Thickness-shear vibration of a quartz plate connected to piezoelectric plates and electric field sensing

We study thickness-shear vibration of a quartz plate connected to two piezoelectric ceramic plates with initial deformations caused by a biasing electric field. The theory for small deformations superposed on finite biasing deformations in an electroelastic body is used. It is shown that the resonant frequencies of the incremental thickness-shear vibration of the quartz plate vary with the biasing electric field. The biasing electric field induced frequency shift depends linearly on the field. Therefore this effect may be used for electric field sensing. The dependence of the electric field induced frequency shift on various material and geometric parameters is examined. When the electric field is of the order of 100 V/mm, the relative frequency shift is of the order of 10⁻⁵. The case when the piezoelectric plates are replaced by piezomagnetic plates is also investigated for magnetic field sensing, and similar results are obtained.     

Vibration of nanobeams of different boundary conditions with multiple cracks based on nonlocal elasticity theory

The aim of this paper is to study the free vibration of nanobeams with multiple cracks. The analysis procedure is based on nonlocal elasticity theory. This theory states that stress at a point is a function of strains at all points in the continuum. The nonlocal elasticity theory becomes significant for small length scale in micro and nanostructures. The effects of nonlocality, crack location and crack parameter are investigated on the natural frequencies of the cracked nanobeam. In this study, analytical solutions are given for cracked Euler–Bernoulli nanobeams of different boundary conditions.     

Utilization of characteristic polynomials in vibration analysis of non-uniform beams under a moving mass excitation

Vibration of non-uniform beams with different boundary conditions subjected to a moving mass is investigated. The beam is modeled using Euler–Bernoulli beam theory. Applying the method of eigenfunction expansion, equation of motion has been transformed into a number of coupled linear time-varying ordinary differential equations. In non-uniform beams, the exact vibration functions do not exist and in order to solve these equations using eigenfunction expansion method, an adequate set of functions must be selected as the assumed vibration modes. A set of polynomial functions called as beam characteristic polynomials, which is constructed by considering beam boundary conditions, have been used along with the vibration functions of the equivalent uniform beam with similar boundary conditions, as the assumed vibration functions. Orthogonal polynomials which are generated by utilizing a Gram–Schmidt process are also used, and results of their application show no advantage over the set of simple non-orthogonal polynomials. In the numerical examples, both natural frequencies and forced vibration of three different non-uniform beams with different shapes and boundary conditions are scrutinized.     

Exact boundary controllability of vibrating non-classical Euler–Bernoulli micro-scale beams

This study investigates the exact controllability problem for a vibrating non-classical Euler–Bernoulli micro-beam whose governing partial differential equation (PDE) of motion is derived based on the non-classical continuum mechanics. In this paper, it is proved that via boundary controls, it is possible to obtain exact controllability which consists of driving the vibrating system to rest in finite time. This control objective is achieved based on the PDE model of the system which causes that spillover instabilities do not occur.     

热氢原子碰撞导致的CO2(v3)的高振动激发

用时间分辨-傅里叶变换红外发射光谱研究了热的氢原子与C02分子间高效率的平动—振动(T—V)能传递．热的氢原子由ArF激光光解H2S得到，这种氢原子的平动能为223kJ／mo1。实验中观察到了从2130cm^-1到2400cm^-1的红外发射谱带，它归属于高振动激发的CO2分子的非对称伸缩振动(v3)．对这一发射谱带的光谱拟合显示CO2的非对称伸缩振动被激发到了较高的振动态，振动量子数达到了v=7。并且有5580cm^-1的能量经传能过程由氢原子到达了CO2的v3模。实验条件下氢原子与C02的T—V传能效率为0.30。实验结果与Schatz等人的用3D半经典计算预测的碰撞截面符合的很好．     

Electromechanical coupled nonlinear dynamics for microbeams

In this paper, an electromechanical coupled nonlinear dynamic equation of a microbeam under an electrostatic force is presented. Using the nonlinear dynamic equations and perturbation method, we investigated nonlinear free vibrations, forced responses far from and near to natural frequency, respectively. Nonlinear natural frequencies and vibrating amplitudes of the electromechanical coupled microbeam are dependent on the mechanical and electric parameters. Compared with linear forced responses, the obvious shift of the mean dynamic response occurs. Under certain condition, the jump phenomenon will occur. The studies can be used to design parameters of the microbeam and remove undesirable dynamic behavior such as jump phenomenon, etc.     

动圈传声器振动膜的工艺分析

振动膜的工艺及设计，是动圈传声器设计中的主要技术，文中论述了振动膜的设计及压制工艺，并介绍了几种优良的振动系统。     

Nonlinear dynamic strain analysis on rotor bladestructures with embedded piezoceramic sensors for activevibration control

In this paper, a relative index method is proposed to analyze the nonlinear VonKarman strain effects on a rotor blade structure with embedded piezoceramic sensors. Althoughother qualitative and quantitative methods are available for nonlinear strain analysis, thesemethods have inherent drawbacks. The proposed relative index method circumvents thedrawbacks of both qualitative and quantitative methods. Firstly, it measures the nonlinear effectand converts it into a numerical value. The value is in the range of zero to one in which zerocorresponds to negligible effects and one indicates the highest severity of the nonlinear effects. Inaddition, to generate the index value, this method takes the whole picture of nonlinear effectresponse into consideration.

The results of using the relative index method show that at any given mode of vibrationthe nonlinear effect on the sensor is relatively negligible at a high rate of rotation rather than onlow. The results also indicate that the nonlinear effect increases at lower modes of vibration butits effect on the sensor almost levels off at higher modes. Moreover, if comparing index value ofgiven modes of vibration with the index value of its preceding modes, the effect of nonlinearitydecreases. In addition, the results also suggest that at any given instantaneous speed of rotationthe level of the nonlinear effect diminishes with the higher accelerationdeceleration operation ofthe blade.     

ESPI solution for non-contacting MEMS-on-wafer testing

Rapid progress in the field of micro-electro-mechanical systems (MEMS) makes the development of appropriate measuring and testing means timely. Characterizing the mechanical properties of MEMS structures at a very early stage of manufacturing is a challenging task for quality assurance in this field. The paper describes a new solution that is based upon the vibration analysis of the microparts. The nanometer amplitudes are detected by advanced electronic speckle pattern interferometry (ESPI). A specific signal processing technique has been applied to make the solution robust. Comprehensive numerical simulations provide the theoretical base for the HNDT concept. A laboratory system for 4″ wafer has been built, and extensive tests show that such key properties as e.g. the thickness of springs or membranes can be determined exactly. Automated frequency scanning and corresponding digital image processing open the way to reliable and fast industrial systems for MEMS testing on wafer level.