Green function and its application for a piezoelectric plate with various openings

Summary For a two-dimensional piezoelectric plate subjected to mechanical and electric load, a Green function satisfying traction free and exact electric boundary conditions along a hole is developed using Lekhnitskii's formalism and the technique of conformal mapping. The critical points for the mapping function used is investigated numerically, and the study indicates that the transformation of a polygonal hole in a piezoelectric plate into a unit circle is nonsingle-valued. A simple approach is presented to treat such a situation. Based on the Green function developed in this paper, a system of singular integral equations for the unknown dislocation defined on crack faces is presented to study the interaction between cracks and holes. Numerical results are presented to elucidate the effects of crack orientation on stress and electric displacement (SED) intensity factors and to illustrate the application of the proposed formulation. Received 4 June 1998, accepted for publication 15 July 1988     

用于液相中检测的压电免疫传感器研究

利用聚乙烯亚胺法,将Ｃ２型葡萄菌肠毒素（ＳＥ）抗体固化在未抛光的压电晶体的金电极上,利用双调式振荡电路制作的振荡器,构建压电免疫传感器,其稳定性,特异性都较好。     

压电免疫质量传感器中生物大分子的固定化方法

评述了近十几年来压电免疫质量传感器研究中的关键技术－生物分子固定化方法的研究应用,并对固定化方法的发展予以展望。     

补体C1q压电免疫传感器的研究

研制了一种可重复使用的压电免疫传感器用于检测补体C1q.比较了聚乙烯亚胺粘附、戊二醛交联法,物理吸附法以及蛋白A法三种固定化抗体蛋白的方法.使用蛋白A法,补体C1q在所测浓度范围内有良好的线性关系.使用过的晶片用0.1 mol/L柠檬酸盐缓冲溶液(pH 3.0)解吸,可重复使用4次.     

Lead zirconate titanate cantilever for noncontact atomic force microscopy

Noncontact atomic force microscopy with frequency modulation detection is a promising technique for surface observation with true atomic resolution. The piezoelectric material itself can be an actuator and sensor of the oscillating probe simultaneously, without the need for additional electro-mechanical transducers or other measurement systems. A vertical resolution of 0.01 nm rms has been achieved using a microfabricated cantilever with lead zirconate titanate thin film in noncontact mode frequency modulation detection. The cantilever also has a sharpened pyramidal stylus with a radius of about 10 nm for noncontact atomic force microscopy.     

Measurement of concrete internal strain using a three-dimensional transducer system

A new three-dimensional transducer system is introduced in this paper, which enables the measurement of six internal components of strain tensor in concrete members. Laboratory tests and strain analyses were carried out to evaluate this tranducer system. The results show that the system is effective in measuring internal strains of concrete members. It was then embedded in a reinforced concrete bridge deck in Macomb County, Michigan. Field tests were conducted to measure the strains in the deck under truck wheel load. The results were used to understand the deck's strain and stress behavior under truck wheel load.     

面向空耦电声换能器应用的高性能FEP/PTFE复合膜压电驻极体

压电驻极体(也称为铁电驻极体)是一类具有强压电效应的微孔结构驻极体材料,具有柔韧、低密度、低特性声阻抗等特征,是制备柔性空气耦合声电换能器的理想材料.针对器件对高灵敏度和高温工作环境的应用需求,本文报道高性能氟化乙丙烯/聚四氟乙烯(FEP/PTFE)复合膜压电驻极体的制备和性能表征.研究结果表明,FEP/PTFE膜的特...     

Opening and contact zones of an interface crack in a piezoelectric bimaterial under combined compressive-shear loading

A plane problem for a tunnel electrically permeable interface crack between two semi-infinite piezoelectric spaces is studied. A remote mechanical and electrical loading is applied. Elastic displacements and potential jumps as well as stresses and electrical displacement along the interface are presented using a sectionally holomorphic vector function. It is assumed that the interface crack includes zones of crack opening and frictionless contact. The problem is reduced to a combined Dirichlet–Riemann boundary value problem which is solved analytically. From the obtained solution, simple analytical expressions are derived for all mechanical and electrical characteristics at the interface. A quite simple transcendental equation, which determines the point of separation of open and close sections of the crack, is found. For the analysis of the obtained results, the main attention is devoted to the case of compressive-shear loading. The analytical analysis and numerical results show that, even if the applied normal stress is compressive, a certain crack opening zone exists for all considered loading values provided the shear field is present. It is found that the shear stress intensity factor at the closed crack tip and the energy release rates at the both crack tips depend very slightly on the magnitude of compressive loading.     

夹心式压电换能器的谐振频率跟踪方案设计

分析了夹心式压电换能器的阻抗特性,讨论了基于相位方式的现有跟踪方案的不足,提出了一种新的频率跟踪方案,介绍了实现该方案的电路系统。该方案的特点是:采用先扫频后跟踪的策略,解决了频率范围设定难的问题;增加解锁控制,使得系统在死锁或误跟踪时自动回到频率搜索状态;采用直接数字合成器(DDS)作为频率调整和信号产生的器件,实现了全数字系统,调整方便,精度高;采用复杂可编程逻辑器件(CPLD)做相位比较和DDS控制,使频率跟踪速度快,并且跟踪精度和速度均可控制。     

一种拓宽凸球面压电换能器指向性的方法

利用有限元和边界元耦合的方法对涂环氧树脂后的压电陶瓷凸球面换能器进行了指向性仿真计算,发现这种形式的换能器具有较宽的指向性开角。实验测量结果证明了上述结论。