The influence of piezoceramic stack location on nonlinear behavior of langevin transducers

Abstract

Power ultrasonic applications such as cutting, welding, and sonochemistry often use Langevin transducers to generate power ultrasound. Traditionally, it has been proposed that the piezoceramic stack of a Langevin transducer should be located in the nodal plane of the longitudinal mode of vibration, ensuring that the piezoceramic elements are positioned under a uniform stress during transducer operation, maximizing element efficiency and minimizing piezoceramic aging. However, this general design rule is often partially broken during the design phase if features such as a support flange or multiple piezoceramic stacks are incorporated into the transducer architecture. Meanwhile, it has also been well documented in the literature that power ultrasonic devices driven at high excitation levels exhibit nonlinear behaviors similar to those observed in Duffing-type systems, such as resonant frequency shifts, the jump phenomenon, and hysteretic regions. This study investigates three Langevin transducers with different piezoceramic stack locations by characterizing their linear and nonlinear vibrational responses to understand how the stack location influences nonlinear behavior.

Hydrodynamics and mass transfer of oscillating gas‐liquid flow in ultrasonic microreactors

“…The antinode plane with highest sound intensity is located at the microreactor, while the node plane with highest stress located at the piezoelectric pieces, as shown in Figure a. This novel design not only realizes highest ultrasound power density in the microreactor but also maximizes the energy efficiency and lifespan of the ultrasonic transducer . The fabricated USMR with a maximum power of 100 W and a resonance frequency around 20 kHz is shown in Figure b.…”

Nonlinear characterization of a single-axis acoustic levitator

“…However, for high displacement amplitudes, the acoustic radiation force increases gradually with the distance and suddenly drops after reaching a certain force value. A very similar behavior has been observed in Duffing oscillators 53 and in piezoelectric transducers, 47,48,54 where the sudden drop is referred to as "jump phenomenon." This phenomenon has a practical interest in acoustic levitation, because it is often necessary to adjust the separation distance between the transducer and the reflector during an experiment.…”

“…Another reason to measure the displacement amplitude is to prevent the transducer from operating at the nonlinear regime. 47,48 In this way, the displacement amplitude measurement is also used to ensure that the observed nonlinear effects are caused by the wave propagation in air, not in the transducer. The nonlinear characterization of a single-axis acoustic levitator is performed by using the experimental setup of Fig.…”

Guidelines for the design of efficient sono-microreactors

“…Consequently, l p is the thickness of the piezoelectric material, while l r is the thickness of the Teflon layer behind the piezo (reflector) and l e is that of the layer before it (emitter). It is necessary to define the size of the piezoelectric ceramic because it should be located at a vibration node [25] allowing the division of the transducer into two sections, where each one will develop a quarter of the wavelength of the resonator (Figure 3). In this way, Equation 1 can be splitted into Equations 2 and 3 ( Figure 3).…”