基于2D-FFT的超声导波模态识别系统设计

发布时间：2018-04-24 12:40

本文选题：超声导波 + 模态识别　；参考：《北京交通大学》2016年硕士论文

【摘要】：超声导波具有传输距离远的特点,可以实现被测物的大范围检测,特别适合各种管线探伤、钢轨探伤等检测任务。超声导波具有频散和多模态现象,且多模态的识别是各类检测任务的基础,需要采用阵列式换能器提取模态特征信号。本论文针对超声导波的模态分析与相速度测量,研制了超声导波模态识别系统。在综合对比现有基于时域和频域的导波模态识别方法后,本文采用基于2D-FFT的时空频率估计方法进行导波模态识别。具有时间-空间信息的数据矩阵经过2D-FFT的处理,可以得到导波频率与波数的对应关系,在特定频率下,提取存在的不同波数值,根据波数-相速度公式可以计算出不同模态对应的相速度值,与理论值对比可识别此频率下的不同模态。本文研究了基于2D-FFT方法识别导波模态的算法,提出了模态识别系统的总体方案、线性阵列探头的选用参数；针对阵列探头的信号采集,重点介绍了基于FPGA和ARM的系统设计;通过硬件与软件的设计优化,实现了32通道数据的同步高速采集,并可将数据传至上位机进行显示、保存：论文最后开展了模态识别系统的实验验证,以半解析有限元方法的相速度为理论值进行结果对比,证明了该系统可以很好地实现铁板、铝板中的导波模态识别。本文完成了基于2D-FFT的超声导波模态识别系统的设计、制作、调试的全部工作,并通过实验证明了系统有着良好的导波模态识别能力,为无缝钢轨探伤、纵向应力检测等领域奠定了良好的基础。
[Abstract]:Ultrasonic guided wave has the characteristics of long transmission distance, it can be used to detect the object in a wide range, especially suitable for various pipeline inspection, rail detection and other detection tasks. Ultrasonic guided wave has the phenomenon of dispersion and multi-mode, and the identification of multi-mode is the basis of all kinds of detection tasks, so it is necessary to use array transducer to extract modal characteristic signal. In this paper, the ultrasonic guided wave modal identification system is developed for ultrasonic guided wave modal analysis and phase velocity measurement. After a comprehensive comparison of the existing guided wave modal identification methods based on time domain and frequency domain, this paper uses the spatio-temporal frequency estimation method based on 2D-FFT to carry out guided wave modal identification. The data matrix with time-space information can be processed by 2D-FFT to get the corresponding relation between the guided wave frequency and the wavenumber. According to the wavenumber-phase velocity formula, the phase velocities corresponding to different modes can be calculated, and the different modes at this frequency can be identified by comparing with the theoretical values. In this paper, the algorithm of identifying guided wave mode based on 2D-FFT method is studied, and the overall scheme of modal identification system and the selection parameters of linear array probe are put forward, and the system design based on FPGA and ARM is introduced emphatically for the signal acquisition of array probe. Through the design optimization of hardware and software, the synchronous high-speed data acquisition of 32 channels is realized, and the data can be transmitted to the upper computer for display and save. Finally, the experiment verification of modal identification system is carried out. By comparing the results with the phase velocity of the semi-analytical finite element method, it is proved that the system can well realize the modal identification of guided waves in the iron plate and aluminum plate. In this paper, the design, manufacture and debugging of ultrasonic guided wave modal identification system based on 2D-FFT have been completed, and it has been proved by experiments that the system has a good capability of guided wave modal identification, which is a seamless rail flaw detection. Longitudinal stress detection and other fields have laid a good foundation.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH878.2

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