Magnetostrictive Ultrasonic Transducer Research Articles

Biomimetic Ultrasonic Vibrator with Broadband Characteristics Inspired by Leaf-Cutting Ants.

Power ultrasound is widely used in industrial production, medical equipment, aerospace, and other fields. Currently, there are two main types of commonly used power generation devices: piezoelectric ultrasonic transducers and magnetostrictive ultrasonic transducers. However, in certain situations with limited external dimensions, the applications of existing power ultrasound devices are limited. In nature, leaf-cutting ants excite vibrations through their tiny organs. Inspired by the vibratory organs of leaf-cutting ants, a new type of biomimetic ultrasonic vibrator (BUV) comprising a scraper, dentate disc, and fixture system was proposed, fabricated, and tested in this study. The experimental results showed that the BUV could operate in the frequency range of 16.8-19 kHz. Within the working frequency range, the vibration of the BUV was stable and the amplitude of the vibration displacement was greater than 22 µm. The operating frequency band of the BUV was broader than those of the piezoelectric and magnetostrictive ultrasonic transducers. In addition, the BUV can cut soft rubber and pig tissues with sufficient output power and load-carrying capacity. The BUV, as a new type of power ultrasonic excitation device, is expected to be applied in high-power micro operating scenarios, such as minimally invasive surgical instruments.

Повышение эффективности очистки канализационных труб

Today, the level of accessibility to water supply and sewage systems, their technical condition, and the quality of maintenance and cleaning are among the elements determining the quality of life in cities and small settlements. Efficient sewage systems are vital to maintaining environmental safety, the established sanitary norms, and the conditions of people’s comfortable accommodation. All these factors require the communal services of cities and megalopolises to maintain sewage systems in proper technical conditions, minimize operational costs, extend the service life of the systems, and organize and implement new treatment technologies. According to experts, the main enemy of the internal sewage systems is grease abundant in domestic wastewater. The initially warm wastewaters are soon cooled in the pipe, and grease impurities settle on the walls of the sewage pipe. The layer of grease deposits may trap other impurities, thus contributing to the formation of a larger and more complex clog. The development and implementation of new contemporary methods of treatment of sewage systems and, particularly, the use of ultrasonic vibrations reduces operational costs, extends the service life of the systems, and ensures environmental safety. For these purposes, the ultrasonic generator UZG-10 of 10 kW capacity was used, as well as the magnetostrictive ultrasonic transducer with a magnetoconductor with three rods. The middle rod is equipped with finished windings that rigidly connect the free ends of the other rods. The provided scheme of transducer manufacturing increases the efficiency of pipe treatment and significantly reduces energy costs.

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.

Numerical study of the effect of core geometry on the performance of a magnetostrictive transducer

Intensive ultrasonic waves can be generated based on the magnetostriction effect. These waves are used in many industries such as engineering, agriculture, and food industry. In this study, nickel as a naturally abundant magnetostrictive material was used in the core of a magnetostrictive transducer. This study aimed to investigate the influence of core geometry on the behavioral performance of the magnetostrictive ultrasonic transducer. The results showed that slightly stretching (elongating) the cross-section of the core increases the maximum radial and longitudinal magnetostrictive forces. Moreover, in tapered cores, by increasing the cone angle up to 30°, the maximum radial magnetostrictive force increased and then decreased. By increasing the cone angle, the maximum longitudinal magnetostrictive force and the coil required voltage almost linearly decreased. A proper ultrasonic transducer should have maximum sound pressure variations in the medium (sample). Thus, the variations of the magnetostrictive force in the longitudinal direction (Z axis) should be maximized. The results indicated that the conical core with a cone angle of 30° has the highest variations of magnetostrictive force in the Z-direction.

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.

Investigating vibration characteristics of magnetostrictive transducers for air-coupled ultrasonic NDT of composites

In this study, high-power ultrasonics has been used for non-contact nondestructive testing of composites. Air-coupled magnetostrictive ultrasonic transducers provide reasonable amplitudes of horn oscillations even if this type of ultrasonic stimulation is close to the idle mode. Four types of ultrasonic horns have been designed and manufactured in order to choose an optimal horn configuration. For each horn, the dependence of vibration amplitude on ultrasonic unit power has been found to exhibit a good match between the theoretical and experimental results. The resonance frequencies and amplitudes of oscillatory velocity were experimentally evaluated by using the technique of scanning laser vibrometry and modeled by means of the Autodesk Inventor software. An air-coupled magnetostrictive transducer, in conjunction with an optimized horn, has been used in the evaluation of impact damage in a graphite epoxy composite and detection of water and excessive epoxy adhesive in an aviation honeycomb panel. It is expected that the technique of air-coupled ultrasonics may be useful for inspecting thin, fragile and hydrophilic materials.

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.

A new hybrid longitudinal–torsional magnetostrictive ultrasonic transducer

In this paper, a novel hybrid longitudinal–torsional magnetostrictive ultrasonic transducer (HL–TMUT) is introduced. The transducer is composed of a magnetostrictive exponential horn and a stainless steel tail mass. In this transducer a spiral magnetic field made up of longitudinal and circumferential magnetic fields is applied to the magnetostrictive horn. As a result, the magnetostrictive horn oscillates simultaneously both longitudinally and torsionally in accordance with the Joule and Wiedemann effects. The magnetostrictive exponential horn is designed in such a manner that it has the same longitudinal and torsional resonant frequency. It is made up of ‘2V Permendur’, which has isotropic magnetic properties. The differential equations of the torsional and longitudinal vibration of the horn are derived, and a HL–TMUT is designed with a resonant frequency of 20 573 Hz. The natural frequency and mode shapes of the transducer are considered theoretically and numerically. The experimental results show that this transducer resonates torsionally and longitudinally with frequencies of 20 610 Hz and 20 830 Hz respectively. The maximum torsional displacement is 1.5 mrad m−1 and the maximum longitudinal displacement is 0.6 μm. These are promising features for industrial applications.

Analysis of Dynamic Characteristics of the Magnetostrictive Power Ultrasonic Transducer

The giant magnetostrictive material (GMM) is a novel smart material based on magnetostrictive effect, and it is well suited to power ultrasonic transducer. Based on electromagnetic theory and vibration theory, the design and working principle of the magnetostrictive power ultrasonic transducer has been explained. This paper analyzed the dynamic characteristics of giant magnetostrictive materials under the outside magnetic field and deduced the wave equation of Terfenol-D rod, and the steady-state solution to the equation was obtained under given excitation. The speed and acceleration expressions of Terfenol-D were deduced by differentiating with respect to displacement equation. Based on developing mathematical models, computer imitation was made, and the result of modulation was analyzed from external conditions of transducer and inner structure of magnetostrictive material.

바이어스 자기장용 영구자석 배치에 따른 자왜 초음파 변환기 성능 예측에 관한 연구

The main subject of this paper is to develop analytic method with which output power or sensitivity variations of a magnetostrictive ultrasonic transducer can be estimated with no aid of experiments. After the bias magnetic field deployed over the patch is calculated using finite element analysis for magnetostatics, the representative value is extracted by averaging these field values. The operating point on the characteristic curve for magnetostriction is identified by this value and then the output performance is calculated from it. It is verified that the results from this simple model match well with those of its experimental version and some limits of this modeling technique are also considered.

패치형 자왜 초음파 변환기 성능에 대한 바이어스 자기장의 영향

The effects of biasing magnetic fields on the performances of magnetostrictive ultrasonic transducers are investigated. The transducers are patch-type ones which are used for SHM of plate structures. Various kinds of configurations of biasing magnets are covered experimentally. It is experimentally verified that how the biasing magnetic field deploys is the most significant factors on maximizing the transducer output. From the magnetostriction curve of nickel, it is concluded qualitatively that it is not the absolute values of biasing magnetic field but the slope of magnetostriction curve to be taken account of.

Feature Extraction for Defect Detection in Strands by Guided Ultrasonic Waves

Multi-wire strands are widely used in civil structures as tensioning members in prestressed concrete, cable-stayed and suspension bridges. In recent years, various researchers including the authors have investigated guided ultrasonic waves as a tool for monitoring the health of the strands. Magnetostrictive ultrasonic transducers have been successfully used to excite and detect the guided waves in these components. This study improves the general guided-wave technique with magnetostrictive transducers for the detection and sizing of defects in strands. The improvement consists of extracting sensitive and robust features of the wave signals, and then using these features to construct a damage index (D.I.). The proposed D.I. is unaffected by accidental variations in the excitation power or by changes in the electromechanical coupling efficiency of the transducers. The specific defect under investigation is a notch cut at varying depths in a strand that is subjected to a typical operational load. Features extracted after discrete wavelet processing of the wave signals result in a D.I. that is robust against noise and is linearly related to the notch depth in a logarithmic scale. In particular, the variance of the signal’s wavelet coefficients results in the largest sensitivity to notch depth.

Wavelet-based feature extraction for automatic defect classification in strands by ultrasonic structural monitoring

The structural monitoring of multi-wire strands is of importance to prestressed concrete structures and cable-stayed or suspension bridges. This paper addresses the monitoring of strands by ultrasonic guided waves with emphasis on the signal processing and automatic defect classification. The detection of notch-like defects in the strands is based on the reflections of guided waves that are excited and detected by magnetostrictive ultrasonic transducers. The Discrete Wavelet Transform was used to extract damage-sensitive features from the detected signals and to construct a multi-dimensional Damage Index vector. The Damage Index vector was then fed to an Artificial Neural Network to provide the automatic classification of (a) the size of the notch and (b) the location of the notch from the receiving sensor. Following an optimization study of the network, it was determined that five damage-sensitive features provided the best defect classification performance with an overall success rate of 90.8%. It was thus demonstrated that the wavelet-based multidimensional analysis can provide excellent classification performance for notch-type defects in strands.

EXPERIMENTAL INVESTIGATION AND NUMERICAL ANALYSIS ON ACOUSTIC LEVITATION

A single-axis acoustic levitator driven by a magnetostrictive ultrasonic transducer was developed, which can stably levitate metallic, semiconducting and organic materials as dense as 11.3g/cm3 in ground-based laboratory. Two types of resonant chambers were investigated by using boundary element approachin order to well understand the effect of chamber geometry on the sound field and, more importantly, on the capability and stability of acoustic levitation. The calculated results and experimental research indicate that the chamber possessing both a planar and a conical reflecting surface can produce radial positioning forces at the lowest mode. This makes its positioning capability larger than that of the chamber with only a planar reflecting surface.