Wang Likun

Study of effective properties of modified 1-3 piezocomposites

Based on the piezoelectric theory and a homogeneous mass assumption, the piezoelectric equations for a modified 1-3 (1-3-2) composite, having as structure a piezoelectric ceramic plate and a 1-3 piezoelectric composite, are deduced. The formulas used to calculate the effective parameters of modified 1-3 piezoelectric composites are derived. The influence of piezoelectric phase volume fraction on the properties of the modified 1-3 composites has been analyzed. In addition, some composite samples were fabricated by dice-fill technology and their properties were measured. The results calculated by using the derived formulas agreed with measured data for the piezoceramic volume fraction in the range of 0.4

The Theoretical Model for 1-3-2 Piezoelectric Composites

The calculation formulas of dielectric and piezoelectric constants of 1-3-2 piezoelectric composites were deduced, combine the model of 1–3 piezoelectric composites by Chan and the Newnhams series and parallel theory of composites. Two groups of the 1-3-2 piezoelectric composites samples were fabricated. The characteristics of samples indicated that the theoretic calculation with this model were agreed with measurement results well. Hence the model could be used to estimate the performance of 1-3-2 piezoelectric composites.

Analyses for Radial Vibration of Piezoceramic Disc Stack

The radial vibration of piezoceramic disc stack is investigated by theoretical analysis, numerical simulation, and experimental measurement. Using the piezoelectric constitutive equations, the radial resonant frequency is derived by solving the admittance of the stack and setting it approaching infinity. The frequency equation is calculated numerically with software. Calculation results are compared with the frequency measured by Impedance Analyzer and Laser Scanning Vibrometer. Theoretical calculation shows agreement with experimental measurement. The error is less than 1.5%. Measured results also indicate that the resonant frequency of the disc stack is almost same with a disk at the radial vibration mode.

Influence of clamping plate permeability and metal screen structures on three-dimensional magnetic field and eddy current loss in end region of a turbo-generator by numerical analysis

A significant problem of turbogenerators on complex end structures is overheating of local parts caused by end losses in the end region. Therefore, it is important to investigate the 3-D magnetic field and eddy current loss in the end. In end region of operating large turbogenerator at thermal power plants, magnetic leakage field distribution is complex. In this paper, a 3-D mathematical model used for the calculation of the electromagnetic field in the end region of large turbo-generators is given. The influence of spatial locations of end structures, the actual shape and material of end windings, clamping plate, and copper screen are considered. Adopting the time–step finite element (FE) method and taking the nonlinear characteristics of the core into consideration, a 3-D transient magnetic field is calculated. The objective of this paper is to investigate the influence of clamping plate permeability and metal screen structures on 3-D electromagnetic field distribution and eddy current loss in end regio...

A Novel 3 Phase Multi-Elements Composite for Transducer Array Application

A novel 3 phase (ceramic, epoxy resin and de-coupling material) piezoelectric composite with multi-elements in parallel connection has been developed by using dice-filled technology. The piezoelectric and electromechanical properties of the composite were determined, the resonance uniformity and acoustic coupling between elements in composite were investigated. The results exhibited the piezoelectric coefficient d 33 of 400 pC/N, sound velocity of 3100 m/s, acoustic characteristic impedance of 14.3 MPa°s/m, thickness electromechanical coupling coefficient of 0.4, resonance frequency difference between elements was smaller than 0.76%, acoustic attenuation between adjacent element achieved 94%.

Study on flexural vibration of barrel unimorph

ABSTRACT The barrel unimorph is a specific type of sensing elements consisting of metal barrel shell and piezoelectric wafer attached to the inner bottom of the metal shell. The frequency equations of the barrel unimorph are deduced from Rayleigh-Ritz energy equation and elastic boundary conditions, from which the resonant frequency and effective electromechanical coupling coefficients are obtained. The flexural vibration of unimporh is studied by using numerical calculation and finite element analysis (FEA). The result indicates that the experimental trend of changes with resonance frequency in response to changes in structure parameters of unimorph is matched to the trend simulated by FEA. The effective electromechanical coupling coefficient is optimum when thickness ratio(α) of barrel to bottom (whole of wafer and barrel) is in the range of 0.3∼0.6 and radius ratio(β) of piezoelectric wafer to metal barrel is in the range of 0.6∼0.8. Furthermore, there is a sharp decline in electromechanical properties if α or β is outside of the above range. The conclusions will help to design and manufacture barrel unimorph sensors.

Wide band underwater acoustic transducer for stacked 2-2 piezoelectric composite material tube

ABSTRACT A kind of high frequency wideband underwater acoustic transducer is developed, this transducer is formed by 2-2 type piezoelectric composite tube which is composed of double ring stacked along the axial direction. Through the radial cutting piezoelectric ceramic ring, filled with epoxy resin, samples polished, coated electrode and a series of process, the piezoelectric composite ring is prepared, then, the ring with the same outer diameter and different wall thickness is stacked in the axial direction. A double ring stack piezoelectric composite sensor is prepared, after pouring waterproof permeable layer, the transducer is made. Underwater performance test results show that the resonant frequency of transducer is 410 kHz, the maximum transmit voltage response is 150 dB, the -3dB bandwidth reaches 60 kHz, The bandwidth of the transducer is expanded by the method of composite and dual mode coupling.

The Analysis of Piezoelectric Tube Stack for Radial Vibration Frequency

According to equivalent circuit principle, piezoelectric tube stack equivalent circuit is derived by the admittance of single piezoelectric thin tube, and the resonance frequency of piezoelectric tube stack for radial vibration is also calculated. The relationship between resonance frequency of radial vibration mode and average radius, thickness and height are obtained from analytical calculation. Analytical calculation and experiment results are compared, and they match well with each other.

Analyses for Thickness Vibration of Piezoelectric Ring

The thickness vibration of piezoceramic ring is investigated by theoretical analysis, numerical simulation, and experimental measurement. Based on the piezoelectric constitutive equations and the hypothesis that a ring has no strain in circumference when vibrating, the thickness vibration mode of ring is treated as a radial longitudinal extended vibration equivalently, the equations was simplified and the resonant frequency of thickness vibration is derived. The resonant frequency is also simulated with finite element software and measured by Impedance Analyzer. Theoretic calculation of resonant frequency is compared with the simulation and measurement. The errors between them are analyzed.