铝合金材料腐蚀损伤的声发射评价

为了研究如何利用声发射(AE)技术监测飞机主结构件的腐蚀损伤从而为确定飞机日历寿命提供科学依据。首先介绍了航空铝合金材料在加速腐蚀过程中的AE信号特征,说明如何利用AE技术来监测腐蚀损伤,进而讨论如何对材料的安全性能和剩余寿命进行评估。试验表明, AE能比超声和涡流等常规无损检测方法更早地发现铝合金材料的腐蚀损伤。通过研究加速腐蚀过程中腐蚀损伤程度及腐蚀AE信号随加速腐蚀时间的变化规律,获得了腐蚀损伤与AE参数之间的变化关系。说明AE技术可用于探测早期腐蚀、研究腐蚀发展规律及监测和评估腐蚀损伤方面。     

光纤Sagnac传感器对材料频率特性的实验研究

不同的材料由于物理性质不同,在断裂时会产生不尽相同的声发射信号。光纤声发射传感器以其频带宽,抗电磁干扰,灵敏度高,体积小等优点在声发射（AE）信号探测方面有着广泛的应用前景。本文采用光纤Sangac传感器,对不同材料断裂过程的声发射信号进行检测,通过快速傅立叶变换分析其频谱。实验得知同一种材料断裂的声发射信号具有相同的...     

人耳对复杂信号听测问题的研究

在相同信号形式和噪声背景条件下，通过直接对比人耳的听测性能和两种典型信号检测器的检测性能，在总的趋势上得出：人耳对频率变化规律确知的复杂声信号的听测模型接近于音调相关检测器；对频率变化规律未知的复杂声信号的听测模型接近于能量检测。此外，本文给出了在噪声背景下人耳听测三种频率变化规律的复杂声信号（单跳频、线性跳频、随机跳频）的灵敏度定量差别及人耳听测灵敏度和信号长度之间的定量关系。     

长江口与杭州湾海区水底浮泥地声模型及其声反射特性研究

通过在现场和实验室分别对长江口与杭州湾海区水底浮泥重度ρ随深度变化规律以及声速C与声衰减常数β等浮泥声学参数随ρ及声波频率f的变化规律的测量和分析，得出了这个海区水底浮泥层的地声模型。其主要特点是：重度ρ（kN／m3）在10．1到15．0的范围内，随着深度线性增加，但在12．5左右处线性增加的梯度（斜率）有一个突变（拐点），ρ大于15．0以后，ρ随深度的递增加快，即浮泥层很快过渡到硬性泥层或沙层；声速c（m／s）随ρ增大的变化不明显（在±1．5％以内），但在ρ为14．0附近存在一个最小值；声衰减常数ρ（dB/m）则分别随ρ和f（kHz）线性增加。根据实测的地声模型，通过理论计算，对长江口和杭州湾海区水底浮泥层的声反射信号进行了正演模拟研究，得到了在拐点处出现的声反射特性预射波的幅度和极性）与梯度变化的关系，为解决浮泥层重度的回声探测问题提供了依据。     

利用压电光声光谱测量镁掺杂氧化锌薄膜的光吸收特性

采用由射频磁控溅射方法在玻璃衬底制备的镁掺杂氧化锌（ZnO：Mg）薄膜材料,通过压电光声光谱法测量其在可见光波段的光吸收特性,并与透射光谱法测得的吸收率数据进行了比较,得到了一致性较好的结果。同时,从理论上推导分析了玻璃衬底上ZnO：Mg压电光声信号与光吸收率的关系及变化规律,并由实验证实：光声信号为玻璃基底与ZnO：Mg薄膜的共同贡献,光声信号的幅值与吸收率呈反相关,这一结论与理论分析得到的结果一致。     

表面波电磁声换能器的设计

简要介绍了产生表面波的电磁声换能器（EMAT）的工作原理，设计，制作了收发分开的两种EMAT，并建立了实验测试系统、测量了信号和发射EMAT提离距离的关系曲线，研究了激励脉冲个数、接收线圈的匝数对换能器信号的影响等。     

木塑复合材料缺陷及损伤的声发射信号特征分析及神经网络模式识别

针对木塑复合材料五种典型的缺陷及损伤机制，选择合适的木塑试样，应用三点弯曲的加载方法采集声发射信号。对主损伤区附近的声发射事件，应用小波变换提取特征参数，确定五类主要损伤机制所对应的声发射信号特征。采用B—P型反向传播神经网络构成的智能化模式分类器，对此五类声发射信号进行识别，获得了满意的效果。     

不同温度下劈裂加载JOB-9003炸药的声发射特性

JOB-9003炸药力学性能强烈地依赖于成型工艺、温度、长期库存时间及湿度等环境条件，并呈现出非线性黏弹性，从实验角度深入研究这类材料的力学特性与表征，对于认清其物理规律，建立JOB-9003炸药本构模型，确定材料参数乃至对工程结构进行定量分析具有重要的现实意义。声发射（AE）技术可揭示应力引起的开裂、扩展和变形，对研究中的裂纹初期和微裂纹敏感，具有连续、实时监测等特点，已成为 评价结构的完整性以及分析结构破坏全过程的重要手段。     

实验室里的传感器

实验室里的传感器刘秀梅，陶英伟（山东省菏泽教育学院物理系２７４００１６）在物理实验室里，我们经常需要用传感器将各种物理量转换成电文信号输出，以便于测试或用其来控制研究对象。有人将传感器比喻成“电五官”，有能感受光信息的光传感器．能感受声信息的声传感器...     

基于OPO脉冲激光激发光声光谱的真假血液分类鉴别

为了实现快速准确并可回收再利用地鉴别真血和假血,采用光声光谱技术构建了一套血液光声检测系统并获取血样的光声信号。选取三种动物真血（马血、牛血和兔血）和两种假血（道具假血和红墨汁）共125组血样作为实验样本。获取了700～1 064 nm波段内所有样本的光声信号和光声峰峰值谱。实验表明,真血和假血的光声信号幅度、轮廓、峰值时间点和光声峰峰值均存在差异。为了实现高准确度的真假血液分类识别,采用了遗传优化的小波神经网络（WNN-GA）算法,对全波段100组样本进行训练,并构建了类Morlet小波基函数,然后对25组测试血样进行分类识别。利用遗传算法对WNN网络的权值、阈值和小波基函数平移、伸缩因子进行了优化,同时通过调节两个学习率因子,将真假血液的分类识别率提高了24%。采用主成分分析（PCA）对全波段血样光声峰峰值进行特征提取,再利用WNN-GA算法进行训练和分类识别。结果表明,在主成分个数为6时,PCA-WNN-GA融合算法可以使真假血液的分类识别率提高到100%。与另外6种分类识别算法相对比,该融合算法的识别准确率明显占优。光声光谱技术联合PCA-WNN-GA算法,可以准确地实现真假血液的分类鉴别。     

基于光纤耦合器的声发射传感器

为检测变压器内局部放电产生的声发射信号,介绍了一种基于特殊光纤熔融拉锥耦合器型声发射传感器。它是利用声波引起的扰动改变耦合器两臂光功率输出的特点来检测声发射信号。实验结果表明：此种传感器在10kHz～250kHz范围内对声发射信号有良好响应,在155kHz灵敏度为5.6×10^-6V/Pa,噪声为1.8Pa声压,有望在复合材料与结构、电力无损检测方面得到应用。     

用埋入式光纤传感器探测建筑结构中的声发射

声发射技术已经应用于金属和混凝土结构中,作为探测内部裂缝的一种无损检测方法。目前用的技术都是由压电换能器来采集声发射信号。讨论了基于用光纤技术的声发射传感器的开发和测量方法。它是用埋入式光纤传感器来监测类似桥梁、高速公路、隧道和房屋建筑等混凝土结构中的开裂信号。     

Nonlinear Kalman Filtering for acoustic emission source localization in anisotropic panels

Nonlinear Kalman Filtering is an established field in applied probability and control systems, which plays an important role in many practical applications from target tracking to weather and climate prediction. However, its application for acoustic emission (AE) source localization has been very limited. In this paper, two well-known nonlinear Kalman Filtering algorithms are presented to estimate the location of AE sources in anisotropic panels: the Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF). These algorithms are applied to two cases: velocity profile known (CASE I) and velocity profile unknown (CASE II). The algorithms are compared with a more traditional nonlinear least squares method. Experimental tests are carried out on a carbon-fiber reinforced polymer (CFRP) composite panel instrumented with a sparse array of piezoelectric transducers to validate the proposed approaches. AE sources are simulated using an instrumented miniature impulse hammer. In order to evaluate the performance of the algorithms, two metrics are used: (1) accuracy of the AE source localization and (2) computational cost. Furthermore, it is shown that both EKF and UKF can provide a confidence interval of the estimated AE source location and can account for uncertainty in time of flight measurements.     

钢筋混凝土动态粘结滑移声发射特性试验

为研究不同加载速率下钢筋混凝土粘结-滑移损伤破坏过程中的损伤特征,对钢筋混凝土粘结试件进行了0.01 mm/s～10 mm/s四种不同速度的拔出试验。采用实时动态的声发射监测技术对整个试验过程进行监测,对试验过程中的声发射信号进行声发射振幅-振铃计数特性及功率谱峰值频率特性分析。结果表明,随着滑移速率的增加,声发射振幅-振铃计数拟合曲线变缓,在0～50 k Hz和100～150 k Hz频率范围内的声发射事件比重分别减小和增加。损伤过程的声发射特性对钢筋混凝土粘结滑移损伤演化规律的研究具有重要的价值。     

Study on the acoustic emission-model of concrete damage

I.lntroductiollBecausetherearethedefects.cracksandnon-homologousmicrostructurewithdifferentpropertiesincollcrete,whenaloadisputonconcretematerialthedamageandbreakagemayresultandsoonafterwardsexpanded.Itisadifficutproblem,howtodecidethedamageofconcretematerialwithcracksanddefects.TheacousticemissionisanassociatedphenomenollwiththeprocessofthenonhomologousdeformationorthebreakaeandexPansiollofmaterial.InthispaPertherelationshipbetweentheacousticemis8ionparametersandthedamageparameters,andthedam…     

Proposed method of partial discharge allocation with acoustic emission sensors within power transformers

Employing acoustic emission sensors for detection of partial discharge, PD, introduces many advantages. Besides easy installation and replacement, they are non-invasive and immune to electromagnetic noise and interference and their sensitivity does not vary with object capacitance. For PD allocating utilizing AE sensors, distance calculations are based on the arrival time of acoustic waves to the sensors. Considering structure-borne waves of higher speed, the peaks of some of indirect path AE signals with significant contribution are mistakenly considered as peaks of direct path AE signals. Furthermore, the acoustic signals are propagating through certain parts of the transformer, such as the windings, and this complicates the partial discharge detection and allocation. These would imply an incorrect distance between the source and sensor. A method based on a heuristic algorithm has been proposed which considering all possible indirect paths with the relevant propagation times and all the barriers on the travel path of acoustic signal, calculates the more precise arrival times to sensors. A test chamber has been utilized and artificial PD signals are produced at various points. Output results of algorithm have been compared with results of classic method. It has been shown that proposed method significantly reduces the positioning errors.     

Acoustic streaming in lithotripsy fields: preliminary observation using a particle image velocimetry method

This study considers the acoustic streaming in water produced by a lithotripsy pulse. Particle image velocimetry (PIV) method was employed to visualize the acoustic streaming produced by an electromagnetic shock wave generator using video images of the light scattering particles suspended in water. Visualized streaming features including several local peaks and vortexes around or at the beam focus were easily seen with naked eyes over all settings of the lithotripter from 10 to 18 kV. Magnitudes of the peak streaming velocity measured vary in the range of 10-40 mm s(-1) with charging voltage settings. Since the streaming velocity was estimated on the basis of a series of the video images of particles averaged over 1/60s, the time resolution limited by the video frame rate which is 1-2 orders of magnitude larger than driving acoustic activities, measured velocities are expected to be underestimated and were shown a similar order of magnitude lower than those calculated from a simple theoretical consideration. Despite such an underestimation, it was shown that, as predicted by theory, the magnitude of the streaming velocity measured by the present PIV method was proportional to acoustic intensity. In particular it has almost a linear correlation with peak negative pressures (r=0.98683, p=0.0018).     

金刚石单晶生长的声发射实时检测初探

采用声发射检测技术,对高温高压下人造金刚石单晶的生长过程进行了检测和分析。利用由PCI-8型声发射仪和LMD-800型铰链式六面顶压机组成的声发射检测系统,检测了金刚石单晶的生长过程。将金刚石单晶生长和不生长过程中检测到的声发射信号进行对比和频谱分析,结果表明:声发射信号与金刚石单晶生长过程存在对应关系;金刚石单晶生长对应的声发射信号是一种低频信号,可以利用声发射信号的变化规律研究金刚石单晶在高温高压条件下的原位反应机理。     

Shaft angular misalignment detection using acoustic emission

Shaft angular misalignment (SAM) is a common and crucial problem in rotating machinery. Misalignment can produce several shortcomings such as premature bearing failure, increase in energy consumption, excessive seal lubricant leakage and coupling failure. Vibration analysis has been traditionally used to detect SAM; however, it presents some drawbacks i.e. high influence of machine operational conditions and strong impact of the coupling type and stiffness on vibration spectra. This paper presents an extensive experimental investigation in order to evaluate the possibility of detecting SAM, using acoustic emission (AE) technique. The test rig was operated at under different operational conditions of load and speed in order to evaluate the impact on the AE and vibration signature under normal operating conditions. To the best of the author’s knowledge, this is the first attempt to use AE for the detection of SAM under varying operational conditions. A comparative study of vibration and AE was carried out to demonstrate the potentially better performance of AE. The experimental results show that AE technique can be used as a reliable technique for SAM detection, providing enhancements over vibration analysis.