【作者】 刘红光；

【导师】 骆英；

【作者基本信息】 江苏大学 ， 固体力学， 2007， 硕士

【摘要】 声发射检测(AET)是一种动态被动无损检测技术，所监测的信号直接来自缺陷发展本身，因而比较复杂。但采用特殊的方法，根据声发射信号特征可以实时判断结构缺陷的损伤机理及其严重程度，进而较好地实现结构健康检测。在声发射检测中，传感器是获取损伤信息的重要器件，而对信号的分析处理则是损伤识别的关键。本文首先介绍了声发射信号的特征和声发射传感器的特性，对自制的1-1型正交异性压电复合材料AE传感元件的传感特性进行了系统研究，找到了其对信号的响应规律。基于此规律，通过特定的方法分布式正交异性AE传感器能实现模拟损伤信号的精确定位。然后，针对声发射信号中各种伪信息的存在及有效特征量提取的困难，本文引入了近年新兴的信号处理技术——Hilbert-Huang变换(HHT)。文中系统地阐述了HHT的基本理论、特点及其改进方法，用Matlab软件编程实现了HHT的计算过程，对多个实测AE信号进行了分析处理。结果显示：HHT是一种有效的非线性、非平稳信号处理技术；得到的各阶固有模态函数对研究信号产生机理的分析有巨大帮助；相比于Gabor小波谱，Hilbert谱能更好地反映信号的瞬时特性；论文还借助HHT理论及方法，分析了预应力钢筋混凝土构件在不同破坏阶段的特征信息，获得了破坏过程中裂纹失稳的重要的前兆特征。本论文的研究成果是在实验室环境下完成的，这些成果应用到工程实践中还需要大量的试验去进一步论证和改进。更多还原

【Abstract】 Acoustic emission testing (AET) is a dynamic passive nondestructive evaluation (NDE) technique. We can estimate the nature and mechanism of the damage, using a special method according to the characteristics of the complicated AE signals come from the damage. And then the structure health monitoring technique using acoustic emission technique could be realized.AE sensor is an important device for acquiring damage information, and the analysis processing of the AE signal is the key of damage identification in AET. In this paper, based on the introduction of the characteriscics of AE signals, the sensing characteristics of the 1-1 orthotropic piezoelectric composite materials AE sensors were studied, and the response rule of the sensor to signals was found. Based on the rule, the damage position (simulated by the lead break) coule be located exactly using distributed orthotropic AE sensors through a unique method.For the existences of many spurious signals and the difficulties of AE signals’ feature extraction, Hilbert-Huang transform (HHT) appears resently years was introduced to analysis AE signals. In this article, we illustrated the basic theory, characterics and the improve methods of HHT systermly, and used Matlab sofrware realize the computational process of HHT.The analysis results of several real AE signals show that: HHT is a powerful nonlinearity and non-stationary signal processing method; The Intrinsic Mode Functions are very helpful to study the mechanism of signals’ production; Compared to the Gabor spectrum, Hilbert spectrum could reflect the transient property more clearly. By HHT analysis, the critical states of prestressed concrete beams are found. There are many marked characterics during the failure process of the prestressed concrete specimens. Thus, we can find the important portent that the cracks are unstable.These conclusions result from the experiments carried out in the laboratory, and they might need some deeper reasoning and improvement, if it is applied to the engineering practice.更多还原