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1.
扭转压电复合材料及其应用   总被引:4,自引:1,他引:3       下载免费PDF全文
本文描述了轴向-切向连通的圆柱2-2型压电复合材料。用PZT/环氧树脂制作的普通2-2型压电复合材料可拼接成一种具有扭转振动的压电复合材料。这种压电复合材料和为圆柱2-2型压电复合材料的近似。本文还给出两组这种拼接型压电材料晶片的参数,用这种压电材料制作了产生扭转振动的换能器,测试了换能器的波形,频谱特性和偏振特性,指出了使用适当的高通滤波器可以抑制横波中的径向模,分析了接收波列中纵波抑制较强的原  相似文献   

2.
压电复合材料宽带横波换能器的实验研究   总被引:13,自引:4,他引:9       下载免费PDF全文
本文用实验方法研究了2-2压电复合材料的厚度切变特性,定性地给出了2-2压电复合材料的性能与PZT相体积百分比,以及与共振频率牟关系。并用这种材料作为换能元件,制作出高灵敏度窄脉冲横波换能器。  相似文献   

3.
同时发射和接收纵波和横波的压电复合材料换能器   总被引:2,自引:0,他引:2       下载免费PDF全文
通过控制压电复合材料中压电相的分布形式,本文具有在百度模振动的1-3型压电复合材料和具有扭转模振动的拼接2-2型压电复合材料组合在一起,构成一种混俣模式压电材料,并测试了这种压电材料晶片的性能参数,使用这种晶片作的换能器可以根据使用者的要求,单独产生纵波或横波,也可同时产生这两种波。  相似文献   

4.
本文介绍了一种2-2型压电复合材料,使其中的极化方向和所加电场方向相同,并垂直于该方向而辐射声波。  相似文献   

5.
万奕  李智 《应用声学》1997,16(4):27-31
本文介绍了一种具有2-2结构特征的三相压电复合材料的结构及其制备方法,并与一种二相压电复合材料的类似结构对对比,进行了横向耦合,频率特性,声阻抗和介电性能等方面的测试和讨论,同时介绍了这种三相复合成功地应用于线阵换能器的结果。  相似文献   

6.
在固体测量中,横波换能器所产生的波列中常伴随有纵波,认识纵波产生的原因可以解释横波测试中出现的现象,以及抑制纵波提供有效的方法,本文利用实验研究的方法,用一对纵波偶极子换能器的对比实验,分析了2-2型压电复合材料厚度切变换能器产生纵波的机理,发现这是一种伴随着晶片厚度切变振动而产生的“偶极子”纵波,并由此解释了这种纵波的伴随性,频率特性及其首波与横波首波位相相反等问题。  相似文献   

7.
矩形扭转压电换能器的研制   总被引:1,自引:0,他引:1       下载免费PDF全文
本文从压电和机械振动等基本理论出发,首次较系统地建立了矩形扭转压电换能器的理论,推导出频率方程,并通过实验进行了验证。  相似文献   

8.
本文利用1-3压电复合材料作为换能元件,通过特殊工艺制备成一面是平面,一面是球面的非均匀厚度压电振子,这种压电晶片加上激励电压后,不同厚度处以不同的共振频率振动,从而使压电晶片的振动频带加宽,本文介绍了这种压电晶片的机电特性,以及用这种压电晶片制成的宽带聚焦超声换能器的脉冲回波特性,此外,文中还对这种换能器与均匀厚度压电晶片换能器的脉冲回波特性进行了比较。  相似文献   

9.
压电换能器阻抗匹配技术研究   总被引:9,自引:3,他引:9       下载免费PDF全文
潘仲明  祝琴 《应用声学》2007,26(6):357-361
超声测距传感器是由压电换能器及其收、发电路所组成的,其中压电换能器的阻抗特性直接影响着超声测距传感器的性能。为提高超声波回波信号的强度,扩大超声测距传感器的作用距离,对压电换能器的阻抗特性进行了分析与测试,设计了压电换能器的阻抗匹配电路,并进行了实验验证。  相似文献   

10.
惠辉  王宏伟  荣畋 《应用声学》2022,41(6):998-1003
研制了一种嵌套式高频宽带复合材料换能器,利用1-3型压电复合材料Q值较低、频带较宽的特点,采用组合式的结构拓展换能器的工作带宽。通过切割框型压电陶瓷、灌注环氧树脂得到压电复合材料框型敏感元件,再将不同厚度的框型敏感元件沿轴向嵌套从而制成多层嵌套的压电复合材料敏感元件。建立1-3型压电复合材料中压电小柱的等效电路,根据等效电路计算出压电小柱的谐振频率,并与1-3型压电复合材料的谐振频率理论计算结果进行对比。通过ANSYS软件对敏感元件结构进行仿真,并根据仿真结果确定了敏感元件的最佳设计方案。最终制作出的换能器进行水下测试,该换能器的谐振频率为310kHz,最大发送电压响应为188.5dB,-3dB带宽可达130kHz,接收灵敏度最大可达-186.8dB,-3dB带宽可达90kHz,谐振频率处-3dB的指向性开角约为2.4°。该嵌套式敏感元件可实现换能器宽带发射与接收声波的目标。  相似文献   

11.
本文通过控制压电相在压电复合材料中的分布形式,把四块完全相同的等腰直角王角形2-2型压电复合材料拼接起来,四个直角顶点位于晶片的中心,相邻块压电相的极化方向相对.这种新型材料可产生面切变振动,其换能器可辐射面切变波.波列中的纵波具有伴随性且其首波位相与面切变波首波位相相反  相似文献   

12.
In vitro experiments and an elastic wave model were used to analyze how stress is induced in kidney stones by lithotripsy and to test the roles of individual mechanisms-spallation, squeezing, and cavitation. Cylindrical U30 cement stones were treated in an HM-3-style lithotripter. Baffles were used to block specific waves responsible for spallation or squeezing. Stones with and without surface cracks added to simulate cavitation damage were tested in glycerol (a cavitation suppressive medium). Each case was simulated using the elasticity equations for an isotropic medium. The calculated location of maximum stress compared well with the experimental observations of where stones fractured in two pieces. Higher calculated maximum tensile stress correlated with fewer shock waves required for fracture. The highest calculated tensile stresses resulted from shear waves initiated at the proximal corners and strengthened along the side surfaces of the stone by the liquid-borne lithotripter shock wave. Peak tensile stress was in the distal end of the stone where fracture occurred. Reflection of the longitudinal wave from the distal face of the stone--spallation-produced lower stresses. Surface cracks accelerated fragmentation when created near the location where the maximum stress was predicted.  相似文献   

13.
Phenomena such as shear thinning and thickening, occurring when complex materials are exposed to external forces, are generally believed to be closely connected to changes in the microstructure. Here, we establish a direct and quantitative relation between shear thinning in a colloidal crystal and the surface area of the locally melted region by dragging a probe particle through the crystal using optical tweezing. We show that shear thinning originates from the nonlinear dependence of the locally melted surface area on the drag velocity. Our observations provide unprecedented quantitative evidence for the intimate relation between mechanical properties and underlying changes in microscopic structure.  相似文献   

14.
We investigate the nucleation of ordered phases, their symmetries, and distributions in dense frictional hard sphere packings as a function of particle volume fraction ?, by imposing cyclic shear and constant applied pressure conditions. We show, with internal imaging, that the nucleating crystallites in the bulk consist of 10-60 spheres with hexagonal close packed (hcp) order and nonspherical shape, that are oriented preferentially along the shear axis. Above ?=0.62±0.005, crystallites with face centered cubic (fcc) order are observed with increasing probability, and ordered domains grow rapidly. A polycrystalline phase with domains of fcc and hcp order is observed after hundreds of thousands of shear cycles.  相似文献   

15.
The infinite unitary irreducible spinor representations of the SL(3, R) algebra of hadron excitations are embedded in a global GA(4, R) with intrinsic dilation, shear and spin pieces in its hypermomentum current (i.e. the affine generalization of angular momentum). When gauged over a spacetime with a local Minkowski metric, GA(4, R) reproduces the metric-affine theory of gravity, in which the hypermomentum is coupled to the connection and the energy-momentum to the tetrad.  相似文献   

16.
In a recent study a new analytical solution was developed and validated experimentally for the problem of surface wave generation on a linear viscoelastic half-space by a rigid circular disk located on the surface and oscillating normal to it. The results of that study suggested that, for the low audible frequency range, some previously reported values of shear viscosity for soft biological tissues may be inaccurate. Those values were determined by matching radiation impedance measurements with theoretical calculations reported previously. In the current study, the sensitivity to shear viscoelastic material constants of theoretical solutions for radiation impedance and surface wave motion are compared. Theoretical solutions are also compared to experimental measurements and numerical results from finite-element analysis. It is found that, while prior theoretical solutions for radiation impedance are accurate, use of such measurements to estimate shear viscoelastic constants is not as precise as the use of surface wave measurements.  相似文献   

17.
剪切差对入射角不敏感的平行分束偏光镜的设计   总被引:7,自引:1,他引:6  
任树锋  吴福全  赵培 《光学技术》2005,31(5):749-750
就入射面为主截面的情况,分析了入射角对平行分束偏光镜剪切差的影响规律,从而得出一种当入射角在一定范围内变化时,剪切差对入射角不敏感的平行分束偏光镜的设计方法,并且这种设计是消色差的。  相似文献   

18.
We study the effects of couplings to flexure and face-shear modes on the admittance of an AT-cut quartz plate thickness-shear mode resonator. Mindlin’s two-dimensional equations for piezoelectric plates are employed. Electrically forced vibration solutions are obtained for three cases: pure thickness-shear mode alone; two coupled modes of thickness shear and flexure; and three coupled modes of thickness shear, flexure, and face shear. Admittance is calculated and its dependence on the driving frequency and the length/thickness ratio of the resonator is examined. Results show that near the thickness-shear resonance, admittance assumes maxima, and that for certain values of the length/thickness ratio, the coupling to flexure causes severe admittance drops, while the coupling to the face-shear mode causes additional admittance changes that were previously unknown and hence are not considered in current resonator design practice.  相似文献   

19.
 采用有限元方法对钼基体上不同厚度(20~1 000 μm)金刚石膜的热残余应力进行了全面的模拟与分析,得出了它们在膜内分布的等值线图,研究了金刚石膜厚度尺寸对整个膜内的最大主拉应力和界面处每个应力分量最大值的影响。结果表明:在整个膜内,最大主拉应力的位置出现在膜的表面、界面或侧面,其值随膜厚度的增加而增大;在界面处,最大轴向应力随膜厚度的增加而增大,而最大径向压应力、最大周向压应力和最大剪应力则随膜厚度的增加而减小,其中最大剪应力减幅较小;膜厚度越大时,以上各量随厚度增(减)的速度越慢。其结论对于在金刚石膜的制备中合理地选择厚度、有效地进行应力控制有一定的参考价值。  相似文献   

20.
We present measurements of the particle velocity distribution in the slow flow of granular material through vertical channels. The velocities of particles adjacent to the smooth, transparent front face of the channel were determined by video imaging and particle tracking. We find that the mean velocity changes sharply in shear layers near the side walls, but remains constant in a substantial core. The velocity distribution is non-Gaussian, is anisotropic, and follows a power law at large velocities. Remarkably, the distribution is identical in the shear layer and the core. We show evidence of spatially correlated motion, and propose a mechanism for the generation of fluctuational motion in the absence of shear.  相似文献   

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