压电陶瓷发射换能器的瞬态抑制

提出了一种针对压电陶瓷发射换能器的瞬态响应的抑制方法。该方法通过对发射信号的控制,即发射的信号是在原有的信号上叠加若干消影脉冲,抑制换能器的输出瞬态响应的影响,从而实现窄带换能器发宽带信号的目的。分别用正弦脉冲和调相脉冲进行了实验,实验取得了和理论较为一致的结果,均很好地抑制了瞬态响应对发射波形的影响。     

应崇福院士90生辰学术报告会论文超声检测用压电换能器瞬态特性可控可调

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.     

超声检测用压电换能器瞬态特性可控可调

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。     

PVDF梳状换能器接收非线性兰姆波的实验研究*

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。     

一种基于互易原理的超声功率新测量方法

本文从换能器的互易原理出发，利用平面波自易校准法获得换能器的自由场发送电流响应．根据平面活塞型换能器的衍射规律，推导出发射声功率的表达式．由此计算互易换能器在给定驱动电流（或电压）作用下的辐射超声功率．基于上述原理，使用自易校准装置测量了互易换能器的声功率一频率曲线．估计的测量不确定优于±20％．     

磁致伸缩-压电联合激励凹筒型发射换能器

设计制作了一种新型磁致伸缩-压电联合激励凹筒型发射换能器,采用稀土超磁致伸缩材料Terfenol-D与PZT压电陶瓷作为联合激励元件,模拟计算与实测结果均表明,与采用单一振子激励的凹筒型发射换能器相比,此种新型换能器在保持尺寸小、频率低等优点的同时,显著拓宽了工作频带并提高了辐射声功率.换能器外型尺寸为φ88 mm×316 mm,水中谐振频率1.30 kHz,-3 dB带通Q值1.43,谐振频率下发射电压响应级135.1 dB.     

磁致伸缩-压电联合激励凹简型发射换能器

设计制作了一种新型磁致伸缩-压电联合激励凹简型发射换能器,采用稀土超磁致伸缩材料Terfenol-D与PZT压电陶瓷作为联合激励元件,模拟计算与实测结果均表明,与采用单一振子激励的凹筒型发射换能器相比,此种新型换能器在保持尺寸小、频率低等优点的同时,显著拓宽了工作频带并提高了辐射声功率。换能器外型尺寸为φ88 mm×316 mm,水中谐振频率1．30 kHz,-3 dB带通Q值1．43,谐振频率下发射电压响应级135．1 dB。     

PVDF压电计的动态响应特性及其在橡胶材料SHPB实验中的应用

通过夹心式PVDF(Polyvinylide Fluoride)压电计的动态分离式Hopkinson压杆(SHPB)标定实验,系统地讨论了传感器的动态响应特性,其中包括测量电路、PVDF表面应力集中、压电计的材料及结构特性和同一压电计受多次撞击对测试信号的影响,为PVDF压电计的制作工艺研究提供参考。利用标定好的压电计测试了橡胶材料在SHPB实验中的动态应力均匀过程。结果表明:调节并联电阻值可以提高压电计的传感精度;增大压电计的敏感面积可以减小因应力集中所造成的信号失真;材料的热粘塑性性质、摩擦效应等将使信号振荡幅度偏小;多次撞击对信号的加载与卸载段都将产生影响,但当传感器表面未发生明显损伤时,测试的应力平台平均值与真实信号近似相同。     

相控阵井壁成像仪高压电源纹波噪声抑制研究

针对超声相控阵井壁成像仪工作环境恶劣以及超声脉冲发射所需高压电源纹波噪声对超声回波信号干扰大的问题,提出一种高温环境下高压电源纹波噪声抑制方法并进行设计分析。本方法综合开关电源与线性稳压电源各自的技术优势且注重纹波噪声抑制和耐高温设计。利用开关电源完成不同电压幅值的高效转换并在电源输出端增设专门的EMI滤波电路,再利用屏蔽罩对电源进行屏蔽,最后输出电压再经过一级线性稳压电路进一步进行稳压滤波。实测结果表明,利用该方法,电源的纹波与辐射噪声得到了抑制,有效减少电源对回波信号的干扰,且输出电压稳定,提高了超声相控阵井壁成像仪井下工作的稳定性。     

PB-1型窄脉冲压电薄膜可逆式换能器

本文著者研制成PB-1型PVDF可逆式压电换能器。它的通频带较宽,中心频率500—900KHz,通带Q值1.5,发送电压响应[级]148.9dB(re:1μPa/V),灵敏度-210dB(re:1V/μPa)。在水中声脉冲持续时间7—10μs,并有足够的声功率输出,电声效率约10％。 本文介绍了该换能器的结构、理论分析、测量结果及应用效果。证明了理论与实验的一致性。可供电声、水声、超声等其它PVDF传感器设计时参考。     

Application of piezoelectric transient response in transducer acoustic power measurement

To explore a more convenient method for measuring the focused ultrasound power,a piezoelectric ceramic plate was used to receive ultrasonic signal directly.Due to an acoustic force acts on the surface of piezoelectric ceramic plate,the piezoelectric response was obtained by means of electromechanical analogy,which was composed of voltage response caused by forced vibration and high frequency attenuation response caused by natural vibration.The conversion relationship between output signal of piezoelectric ceramic plate and acoustic power of transducer was analyzed.The envelope of output piezoelectric signal was extracted in twice,and a voltage amplitude curve with sinusoidal distribution that could describe the changes of acoustic power was obtained.Under different drive voltage of transducer,the maximum peak voltage of envelope curve was found respectively.Their squared values were made a linear fitting with acoustic power measured by acoustic power meter,and then the proportional coefficient of theoretical relational expression was calibrated.The experimental results are in good agreement with the theory.The relative error between calibrated theoretical acoustic power and that measured by acoustic power meter was less than 8.7%.The paper can provide a guideline for measuring acoustic power of transducer by using piezoelectric signal.     

采用Helmholtz共鸣器与悬臂梁压电换能器的声能采集器研究

针对环境中广泛存在的声能,提出了一种采用Helmholtz共鸣器和悬臂梁压电换能器的声能采集器。Helmholtz共鸣器对入射声压进行放大,放大后的声压引起共鸣器弹性薄壁振动,薄壁的振动传递到压电换能器产生电能输出。建立了带弹性壁的立方形共鸣器的等效集中参数理论模型,并与压电换能器的机电特性结合,分析了声能采集器的声-机-电转换原理,研究了声压、声波频率和负载阻抗对输出功率的影响,研究结果为此类声能采集器的优化设计及工程应用提供了一种可行的方法。实验中,声源通过声波导管输出声能,当共鸣器管口处的声压级为94 dB时,系统实测最大输出功率达240μW。该采集器不仅可作为声能自供能采集器,还可在较远距离为低能耗电子装置进行有源声供能。      

The transient suppression for piezoelectric ceramic emission transducer

A transient suppression method for piezoelectric ceramic transducer is presented. By adding some special pedestal pulses to the original transmitted signal, the transient effects in the output of the transducer can be just precisely transmission by use of a narrowband transducer. canceled, thereby achieving the broadband The experimental results show that the transient responses of the sinusoid pulses and coded signals are suppressed successfully and the acoustic waveforms radiated into the surrounding water are improved significantly.     

A tri-modal directional transducer

Acoustic transducers made from piezoelectric ceramic cylinders usually exploit the breathing or omnidirectional (omni) mode of vibration. However, with suitable voltage distribution, higher order extensional modes of the cylinder can be excited which produce directional radiation patterns. These modal radiation patterns can then be combined to synthesize desired beam patterns which may be steered by incrementing the excitation. This paper describes a model for the combined acoustic response of the extensional modes of vibration of a piezoelectric ceramic cylinder, a method of synthesizing a desired radiation pattern, and an experimental implementation of a directional transducer that uses these techniques. This tri-modal transducer is broadband and directional with a frequency independent beam pattern yet simple, small, and lightweight.     

Characteristics of thermal acoustic radiation as a source of acoustic signals

A linear dependence of the output voltage of an acoustic thermometer on the temperature difference between the source and the piezoelectric transducer is demonstrated experimentally. The constant component of the output voltage is determined by the noise temperature of the receiving device. The main feature of the thermal acoustic radiation as a source of acoustic signals is that the signal is represented not by the total thermal radiation of the object, which is proportional to the absolute temperature of the latter, but by the part of this radiation that is proportional to the temperature difference between the object and the transducer.     

Study on the high power air-coupled ultrasonic compound transducer

The high power air-coupled compound ultrasonic transducer in flexural vibration is studied. The transducer consists of a sandwich longitudinal piezoelectric transducer and a circular thin plate in flexural vibration. The resonance frequency equation and the equivalent circuit of a circular radiator with clamped boundary condition are derived. The resonance frequency equation and the equivalent circuit of the compound transducer are also obtained. The radiated acoustic field of the circular thin plate radiator is analyzed and the directional pattern is calculated. It can be seen that when the vibrational order of the circular thin plate in flexural vibration is increased, the radiated acoustic field becomes complex.     

弛豫铁电单晶/压电陶瓷混合激励换能器EI北大核心CSCD

为了降低纵向换能器尺寸并提高发射带宽和发送电压响应,研究了一种弛豫铁电单晶/压电陶瓷混合激励换能器,换能器由[011]方向极化PIN-PMN-PT单晶和PZT-4压电陶瓷混合激励,利用多模态振动耦合的原理,通过单晶的32模式振动,可以灵活调整两种振子之间的驱动能力和刚度分配。首先通过四端网络法得到了换能器等效电路并计算了其谐振频率,然后利用有限元方法对换能器进行了仿真优化,最后制作了试验样机并进行了测试分析。换能器样机外径86 mm、长度80 mm,工作频带13~38 kHz,最大发送电压响应为144.9 dB,带内发送电压响应起伏小于6 dB,具有良好的宽带、小尺寸工作性能。     

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.     

Reduction of radiated exterior noise from the flexible vibrating plate of a rectangular enclosure using multi-channel active control

This study attempted to control the radiated exterior noise from a rectangular enclosure in which an internal plate vibrates by acoustic excitation and noise is thus radiated from that plate. Multi-channel active control was applied to reduce the vibration and external radiation of this enclosed plate. A piezoelectric ceramic was used as a distributed actuator for multiple mode control of the vibration and radiated noise in the acoustically excited plate. To maximize the effective control, an approach was proposed for attachment the piezoelectric actuator in the optimal location. The plate and internal acoustic space in the enclosure are coupled with each other. This will change dominant frequency characteristics of the plate and, thus, those of the externally radiated noise. Active noise control was accomplished using an accelerometer attached to the plate and a microphone placed adjacent to that plate as an error sensor under acoustic excitation of sine wave and white noise. It was found that the control of radiated external radiation noise requires a microphone as an error sensor, a sound pressure sensor due to vibration of the plate, differences in the dominant frequency of externally radiated noise, and complex vibration modes of the plate.     

Theoretical analysis and experimental validation of radial cascaded composite ultrasonic transducer

A radial cascaded composite ultrasonic transducer is analyzed.The transducer consists of three short metal tubes and two radially polarized piezoelectric ceramic short tubes arranged alternately along the radial direction.The short metal tubes and the piezoelectric ceramic short tubes are connected in parallel electrically and in series mechanically,which can multiply the input sound power and sound intensity.Based on the theory of plane stress,the electro-mechanical equivalent circuit of radial vibration of the transducer is derived firstly.The resonance/anti-resonance frequency equation and the expression of the effective electromechanical coupling coefficient are obtained.Excellent electromechanical characteristics are determined by changing the radial geometric dimensions.Two prototypes of the transducers are designed and manufactured to support the analytical theory.It is concluded that the theoretical resonance/anti-resonance frequencies are consistent with the numerical and experimental results.When R_2 is at certain values,both the anti-resonance frequency and effective electromechanical coupling coefficient corresponding to the second mode have maximal values.The radial cascaded composite ultrasonic transducer is expected to be used in the fields of ultrasonic water treatment and underwater acoustics.