一种立方体监测网络的声发射源和微震源解析定位方法(英文)

通过选取合理的坐标原点及传感器位置简化声发射源定位方程, 得到声发射源或微震源三维定位方法的解析解。算例研究表明,对于传感器阵列内、外的声发射源事件, 解析方法定位结果完全与实际坐标一致;对于传感器阵列内的声发射源事件,传统方法略有误差,一般为 0.010.03m, 而对于传感器阵列外的微震源, 传统时差定位方法的定位误差很大,最大的达到 1080986 m;采用横截面为 100mm×98mm、长度为350mm 的花岗岩试样, 进行 5 次断铅定位实验,分别用传统方法和解析方法进行定位,结果发现在监测网络外的4个声发射事件, 解析定位的误差亦小于传统方法的定位误差。可见解析定位精度较传统方法有明显提高,最高可提高 17.61mm;利用解析解定位, 无需确定拟合初值和拟合迭代算法, 仅通过简单的四则运算即可定位,用常规的计算器或Microsoft Excel 即可求解。     

基于平行压电阵列的阀门泄漏声发射源定位方法

针对阀门泄漏故障的问题,提出了基于平行压电阵列的阀门泄漏声发射源定位方法。针对阀门曲面结构的特点,在阀体底部布置了两条平行线性传感器阵列。首先,利用平行压电阵列采集阀门泄漏时产生的声发射信号;其次,计算各自阵列协方差及其特征值,通过比较特征值的大小,确定声发射信号源的大致区域,再利用近场多重信号分类算法进行空间谱估计,在子阵列上建立局部坐标,得到与声发射源对应参考阵元的极坐标,即距离和角度;最后,通过坐标变换,将局部坐标轴中的极坐标转换到整体坐标中。通过DN50的闸阀进行了试验,试验结果表明:该方法可以有效地对阀门声发射源进行定位,减小了阀门泄漏故障的误判,可为阀门故障预测提供参考知识。     

基于Lamb波频散特性的声发射源平面定位新方法

针对传统的声发射源平面定位中各传感器灵敏度差异和门槛值设置不同对时差定位精度影响较大的问题，通过研究弹性波在薄板中传播的特性即Lamb板波频散特性，借用模态声发射的概念将单个传感器接收到的信号利用Gabor小波时频分析得到不同模态的峰值到达时间，并在引入速度因子概念的基础上，讨论了两种不同的声发射源平面定位方法，即同一频率不同模态的定位方法和同一模态不同频率的定位方法，试验证明两种方法都能得到模拟源的正确定位，不仅从根本上避免了传感器间灵敏度差异对时差定位精度的影响，而且还可以减少平面定位中传感器的数量，避免三角形定位中伪定位的出现，并适用于传统的声发射源平面定位中不易布置传感器阵列的结构健康无损监测。     

简述大型岩体稳定性声发射监测的三个环节

大型岩体稳定性AE监测作业范围大,地质结构复杂,周期性长,环境嘈杂,科学认证、正确处理大型岩体稳定性AE监测中的每个环节是监测工作有效和可靠的保障。以三峡永久船闸边坡稳定性AE监测取得的成果,阐述了永久船闸边坡稳定性声发射(AE)监测方法中的三个重要环节,即大型岩体稳定性AE监测的可行性分析、大型岩体稳定性AE监测的设计原则、大型岩体的稳定性分析。它们是大型岩体稳定性AE监测方法的重要成果,对大型岩体稳定性AE监测具有重要的参考价值。     

基于声发射传感器阵列的风机叶片结构健康监测方法

风机叶片结构健康监测是一个迫切需要解决的问题。通过分析各种风力机叶片的损伤检测方法,结合声发射技术特点,研究了基于声发射传感器阵列的风机叶片结构健康监测方法。其中,PZT压电陶瓷传感器阵列布设于受损率较高的叶片部位,对叶片按20%最大设计载荷的增量施加载荷,结合Kaiser效应和Felicity效应,分析采集到的声发射信号,统计声发射波击数,从而判断损伤发生的区域。该方法相比于其他检测技术具有灵敏度高、定位准确和实时性好的特点,在风机叶片结构健康监测研究领域具有较大的意义。     

基于声发射信号的铝合金LSP弹塑性波传播规律探究

目的 为提高激光冲击强化(LSP)的声发射(AE)监测精度,结合AE监测技术与LSP弹塑性波理论,探究LSP过程中弹塑性波传播规律。方法 首先,基于弹塑性波理论设计LSP试验,采用AE监测技术实时获取冲击信号,并测量冲击后铝合金7075的塑性变形程度。然后,基于AE信号的时域波形,提出包络欧式距离法,确定对加工质量敏感的感兴趣片段(FOI)。进一步基于FOI,结合实际加工条件,定义了新的累积AE波形熵特征。最后,基于AE信号的多模态和非平稳信息,定义瞬时峰值能量曲线(IPEC),并进一步提取相关特征,从而探究弹塑性波传播规律、衡量传感器优劣。结果 仅包含弹性波的AE信号波形明显区别于弹塑性双波,塑性波传播速度明显落后于弹性波。包络欧式距离法确定的FOI能很好地定位弹塑性波。相较于AE波形熵,累积AE波形熵特征能很好地区分不同程度的弹塑性波。对比弹性波,塑性波主要集中在中低频段(200 kHz以下)。IPEC曲线精准确定31 kHz模态为塑性波的主要成分。进一步提取的峰值变化量 和峰值延迟时间 表明:相较于谐振传感器,宽频传感器对塑性波更加敏感。结论 所提方法和特征分别从时域和时频域上探究了弹塑性波的传播规律,所得的结论为规范和提高LSP的AE监测技术提供了理论支持与指导。     

基于多场耦合分析和微震监测的岩体失稳预警（英文）

针对当前岩体失稳预警多从单个角度入手,缺乏对灾害孕育内在机理的深入考虑,开展基于多场耦合分析和微震监测的岩体失稳预警研究。建立考虑损伤的岩体多场耦合模型,并编制相应的解算程序。对微震活动性参数与岩体稳定性之间的关系进行分析,建立多参量预警指标体系。基于D-S数据融合理论,构建多场耦合分析和微震监测融合的岩体失稳预警模型。以某地下矿山采场为研究对象,应用多场耦合模型及其解算程序进行采动响应特征分析,运用微震实测数据验证多场耦合分析的正确性。通过构建的预警模型对采场岩体失稳进行预警,预警结果与现场实际情况吻合,验证了预警模型的有效性。     

基于微震监测的深部岩体开挖过程中围岩稳定性研究

针对阿舍勒铜矿深部岩体开挖过程中地压灾害日益突出的问题,建立微震监测系统对开挖过程中围岩体的稳定性进行研究。通过对微震监测数据进行分析,揭示深部围岩体的微震活动性与回采工序和炸药使用量的相关关系,并采用能量指数与累积视体积、微震活动b值等参数对岩石破裂过程中微裂纹演化规律进行研究,捕捉岩石失稳破坏的前兆特征。研究表明:大规模集中爆破对深部围岩体的损伤非常大,开挖破坏了围岩岩体原有的应力场,围岩岩体需要在开挖后很长一段时间才能达到新的应力平衡:能量指数急速下降而累积视体积不断增加、微震活动b值特征出现明显下降等现象都可以作为深部岩体开挖过程中岩爆和大尺度岩体破裂发生的前兆信息,为微震监测技术在深井矿山开挖过程中的研究奠定基础。     

基于独立分量分析的缺陷信号串扰消除

漏磁检测设备中纵向传感器阵列特殊的物理结构,使得采集的缺陷信号之间不可避免地产生串扰,因而降低了检测设备的可靠性。结合采集信号的阵列特性,通过使用基于独立分量分析(ICA)的阵列信号处理方法,分离出各路消除串扰的源信号。仿真试验结果表明,ICA的定点算法可以消除信号之间的串扰,满足检测设备要求,具有较大的应用潜能。     

多层包扎氨合成塔的在线声发射检测

利用声发射(AE)检测技术进行现场多层包扎氨合成塔的在线检测及诊断工作。氨合成塔处于高温复杂的工作环境,采用有限元法进行模拟分析,利用波导杆对设备的声发射信号进行采集。根据采集的信号判断声发射信号源的位置并采用磁粉及超声检测法进行复验,分析了声发射源信号的特征,并对其产生的原因进行了推测。在线检测结果可辅助诊断设备的使用状态是否安全。     

煤矿声发射监测中传感器阵列的布置

在声发射监测过程中,传感器的空间布置是影响声源定位不准的关键之一。根据矿区监测特点,从传感器空间布置进行讨论,即开采的区域是动态的,也就要求被监测的区域是动态的变化的,为了在不改变原有传感器阵列基础上,通过增加少量传感器的方法,提高定位的精度,提出了动静结合的传感器布置策略,同时为弥补以往传感器布置不容易监测较小声源信号的特点,通过与无线传感网络相结合,形成传感器阵列的方法,提高监测的精度,到达预测的效果。     

Influence of temperature on acoustic emission source location accuracy in underground structure

An acoustic emission (AE) experiment was carried out to explore the AE location accuracy influenced by temperature. A hollow hemispherical specimen was used to simulate common underground structures. In the process of heating with the flame, the pulse signal of constant frequency was stimulated as an AE source. Then AE signals received by each sensor were collected and used for comparing localization accuracy at different temperatures. Results show that location errors of AE keep the same phenomenon in the early and middle heating stages. In the later stage of heating, location errors of AE increase sharply due to the appearance of cracks. This provides some beneficial suggestions on decreasing location errors of structural cracks caused by temperature and improves the ability of underground structure disaster prevention and control.     

An approach to use an array of three acoustic emission sensors to locate uneven events in machining—Part 1: method and validation

The paper reports on an approach to use the triangulation technique applied to arrays of acoustic emission sensors for the location of uneven events occurring during machining. The generation of some uneven events (e.g. workpiece surface discontinuities, plucking, smearing) in machining can be associated with the release of acoustic emission energy. When more than one cutting edge is in contact with the workpiece (e.g. broaching, milling) it is difficult to associate the burst of acoustic emission signal with the tooth that generated it and therefore to locate, relatively to the workpiece surface, the position of acoustic source. The location of the acoustic source, related to the occurrence of the uneven event, is evaluated by feeding the time delays in detecting the same burst signal by three acoustic sensors placed on the workpiece, into an analytical geometry model. Using numerical methods in Matlab, the analytical solution for the location of acoustic source was found by adding to the system formed by three spherical analytical equations, with the acoustic emission sensors as their centres, the characteristics of the cutting tool path. The methodology has been calibrated using pencil break lead tests to asses the accuracy of the acoustic source location and the requirements of the data acquisition system. ‘Near-orthogonal’ cutting trials were carried out using two different arrays of acoustic emission sensors and the uneven events located relatively to the workpiece surface. It was found that the proposed methodology has potential to locate, at a reasonable accuracy, the acoustic sources that are related to the occurrence of uneven events in machining. This work represents a preliminary investigation to be used for the location of workpiece defects during machining with multiple cutting edge tools.     

Study of acoustic signal in the process of resistance spot welding based on array sensor system

This investigation was performed to study acoustic field signal in order to improve RSW quality. Researchers firstly built an acoustic array sensor system, which included 8 MPA-416 acoustic sensors, data acquisition card and LabVIEW. The system obtained the acoustic field information in the process of nugget growing. Due to the nonlinearity field signal, array sensor algorithm was utilized to quantitatively analyze the characteristics of acoustic field and reduced noise. The experiment and calculation results show that array sensor system can acquire acoustic field signal of nugget growing in the RSW process and array processing algorithm based on acoustic field can extract characteristic parameters to evaluate RSW quality. It was concluded that the acoustic array sensor system offers a new methodology for RSW quality inspection.     

Acoustic emission source location considering refraction in layered media with cylindrical surface

To solve the problem that the existing acoustic emission (AE) source location algorithms cannot always obtain accurate results for multilayer cylindrical media, a new acoustic emission source location method considering refraction was proposed. AE source coordinates were solved by the complex method. Pencil-lead-break experiments were used to verify this method. The absolute distance errors of location results are less than 3 mm, much less than those by the traditional method. The numerical experiments were used to further analyze factors that affect location accuracy. The results of numerical experiments show that the location accuracy of the proposed method is not affected by the ratio of wave velocities but affected by the measurement accuracy of wave velocity. These results show that new method can obtain accurate AE source location in the two-layered cylindrical surface media such as the triaxial compression test.     

声发射源多传感器数据融合识别技术研究

波形数字声发射技术的发展给声发射源的特性识别带来了可能。噪声的影响和声发射信号传播过程的复杂性给声源的识别带来一定的困难。为了解决干扰情况下声发射源的定性问题，提出了在决策层上的多传感器数据融合的识别方法。利用定位传感器组中各个传感器得到的数据，同时考虑在同一个定位组中各个传感器所得数据的置信度不同，来对声发射源性质进行识别。实验结果证明，数据融合后声发射源特性识别的可靠性明显大于单个传感器，表明了多传感器融合识别的可能性和有效性。     

岩石力学试验中的声发射源定位技术

在岩石力学实验中，声发射源定位的研究方法，是实验室声发射研究的重要方面。在总结前人关于声发射源定位在实验硬件和定位算法两方面工作的基础上，从定位算法上着重分析了当前几种地震模拟岩石力学实验室声发射定位方法的利弊，指出了未来声发射定位方法可能的发展方向，并从定位算法上阐述了提高AE定位精度所必须克服的障碍。     

换热器管板声发射在线检测及评价方法

换热器管板属于多孔结构，制造工艺复杂，容易产生缺陷，且管板与换热管连接处连接质量不易检查。针对上述问题，采用声发射检测技术，将传感器通过专用波导杆与换热管连接，根据衰减测量结果确定管板上传感器的布置阵列。通过壳程水压试验二次加载方式对其进行声发射检测。采取区域定位方法，通过对不同阶段保压信号的分析，综合考虑声发射信号的活性和强度，制定了换热器管板声发射检测及评价方法，实现了对换热器管板质量的分级评价。     

A self-calibrating piezoelectric transducer with integral sensor for in situ energy calibration of acoustic emission

Piezoelectric transducers are used as both transmitters and sensors in acoustic emission (AE) testing applications. However, the transducer outputs are significantly affected by the coupling between the transducer and the structure. This means that the coupling must be very carefully controlled or assessed if reliable AE calibration sources are to be generated, and be considered in the AE system calibration if reliable AE measurements are to be made. The paper shows that by integrating a piezoelectric AE sensor to the backing of a conical piezoelectric transducer acting as the transmitter, a self-calibrating AE energy point source can be obtained. There is a negative linear relationship between the AE signal energy from the backing sensor and the coupling efficiency for a constant electrical input to the transmitter over the frequency range of interest in AE measurements (100 kHz to around 1 MHz). This should enable the strength of the simulated AE point source to be determined using the AE measurement from the backing sensor, and hence to facilitate in situ energy calibration of AEs in structures.