Longitudinal Vibration Transducers Research Articles

Theoretical study on resonance frequencies of vibration modes of Janus-Helmholtz transducer

Janus-Helmholtz transducer has the characteristics of high-power and broadband transmission due to the coupling between the longitudinal resonance of the driver and the liquid cavity resonance of Helmholtz resonator. Traditional view holds that the low frequency resonance peak in the transmitting voltage response curve in water is fluid cavity mode of Helmholtz resonator while the high frequency resonance is the longitudinal mode of Janus transducer. However, in the past few decades, a large number of experimental studies have found that this conclusion is questionable. This work is to distinguish the two resonances in the response curve and the two vibration modes of Janus-Helmholtz transducer. Based on the Janus-Helmholtz transducer prototype reported in the literature, the resonance frequencies of the vibration modes of Janus-Helmholtz transducer are studied theoretically. The structure dimensions and material parameters of the prototype are listed in detail. The test results and simulation results of conductivity are also presented. The longitudinal resonance of the driver is determined by using the equivalent circuit method and finite element analysis. Radiation masses of both Janus transducer and typical longitudinal vibration transducer are also calculated to analyze the phenomenon of the sharp decrease of longitudinal resonance frequency in water. Acoustic modal analysis by using ANSYS software is performed to investigate the resonance frequency of complex Helmholtz resonator in Janus-Helmholtz transducer. Correction length on the vent introduced by external fluid sound radiation is used to obtain the accurate Helmholtz resonance frequency. The sound pressure distribution of Helmholtz resonator obtained through finite element method is investigated, and the correct equivalent formula for solving the Helmholtz resonance frequency is obtained. The results reveal that the first resonance in the response curve is driver resonance while the second one is Helmholtz resonance, which is contrary to the traditional view. The considerable reduction of driver resonance frequency in water is mainly due to the large radiation mass on the four large radiation surfaces of the Janus transducer, which also causes the sharp response of driver resonance. In Janus-Helmholtz transducer, there are two Helmholtz resonators with the same size, instead of only one resonator in the traditional view. The two resonance frequencies solved by the method proposed in this work are in good agreement with the test and simulation results. These conclusions play an important role in correctly understanding the structure and characteristics of Janus-Helmholtz transducer at source, as well as provide technical support for structural optimization and innovation, thus improving the acoustic emission properties of the transducer.

Optimization of a sandwich longitudinal vibration transducer with a large radiation surface based on hole structure of near-periodic phononic crystal

<p indent="0mm">The existence of radial vibration in a large-dimension sandwich longitudinal vibration piezoelectric ceramic transducer will reduce the longitudinal radiated sound power and shorten the service life of the transducer, which seriously affects its performance and reliability. To reduce the strong coupling between longitudinal and radial vibration, ensure high longitudinal working efficiency and reliability, and overcome the disadvantages of narrow working bandwidth, poor uniformity of amplitude distribution, and small displacement amplitude, the large-dimension sandwich longitudinal vibration piezoelectric ceramic transducer is optimized through machining several periodic holes on the front cover plate of the transducer to form a multi-point deformation defect structure. In this study, the simulation software is used to simulate and analyze the performance index of the optimized transducer, and the optimization effect is verified through experiments. The results show that the large-dimension piezoelectric ceramic transducer based on a multi-point deformation defect near-periodic phononic crystal structure has a single longitudinal vibration mode, which can effectively improve the displacement amplitude and amplitude distribution uniformity of the radiation surface of a large-dimension transducer and broaden the transducer’s working bandwidth.

Design and experimental study of longitudinal-torsional ultrasonic transducer with helical slots considering the stiffness variation

The ultrasonic transducer employing helical slots to generate longitudinal-torsional (L&T) ultrasonic vibration is popular in the field of hard and brittle material machining. However, the design approach for this type of L&T ultrasonic transducer is not well established. An improved design model combining equivalent circuit theory and material parameter equivalent method based on stiffness variation was proposed in this study. The structure parameters of the transducer can be obtained according to given resonance frequency and nodal position. The model can further predict electrical characteristics and mechanical responses under specific excitation. For the preliminary verification of this theoretical model and the optimization of the transducer, finite element analyses were carried out to investigate the influences of slot structure parameters on dynamic performances in terms of resonance frequency, frequency separation, and amplitude of L&T vibration. After that, a prototype was manufactured according to the design results, and the measurements of impedance curve and vibration amplitude were conducted. The experimental results indicate that this prototype resonates at 24,920 Hz with an effective electromechanical coupling coefficient of 0.19. Meanwhile, the vibration amplitude in longitudinal direction is 8.1 μm and that in tangential direction is 5.6 μm under 70-V sinusoidal voltage excitation, which are consistent with the theoretical design and simulation results. Furthermore, machining tests demonstrate that surface roughness reduction and surface quality improvement can be gained by adopting this L&T ultrasonic transducer, compared to using the longitudinal vibration transducer. The proposed design approach was validated and this study can provide guidelines for the design of L&T ultrasonic transducer for rotary ultrasonic machining (RUM).

Ultrasonic complex vibration source using two longitudinal vibration transducers and a uniform rod with diagonal slits

It has been reported that ultrasonic welding using planar vibrations results in higher weld strength and less damage to the work pieces compared with ultrasonic welding using linear vibrations. However, torsional vibration transducers are small and expensive, thus reducing flexibility in the use of the vibration source. Therefore, in this study, we developed an ultrasonic longitudinal-torsional vibration source using longitudinal vibration transducers and a uniform rod with diagonal slits. The proposed vibration source generates torsional vibration by using a uniform rod with diagonal slits instead of a conventional torsional vibration transducer. As a result, it is found that a planar vibration locus is obtained by inputting two resonance frequencies simultaneously.

Experimental Investigation of Peening Cylindrical Workpieces Utilizing a Transducer with Ring Sonotrode

In industrial applications, the shafting components with high stress are easily damaged due to cyclic loads if there is no surface treatment. With the use of ultrasonic cavitation peening, the residual compressive stress and the surface hardness of these components can be improved. While traditional longitudinal vibration transducers are used to treat cylindrical workpieces, the treated areas are limited, and the treatment period is relatively long. To solve these problems, we designed a novel configuration of the piezoelectric transducer as a type of the combination of rod and ring. During ultrasonic cavitation peening, we placed the cylindrical workpieces in the ring tool to improve the limitation. However, the treated surface properties were largely influenced by the input parameters (driving voltage and rod diameters). In this investigation, the cylindrical workpieces, which were covered with aluminum foils, were first treated by ultrasonic cavitation peening to detect the intensity and distribution of the cavitation bubbles on the treated surface. Then, the sonochemiluminescence method was utilized as an additional way to find the optimal operation parameters (190 V and 16 mm). Finally, the ultrasonic cavitation process was conducted with the optimal parameters. The treatment results showed that the surface hardness increased by about 36% without significant increase of the surface roughness.

3Pa4-6 Development of complex vibration source using longitudinal vibration transducers and diagonal slits –Case of considering vibration of flange–

3Pa4-6 Development of complex vibration source using longitudinal vibration transducers and diagonal slits –Case of considering vibration of flange–

A low-frequency longitudinal vibration transducer with a helical slot structure.

In this paper, the authors design a longitudinal vibration transducer with a low resonance frequency and a large longitudinal amplitude by carving helical slots on the surface of the hollow cylinder front mass. The resonance frequency of the transducer is calculated by frequency equations obtained from the equivalent circuit of the transducer. A finite element model (FEM) of the transducer is set up, and it is used to compute the admittance and the longitudinal vibration amplitude of the transducer. The influences of the slot number, the width of the slot, the number of spires of the spring, and the helix pitch on the performance of the transducer are analyzed by numerical simulation. The simulation results show that the resonance frequency of the transducer with helical slots is much lower than that of the transducer without slots. A prototype transducer with helical slots is constructed, and the admittance and longitudinal vibration amplitude are measured experimentally. The measured resonance frequency of the transducer is in good agreement with the simulation results. The measured longitudinal vibration amplitude is lower than that computed by the FEM, which may be due to the damping of the materials.

An experiment study on temperature characteristics of a linear ultrasonic motor using longitudinal transducers

The temperature characteristics of a T-shaped linear ultrasonic motor using longitudinal vibration transducers are reported. When the ultrasonic motor is excited by different voltages, the surface temperatures at the driving foot, PZT ceramic and end cap are tested by a thermal imager for obtaining the thermal characteristics of the motor under no-load condition. PZT ceramic shows the maximum temperature increase. Then, the variations of resonant frequencies, electromechanical coupling factors and mechanical Q-factors versus time, as well as the effect of the temperature on the resonance frequencies, electromechanical coupling factors and mechanical Q-factors, is measured and analysed under the long-term running. It is found that all the resonance frequencies and electromechanical coupling factors decrease as the increase of the temperature, as well as the mechanical Q-factors. In addition, the change of the output speed over temperature is tested and the obtained result shows the trend of decline. This work can provide useful guidelines for the design and optimization of linear ultrasonic motor operating in wide temperature range.

Finite Element Calculation with Experimental Verification for a Free-Flooded Transducer Based on Fluid Cavity Structure

A free-flooded transducer that couples the vibration of a longitudinal vibration transducer and the fluid cavity of an aluminum ring was investigated. Given the transducer is based on a fluid cavity structure and has no air cavity, it can resist high hydrostatic pressure when working underwater, which is suitable for application in the deep sea. At first, the structure and working principle of the transducer were introduced. Then, the axisymmetric finite element model of the transducer was established; and the transmitting voltage response, admittance, and radiation directivity of the transducer were simulated using the finite element method. According to the size of the finite element model, a prototype of the transducer was designed and fabricated, and the electro-acoustic performance of the prototype was measured in an anechoic water tank. The experimental results were consistent with the simulation results and showed a good performance of the transducer. Finally, the improvement of the radiation directivity of the transducer by the optimal design of the free-flooded aluminum ring was obtained using the finite element method and verified by experiments.

Effect of ultrasonic transducer structure on friction plasticizing heating rate under the longitudinal vibration excitation

The different structural parameter combinations of the transducer and the interaction mechanism of friction heating and plasticizing polymer granulates under the longitudinal vibration excitation were introduced to study ultrasonic plasticizing of polymer granulates, the structure parameters of the ultrasonic transducer with known resonant frequency and the particle output amplitude at the tool head front end were utilized to establish the friction plasticizing heating equations of the polymer granulates under the longitudinal vibration excitation. The dominant influence relationship between the structural parameters of the transducer and the heating rate of the polymer granulates was obtained by using Mathematica software, the results of further regression analysis show that the amplification ratio of the horn has the greatest effect on the friction plasticizing heating rate in structure parameters of the longitudinal vibration transducer, the effect of the front cover length, the ultrasonic tool head length and the horn length on the heating rate are smaller, the influence of the thickness of the piezoelectric ceramic and the length of the rear cover on the heating rate are smallest.

Ultrasonic metal welding with a vibration source using longitudinal and torsional vibration transducers

Conventional ultrasonic metal welding for joining dissimilar metals uses a linear vibration locus, although this method suffers from problems such as low overall weld strength. Our previous studies have shown that ultrasonic welding with a planar vibration locus improves the weld strength. However, the vibration source in our previous studies had problems in longitudinal-torsional vibration controllability and small welding tip. Therefore, the study of the optimal shape of the vibration locus was difficult. Furthermore, improvement of weld strength cannot be expected. We have developed a new ultrasonic vibration source that can control the longitudinal-torsional vibration and can connect to a large welding tip. In this study, we clarified the longitudinal-torsional vibration controllability of the developed ultrasonic vibration source. Moreover, we clarified that using the planar locus of the developed vibration source produced a higher weld strength than our previous studies, and clarified the optimal shape of the vibration locus.

An I-shape linear piezoelectric actuator using resonant type longitudinal vibration transducers

Resonant type longitudinal vibration transducers are used in this work to construct a linear piezoelectric actuator with four driving feet. Totally three longitudinal transducers are integrated in I-shape to form the proposed actuator, which contains one vertical transducer and two horizontal transducers. These three transducers vibrate under longitudinal modes with certain temporal sequence, whose vibrations are superimposed in the actuator to generate elliptical motions on the four driving feet. The three transducers are tuned to be suitable dimensions, under which they have very close 1st longitudinal resonance frequencies; the working frequency of the piezoelectric actuator is designed to be about 31.3kHz. The vibration coupling problem between the longitudinal transducers are studied by calculating the motion trajectories of the four feet. It is found that the temporal shift of the longitudinal vibrations can be used to tune the movement trajectories; the four feet can get nearly the same vertical displacements under a phase shift of 105°. At last, the vibration characteristics and mechanical output performances of a prototype are measured. The working frequency of the prototype, the maximum speed, and the maximum thrust force are measured to be 33.15kHz, 1563mm/s, and 158.2N, respectively.

Multi-fluid cavity underwater acoustic transducer

A multi- fluid cavity underwater acoustic transducer is developed. The main structures of the transducer include inner Helmholtz resonator, Janus longitudinal vibration transducer and two outer Helmholtz resonators. The vibration of Janus transducer at low frequencies is enlarged by the inner Helmholtz resonator, and the vibration of Janus transducer at high frequencies is enlarged by the two outer Helmholtz resonators, so this kind of transducer can transmit broadband acoustic signal in water. Operation bandwidth of the multi-fluid cavity underwater acoustic transducer is usually more than two octaves. The broadband operating mechanism of the transducer is studied. The effect of some of the major structural parameters on the operation bandwidth and Helmholtz resonance frequency is studied by finite element software ANSYS. The structure size of virtual prototype is obtained. A prototype is produced based on finite element design results, the electro-acoustic performance are tested in anechoic tank. The results agree well with the simulation results. Operation bandwidth of the prototype is 500 Hz–2500 Hz, the maximum source level greater than 200 dB.

Design of Multi-step Plate in Flexural Vibration

Combing the stepped thin plate in flexural vibration with the longitudinal vibration transducer into a compound of radiator, it has a numerous applications in air in high power ultrasonic field due to its extensive radiated surface and high radiated efficiency. However, design of this kind of radiator appears very complicated for a number of special functions and equations to be solved in its frequency equation. Taking the plate in flexural vibration with two steps at a free edge as an example, an algorithm for design of this kind of radiator by numerical calculation and program is proposed under given conditions of operating frequency, base thickness and material. It is shown that the tested results are in good agreement with the theoretical ones. The study provides a new method for design of the multi-step plate in flexural vibration.

Research of Frequency Band by Multiple-Mode Extended for Longitudinal Vibration Acoustic Transducer

The problem of frequency band of acoustic transducer is the key research field. By summarizing of Tonpilz and Janus-type transducer influence factors,such as transducer structure type, geometry parameters, the rule of redressing the mechanical quality factor Qm is investigated, and the trend of extending the frequency band by multi-mode coupling is got. By analyzing the multi-modal forms of vibration of double and triple resonance resonant, several types of extending frequency band of transducer are categorized under this forms. The advantages and disadvantages are investigated by general theory analysis of extending longitudinal vibration transducer, and the state of the art and the applications are displayed. So that the researchers are easier to understand the transducer, and can offer ideas for new design.

A rectangle-type linear ultrasonic motor using longitudinal vibration transducers with four driving feet

To make full use of the vibrational energy of a longitudinal transducer, a rectangle-type linear ultrasonic motor with four driving feet is proposed in this paper. This new motor consists of four longitudinal vibration transducers which are arranged in a rectangle and form an enclosed construction. Lead zirconate titanate ceramics are embedded into the middle of the transducer and fastened by a wedge-caulking mechanism. Each transducer includes an exponentially shaped horn located on each end. The horns of the vertical transducers intersect at the base of the horizontal transducers' horns; the tip ends of the horizontal transducers' horns are used as the driving feet. Longitudinal vibrations are superimposed in the motor and generate elliptical movements at the tip ends of the horns. The working principle of the proposed motor is analyzed. The resonance frequencies of two working modes are tuned to be close to each other by adjusting the structural parameters. Transient analysis is developed to gain the vibration characteristics of the motor. A prototype motor is fabricated and measured. The vibration test results verify the feasibility of the proposed design. Typical output of the prototype is a no-load speed of 928 mm/s and maximum thrust force of 60 N at a voltage of 200 Vrms.

A u-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet was proposed in this paper. The proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns of the horizontal transducer and the vertical transducer intersect at the tip ends where the driving feet are located. Longitudinal vibrations are superimposed in the motor and generate elliptical motions at the driving feet. The two vibration modes of the motor are discussed, and the motion trajectories of driving feet are deduced. By adjusting the structural parameters, the resonance frequencies of two vibration modes were degenerated. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 854 mm/s and maximum thrust force of 40 N at a voltage of 200 V(rms).

A square-type rotary ultrasonic motor with four driving feet

This paper presents and verifies a new idea for constructing rotary ultrasonic motor that may effectively make use of the longitudinal vibrations of the bolt-clamped transducers. Based on the idea of generating elliptical motion on the driving tip by superimposing longitudinal vibrations, a square-type rotary ultrasonic motor with four driving feet is proposed. This new motor consists of four longitudinal vibration transducers, which are located in square-type and form an enclosed construction. The longitudinal vibrations of the four transducers are superimposed to produce the same circular movements on the four feet, which can push the rotor into motion when a preload is applied. By using FEM method, the proposed motor is designed and analyzed, and circular trajectories on the driving feet are gained. The vibration and input impedance characteristics of the motor are measured after the fabricating of a prototype, and the test results are in good agreement with the FEM analysis results. Typical output of the prototype is no-load speed of 71r/min and maximum torque of 12.3Nm at an exciting voltage of 200Vrms.

Study on Ultrasonic Micromateriel Transmission System

A new type ultrasonic materiel transmission system is proposed in this study. In this new design, bending vibration traveling wave is generated in an elastic pipe by using two uniform sandwich type longitudinal vibration transducers. Thus, elliptical trajectory motions can be formed at particles on the pipe wall, which can drive the materiel by frictional force. The adopting of sandwich transducer in this device can gain large vibration amplitude and improve the electromechanical coupling efficiency. The structure and working principle of the proposed design are introduced. The transducer and the pipe are designed and analyzed by using FEM method. The longitudinal vibration mode of the transducer and the bending vibration mode of the pipe are analyzed, and the resonant frequencies of these two modes are tuned to be close. A prototype system is fabricated and measured.

A Standing Wave Ultrasonic Motor Using Longitudinal Vibration Transducers

A new type standing wave ultrasonic motor is proposed in this study. In this design, three longitudinal vibration transducers are clamped on the inner side of a ring with driving teeth by screws. Bending standing wave can be generated in the ring by the longitudinal vibrations of the transducers. Thus, oblique linear simple harmonic vibrations are formed on the teeth, which can drive the rotor by frictional force. The structure and working principle of the proposed design are introduced. The motor is designed and analyzed by using FEM method. A standing wave is gained after the degeneration between the bending vibration of the ring and the longitudinal vibration of the transducer. The test results of the prototype motor verify the feasibility of the proposed design.