夹心式纵-扭复合模式压电超声换能器的共振频率

本文对夹心式纵－扭复合振动模式压电超声换能进行了研究，从换能器的等效电路出发，在无耦合时，得出换热能器纵向振动模式及扭转振动模式的各自共振频率方程，实验表明，换能器各自共振频率的测试值与理论计算值基本符合。     

模式转换弯曲振动超声换能器的研究

本文研制了一种由纵向振动夹心式压电换能器和弯曲振动细棒组成的纵一弯模式转换弯曲振动超声换能器，从理论上分析了此类换能器的两种振动模式，井推出了其共振条件．实验表明，换能器共振频率的测量值与理论值符合很好，弯曲振动换能器的能量转换效率较高，性能稳定，在实际生产中具有广泛的应用．     

纵－扭复合模式夹心式功率超声压电换能器的研究

本文对纵－扭复合模式功率超声换能器进行了研究，该换能器由指数型前后金属喇叭盖板以及轴向极化和切向极化的两组压电陶瓷晶片组成。文中推出了换能器中纵向及扭转两种振动模式的共振频率方程。通过改变换能器前后指数型盖板的半径减编系数，得出了换能器中纵向与扭转两种振动模式同频共振的条件。实验表明，换能器的设计频率与测试频率基本一致，而且，换能器的纵向及扭转共振频率也比较接近，该换能器可望应用于超声加工及焊接等高振幅的功率超声技术中。     

矩形辐射器压电多频超声换能器的研究

研究了一种具有多个共振频率的矩形辐射器夹心式超声换能器,换能器由圆柱形后盖板、压电陶瓷晶堆及矩形六面体辐射器前盖板组合而成。利用表观弹性法和一维近似理论给出了多频换能器横向及纵向理论共振频率方程。对一种特殊情况下的此类换能器进行了有限元及实验分析,给出了各自的频率输入导纳曲线。对理论和实验结果进行分析后表明,此类矩形辐射器夹心式超声换能器可以在不同的振动模态上工作,具有多个共振频率.     

斜槽式纵-扭复合模式压电超声换能器的研究

对斜槽式纵-扭复合振动模式压电超声换能器进行了理论及实验研究。推出了换能器的机电等效电路,探讨了槽的倾斜程度对复合超声换能器的共振频率的影响。实验表明,理论预测频率与实测频率基本一致。     

阶梯圆环压电超声换能器径向振动性能的理论研究*

提出了一种阶梯圆环径向振动压电超声换能器,根据力电类比原理建立了阶梯圆环及阶梯圆环换能器的径向振动等效电路,推导了阶梯圆环的径向共振频率方程和位移放大系数,在此基础上进一步推导了换能器的径向共振和反共振频率方程。通过理论推导和有限元仿真模拟分析了阶梯圆环压电超声换能器的径向振动性能。结果表明,增大阶梯圆环中内外环的径向厚度之比K1或减小轴向厚度之比K2,阶梯圆环的一阶径向共振频率减小,二阶径向共振频率增大;在二阶径向共振模式下,K1、K2值在一定范围内阶梯圆环可实现由内向外的径向位移振幅放大;随着压电陶瓷圆环的内半径增大,阶梯圆环压电超声换能器的一阶、二阶径向共振和反共振频率减小,二阶径向共振下的有效机电转换系数趋于零;增大阶梯圆环内环的外半径,换能器的一阶径向共振和反共振频率减小,二阶径向共振和反共振频率先增大后减小,理论推导与仿真模拟结果符合良好。本文研究结果为阶梯圆环压电超声换能器的工程应用提供理论参考。     

基于2-2型压电复合材料的新型宽频带径向振动超声换能器

本文提出了一种基于2-2型压电复合材料的新型宽频带径向振动超声换能器,它主要由内金属圆环和外压电陶瓷复合材料圆环组成.首先利用Newnham串并联理论和均匀场理论推导了2-2型压电复合材料的等效参数;其次利用解析法得到了金属圆环和径向极化压电复合陶瓷圆环径向振动的机电等效电路;最后得到了换能器的六端机电等效电路,从而得到了换能器的频率方程.接着分析了换能器共振频率和反共振频率以及有效机电耦合系数与几何尺寸、两相体积占比的关系,采用仿真软件对新型换能器的径向振动进行了数值模拟.结果表明,利用解析法得到的共振频率和反共振频率与数值模拟结果吻合较好.此外,对换能器在水下的辐射声场进行了仿真研究,结果表明新型复合材料径向换能器相比传统纯陶瓷径向换能器,发射电压响应幅值更大,工作带宽提高接近一倍,声匹配更佳.     

锥形剖面径向复合超声换能器的机电等效电路

研究了一种锥形剖面径向复合超声换能器。该换能器由一个等截面内金属圆环、一个轴向极化的压电陶瓷圆环和一个锥形剖面外金属圆环沿径向复合而成,且换能器的径向尺寸远大于高度。锥形剖面外金属圆环满足关系式h=h₀r,h₀为厚度变化常数。基于平面应力径向振动理论,推导了换能器的机电等效电路,得到了共振频率方程和反共振频率方程,进而研究了换能器的振动特性。并将理论计算的第1阶、第2阶径向共振频率和反共振频率与数值仿真结果相比较,二者结果一致。研究表明:锥形剖面换能器第1阶、第2阶径向共振频率、反共振频率、有效机电耦合系数不仅与换能器各部分的材料、径向几何尺寸有关,还与h₀有关。h₀越大,第1阶径向共振频率、反共振频率越大,有效机电耦合系数先增大后减小。与等截面相比,锥形剖面换能器沿径向向外辐射声波,辐射面积更大,辐射声功率更高,指向性更好。      

矩形板高阶模式超声振动辐射器的研究

在耦合振动理论以及矩形截面细棒弯曲振动的基础上,本文对矩形薄板的弯曲振动进行了研究,推出了自由边界矩形薄板的弯曲振动频率方程,研究了薄板的振动模式及其与共振频率的关系.实验表明,矩形薄板弯曲振动共振频率的测量值与计算值符合很好.用共振式矩形薄板作为超声清洗等液体中超声应用技术的声波辐射器具有声场分布均匀,换能器频率调节容易,声波辐射面大等优点,是一种很有前途的新型超声源.     

声子晶体结构在功率超声换能器中的应用*

该文提出了一种二维声子晶体结构模型,并将该模型应用于横向尺寸较大的功率超声换能器的前盖板中,避免了形成耦合振动对换能器的影响,从而优化了该类换能器的工作性能。首先设计了一种具有近周期性结构的圆柱形孔的前盖板,然后研究了声子晶体结构前盖板散射体的半径大小和高度对换能器共振频率以及前盖板带隙的影响。结果表明,随着散射体半径和高度的增大,换能器的共振频率会随之发生改变,带隙范围也在发生变化,可以通过调节使换能器的共振频率处于声子晶体的带隙范围内,可以有效抑制换能器的横向振动。     

Study on the Langevin piezoelectric ceramic ultrasonic transducer of longitudinal-flexural composite vibrational mode

In this paper, the Langevin longitudinal-flexural composite mode piezoelectric ultrasonic transducer is studied. This type of transducers consists of slender metal rods and longitudinally polarized piezoelectric ceramic rings. The resonance frequency equations for the longitudinal and flexural vibrations in the transducer are derived. By correcting the length of the metal slender rods, the simultaneous resonance of the longitudinal and flexural vibrations in the transducer is acquired. The experimental results show that the measured resonance frequencies of the transducers are in good agreement with the computed ones, and the measured resonance frequencies of the longitudinal and the flexural vibrations in the composite transducers are also in good agreement with each other.     

Flexural vibration analyses of piezoelectric ceramic tubes with mass loads in ultrasonic actuators

Based on Timoshenko beam model, a theoretical model of radially polarized piezoelectric ceramic tubes is investigated. In the model, the piezoelectric effects are considered, and the shear correction factor is introduced which reveals effects of the size of the cross-section and Poisson’s ratio. Based on the model, the particular attentions are devoted to effects of the boundary conditions at two ends on flexural resonance frequencies of the piezoelectric ceramic tubes. Changing the sizes of the tubes and the mass loads at both free ends, the variations of the flexural resonance frequencies of free–free piezoelectric ceramic tubes are calculated theoretically. Besides, the flexural resonance frequencies of the piezoelectric ceramic tube cantilevers with mass loads at one free end are also investigated theoretically. To verify accuracy of the theoretical mode, the flexural resonance frequencies for different lengths of the piezoelectric ceramic tubes and different loaded masses are measured experimentally. The theoretical results agree well with the experimental measurement, which demonstrates that the model is accurate for analyzing the flexural resonance frequencies of the piezoelectric ceramic tubes with mass loads.     

Simplified formulae to investigate flexural vibration characteristics of piezoelectric tubes in ultrasonic micro-actuators

Based on the Rayleigh energy theory combining with Timoshenko beam model, the flexural vibration characteristics of piezoelectric tubes in ultrasonic micro-actuators are investigated. Additionally, the simplified formulae are derived to study the fundamental flexural resonance frequencies of the piezoelectric tubes with free-free ends and cantilevers. By changing the sizes of the tubes and the mass loads at the free ends, the variations of the flexural resonance frequencies of the piezoelectric tubes and cantilevers are calculated theoretically. To verify accuracy of the simplified formulae, by changing the lengths of the tubes and the mass loads the flexural resonance frequencies of the piezoelectric tube with free-free ends are measured experimentally. The theoretical results agree well with the experimental measurements, which demonstrate that the simplified formulae are accurate and effective for analyzing the flexural vibration characteristics of the piezoelectric tubes in the ultrasonic micro-actuators.     

微液滴在超疏水表面的受迫振动及其接触线的固着-移动转变

利用高速摄影技术对超疏水表面液滴振动的动态行为进行观测,研究液滴在不同频率下的振动特性. 实验发现,液滴的共振频率满足Rayleigh方程,微液滴在超疏水表面具有自由液滴的振动性质. 在80–200 Hz的驱动频率范围内,接触线出现了明显的固着-移动现象,液滴的振动频率是驱动频率的一半,液滴振动时的形变较大. 当驱动频率大于200 Hz时,接触线基本固着,液滴的振动频率近似等于驱动频率,液滴共振时的形态边缘始终有节点存在. 分析表明,液滴对外界驱动的不同响应与接触线的振荡行为和变形程度密切相关 关键词： 超疏水表面 受迫振动 共振 接触线     

压电陶瓷薄圆环振子径向振动的机电等效电路及其分析

本文对轴向极化压电陶瓷薄圆环的径向振动进行了研究，推出了其机电等效电路，得出了振子的共振和反共振频率方程并进行了实验验证。探讨了振子的共振和反共振频率与其材料和几何尺寸之间的依赖关系。     

Flexural resonance vibrations of piezoelectric ceramic tubes in Besocke-style scanners

Flexural resonance vibrations of piezoelectric ceramic tubes in Besocke-style scanners with nanometer resolution are studied by using an electro-mechanical coupling Timoshenko beam model.Meanwhile,the effects of friction,the first moment,and moment of inertia induced by mass loads are considered.The predicted resonance frequencies of the ceramic tubes are sensitive to not only the mechanical parameters of the scanners,but also the friction acting on the attached shaking ball and corresponding bending moment on the tubes.The theoretical results are in excellent agreement with the related experimental measurements.This model and corresponding results are applicable for optimizing the structures and performances of the scanners.     

Asymptotic analysis of a vibrating cantilever with a nonlinear boundary

Nonlinear vibration of a cantilever in a contact atomic force microscope is analyzed via an asymptotic approach. The asymptotic solution is sought for a beam equation with a nonlinear boundary condition. The steady-state responses are determined in primary resonance and subharmonic resonance. The relations between the response amplitudes and the excitation frequencies and amplitudes are derived from the solvability condition. Multivaluedness occurs in the relations as a consequence of the nonlinearity. The stability of steady-state responses is analyzed by use of the Lyapunov linearized stability theory. The stability analysis predicts the jumping phenomenon for certain parameters. The curves of the response amplitudes changing with the excitation frequencies are numerically compared with those obtained via the method of multiple scales. The calculation results demonstrate that the two methods predict the same varying tendencies while there are small quantitative differences. Supported by the National Outstanding Young Scientists Fund of China (Grant No. 10725209), the Shanghai Leading Academic Discipline Project (Grant No. S30106), and Shandong Jiaotong University Science Foundation (Grant No. Z200812) Recommended by LIAO ShiJun     

Temperature dependence of79BrNQR frequency in cadmium strontium,barium, zinc,magnesium and nickel bromates

The⁷⁹Br quadrupole resonance in cadmium, strontium, barium, zinc, magnesium and nickel bromates is studied in the range 77 to 305 K. The temperature dependence of the resonance frequencies in these systems has been analysed on the basis of the torsional motion of the BrO ₃ ⁻ groups. The torsional frequency and its temperature behaviour have been analysed.