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1.
超声检测用压电换能器瞬态特性主要包括瞬态空间响应和瞬态时间响应.本文通过调整控制换能器和激励源,实现瞬态空间响应和瞬态时间响应的某些特性的可控可调.其中包括在空间响应方面消除边缘波以获得平行声束和消除平面波以获得聚焦绳声束;在时间响应方面,调整换能器的背衬阻抗以获得可调首次波幅比和调整换能器结构和激励电信号以获得任意检测信号等.  相似文献   

2.
本文利用拉普拉斯变换、牛顿方程和压电方程,求出了厚度方式的压电换能器在用作接收和发射超声时的瞬态响应。计算了一个δ函数激励的例子,在忽略机电耦合系数k_t时它的瞬态响应是一串脉冲序列,脉冲彼此间隔为t=l/v的时间。同时也简单地讨论了换能器周围介质对脉冲响应的影响。从推导的结果可看出如何考虑声匹配层,以期获得良好的脉冲响应。  相似文献   

3.
水声测量用声脉冲瞬态抑制方法的研究   总被引:2,自引:0,他引:2       下载免费PDF全文
陈毅  袁文俊  赵涵 《应用声学》2002,21(4):10-15,48
脉冲声技术是一种很常用的水声测量技术,但由于脉冲声存在着瞬态过程,严重影响了它在低频下的使用,本文中研究的水声测量用声脉冲瞬态抑制方法,通过瞬态抑制等效消除换能器的瞬态过程,从而为在有限尺寸水域内扩展水声测量低频限创造了条件。  相似文献   

4.
曾淼  沈勇  黎付  杨增涛  王华 《声学学报》2017,42(1):103-108
探索一种简便的聚焦超声功率测量方法,利用压电陶瓷片直接接收超声信号,通过机电类比得到压电瞬态响应由压电片在声波作用力下引起受迫振动产生的电压响应与固有振动产生的高频衰减响应叠加而成,分析输出压电信号与换能器声功率之间的换算关系。对输出压电信号进行二次包络提取,获得表征声功率变化的电压幅度曲线,分别找出不同换能器驱动电压下包络曲线的最大峰值电压,将其平方值与声功率计所测声功率进行线性拟合,并对理论关系式中的比例系数进行标定。实验结果所得线性拟合度较高,且标定后所得声功率与声功率计所测值相对误差低于8.7%,证明了通过压电瞬态响应测量换能器声功率具有可行性。   相似文献   

5.
空腔、消声器和隔声结构的声学特性通常是使用连续正弦声波来测量,各种多孔材料的吸声特性也是在驻波管中用正弦波来测量。这些测量给出的资料与稳态激励有关,冲击波如轰声(sonic booms),冲床撞击辐射的冲击声等等对它们的发生机理和传播特性,特别是非线性方面和高声强噪声控制问题是目前流行的课题。一般,冲击声的能量是分布在空间一个小范围内,也限制在很短持续时间之内,该现象本质上是瞬态的,在研究这种现象中为获得非稳态激励的任何瞬态响应就使用声脉冲。  相似文献   

6.
林玉童  秦鹏 《声学学报》2018,43(2):202-208
将SonoVue微泡从临床疾病诊断拓展至治疗引起了诸多研究人员的兴趣。为了平衡治疗效率和生物安全性,深入理解声学参数和SonoVue微泡瞬态空化的关系至关重要。本研究自行制备仿体容器放置SonoVue微泡,使用1 MHz发射换能器激励其产生空化效应,另一个7.5 MHz的聚焦换能器接收声信号,经放大及高速数据采集后送上位机处理。通过深入分析信号的时频域特征,我们提出以宽带信号的能量及其随时间变化曲线的半高宽来表征瞬态空化的剂量(ICD)和相对持续时间(ICP),并确定:瞬态空化的发生和ICD依赖于峰值负声压,但ICP随峰值负声压的增加而减小;脉冲重复频率和脉冲持续时间都和ICD及ICP正相关;且脉冲持续时间的影响较大。这些结果有望为SonoVue微泡的治疗应用提供理论支持。   相似文献   

7.
厅堂内一点接收到的各早期反射声,对该点的音质影响很大。但一般从示波器上所摄得的早期反射声图诸,有时并不可靠.为了在设计过程中对这些反射声图谱进行比较或改进,可以利用计算机和以瞬态扩散的概念为基础,从各早期反射声在时间、空间和幅度三方面扩散是否均匀来考虑,定义出一个单一的量瞬态扩散系数D.利用D就可以对厅堂内各点或各厅堂之间的反射声图谱定量地进行比较.D也可用于厅堂内瞬态响应的分析和研究.  相似文献   

8.
为测量超声马达的一些特性,如最大力矩、负载特性(即力矩-速度特性)、转子和定子接触面上的摩擦系数等,本文提出一种由瞬态响应来估算的方法,由接通电源时马达转速阶跃响应的上开曲线可算出其负载特性,而由切断电源时的下降曲线得出接触面的摩擦系数。本方法测量时间快,故不受因温升导致的共振频率漂移等一些问题的困扰。对一混合换能器型旋转马达得到的负载特性与用拉重法所得结果符合很好。对一行波直线马达则考察了摩擦材料的杨氏模量和摩擦系数等参数对马达性能的影响。  相似文献   

9.
李明轩 《应用声学》1995,14(1):48-48
中科院声学所超声研究室的换能器研究,曾获得中国科学院重大成果一等奖和国家自然科学奖,在国内外有较大影响.在理论研究的基础上,研究室近年来推出超声检测用换能器系列产品,其中包括气介式检测、液浸式检测和固体耦合式检测几大类换能器.每一类中又有特殊的空间响应和时间响应探头和常规探头,频率一般在几千赫至100兆赫.使扶探头:.高灵敏度窄脉冲探头(灵敏度和相对带宽普遍高于市场商品探头6-20dB).无旁瓣高斯探头.平面接触绳声束聚焦窄脉冲探头(专利产品).首次波幅度比大于1的测量探头.直接耦会横渡直探头.有信号处…  相似文献   

10.
基于温度激励的光纤陀螺光纤环瞬态特性检测   总被引:3,自引:1,他引:2  
光纤陀螺基于萨尼亚克效应测量垂直于光纤环平面的敏感轴方向上的旋转分量。光纤环是光纤陀螺的核心部件,光纤环的缠绕质量直接影响着光纤陀螺的整体性能,对光纤环的缠绕质量全面检测十分必要。针对目前光纤环检测手段的局限性,提出了一种基于温度激励的光纤陀螺光纤环瞬态特性检测方法,全面表征了光纤环的缠绕质量。建立了光纤环柱面坐标三维计算模型,采用有限元方法定量分析光纤环不对称度和局部温度激励位置精度对光纤环瞬态响应的影响,同时开展了光纤环温度激励相应实验,实验结果与光纤环三维物理模型数值计算结果相一致,在理论和实验上验证了光纤环瞬态特性检测方法的可行性。  相似文献   

11.
Jung SS  Kim YT  Pu YC  Kim MG  Kim HC 《Ultrasonics》2006,44(1):12-16
We report a non-contact and non-invasive method of sound speed measurement by optical probing of deflected laser beam due to normally incident degenerated shock wave. In this study the shock wave from an exploding wire was degenerated to an ordinary sound wave at the distance exceeding 0.23 m. Temporal resolution of the deflected beam signal was improved by passing through an adequate electronic high-pass filter, as a result we obtained a better temporal resolution than that of the acoustic pressure detection by PZT transducer in terms of rising time. The spatial resolution was improved by passing the refracted beam signal into the edge of focusing lens to make a larger deflection angle. Sound speed was calculated by monitoring the time of flight of transient deflected signal at the predetermined position. Sound speed has been measured in air, distilled water and acryl, agreed well with the published values. The sound speed measured in the solution of glycerin, magnesium sulfate (MgSO4), and dimethylformamide with various mole fractions also agrees within 3% of relative error with those measured in the present work by ultrasonic pulse echo method. The results suggest that the method proposed is to be reliable and reproducible.  相似文献   

12.
R.E. Challis 《Ultrasonics》1982,20(4):168-172
Transient diffraction phenomena in the field of a piston transducer have been explained theoretically in terms of the direct and edge wave contributions to the piston response. Previous experimental studies by other workers have verified this concept for single cycles of 4 MHz radiation. Faster transients are difficult to study using thin piezoelectric transducers due to transducer resonance. Thick piezoelectric transducers of very low resonant frequency can be used to generate and receive step function acoustic transients with rise times of 20 ns or less and the problems of transducer resonance can be avoided. Experimental results are presented which show that when such a step function is propagated between two thick transducers the time course of the received wave can be explained in terms of the direct wave/edge wave model in conjunction with the theory of transient reverberations in piezoelectric elements.  相似文献   

13.
Ahmad ZA  Gabbert U 《Ultrasonics》2012,52(7):815-820
In typical Lamb wave simulation practices, effects of plate edge reflections are often not considered in order to simplify the wave signal interpretations. Methods that are based on infinite plates such as the semi-analytical finite element method is effective in simulating Lamb waves as it excludes the effect of plate edges. However, the inclusion of plate edges in a finite plate could render this method inapplicable, especially for transient response simulations. Here, by applying the ratio of Lamb mode reflections at plate edges, and representing the reflection at plate edges using infinite plate solutions, the semi-analytical finite element method can be applied for transient response simulation, even when the plate is no longer infinite.  相似文献   

14.
该文基于PVDF压电薄膜对梳状换能器进行设计制作,并将该换能器应用于接收非线性兰姆波信号实验研究。首先通过输出矢量和方法分析PVDF梳状换能器的工作特性,然后将设计制作的PVDF梳状换能器应用于铝板中非线性兰姆波信号的接收,并与传统压电陶瓷换能器经斜劈接收的非线性兰姆波信号进行比较分析。实验结果表明,两种换能器所接收到的信号幅值随传播距离的变化趋势相近,线性增长的积累效应表征结果相似,且PVDF梳状换能器可以对基波和二次谐波信号同时响应。除此之外,PVDF梳状换能器用于接收非线性兰姆波信号更加稳定。因此,PVDF梳状换能器有望应用于复杂构件的在线检测与监测研究。  相似文献   

15.
耦合环形腔马赫-曾德尔干涉仪瞬态响应及应用   总被引:1,自引:0,他引:1  
李立  张新陆  孙平平  陈历学 《光子学报》2007,36(10):1788-1792
对耦合环形腔马赫-曾德尔干涉仪光脉冲瞬态响应进行了理论和数值研究.利用光束追迹法推导了脉冲传输的解析关系,并数值模拟了传输光场随时间的演化.输出脉冲形状可通过控制损耗进行调解,响应速度为皮秒量级.由于马赫-曾德尔干涉仪两输出端口的互补性,在输出端可同时实现光脉冲微分和积分操作.利用损耗控制机制,可实现单通道脉冲微分和积分操作转换.引入增益补偿损耗,可实现脉冲压缩及产生可调单一触发光脉冲.  相似文献   

16.
In this paper, a method of crack detection in beam is provided by wavelet analysis of transient flexural wave. Firstly, we introduce a rotational spring in the cracked-beam model, and calculate the transient flexural wave propagation by the Reverberation Matrix Method. Secondly, at any point in this beam, the arrival time of waves with different group velocities can be identified by means of analysis of wavelet transform. From the signal of mid-frequency flexural wave extracted by wavelet transform, we can exactly determine the existence and position of crack in the beam. Here, a similar experiment is also produced to test the transient strain signal in beam, and the result after wavelet transform analysis is shown in accord with the theoretical one. Therefore, a powerful method is proved by the theoretical and experimental studies on the cracked beam, which can detect the crack accurately utilizing the wavelet analysis of the mid-frequency flexural wave.  相似文献   

17.
We report the acoustic imaging frequency dynamics of ferroelectric domains by low-frequency acoustic probe microscopy based on the commercial atomic force microscopy. It is found that ferroelectric domain could be firstly visualized at lower frequency down to 0.5 kHz by AFM-based acoustic microscopy. The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7kHz to 10 kHz, and reached maximum at 8.1 kHz. The acoustic contrast mechanism can be ascribed to the different elastic response of ferroelectric microstructures to local elastic stress fields, which is induced by the acoustic wave transmitting in the sample when the piezoelectric transducer is vibrating and exciting acoustic wave under ac electric fields due to normal piezoelectric effects.  相似文献   

18.
张学聪  吕炎  吴斌  何存富 《声学学报》2020,45(3):359-366
通过实验研究了声束偏转不同角度和声场半径变化时线性相控阵的声场特性,并与基于瞬态波位移解析解的相控阵声场计算方法得到的理论结果进行了对比。首先研究了基于半圆圆弧离面瞬态位移的声场计算方法,并进行了数值计算可靠性的优化。然后建立了一套相控阵瞬态波位移场的测量系统,以半圆形钢板为试件,纵波传感器为接收传感器,测量了偏转角度为-10°,-30°,-50°,-70°,及声场半径为50 mm,75 mm,100 mm和125 mm时线性超声相控阵的声束指向性;同时以基于瞬态波位移解析解的相控阵声场计算方法,计算了相同条件下该相控阵的声束指向性。最后将实验结果与理论结果进行了对比,取得了较好的一致。说明基于瞬态波位移的相控阵声场计算方法可以较好地计算线阵的声场,对于声束偏转较大角度和声场半径变化时也同样有效。   相似文献   

19.
The early transient responses of multi-span stepped single walled carbon nanotubes (SWCNTs) under impact loadings are studied by the method of reverberation ray matrix (MRRM). The dynamics model of the carbon nanotubes is established in the Fourier phase space on the basis of the nonlocal Timoshenko beam model. The wave solutions of SWCNTs with arbitrary boundary conditions are obtained by the wave method. The reverberation ray matrix of the multi-span stepped SWCNTs is the product of scattering, phase and permutation matrices, which can be determined by the impact loadings, continuous conditions and boundary conditions. The early transient responses can be calculated by the inverse Fourier transform of the sum of initial ray groups. It can be found that the early transient displacement response in the very short time subjected to the impact loading is very small, while the transient transverse shear strain becomes large in the very short time. The influences of nanotubes span number, nanotubes type and boundary conditions on the early transient responses of multi-span stepped SWCNTs are investigated.  相似文献   

20.
A method of shortening the transient response of a piezoelectric transducer is described. It can be applied to thickness mode piezoelectric transducers of arbitrary electromechanical coupling. The system incorporates electrical correcting circuits and can produce a transient response with a duration much shorter than the transit time of an ultrasonic wave travelling through the piezoelectric plate.  相似文献   

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