电磁激励声发射的关键技术研究

发布时间：2018-01-20 14:25

本文关键词： 无损检测电磁声发射时频分析经验模态分解希尔伯特黄变换　出处：《重庆三峡学院》2017年硕士论文　论文类型：学位论文

【摘要】：电磁声发射(Electromagnetically Acoustic Emission,EMA)技术是一种新型的无损检测技术,凭借其检测方式简单,具有重大的应用价值。通过设计实验系统,采用了新的电磁加载方式,实现更加稳定可靠的非接触式电磁加载方案,激励产生声发射信号。由于声发射信号的非线性,非平稳特点,针对性的采用时频分析技术对信号进行分析,从而得到了缺陷信号的时频特征。主要研究工作如下:(1)电磁加载激发声发射信号的核心步骤是对有缺陷的金属试样施加电磁加载,因此稳定的电磁加载尤为重要。建立了稳定高效的电磁加载实验平台,将核心电磁加载器件CH130电磁铁、MAN-10030电流源和SAEU2S声发射系统有机结合,实现了对有无缺陷试样,不同材料试样的非接触式电磁加载,并成功采集到电磁声发射信号。(2)针对电磁声发射信号,采用多种时频分析法,分析信号的时频特性表现,综合对比研究了维格-纳威利分布,伪维格-纳威利分布,平滑伪维格-纳威利分布和小波变换时频分析技术,从时频聚集角度,交叉项干扰,时频分辨率,初动点,声发射能量释放等多角度深入探讨了缺陷电磁声发射信号的不同特征。(3)对时频分析技术进一步探究,采用希尔伯特黄变换,从电磁声发射信号本身出发,将复杂信号分解为拥有固定模式的不同的本征模态函数,反应了电磁声发射信号的阶段性,分析了每一阶段的频率,幅值,能量等重要参数变化特性。(4)通过经验模态分解算法,从复杂的非线性、非平稳信号中提取出奇异点,能量释放时间,持续时间等关键的物理变量,并通过信号分量包络谱和瞬时频率的变化阐述原信号重要特征。
[Abstract]:Electromagnetic acoustic emission (Acoustic) technique is a new nondestructive testing technique. With its simple detection method, it has great application value. By designing the experimental system, a new electromagnetic loading method is adopted to realize a more stable and reliable non-contact electromagnetic loading scheme. Acoustic emission signals are generated by excitation. Due to the nonlinear and non-stationary characteristics of acoustic emission signals, time-frequency analysis technology is used to analyze the signals. The main research work is as follows: 1) the core step of the electromagnetic loading excitation acoustic emission signal is to apply electromagnetic loading to the defective metal sample. Therefore, stable electromagnetic loading is particularly important. A stable and efficient electromagnetic loading experimental platform is established, and the core electromagnetic loading device CH130 electromagnet is put forward. The MAN-10030 current source and the SAEU2S acoustic emission system are combined to realize the non-contact electromagnetic loading on the samples with or without defects and the samples of different materials. The electromagnetic acoustic emission (EAE) signal is successfully collected. (2) aiming at the electromagnetic acoustic emission signal, various time-frequency analysis methods are used to analyze the time-frequency characteristic of the signal, and a comprehensive comparative study of the Weig-Navelli distribution is made. Pseudo-VG-Navilli distribution smoothing pseudo-VG-Neville distribution and wavelet transform time-frequency analysis technology from the angle of time-frequency clustering cross-term interference time-frequency resolution initial point. The different characteristics of electromagnetic acoustic emission (EAE) signals with defects are discussed in detail. The time-frequency analysis technology is further explored. The Hilbert-Huang transform is used to start from the electromagnetic acoustic emission signal itself. The complex signal is decomposed into different intrinsic mode functions with fixed mode, which reflects the phase of electromagnetic acoustic emission signal, and analyzes the frequency and amplitude of each stage. The key physical variables such as singularity, energy release time, duration and so on are extracted from complex nonlinear and non-stationary signals by empirical mode decomposition (EMD) algorithm. The important characteristics of the original signal are explained by the variation of the envelope spectrum and the instantaneous frequency of the signal.
【学位授予单位】：重庆三峡学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O441

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