimensional axial response frequency of the transducer and the length of each component was obtained. Based on the half wavelength theory, a transducer with the vibration node in the crystal stack and an inherent frequency of 15 kHz was designed and fabricated. In order to verify the natural frequency and vibration characteristics of the piezoelectric transducer, a laser vibration measurement system was built in this study. The vibration characteristics of the transducer under different parameters such as voltage and frequency were analyzed, and the accuracy of the vibration model was verified. The vibration states of the end surface of the transducer and the radial surface were evaluated at the first-order inherent frequency and second-order inherent frequency. The results show that the equivalent simplified model established in this study can effectively design the inherent frequency of the transducer, and the operation at the first-order inherent frequency meets the one-dimensional assumptions of this study. The transducer operating conditions measured in this study also provide a more detailed reference for ultrasonic processing applications.

Three-dimensional coupled vibration of the rectangular piezoelectric ceramic stack

The three-dimensional coupled vibration of the rectangular piezoelectric ceramic stack is analyzed by adopting the equivalent elastic method, which is an approximate analytical method. When the shear stress and strain are ignored, the complex coupled vibration of the rectangular piezoelectric ceramic stack is simplified to three one-dimensional coupled vibrations by defining three mechanical coupled coefficients. The three-dimensional electromechanical equivalent circuit is established on the basis of the analysis. The resonance frequency equation which determines the vibration mode of the piezoelectric vibrator is derived and the resonance frequencies of different modes can be calculated. According to the resonance frequency equation of coupled vibration, the effects of the length, width, and thickness of the rectangular piezoelectric ceramic stack on the resonance frequency are analyzed. Three groups of the rectangular piezoelectric ceramic stack of different dimensions are made for experiments and numerical simulations. The results show that the theoretical results are in good agreement with the experimental analysis and simulation results, which provide theoretical support for expanding the application of rectangular piezoelectric vibrators.

An Ultrasonic Laminated Transducer for Viscoelastic Media Detection

Based on the principle of underwater transducers, an ultrasonic four-laminated transducer with a frequency of 1 MHz was proposed to solve the problem of large energy attenuation when ultrasonic waves propagate in viscoelastic media. First, this study targeted solid rocket propellant as the research object, and the energy attenuation characteristics of ultrasonic waves propagating in viscoelastic media were analyzed through the derivation of the wave equation. Second, the structure of a four-laminated transducer with a frequency of 1 MHz was designed, and the resonance frequency was obtained by a graphical method. The sound field simulation and experimental results showed that the gain of the four-laminated transducer was 15 dB higher than that of the single-wafer transducer. An ultrasonic feature scanning system was built to complete the qualitative and quantitative detection of the smallest artificial hole (ϕ2 mm × 10 mm). Finally, two different natural defects were scanned, and the results were compared with those obtained using an industrial computed tomography detection system. The results showed that the ultrasonic method was more accurate in characterizing two natural defects. The primary cause was that the industrial CT was not sensitive to defects parallel to the incident direction of the ray. Therefore, this study not only achieved the qualitative and quantitative nondestructive testing of solid rocket propellants, but also provides an important reference for other viscoelastic components.