We study the propagation of plane waves in an unbounded body of a saturated ferromagnetoelastic solid. Tiersten's equations form small fields superposed on finite initial fields in a saturated ferromagnetoelastic material are employed, with their quasi static magnetic field extended to dynamic electric and magnetic fields governed by Maxwell's equations for electromagnetic waves. Dispersion relations of the plane waves are obtained. The cutoff frequencies and long-wave approximation of the dispersion curves are determined. Results show that acoustic, electromagnetic and magnetic spin waves are coupled in such a material. For YIG which is a cubic crystal without piezoelectric coupling, the acoustic and electromagnetic waves are not directly coupled but they can still interact indirectly through spin waves.
This study presents a linear ultrasonic motor. The structure is symmetrical and two groups of piezoelectric ceramics (PZT-8) are arranged along an axis. This way can make the motor structure compact. Operation principle of this motor is analyzed. Make and test a prototype to verify the feasibility of the principle. The experimental results show that the maximum no-load speed of the motor is 1289mm/s under the excitation of electrical signal with frequency of 29.96 kHz and voltage of 300VP-P.
Eshelby tensors is the basis of the micromechanics theory of composite materials and it is the key to solve the inclusion problem. In this paper, the Eshelby tensors of elastic isotropic inclusions are extended to the case of two-dimensional piezoelectric quasicrystal. By employing the Cauchy’s residue theorem, simplified and closed-form expressions of the two-dimensional piezoelectric quasicrystals Eshelby tensors of an elliptical inclusion embedded in the piezoelectric matrix are obtained. In the present theory, the coupling effect of phonon field, phason field and electric field are considered. These solutions are verified by degrading the quasicrystals into isotropic materials. Finally, some numerical results are investigated to shown the effect of the aspect ratio on the Eshelby tensors, which shown out the electric field affect the Eshebly tensors obviously. The obtained solutions can serve as the theoretical basis for the potential application in the field as fracture mechanics, piezoelectric composites, thermal and defection-related composites.
The purpose of this paper is to evaluate the scattering of flexural waves by a circular hole in a semi-infinite piezoelectric thin plate subjected to electric filed loading. A solution for the applied electric field in the thickness direction of the piezoelectric thin plate is developed. The mechanical model and solutions for the dynamic analysis of the piezoelectric plate with a circular hole are then established based on the Kirchhoff's thin plate assumption and linear piezoelectric dynamics theory. The dynamic moment concentration factor (DMCF) at different incident angles and incident wave frequencies are given in the numerical calculation. The numerical results show that the peaks of the circular hole's DMCFs appear at θ=π/2 and θ=3π/2. In the region of low-frequency, the DMCFs of the circular hole is insensitive to the different incident angles and the DMCFs is larger, but it is the opposite in the high-frequency region.
Generally, the noise caused by mechanical vibration often affect our health, especially from airplanes and automobiles and trains, etc. The traditional viscoelastic damping materials have any issues to control the low frequency vibration. Recently, the numerous research findings of locally resonant metamaterials have been achieved to improve the absorption functionality in the low frequency vibration. The dispersion curves of ABSPMMA polymer bipanel have been studied by using the finite element method (FEM) and their flexural wave bandgap with the steel mass blocks has been computed in ultralow frequency range from 54 Hz to 65 Hz at the subwavelength size. The frequency domain with negative density is the good agreement with the flexural wave bandgap. Thus, this original metamaterial bipanel with the resonance blocks can render the flexural wave bandgap to control the ultralow frequency vibration.
This paper proposes a bonded type longitudinal bending hybrid 2-DoF ultrasonic motor with a simple structure, compact volume, and lightweight to satisfy the demands for precision driving and control in narrow space. The motor has a pyramid-shaped piezoelectric mover and a friction base with concave spherical surface as a stator, and the preloading force is provided by a pressure spring placed inside the piezoelectric mover. The bending vibration and longitudinal vibration of the mover are used as the working modes. The ultrasonic motor has the characteristics of small volume, lightweight, high output force, and quickly moves. Experimental results indicated that 1) Under the excitation voltage of 550 Vpp, the maximum angular velocity in x and y directions can reach 414 deg/s; 2) Under the excitation voltage of 525 Vpp, the maximum output forces of the motor in x and y directions were 5.25 N and 5.34 N, respectively.
Interdigital transducer (IDT) has been gradually applied to SHM systems due to its designable operating frequency, low cost, adjustable frequency band, and low loss. In order to verify the optimal geometric size and electrode arrangement of the annular IDT, the optimally sized annular IDT will be processed by simulation. The precision electric field driven jet deposition 3D printer was proposed to prepare the Dielectric elastomer interdigital transducer (DE-IDT) according to the simulation results. Which provide a basis for the performance experiments.
For the weak fault signal from the variable speed gear, the extraction effect of SWT tacho-less order tracking method is poor. Based on this, a tacho-less order tracking method was proposed to extract the gear time-varying low-frequency fault characteristics. This method combines the advantages of chirplet path persuit (CPP) and synchrosqueezing wavelet transform (SWT). Based on CPP, the instantaneous frequency of vibration fault signal was estimated to obtain the phase of reference axis. The angle-domain stationary signal was obtained by equal angle resampling for the original vibration signal, and then its order spectrum and SWT decomposition were performed. Finally, the SWT decomposition components were selected for order spectrum and order envelope spectrum analysis, from which the time-varying fault characteristics of the fault gear with a missing tooth were extracted. Experimental results verified the effectiveness and superiority of this method.
In order to meet the power generation performance requirements of low-power power supplies and improve the energy collection efficiency of the new power supply airflow-induced acoustic piezoelectric generators, domestic GaN rectifier diodes are applied to low-power circuits, and the low dropout voltage of the airflow-induced acoustic piezoelectric generator power supply circuit has been developed. Gallium nitride (GaN) rectifier bridge, designed a low-dropout gallium nitride (GaN) rectifier bridge energy harvesting circuit. The static and dynamic experimental tests show that the domestic GaN rectification scheme can realize the dynamic rectification of the air-induced acoustic piezoelectric generator, with lower circuit loss, and can meet the domestic demand for low-power power supplies.
The sandwich metamaterial is a kind of artificial periodic sandwich structure. Due to its special properties such as negative equivalent density and negative equivalent volume modulus, it has great properties in vibration isolation performance and lightweight characteristics, which is now opening up a new research field of vibration and noise reduction. To improve its sound insulation performance, a new sandwich acoustic metamaterial with built-in active resonators is designed. Its sound insulation performance is verified by numerical simulation, and the influence of its internal parameters is analyzed.
On the basis of analysis by analytic theory and finite element method, the manufacturing and test are both done about the plane and spherical surface transducer. We can find, on the same radiation diameter, the later can be applied more electric power and have wider radiation range, more beautiful shape than the former. The washing machine using the spherical radiation transducer has the advantages of bigger power, more efficiency, better effect etc. By cooperating with third -party authority, the abilities of sterilization and pesticide residue removal are both tested by using the washing machine based on the spherical radiation transducer. The laws have been grasped about the effects of sterilization and pesticide residue removal changing with temperature, power, the volume of the container. The best working points have been obtained about the sterilization and pesticide residue removal on the specified conditions. We can conclude that the washing machine based on the spherical radiation transducer does not only have the good washing ability, but also have good effect of sterilization and pesticide residue removal.
Pipeline transportation is widely used in the transportation of oil and gas and other resources. The safety of oil pipeline is related to the safety of national strategic resources. Therefore, it is necessary to monitor the operation state of oil pipeline. In this paper, the design of piezoelectric vibration sensor is completed from the aspects of sensitive element design, structure design and signal conditioning circuit design. Among them, in the sensitive element design part, the compression structure is used; In the structural design part, the appropriate mechanical structure and fixed structure are also selected for the structural design of the sensor. In the part of signal conditioning circuit, it is designed from the aspects of charge conversion circuit, conditioning amplification circuit, filter circuit, output amplification circuit and regulated power supply. Finally, an experimental system is built to test the linearity, sensitivity and repeatability error of the designed piezoelectric vibration sensor.
Multibeam forward looking sonar can make sure that the vehicle avoide obstacle immediately, effectively and safely. The projector array has the advantages of wide-band, wide-beam and deep-water operation. The matching layer is used to expand the bandwidth of the array. Curved radiating surface of the projector array is used to achieve wide beam directivity. A final projector array was designed, fabricated and measured. The bandwidth of the array is 85kHz-180kHz, in which the ripple of the transmitting voltage response and receiving voltage sensitivity does not exceed ±2.5dB. There are several conclusions from the research: the bandwidth of the array can be expanded by the matching layer, the wide beam acoustic radiation can be obtained by curved radiating surface technology, and it achieved 20MPa pressure working characteristics by filling the inner cavity of the array with oil and applying high-pressure resistant materials.
In this paper, an annular piezoelectric actuator which can realize reciprocating motion is proposed to provide power for deep-sea bionic system. The actuator adopts a fully open structure, which does not need to consider the problems of sealing and pressure resistance caused by deep-sea pressure. Compared with the DC motor used in traditional underwater propeller, the structure is simpler. At the same time, the actuator is a single-mode actuator with simple control. By using piezoelectric ceramics, the second-order in-plane bending vibration of the stator is excited to drive the rotor to move back and forth along the inner diameter of the stator. A prototype is manufactured and a series of experiments are carried out to reveal its working performance, including the load characteristics of annular piezoelectric actuator, the relationship between swing frequency and driving frequency, and the relationship between swing frequency and voltage. The maximum load of the actuator is 0.2N, the optimal driving frequency is 1235Hz, and the swing frequency is directly proportional to the voltage.
The mechanical properties of materials directly affect the service life and safety of mechanism components. Elastic constant is an important index of mechanical properties and can be measured by simulation. The finite element software was used to simulate the surface waves and longitudinal waves generated by the piezoelectric materials due to piezoelectric effect and the laser through thermal expansion, and the probe point was set to receive ultrasonic signals. The elastic constants of materials can be determined from the relationship of the longitudinal wave and surface wave sound velocities with the Poisson’s ratio and elastic modulus. The simulation results are in good agreement with the theoretical values, indicating that the established finite element model can effectively simulate the physical process of ultrasonic wave generation. This work provides a basis for further studies on the mechanical properties of materials by ultrasonic technology.
In this paper, a method based on half-wave full transmission principle is introduced to detect the thickness of the device. Firstly, acoustic signal penetrating through the device can be converted into electrical signal by using acoustic sensor. Then the A/D conversion module of STM32 is used to convert the electrical signal into digital signal. After that, through serial port communication, the data information collected by STM32 is transmitted to the computer and the threshold value is set by Matlab software. If the collected data is higher than the threshold value, it is considered qualified, and if it is less than the threshold value, it is considered unqualified, so as to analyze whether the thickness of the device is qualified. The system can provide new ideas and methods for detecting whether the thickness of the device is qualified and also save time, improve efficiency and accuracy.
The shape of quartz blanks has a significant effect on the electrical performance of the quartz crystal resonators. In order to obtain a better electrical performance, the beveled blanks with thinner edge are always required. The beveling shape is mainly determined by the beveling barrels, but yet there is no study on the 2-dimension model for the beveling process to provide references for the beveling barrel design. In this paper, a difference equation model for the variation of 2-dimension surface formed during the bevel process is developed, based on the study of the geometrical relationship between the blank and the barrel’s internal face, and the study of the characteristics of the material removal rate. Finally, the simulation model is validated by experiment under different conditions of beveling barrel.
The reconstruction of cavity or thinning shapes in elastic plates and pipes by use of reflection data from ultrasonic elastic waves has drawn much attention by many researchers and engineers. A quantitative non-destructive evaluation (QNDE) algorithm requires thorough understanding of wave equations in both forward and inverse manners. Previously, an inverse scattering method based on Born approximation and space-wavenumber inverse Fourier transform has been suggested, which has been able to depict the locations and shapes of flaws, and can be easily understood mathematically. However, the algorithm requires reflection data in full wavenumber range, which is impractical in engineering application. The paper proposes an improved inversion algorithm using only discrete wavenumbers in specialized frequency ranges. Validity of the algorithm is illustrated by numerical examples, and methods for improving accuracy are suggested.
High power density is a hot pursuit in piezoelectric vibration energy harvester (PVEH) design. The assembly process has a great impact on the stiffness and damping of PVEH, and then affects the resonant frequency and output power of the system. The acrylic epoxy bonding assembly process has large damping and low stiffness. Here, we propose a PVEH inserted with aluminum alloy frame bonding assembly process, which has large stiffness, small damping, high resonant frequency of 125 Hz and high output power of 0.185 mW at 0.1g acceleration, with a high power density of 3.63 mWꞏcm-3ꞏg-2 in test.
