基于磁导体环形结构的小径管周向裂纹脉冲涡流检测研究

发布时间：2018-02-04 07:45

本文关键词： 磁导体环形结构小径管脉冲涡流周向裂纹有限元仿真　出处：《南昌航空大学》2017年硕士论文　论文类型：学位论文

【摘要】：小直径金属管在电力、航空航天、石油能源等行业应用广泛。管道的周向裂纹缺陷是一种易导致断裂的缺陷。常规的涡流检测其涡流走向平行于周向裂纹,因而对周向裂纹容易漏检,其他无损检测方法由于管径小管壁薄也不易检测,而阵列涡流、旋转磁场扫描技术等先进的无损检测技术由于成本高、机械装置复杂等缺点,在实际检测中难以大范围推广应用。本论文旨在探索一种低成本的对于周向裂纹的检测技术。本课题根据磁场与电场的正交对称性设计了磁导体环形结构传感器,形成垂直于周向裂纹的电场,利用近年发展的脉冲涡流检测技术,对小径管周向裂纹缺陷检测进行了研究。首先建立了检测平台,然后以实验研究结合ANSYS有限元仿真的方式,从探头结构、激励电压以及激励频率等方面对小径管周向裂纹脉冲涡流检测方法及机理进行了深入研究。项目制作了单层单片式双激励、单层双片式双激励以及单层分散式双激励三种探头,通过实验对探头结构对检测效果的影响进行了研究,并进行了仿真分析。实验结果表明单片式探头对小径管周向裂纹的检测效果最好,检测信号的信噪比最好,对0.5mm深以下小尺寸裂纹的检测能力最强;双片式探头对0.7mm深以上大尺寸裂纹具有较好的检测效果,对小尺寸裂纹的检测易受到背景噪声的干扰;分散式探头检测效果最差。仿真结果与实验结果相一致。研究了不同幅值的激励电压对检测的影响。实验设置了激励电压为1V、2V、3V和5V,分别对小径管试件上三组裂纹缺陷进行检测。提取管道法向方向磁场数据结果发现:随着激励电压的增大,在检测较深裂纹时效果逐渐增强;但在检测浅裂纹时,3V、5V激励的检测效果差异不明显。就信号的信噪比而言,激励电压越大,信噪比越高。随后进行了仿真研究,通过仿真结果的接收电压归一化曲线可以看出,不同激励电压下接收信号归一化值在小裂纹缺陷处区分并不明显,与实验结果一致。激励频率主要影响了脉冲涡流检测的渗透深度。在50Hz、100Hz、200Hz、300Hz、400Hz、500Hz激励频率下进行实验及仿真分析发现,增大激励频率后虽然管道法向方向磁场信号的幅值略有减小,但是信号的信噪比明显提高,检测灵敏度增强。
[Abstract]:Small-diameter metal pipes are widely used in power, aerospace, petroleum and energy industries. The circumferential crack defects of pipelines are a kind of defects that lead to fracture. The conventional eddy current detection of the eddy current direction is parallel to the circumferential cracks. Therefore, the circumferential crack is easy to be detected, other nondestructive testing methods are difficult to detect because of the thin tube wall with small diameter, and the advanced nondestructive testing technology such as array eddy current, rotating magnetic field scanning technology, etc., due to the high cost. The mechanical device is complex and so on. The purpose of this paper is to explore a low-cost detection technique for circumferential cracks. Based on the orthogonal symmetry of magnetic field and electric field, a magnetic conductor ring structure sensor is designed. . In order to form an electric field perpendicular to the circumferential crack, the detection of the circumferential crack defects in the small diameter tube is studied by using the pulse eddy current testing technique developed in recent years. Firstly, the detection platform is established. Then with the experimental study combined with the ANSYS finite element simulation method, from the probe structure. The method and mechanism of pulse eddy current detection for circumferential crack of small diameter tube are studied in detail from the aspects of excitation voltage and excitation frequency. Single layer single chip double excitation is made in the project. The influence of the structure of the probe on the detection effect was studied by experiments. The experimental results show that the single-chip probe has the best detection effect on circumferential crack of small diameter tube and the best signal-to-noise ratio (SNR) of detection signal, and the best detection ability for small size crack below 0.5 mm depth. The double-chip probe has a good effect on the detection of large size crack over 0.7 mm depth, and the detection of small size crack is easily disturbed by background noise. The effect of the distributed probe is the worst. The simulation results are consistent with the experimental results. The effects of different amplitudes of excitation voltage on the detection are studied. The excitation voltage is set to be 1V / 2V ~ (3V) and 5V in the experiment. Three groups of crack defects on the specimen of small diameter tube were detected respectively. The results of extracting the normal magnetic field data of the pipe show that the effect of detecting the deep crack increases gradually with the increase of the excitation voltage. However, there is no significant difference in the detection effect of 3V / 5V excitation when detecting shallow cracks. As far as the signal to noise ratio is concerned, the greater the excitation voltage, the higher the signal-to-noise ratio (SNR). Then the simulation study is carried out. Through the simulation results of the received voltage normalization curve, it can be seen that under different excitation voltage, the difference of the received signal normalization value in the small crack defects is not obvious. The results are in agreement with the experimental results. The exciting frequency mainly affects the penetration depth of the pulsed eddy current detection. The experiment and simulation at 500Hz excitation frequency show that the signal-to-noise ratio (SNR) and detection sensitivity of the signal to noise ratio (SNR) of the normal magnetic field signal decrease slightly after increasing the excitation frequency.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG115.28

【参考文献】