基于超声导波的管道非通透缺陷模拟研究

发布时间：2018-02-28 22:05

本文关键词： 管道超声导波非通透缺陷时间反转法数值模拟　出处：《华东理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：管道经过长期服役后,由于磨损、腐蚀和意外损伤等原因,对管道正常运行产生危害。在实际工况中,小的腐蚀缺陷容易发展成腐蚀穿孔、浅层的小裂纹容易发展成穿透型裂纹,因此探究如何有效的检测出管道非通透缺陷是很有必要的。本文采用ANSYS有限元分析软件,对空管和充水管道中的非通透缺陷进行模拟检测。采用有限元方法,首先分别用L(0,2)模态和T(0,1)模态针对空管道中的周向和轴向裂纹进行检测模拟,得到反射系数与缺陷特征尺寸间的关系,利用纵向L(0,2)模态对位于管道内侧或外侧的圆孔形减薄缺陷进行检测模拟,并将得到的检测信号进行对比,发现位于管道内外两侧的圆孔形减薄缺陷的反射系数几乎相同,然后针对相同横截面积下不同径向深度缺陷的检测灵敏度差异,发现导波对窄深形缺陷更敏感;而后利用时间反转法针对空管中小尺寸缺陷的信号放大和缺陷周向定位问题进行了研究,结果说明利用时间反转法可以有效放大缺陷回波的信号,使缺陷回波容易被识别,还可以对斜裂纹缺陷进行有效的周向定位与缺陷形状判别;采用L(0,2)模态针对充水管道的单周向裂纹缺陷和多周向裂纹缺陷进行了模拟检测,得到反射系数与缺陷周向长度间的关系,并将反射系数与空管时得到的反射系数进行对比,发现当被检缺陷相同时充水管的缺陷反射系数始终小于空管缺陷反射系数;利用时间反转法,对充水管道中各种类型的单缺陷和多缺陷进行了信号放大和缺陷定位研究,模拟结果表明,对信号进行时反处理后并重新激励,可以对充水管道中多类型的单缺陷和多缺陷进行有效的周向定位以及缺陷形状判别,同时发现利用时间反转法对轴向位置不同的两个小尺寸圆孔形内减薄缺陷进行信号放大,可以有效的得到缺陷的个数及各个缺陷的轴向位置。
[Abstract]:After long service, due to wear, corrosion and accidental damage, the pipeline is harmful to the normal operation of the pipeline. In actual working conditions, small corrosion defects can easily develop into corrosion and perforation. Shallow small cracks are easy to develop into penetrating cracks, so it is necessary to explore how to detect pipeline non-permeable defects effectively. In this paper, ANSYS finite element analysis software is used. The non-permeable defects in empty pipe and water-filled pipeline are tested by simulation. Using the finite element method, the circumferential and axial cracks in the empty pipe are detected and simulated by using the L0 ~ (2)) mode and the T _ (0 ~ (1)) mode, respectively. The relationship between the reflection coefficient and the characteristic size of the defect is obtained. The circular hole thinning defect located inside or outside the pipeline is detected and simulated by using the longitudinal L0 / 2) mode, and the detected signals are compared. It is found that the reflection coefficient of the circular hole thinning defect located on both sides of the pipeline is almost the same, and then according to the difference of the detection sensitivity of different radial depth defects under the same cross-sectional area, it is found that the guided wave is more sensitive to the narrow and deep defect. Then the time reversal method is used to study the problem of signal amplification and defect circumferential localization for the small and medium size defects in the air tube. The results show that the time reversal method can effectively amplify the signal of the defect echo and make the defect echo be easily recognized. It is also possible to perform effective circumferential localization and defect shape discrimination for oblique crack defects, and to simulate the detection of one-cycle crack defects and multi-circumferential crack defects in water-filled pipes by using LZO _ (2) mode. The relationship between the reflection coefficient and the circumferential length of the defect is obtained, and the reflection coefficient is compared with the reflection coefficient obtained when the defect is the same. It is found that the reflection coefficient of the filled pipe is always smaller than that of the empty tube defect when the defect is the same. The signal amplification and defect localization of various types of single and multiple defects in water-filled pipeline are studied by using time reversal method. The simulation results show that the signal is re-excited after the signal is backprocessed. Many types of single and multiple defects in water-filled pipeline can be effectively located in the circumferential direction and the shape of the defects can be distinguished. At the same time, it is found that the time reversal method is used to amplify the signal of two small size circular hole thinning defects in different axial positions. The number of defects and the axial position of each defect can be obtained effectively.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U178

【相似文献】