Giant Magnetostrictive Ultrasonic Transducer Research Articles

Modeling the optimal compensation capacitance of a giant magnetostrictive ultrasonic transducer with a loosely-coupled contactless power transfer system

Modeling the optimal compensation capacitance of a giant magnetostrictive ultrasonic transducer with a loosely-coupled contactless power transfer system

Investigations on a mathematical model for optimum impedance compensation of a giant magnetostrictive ultrasonic transducer and its resonance characteristics

Giant magnetostrictive materials (GMMs) have been widely used to fabricate transducers with high-energy output because of their excellent properties. However, there are few reports on mathematical models to optimize the impedance compensation and resonance characteristics of giant magnetostrictive transducers. In this study, a giant magnetostrictive ultrasonic transducer (GMUT) suitable for rotary ultrasonic machining systems is proposed. A mathematical model for optimum impedance compensation that considers the loss in energy conversion is established to maximize the use of ultrasonic energy. The frequency characteristics of the electrical feedback signal in the resonance state are investigated, and the resonance zone found is used for frequency tracking. An impedance analyzer is used to determine the parameters of the mathematical model, and the validity of the optimum compensation capacitance is verified by experiments. The frequency characteristics of the minimum current, active power, and amplitude are obtained to obtain the resonance zone in the GMUT with the lowest energy consumption. The results of this study provide a reference for frequency tracking.

On the optimum resonance of giant magnetostrictive ultrasonic transducer with capacitance-based impedance compensation

Due to the large magnetostrictive coefficient, high power density and fast response speed of giant magnetostrictive materials, the giant magnetostrictive ultrasonic transducer (GMUT) becomes an increasingly popular research topic in making a high-power ultrasonic vibration. However, due to the complex energy conversion mechanism of the GMUT, the optimum resonance of the GMUT cannot be determined to utilize the ultrasonic energy to the maximum extent. To solve this problem, an equivalent circuit model of the GMUT is improved with capacitance-based impedance compensation, and the influence of the compensation capacitance on the GMUT is studied by the parameter characterization of the extreme currents and resistance points (X = 0 Ω) in the impedance circle derived from the improved model. Thus, an impedance-compensation method for determining the maximum amplitude of the GMUT is proposed to reach the optimum resonance. Experimental results show that the improved model corresponds well with the impedance circle under different compensation capacitances, and the maximum amplitude related to the optimum resonance is determined at the optimal point where the mechanical resonance and electrical resonance occur nearly simultaneously.

Effect of Terfenol-D rod structure on vibration performance of giant magnetostrictive ultrasonic transducer

In this study, a giant magnetostrictive ultrasonic transducer was designed with Terfenol-D as the active material. The influence of different Terfenol-D rod structures on the performance of the giant magnetostrictive transducer was investigated. Finite element analysis was used to analyze the dynamics of the theoretical giant magnetostrictive transducer and to validate the design. Eddy current losses were simulated for Terfenol-D rods of various structures using finite element analysis in ANSYS Maxwell. Two different Terfenol-D rods were then fabricated with either slices along the axial direction or slit along the radial direction, then the impedance and amplitude of the magnetostrictive ultrasonic transducer composed of the two Terfenol-D rods were measured. The results suggest that sliced Terfenol-D rods can suppress eddy currents more effectively, resulting in higher energy conversion efficiency; therefore, the Terfenol-D rods of small giant magnetostrictive transducers should be sliced along the axial direction to suppress eddy currents, whereas radial slits should be adopted for the rods of large giant magnetostrictive transducers to ensure integrity of the Terfenol-D rod and avoid adverse effects on the vibration performance of the giant magnetostrictive transducer that are caused by cutting the rods.

An amplitude prediction model for a giant magnetostrictive ultrasonic transducer

Rotary ultrasonic machining (RUM) is widely used in the processing of brittle and hard materials. The application of giant magnetostrictive ultrasonic transducers (GMUT) with effective vibration performance is an increasingly popular field of research within RUM. A generalized amplitude prediction model for GMUT is obtained in this paper by first providing an equivalent kinetics model of the GMUT. Considering the influence on interaction force between Terfenol-D and the external mechanical mechanism, the prestress mechanism of Terfenol-D and the joint face of the horn are determined as equivalent to two spring-damping systems in series, and a general GMUT vibration equation is established. The equivalent stiffness of the prestress mechanism is then identified, and the mechanical quality factor of the vibration system is calculated by impedance analysis. The influence of the joint face of the horn and the prestress mechanism on the amplitude is then studied by nonlinear least square fitting. Based on a magnetostriction and magnetization model, an odd power amplitude prediction model with mechanical quality factor, excitation current amplitude, and excitation frequency is proposed. The experimental results demonstrate that the proposed model can effectively predict the output amplitude of the GMUT with different mechanical quality factors for different excitation signals, providing a method for system design and optimization of the GMUT.

Nonlinear Dynamic Characteristics and Control of Giant Magnetostrictive Ultrasonic Transducer

The nonlinear dynamic characteristics of giant magnetostrictive ultrasonic transducer (GMUT) are researched in this paper, and the optimal control strategy is proposed. New nonlinear differential terms are introduced to explain the hysteretic phenomena of giant magnetostrictive materials (GMM), and the nonlinear dynamic model of a giant magnetostrictive ultrasonic transducer subjected to harmonic magnetic field and stochastic disturbance is developed. The system’s nonlinear dynamic responses are discussed, and the optimal control strategy is proposed to improve the system’s accuracy. Numerical simulation and experiment results show that there are abundant nonlinear dynamic behaviors in the system; the stability of the system varies with the parameters, which causes stochastic bifurcation; the system’s accuracy is improved through stochastic optimal control. The results of this study are helpful for the application of giant magnetostrictive ultrasonic transducer in engineering fields.

The Design of Rare-Earth Giant Magnetostrictive Ultrasonic Transducer and Experimental Study on Its Application of Ultrasonic Surface Strengthening.

Ultrasonic transducer based on rare-earth giant magnetostrictive materials was designed in accordance with the technical requirements of ultrasonic surface strengthening. The whole structure of the transducer was designed. Modal analysis is made to get the natural frequency of the compound oscillator. The working frequency of the transducer should be guaranteed at about 15.2 kHz and the composite oscillator should have relatively better vibration mode. The magnetic field of the transducer is well sealed and the transducer will not show obvious magnetic flux leakage phenomenon. Which shows the rationality of structural design. Based on this transducer, the ultrasonic surface strengthening experiment on 40 steel was conducted. The surface roughness and hardness of the parts were analyzed after the experiment. The results show that the surface of the parts reach the mirror surface result after the ultrasonic strengthening. When compared to the previous process, the roughness decreases by about 75%, and the surface hardness increases by more than 20%.

Design and numerical simulation of novel giant magnetostrictive ultrasonic transducer

This paper provides a design method of a novel giant magnetostrictive ultrasonic transducer utilized in incremental sheet metal forming. The frequency equations of the ultrasonic vibrator were deduced and the corresponding correctness verified by the modal and harmonic response characteristic through the finite element method (FEM) and ANSYS software. In addition, the magnetic field of the vibrator system was designed and verified by the ANSYS. Finally, the frequency tests based on the impedance response analysis and the amplitude measurements based on the laser displacement sensor were performed on the prototype. The results confirmed the appropriate design of this transducer, setting the foundation for a low mechanical quality factor and satisfying amplitude.

Effect of temperature on the performance of a giant magnetostrictive ultrasonic transducer

The effect of temperature on the performance of a giant magnetostrictive ultrasonic transducer (GMUT) was investigated by measuring variations in the resonance frequency and mechanical quality factor of the GMUT at different temperatures. The equivalent circuit model of the GMUT was presented and the total electrical impedance equation was obtained. Curves of the impedance circle were obtained at different temperatures to determine the resonance frequency and mechanical quality factor. To verify the impedance-based results and obtain precise values of the resonance frequency and effective frequency bandwidth, the amplitude-frequency response within the same temperature range was examined experimentally. These results were consistent with those of the impedance analysis, which demonstrates the validity of the equivalent circuit model. Moreover, the resonance frequency and effective bandwidth of the GMUT were found to decrease with increasing temperature, which means that the vibration amplitude is more sensitive to variation in the resonance frequency at high temperature owing, for example, to static or dynamic system loading, changes in the material properties, or drive-signal variability. Accordingly, the temperature in the GMUT should be precisely controlled to improve the stability of vibration.