基于弱磁检测的小径管焊缝检测技术研究

发布时间：2018-03-07 19:17

本文选题：小径管焊缝　切入点：弱磁检测　出处：《南昌航空大学》2016年硕士论文　论文类型：学位论文

【摘要】：小径管被广泛应用于电场设备中,焊接是其最普遍的连接方式。输送介质是小径管最常见的功能,长期带压运行,工作环境恶劣,对其焊接质量带来了很大的挑战,无论是在焊接加工时,还是在长期运行过程中均需要质量检测。在传统检测条件下,对小径管焊缝实施全覆盖式检测需要多种检测方法的结合,效率很低。针对这一状况,本文提出将弱磁检测应用在小径管焊缝检测中,实现常见类型缺陷的快速检测。本文首先分析了弱磁检测的技术原理与小径管焊缝的特征,指出了其检测的难点,并利用仿真计算论证了小径管焊缝弱磁检测的可行性。根据小径管焊缝的几何形态及缺陷信号特点提出了三种检测方案:旋管法向检测、侧向扫查检测和法向扫查检测。然后,采用便携式弱磁检测设备对两个小径管焊缝试件进行检测,并对三种检测方案的结果进行分析。前两种检测方案的结果曲线比较明显,结合经验即可完成简单的缺陷评判,利用小波分析消除了法向扫查检测时的背景磁场干扰信号,成功的提取到了缺陷信号。与DR检测结果进行了对比,验证了各个检测方案的有效性,并总结了各个方案的优缺点。最后,针对缺陷定性的困难,提出了一种缺陷识别算法,能够减少经验判断带来的误差。将缺陷归为裂纹类与气孔类两大类,利用小波包能量谱作为缺陷的特征参数,根据距离判别分析法建立了缺陷的分类识别模型。应用小径管焊缝缺陷样本数据训练模型,确定了缺陷分类的判别函数,并对预留的20组缺陷样本进行了识别,识别结果显示:气孔的识别准确率达到70%,裂纹的识别准确率达到90%,验证了缺陷识别模型的有效性。弱磁检测方案及缺陷识别技术的研究为小径管焊缝的快速检测提供了新的方法与思路。
[Abstract]:Small diameter tube is widely used in electric field equipment, welding is the most common connection mode, conveying medium is the most common function of small diameter tube, it has long run with pressure and bad working environment, which brings great challenge to its welding quality. Both in welding process and in long-term operation, quality testing is required. Under the condition of traditional inspection, it is necessary to combine many kinds of testing methods for the weld seam of small diameter tube, and the efficiency is very low. In view of this situation, In this paper, the application of weak magnetic field detection in weld detection of small diameter tube is proposed to realize the rapid detection of common types of defects. Firstly, the technical principle of weak magnetic field detection and the characteristics of weld seam of small diameter tube are analyzed in this paper, and the difficulties in detection are pointed out. The feasibility of detecting the weak magnetic field of weld seam of small diameter tube is demonstrated by simulation calculation. According to the geometric shape of weld seam of small diameter tube and the characteristics of defect signal, three detection schemes are put forward: normal inspection, lateral scan inspection and normal sweep inspection. The portable weak magnetic testing equipment was used to detect the weld specimens of two small diameter tubes, and the results of the three kinds of test schemes were analyzed. The result curves of the first two kinds of test schemes were obvious, and the simple defect evaluation could be completed by combining experience. The background magnetic field interference signal is eliminated by wavelet analysis, and the defect signal is extracted successfully. Compared with Dr detection results, the validity of each detection scheme is verified. The advantages and disadvantages of each scheme are summarized. Finally, a defect identification algorithm is proposed, which can reduce the error caused by empirical judgment, and classifies the defect into two categories: crack class and pore class. By using wavelet packet energy spectrum as the characteristic parameter of defects, the classification and identification model of defects is established according to distance discriminant analysis, and the discriminant function of defect classification is determined by using the training model of sample data of weld defects in small diameter tubes. And 20 groups of defect samples were identified. The recognition results show that the accuracy of gas hole identification is 70 and that of crack recognition is 90. The validity of the defect identification model is verified. The research of weak magnetic field detection scheme and defect identification technology is the fast detection of weld seam of small diameter tube. New methods and ideas are provided.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG441.7

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