体声波Barker码序列及其在检测超声中的应用

本文提出了一种获得体声波Barker码信号序列的极为简便的方法,并给出了相应的相关处理结果。Barker码声信号采用了单位电脉冲的换能器响应作为单元码,并以此构成了编码序列。由于DATA-2020和DATA-6000具有相当高的稳定度,保证了编码序列的相位精度,因而得到了颇为理想的响应函数。超声换能器的瞬态响应特性和声信号比电信号的滞后特性,是造成偏差的主要因素。     

超声在固体火箭发动机无损检测中的应用

在固体火箭发动机的研制中，无损检测技术非常重要。本文介绍了一些主要的超声检测方法及其应用。脉冲多次反射法用于检测固体火箭发动机壳体与衬层之间的粘结质量。特性参数和扫频超声法以多层介质理论为基础，用于检测固体火箭发动机的深层粘结质量。     

Measuring predictability in ultrasonic signals: An application to scattering material characterization

In this paper, we present a novel and completely different approach to the problem of scattering material characterization: measuring the degree of predictability of the time series. Measuring predictability can provide information of the signal strength of the deterministic component of the time series in relation to the whole time series acquired. This relationship can provide information about coherent reflections in material grains with respect to the rest of incoherent noises that typically appear in non-destructive testing using ultrasonics. This is a non-parametric technique commonly used in chaos theory that does not require making any kind of assumptions about attenuation profiles. In highly scattering media (low SNR), it has been shown theoretically that the degree of predictability allows material characterization. The experimental results obtained in this work with 32 cement probes of 4 different porosities demonstrate the ability of this technique to do classification. It has also been shown that, in this particular application, the measurement of predictability can be used as an indicator of the percentages of porosity of the test samples with great accuracy.     

二维信号分析法在超声无损检测中的应用

本文综述了近年来二维信号分析法在超声无检测（NDT）中的应用,其中包括二维快速Fourier交换（FFT）、Wigner-Ville分布（WWD）、Gabor变换（GT）和小波变换（WT）等,对它们自在NDT应用中的优缺点进行了分析比较和讨论。     

Controlling acoustic streaming in an ultrasonic heptagonal tweezers with application to cell manipulation

Acoustic radiation force has been demonstrated as a method for manipulating micron-scale particles, but is frequently affected by unwanted streaming. In this paper the streaming in a multi-transducer quasi-standing wave acoustic particle manipulation device is assessed, and found to be dominated by a form of Eckart streaming. The experimentally observed streaming takes the form of two main vortices that have their highest velocity in the region where the standing wave is established. A finite element model is developed that agrees well with experimental results, and shows that the Reynolds stresses that give rise to the fluid motion are strongest in the high velocity region. A technical solution to reduce the streaming is explored that entails the introduction of a biocompatible agar gel layer at the bottom of the chamber so as to reduce the fluid depth and volume. By this means, we reduce the region of fluid that experiences the Reynolds stresses; the viscous drag per unit volume of fluid is also increased. Particle Image Velocimetry data is used to observe the streaming as a function of agar-modified cavity depth. It was found that, in an optimised structure, Eckart streaming could be reduced to negligible levels so that we could make a sonotweezers device with a large working area of up to 13 mm × 13 mm.     

超声散斑相关法测量转角的相关性研究

对于在用超声散斑相关法测量时,转角对不同强度散斑的影响及散斑场相关性和转角之间的关系做了研究。为了分析界面位移前后,不同照射区域对散斑振幅是如何影响的,文中把超声照射区域化为M个反射基元,利用大量反射基元的统计规律,推导出了散斑形貌误差和统计误差对散斑场的影响关系,这个关系就是散斑的振幅越大,受转角大小的影响就越小;转角越大统计误差对散斑强度的影响就越大。为了验证这个结论作者建立了实验系统,实验结果显示理论分析是正确的。     

超声波防除积垢节能技术及设备开发

传热设备的积垢问题一直是人们急于解决的一大难题，不仅影响热能利用和生产正常运转，而且会降低产品质量，增加生产成本。通过机理研究、室内试验和工厂试验，揭示了超声波防除积垢的机理，筛选出最佳的声场参数，研制出一种新型的超声波防除积垢设备，室内试验和工厂试验结果表明，超声波技术不但可以防止新垢的产生，而且可以有效地去除已有积垢，显著地提高蒸发系统传热系数和生产能力，可停止使用化学清洗剂，从而延长传热设备使用寿命，避免污染环境，该技术有可能广泛地应用于制糖工业、化肥工业、制浆造纸工业等诸多领域。     

Coded excitation of ultrasonic guided waves in long bone fracture assessment

Ultrasonic guided wave (GW) assessment of long bone fracture have conventionally been based on pulse excitation. However, the high attenuation during propagation diminishes the amplitude of received GWs and results in low signal-to-noise ratio (SNR). The Barker code (BC) excitation and the optimal binary code (OBC) excitation were utilized in this study to overcome this limitation. Both simulations and in vitro experiments were performed on the fractured cortical bone plate model, and measured signals from both the BC and OBC excitations were decoded using the finite impulse response least squares inverse filter (FIR-LSIF) and then compared with sine pulse (SP) excited signals. The results suggest the efficiency of coded excitation for amplitude and SNR improvement. Furthermore, time–frequency representation (TFR) analysis was applied to experimental signals; with increasing fracture depth, energy transformation between predominate GW modes A1 and S2 was confirmed. These results show the potential of using BC and OBC excitations to evaluate the depth of long bone fracture.     

Pitfalls in the experimental recording of ultrasonic (backscatter) polar scans for material characterization

The ultrasonic polar scan (UPS), either in transmission, reflection or backscatter mode, is a promising non-destructive testing technique for the characterization of composites, providing information about the mechanical anisotropy, the viscoelastic damping, the surface roughness, and more. At present, the technique is merely being used for qualitative purposes. The limited quantitative exploration and use of the technique can be primarily ascribed to limitations of current theoretical models as well as the difficulty to perform accurate, and more importantly, reproducible UPS experiments. Over the last years, we have identified several potential pitfalls in the experimental implementation of the technique which severely deteriorate the accurateness and reproducibility of a UPS. In this paper, we make an inventory of the most important difficulties, illustrate each of them by a real experiment and present a feasible mediation, either numerical or experimental in nature. Once the experimental set-up is fine-tuned to overcome these pitfalls, it is expected that the recording of high-level UPS experiments, in combination with numerical computations, will facilitate the technique to become a fully quantitative non-destructive characterization method.     

Study on the bubble transport mechanism in an acoustic standing wave field

The use of bubbles in applications such as surface chemistry, drug delivery, and ultrasonic cleaning etc. has been enormously popular in the past two decades. It has been recognized that acoustically-driven bubbles can be used to disturb the flow field near a boundary in order to accelerate physical or chemical reactions on the surface. The interactions between bubbles and a surface have been studied experimentally and analytically. However, most of the investigations focused on violently oscillating bubbles (also known as cavitation bubble), less attention has been given to understand the interactions between moderately oscillating bubbles and a boundary. Moreover, cavitation bubbles were normally generated in situ by a high intensity laser beam, little experimental work has been carried out to study the translational trajectory of a moderately oscillating bubble in an acoustic field and subsequent interactions with the surface. This paper describes the design of an ultrasonic test cell and explores the mechanism of bubble manipulation within the test cell. The test cell consists of a transducer, a liquid medium and a glass backing plate. The acoustic field within the multi-layered stack was designed in such a way that it was effectively one dimensional. This was then successfully simulated by a one dimensional network model. The model can accurately predict the impedance of the test cell as well as the mode shape (distribution of particle velocity and stress/pressure field) within the whole assembly. The mode shape of the stack was designed so that bubbles can be pushed from their injection point onto a backing glass plate. Bubble radial oscillation was simulated by a modified Keller–Miksis equation and bubble translational motion was derived from an equation obtained by applying Newton’s second law to a bubble in a liquid medium. Results indicated that the bubble trajectory depends on the acoustic pressure amplitude and initial bubble size: an increase of pressure amplitude or a decrease of bubble size forces bubbles larger than their resonant size to arrive at the target plate at lower heights, while the trajectories of smaller bubbles are less influenced by these factors. The test cell is also suitable for testing the effects of drag force on the bubble motion and for studying the bubble behavior near a surface.     

人类对超声的听觉感知及应用前景

本文对人类通过骨传导所产生的超声听觉感知，就以下四方面进行介绍：１．感知的方法、频率和强度范围；２．感知机理；３．可能的应用；４．值得研究的问题。     

Interaction of ultrasonic wave with void-containing layer in solid

Using a general mode for sound reflection from multilayered media,we present in this paper the expressions for sound reflection and transmissioncoefficients on void-containing interface layer in solid and derive the character-istic equation for symmetric and antisymmetric modes of the interface wavesalong the layer.The method for evaluating the effective elastic moduli ofvoid-containing solid is also introduced.The numerical calculation given in thispaper shows the influences of the void volume concentration and layer thick-ness on the sound reflection coefficients and interface wave velocity,providing atheoretical basis for inverse of the mechanical properties of void-containinglayer based on the ultrasonic measurement.     

超声空化及其声流结构实验研究*

超声空化及其声流效应在医学、化工和能源等领域得到广泛应用。本文采用高速摄像和粒子图像测速系统分别研究了超声场下的空化形态和声流场结构的时空演化规律。实验研究了50W,100W,200W和250W等四种不同输入功率对18kHz的超声变幅杆附近空化及其声流场的影响。研究结果表明：（1）在变幅杆下端面处观察到由大量空化气泡均匀分布组成的倒置锥形空泡结构,并且锥形空泡结构为稳态流动结构。（2）在超声变幅杆附近产生了两种不同的声流形式,第一种是变幅杆底端的射流型声流,第二种是变幅杆两侧的回旋流。此外,通过研究空泡与声流场中最大速度点之间的空间对应关系,发现声流是因为空泡流动带动而产生的。（3）空间位置和输入功率能显著影响射流型声流的流场结构,但是对回旋流的影响十分微弱。     

圆管超声导波频散与多模态特性研究*

超声导波检测技术作为一种新兴的无损检测技术广泛应用于圆管类结构。为选择合适于不同缺陷检测的导波模态,推导分析了圆管导波传播的运动方程和频散方程;利用数值计算的方法得到了超声导波在圆管中传播的频散曲线和各模态沿壁厚方向的位移分布图,分析得出各个模态对不同缺陷的敏感程度;以一种特定的圆管为例,建立圆管缺陷有限元模型,对不同类型圆管缺陷对导波传播特性的影响进行仿真计算。结果表明,纵向模态对周向缺陷比较敏感,而扭转模态则对轴向缺陷更敏感,仿真结果与理论分析结果相吻合,为圆管缺陷检测的超声导波模态选择提供了理论依据。     

Characteristics of ring type traveling wave ultrasonic motor in vacuum

The characteristics of ultrasonic motor strongly depend on the properties of stator/rotor contact interface which are affected by ambient environment. With the developed apparatus, load properties of two ring type traveling wave ultrasonic motors in atmosphere, low vacuum and high vacuum were studied, respectively. Wear of friction material, variations of vacuum degree and the temperature of motor during the experiment were also measured. The results show that load properties of motor A in vacuum were poorer than those in atmosphere, when load torque M_f was less than 0.55 N m. Compared to motor A, load properties of motor B were affected a little by environmental pressure. Wear of friction material in vacuum was more severe than wear in atmosphere. The temperature of motor in vacuum rose more quickly than it in atmosphere and had not reached equilibrium in 2 h experiment. However, the temperature of motor in atmosphere had reached equilibrium in about forth minutes. Furthermore, outgas was also observed during experiment under vacuum conditions.     

Physical and chemical effects of acoustic cavitation in selected ultrasonic cleaning applications

Acoustic cavitation in a liquid medium generates several physical and chemical effects. The oscillation and collapse of cavitation bubbles, driven at low ultrasonic frequencies (e.g., 20 kHz), can generate strong shear forces, microjets, microstreaming and shockwaves. Such strong physical forces have been used in cleaning and flux improvement of ultrafiltration processes. These physical effects have also been shown to deactivate pathogens. The efficiency of deactivation of pathogens is not only dependent on ultrasonic experimental parameters, but also on the properties of the pathogens themselves. Bacteria with thick shell wall are found to be resistant to ultrasonic deactivation process. Some evidence does suggest that the chemical effects (radicals) of acoustic cavitation are also effective in deactivating pathogens. Another aspect of cleaning, namely, purification of water contaminated with organic and inorganic pollutants, has also been discussed in detail. Strong oxidising agents produced within acoustic cavitation bubbles could be used to degrade organic pollutants and convert toxic inorganic pollutants to less harmful substances. The effect of ultrasonic frequency and surface activity of solutes on the sonochemical degradation efficiency has also been discussed in this overview.     

超声测断面形状误差分析及测试方法探讨

本文对超声波斜入射情况下存在的测距误差进行了分析，给出了数学修正的公式，并通过实验进行了验证，对测量不同形状空间的测试方法了探讨。本文的讨论对提高测试精度和选择工程测试方案有参考意义。     

超声波检测计算机模拟和仿真的研究及应用现状

随着高性能计算机的广泛应用，超声检测模拟和仿真的研究方兴未艾。本文对这些研究所选择的数学模型和方法进行了综合评述，探讨了Gaussiam模型、声线模型、衍射理论、有限积分技术等的应用，涉及的方法包括各种解析方法及有限差分、有限元、边界元等数值方法。     

多层介质中超声相控阵声场仿真*

由于良好的声束偏转与聚焦特性,超声相控阵已经广泛应用于多层固体介质的缺陷检测。当超声束经过多层介质时,由于反射、透射以及模式转换的存在,多种声束存在于这种结构中,使得声场分析变得复杂。为了提高多层介质检测的准确性,有必要对超声声场的分布规律进行深入地了解。该文结合高斯声束等效点源模型以及射线追踪法,给出了相控阵声源在多层固体介质中激发声场的仿真方法,并且模拟计算了一维线型相控阵在楔块-铝-黄铜-钢四层固体介质中的辐射声场。通过对不同延时法则的计算,实现了声波在这种复杂介质中的偏转与聚焦,进而研究了不同焦点处聚焦声场的分布。结果表明:相控阵方法能使聚焦点处的声场幅值增大,能量集中,提高了检测分辨率;不同聚焦点处声场聚焦效果不同,实际检测时应根据检测区域结构及位置特点,合理放置相控阵换能器。与瑞利积分法的比较表明,该文的仿真方法适用于多层介质相控阵声场的计算。     

螺栓材料应力与声速、温度关系的测定

基于应力－超声波速度关系方法已用于螺栓轴向应力的测量。而声速与被测材料的许多物理因素有关，如弹性模量，密度与温度。本文介绍了用于分析超声波速度－应力－温度三者关系的实验与计算方法，并给出了三种金属材料的结果。检测的质量。