用DIS数字化信息系统测量金属棒中声速的有效方法

本文设计了一种将驻波法与声波传感器相结合测定金属棒中声速的有效方法.将金属棒固定在中点,沿轴向摩擦激励纵振动并在棒中形成驻波而发声,用DIS数字化信息系统接收声波信号,得到波形图,由此测得棒中声波的基频和声速.本文分别测定了铝、钢、黄铜、紫铜4种不同金属材料棒中的声速.结果表明,同种材料、不同长度金属棒中声速的测量结果基本相同;各种金属棒中声速的测量值与公认值的相对误差小于6.00%.此方法的特点是将声波信号变成可视波形,并可从波形图中直接提取准确的计算参数.     

纵横波测已紧固螺栓轴向应力

本提出了用纵横波声时测已紧固螺栓轴向应力的一种新方法,解决了用超声精确地测已紧固螺栓应力问题,并且利用超声波沿轴向传播的波速同轴向应力以及三阶弹性常数的关系导出了螺栓应力同其材料声速特性、夹紧距离、温度及纵、横波声时的一种新关系,考虑了受应力作用时温度对声速的影响,简化了测量及计算过程,本还介绍了材料的声速特性实验及测量方法;实验结果表明应力低于２５０ＭＰａ,夹紧距离大于３０ｍｍ时,应力超声测     

非对称冲击-卸载实验中纵波声速的特征线分析方法

材料高压声速是获取材料在冲击下的剪切模量、强度和相变信息的重要物理量, 对于研究材料在高速冲击下的行为非常重要. 由于飞片、样品和窗口材料阻抗失配等因素, 传统的声速分析方法无法对非对称冲击-卸载实验中单样品的窗口界面速度进行准确的分析. 本文在反向特征线方法的基础上, 考虑了飞片与样品、样品和窗口界面的相互作用, 建立了适合于仅含单一厚度样品的非对称冲击-卸载实验的特征线声速分析方法, 通过对数值实验给出的速度剖面的分析表明, 该方法能够较为准确地获得待测材料高压下的声速及卸载路径.     

基于四水听器的充水弹性管声速测量方法

实验室中水声材料声学参数的测量主要在水声声管中进行。管内平面波声速是正确测量这些参数的基础。该文提出一种基于四水听器结合不同边界的测量充水弹性管中声速的新方法。该方法利用4个固定位置处的水听器,采用最小二乘的方法,使得两组水听器分别得到的声管末端入射波声压差值的平方最小的声速即为管内平面波声速。该方法利用单频信号,在每一频率点均可测得声速,可以在任一种声管末端边界下进行测量,同时无需知道各水听器到边界的精确距离,在文中的3种边界下声速测量结果具有很好的一致性,实验操作简单、误差很小。该方法的仿真结果与管内声速的理论值吻合得很好,同时实验测量结果与仿真值之间的误差很小,证明了方法的准确性以及鲁棒性,为声管声速测量提供一个很好的思路。     

利用智能手机测量不同传播介质中声速的实验装置设计

利用智能手机自制简易实验装置，搭建了一套驻波法声速测量系统，实现了声波在空气和不同液体介质中的传播速度的准确测量。实验使用手机FreqCounter APP产生单频声波信号，采用DaTuner APP软件检测实时频率和声音强度，通过测得相邻波腹或波节间的距离，根据其与频率和声速间的关系即可求出所测声速值。所取得实验结果与理论值具有良好的一致性。     

利用自发布里渊散射测量液体声速

为了克服共振干涉法在液体的热力学声速和高频声速测量方面精度不高的问题, 本文建立了一种基于自发布里渊散射原理的测定液体声速的实验装置. 利用法布里-珀罗干涉仪对散射光进行扫描滤波, 数据采集卡结合光子计数器对散射光进行探测, 设计了一种散射光信息采集分析方法. 该实验方法有效的解决了传统布里渊散射方法中信号失真的问题, 显著地提升了液体声速测量精度. 对308.6–906.2 MHz内298.15 K饱和液相CCl₄声速进行了测量, 测量结果与文献值具有较好一致性. 利用法布里-珀罗干涉仪周期性扫描的滤波原理, 通过在测量得到的布里渊频移上加减整数倍个自由波谱区, 得到了更大频率的波谱信息, 进而设计一种测定介质高频声速的方法. 对CCl₄在5406.1–5521.0 MHz频段内的声速进行了测量. 实验结果显示, CCl₄的热力学声速随频率无明显变化, 而高频声速随频率的增大呈增大趋势且远大于热力学声速, 证实CCl₄具有色散现象.     

LaCoO3中自旋态转变现象的超声研究

测量了LaCoO3单相多晶样品的纵波与横波超声声速和衰减随温度的变化关系, 在材料的自旋态转变温度附近(≈90K),纵波声速出现明显的软化并伴随一个尖锐的衰减峰,但是在横波的测量中却没有出现类似的超声异常,分析认为LaCoO3在90K附近的自旋态转变是由于Co3+离子是从低自旋态(LS,t62ge0g)转变到中等自旋态(IS,t52ge1g ),而不是高等自旋态(HS,t42ge2g).随着温度的升高,在200K附近纵波和横波测量上都观察到一个伴随着微小声速软化的宽大的衰减峰,这可能是随机分布的IS态Co3+离子的Jahn-Teller效应导致的局域晶格扭曲所造成的.     

用脉冲光声法测量固体介质中声速

提出了一种利用脉冲光声技术测量固体介质中声速的方法,建立了由YAG激光器和超声探测器组成的实验系统,脉冲激光在固体表面产生脉冲超声波,通过测量脉冲声波在固体内多次反射后的出射信号及固体的厚度,即可算出固体介质中的声速.对黄铜及铝的测量结果表明,这是一种准确性较高的固体介质中声速测量方法.该测量方法可作为综合设计性物理实...     

全自动声速测量及实验数据处理研究

针对大学物理实验中传统声速测量装置存在的缺陷,利用单片机、上位机、步进电机、步进电机驱动器、采集卡、有效值检测模块和相位差测量模块等搭建了全自动声速测量系统,利用驻波法和相位比较法对声速进行测量。实验结果表明:新型声速测量仪克服了传统测量装置的缺陷,获得的数据量更大,包含的信息也更丰富。由于次峰的影响,常用的逐差法、最小二乘法和Origin软件线性拟合法处理数据误差较大,不能满足实验需要,有必要寻找声速测量数据处理的新方法。为排除次峰的影响,考虑到声速测量数据中极值点的出现具有空间周期性,利用傅里叶变换处理数据得到待测信号的空间频谱图,确定了声波的波长并计算出声速。数据处理结果表明:由于傅里叶变换排除了次峰干扰,使驻波法和相位比较法测量声速的相对误差分别从1.6%和1.0%减小为0.71%和0.41%,比传统方法更适合于处理声速测量数据;此外,从另一个角度证明次频共振现象是形成次峰的重要原因。     

声速不均匀介质的光声成像重建算法

为提高声速不均匀介质的光声成像精度,提出一种基于反卷积的光声成像重建算法.本算法不需预先知道介质的声速分布.先通过探测到的光声信号构造出一个新函数,并用不同位置探测到的光声信号间的相关性来估计空间两点间的声波传播时间,以补偿声速的不均匀性.然后基于反卷积方法由该函数解出待测组织内的电磁波吸收分布.仿真研究结果表明,当介质声速差异在10%以内时,重建图像能正确反映待测目标的大小、位置和电磁波吸收系数,算法具有良好的抗噪性能.由于生物软组织内的声速差异一般小于10%,因此本算法是一种有效的光声成像重建算法.     

Research on sound velocity measurement in a laboratory for large elastic materials

A measurement scheme carried out in a tank is designed to obtain the compressionaland shear-wave velocities of a large elastic material.A hydrophone is used to receive the high frequency acoustic signals which penetrate the tested material,in order to determine the transmission time from the source to the hydrophone,the transmission time is also calculated according to the ray acoustic theory in layered media.A cost function is built based on the measured and the calculated transmission time,then the compressional- and shear-wave velocities can be obtained using the optimization algorithm.Compared with the traditional measurement scheme,this approach can not only get the 2 kinds of sound velocities in the tested material at the same time,but also keep the integrality of the tested material.With the proposed measurement system,the uncertainty of measurement results is less than 3.5%.     

Geoacoustic Inversion Based on a Vector Hydrophone Array

We propose a geoacoustic inversion scheme employing a vector hydrophone array based on the fact that vector hydrophone can provide more acoustic field information than traditional pressure hydrophones. Firstly, the transmission loss of particle velocities is discussed. Secondly, the sediment sound speed is acquired by a matchedfield processing （MFP） procedure, which is the optimization in combination of the pressure field and vertical particle velocity field. Finally, the bottom attenuation is estimated from the transmission loss difference between the vertical particle velocity and the pressure. The inversion method based on the vector hydrophone array mainly has two advantages： One is that the MFP method based on vector field can decrease the uncertain estimation of the sediment sound speed. The other is that the objective function based on the transmission loss difference has good sensitivity to the sediment attenuation and the inverted sediment attenuation is independent of source level. The validity of the inverted parameters is examined by comparison of the numerical results with the experimental data.     

同振球型矢量水听器声波接收理论研究

对同振球型矢量水听器声压和质点振速的声波接收理论进行了研究。以同振球型振速水听器测量原理为基础,推导了自由运动刚性球体和弹性球体的声波接收响应数学表达式,分析了振速水听器几何尺寸、平均密度与其频响特性曲线之间的关系;另外,根据球面接收器的声波接收理论,推导了矢量水听器声压接收响应数学表达式,通过理论分析和数值计算,研究了振速水听器表面上的声压分布规律以及声压水听器的声波接收压力系数与其接收面的大小、质点振速水听器的半径、布放的位置和半径等参数之间的关系;从理论上建立了矢量水听器声波接收理论模型和分析方法,为矢量水听器的设计和研制提供了理论依据。      

Experimental study of underwater transmission characteristics of high-frequency 30 MHz polyurea ultrasonic transducer

In this paper, we present the transmission characteristics of a polyurea ultrasonic transducer operating in water. In this study, we used a polyurea transducer with fundamental resonance at approximately 30 MHz. Firstly, acoustic pressure radiated from the transducer was measured using a hydrophone, which has a diameter of 0.2 mm. The transmission characteristics such as relative bandwidth, pulse width, and acoustic sensitivity were calculated from the experimental results. The results of the experiment showed a relative bandwidth of 50% and a pulse width of 0.061 μs. The acoustic sensitivity was 0.60 kPa/V with good linearity, where the correlation coefficient R in the fitting calculation was 0.996. A maximum pressure of 13.1 kPa was observed when the transducer was excited at a zero-to-peak voltage of 21 V. Moreover, we experimentally verified the results. The results of the pulse/echo experiment showed that the estimated diameters of the copper wires were 458 and 726 μm, where the differences between the actual and measured values were 15% and 4%, respectively. Acoustic streaming was also observed so that a particle velocity map was estimated by particle image velocimetry (PIV). The sound pressure calculated from the particle velocity obtained by PIV showed good agreement with the acoustic pressure measured using the hydrophone, where the differences between the calculated and measured values were 12–19%.     

干涉型光纤水听器相位载波调制-解调中信号混叠产生的机理及解决方案

信号混叠是制约基于相位载波调制-解调的光纤水听器系统走向应用的一个关键问题。对信号混叠产生的机理进行了详细的理论分析和仿真,结果表明,提高光源调制频率和降低探头灵敏度都无法有效解决光纤水听器实际应用中遇到的高频干扰引起的混叠问题。基于声学滤波器原理,提出了一种新颖的声低通滤波解决方案。设计并加工制作了一种简单的声低通滤波光纤水听器,在驻波罐中对其声压灵敏度频响进行了测量。实验结果表明,该光纤水听器在测量频带上具有较好的声低通滤波特性,低频声压灵敏度约为-140 dB(0 dB=1 rad/μPa),高频衰减大于20 dB,对高频干扰有较强的抑制能力。该方案十分简单经济,能从根本上有效地解决相位载波调制-解调中的信号混叠问题。     

新型光纤光栅水声传感器的研究

提出了一种新型的光纤布拉格光栅(FBG)水声传感探头结构以及光纤光栅传感信号的自解调方法。利用一对匹配光栅构成推挽结构,实现了传感-解调的合二为一,大大地减小了系统的复杂度;并通过筒状弹性体结构,解决了裸光纤光栅测量水声信号的灵敏度过小的问题,并具有温度补偿作用。仿真与初步实验结果表明,该水听器探头的测量动态范围超过100 dB,在100~200 dB re 1μPa的水声压范围内,测量灵敏度为0.36 nm/Mpa。     

100kHz～500kHz压电复合材料标准水听器

本文介绍了一种我们制作的可应用于100kHz～500kHz频段的标准水听器,水听器敏感元件采用1-3型压电复合材料,通过对敏感元件及水听器结构进行合理设计,从工艺上保证水听器性能的稳定、可靠,制作完成的标准水听器满足高频标准的所有技术指标要求。测试结果表明,水听器的接收灵敏度大于-194dB,频段内灵敏度起伏为2.9dB,最高使用频率-3dB波束宽度大于20度;稳定性考核表明,水听器有良好的温度、时间稳定性,是一种比较理想的中高频标准水听器,适合于水声的校准和中高频声信号测试。     

Pseudo working-point control measurement scheme for acoustic sensitivity of interferometric fiber-optic hydrophones

A novel pseudo working-point control measurement scheme for the acoustic sensitivity of interferometric fiber-optic hydrophones is described and demonstrated.The measurement principle is introduced in detail.An experimental system,which interrogates an interferometric fiber-optic hydrophone with this method,is designed.The acoustic pressure phase sensitivity of the fiber-optic hydrophone is measured over the frequency range of 20-2500Hz.The measured acoustic sensitivity is about-156.5dB re 1rad/μPa with a fluctuation lower than ±1.2dB,which is in good agreement with the results obtained by the method of phase generated carrier.The experimental results testify the validity of this new method which has the advantages of no electric elements in the sensing head,the simplicity of signal processing,and wide working bandwidth.     

Characterization of an optical multilayer hydrophone with constant frequency response in the range from 1 to 75 MHz

The performance of an optical multilayer hydrophone for ultrasound measurements is investigated both in theoretical terms and experimentally. The optical measurement system comprises a thin high-finesse dielectric interference filter structure that is deposited onto a plane glass plate. An incident acoustic pressure wave deforms the layer system, and the induced variation of the optical reflectance is determined. Applying the concept of an optical off-axis detection scheme offers good sensitivity and a simple and low-cost setup. A primary interferometric calibration technique is applied to experimentally determine the pressure-voltage transfer function in the range from 1 to 75 MHz. Within the measurement uncertainty a constant transfer factor is obtained for the whole frequency range. Measurements of broadband ultrasound pulses are influenced neither by acoustic resonances of the very thin sensing element nor by diffraction phenomena that are known to cause waveform distortions in small probe hydrophone measurements. High temporal and spatial resolution is combined with high durability of the probe, which is why the optical multilayer hydrophone is well suited for use as a reference for secondary hydrophone calibration.     

聚焦区域高声强声场分布的测量方法研究

常用的声场分布测量是采用水听器扫描声场的方法,该方法对于声能量密度较大的声场难以测量,因为在这种情况下声振幅比较大,水听器在这种声场中呈现非线性或遭到破坏。设计了一种用辐射压力测量高声强声场分布的方法,该方法利用一根微细管,直接测量声场的冲流压力,通过对声场进行扫描测量可以得到高声强声场压力分布。从理论上分析了这种测量方法的可行性,对测量基本要求及实验装置做了阐述。实验结果证实:该方法可以用来测量高声能密度声场压力分布;测量结果与水听器测量结果基本吻合;测量方法存在测量盲区。