在石油化工等行业中，储罐是储存各种石化原料的重要工具，定期对储罐进行检测以保证工业生产安全至关重要。电磁无损检测(NDT)技术中的涡流检测具有检测灵敏度高、硬件结构简洁、易实现自动化检测等优点，因此本文采用饱和扫频脉冲涡流检测技术实现储罐底板的缺陷检测。 本文首先介绍了目前常用的储罐检测方法及涡流检测技术的研究现状，简述了涡流检测的原理并建立理论模型。提出了一种扫频脉冲激励，以改进缺陷检测效果。指出涡流检测技术难以应用在铁磁性材料中这一问题，并针对该问题采用对材料进行预磁化的方法，随后比较了电磁铁磁化和永磁体磁化两种方案，通过仿真分析确定了磁铁参数。通过仿真分析研究预磁化对脉冲涡流检测的影响，说明饱和扫频脉冲涡流技术能够检测到待测试件的深层缺陷，克服了传统涡流检测的不足。搭建了基于饱和扫频脉冲涡流检测技术的储罐底板缺陷检测实验平台，检测系统主要分为永磁体、主控电路和检测探头阵列三部分，对各部分的原理和实现过程进行了详细说明。在该平台上进行缺陷检测实验，分析实验结果和误差来源，验证了预磁化对于将涡流检测应用于铁磁性材料这一问题的关键性作用。 在待测工件饱和磁化的基础上，研究扫频脉冲激励带宽选择对检测效果的影响，确定了合适的激励信号参数。在该激励下进行缺陷检测实验，采集响应信号数据并进行分析与处理，提取关键特征量，研究缺陷尺寸和缺陷位置与响应信号的关系。实验结果表明，饱和扫频脉冲涡流检测技术能够有效检测出待测工件中不同尺寸、不同位置的缺陷，克服了传统涡流检测无法应用于铁磁性材料的问题。 最后，总结了本文的主要工作，提出仍需进一步探究的问题，并对后续研究做出展望。
In the petrochemical industry, tanks play an important role in storing various petrochemical materials. It is essential to examine the tanks regularly to ensure safety work condition. Eddy current testing in non-destructive testing (NDT) has the advantages of high inspection sensitivity, simple hardware structure and easy roboticized. Therefore, a saturated swept-frequency pulsed eddy current testing technology is proposed to realize defect inspection of tanks floor. First, this paper summarized recent study on tank inspection and eddy current testing, briefly describes the principle of eddy current testing and establishes a theoretical model. A new type of excitation, swept-frequency pulse excitation, is proposed to improve the defect inspection effect. The problem of applying eddy current testing on ferromagnetic materials is pointed out and pre-magnetizing is proposed to solve the problem. The scheme of electromagnet magnetization and permanent magnet magnetization are compared. It is verified by simulation that by using saturated swept-frequency pulsed eddy current technology, it is possible to detect deep defects in ferromagnetic materials. Then, a tank floor defect inspection experimental platform is built, which is mainly consist of three parts: permanent magnet, main control circuit and inspection probe array. The principle and implementation process of each part are described in detail. On the basis of the magnetic saturation, the influence of excitation frequency band is studied and the appropriate excitation parameters are determined. Then feature of the response signal is extracted and analysed. The relationship between defect parameters, defect location and the response signal is studied thouroughly. Experimental results show that saturated swept-frequency pulsed eddy current testing can detect both shallow and deep defects effectively in ferromagnetic material, thus overcome the problem of traditional eddy current testing. Finally, the work of this paper is summarized and future research is expected.
