基于超声导波的管道防腐层检测技术研究

发布时间：2018-06-19 01:55

本文选题：超声导波管道内检测 + 能量衰减　；参考：《沈阳工业大学》2017年硕士论文

【摘要】：服役油气输送管道常采取外敷防腐层的方式对其进行保护。防腐层在土壤中易受到多种原因造成的腐蚀,发生破损,失去保护作用,从而造成管道的断裂,甚至发生爆炸等危险,继而造成能源的浪费、经济损失、危害人身、财产安全等重大隐患。目前,国际上主要采用外检测的方法对防腐层缺陷进行检测,这些方法均是给管道加激励信号,人工在管道沿线上方进行测试,这需要大量的人力、时间,并受地形和天气等自然条件限制。采用超声导波进行管道内检测防腐层缺陷的方法,避免了自然环境对检测的限制,节省了人力、物力。针对管道内检测防腐层缺陷的问题,本文研究了超声导波在单层钢板和敷有完好防腐层的双层板中传播时的传播方式、路径和回波信号的能量、波包独立性等参数之间的差异。对超声导波在固体介质中传播时的能量衰减、临界角和波形转换等特性进行了分析研究。以超声导波在固体介质中传播时的位移场和应力场为基础,结合双层固体介质层间交界面处的衔接条件,推导了超声导波在层间界面处的反射、折射系数。采用三种不同中心频率、三种不同K值的九组压电超声斜探头对防腐层完全剥离的单层板和防腐层完好的双层板结构进行检测,对回波信号的峰峰值、波包独立性、能量均值和峰值比例系数进行了分析,提出了一种适用于管道内检测防腐层剥离的压电超声斜探头选取方法。基于该探头选取方法,选择5MHz、K1的压电超声斜探头对带有防腐层剥离的钢板进行检测,采用最大临界值缺陷识别法对防腐层剥离进行量化和定位。实验研究,结果表明:在收发探头间距一定时,超声导波回波信号的能量随探头中心频率的增加而减小,随探头K值的减小而增大;超声导波在防腐层完全剥离的单层板中传播时接收到的回波信号能量要大于其在防腐层完好的双层板中传播时检测到的回波信号能量。针对本实验的被检对象,采用5MHz、K1压电超声斜探头进行检测时,其回波信号不仅波包独立性好,峰值比例系数也最大,对于判断防腐层是否存在剥离缺陷,是最佳的检测条件。采用最大临界值法对防腐层剥离进行量化和定位,精度随防腐层剥离长度的增加而提高。为采用超声导波进行管道内检测防腐层剥离缺陷的工程化实现提供了依据。
[Abstract]:In service oil and gas transportation pipelines are often protected by external anticorrosive coating. The anticorrosive coating is easy to be corroded by many reasons in the soil, resulting in breakage and loss of protection, resulting in the breakage of pipelines, even explosion and other dangers, resulting in waste of energy, economic losses, and endangering human beings. Property safety and other major hidden dangers. At present, the international inspection methods are mainly used to detect the defects of anticorrosive coating. These methods are all to add the excitation signal to the pipeline and manually test it above the pipeline, which requires a lot of manpower and time. And subject to terrain and weather and other natural conditions. Ultrasonic guided wave is used to detect the defects of anticorrosive coating in pipeline, which avoids the limitation of natural environment and saves manpower and material resources. In order to detect the defects of anticorrosive coating in pipeline, the difference of ultrasonic guided wave propagation mode, the energy of path and echo signal, and the independence of wave packet in single layer steel plate and double layer plate with intact anticorrosive coating are studied in this paper. The energy attenuation, critical angle and waveform conversion of ultrasonic guided waves propagating in solid media are studied. Based on the displacement field and stress field of ultrasonic guided waves propagating in solid media, the reflection and refraction coefficients of ultrasonic guided waves at interlaminar interfaces are derived. Nine groups of piezoelectric ultrasonic oblique probes with three different central frequencies and three different K values were used to detect the single layer plate completely stripped of the anticorrosive coating and the double layer plate structure with intact anticorrosive coating. The peak value of the echo signal and the independence of the wave packet were measured. The energy mean value and peak ratio coefficient are analyzed, and a method of selecting piezoelectric ultrasonic oblique probe suitable for detecting anticorrosive coating exfoliation in pipeline is proposed. Based on the method of selecting the probe, the piezoelectric ultrasonic oblique probe of 5MHz K1 is selected to detect the steel plate with anticorrosive coating peeling, and the maximum critical value defect identification method is used to quantify and locate the anti-corrosion coating peeling. The experimental results show that the energy of ultrasonic guided echo signal decreases with the increase of the central frequency of the probe and increases with the decrease of the K value of the probe when the distance between the transceiver and the transceiver is constant. The echo energy of ultrasonic guided wave propagating in the single layer plate which is completely stripped of the anticorrosion layer is higher than that detected in the propagation of the ultrasonic guided wave in the anti-corrosion layer in the intact double-layer plate. For the subject of this experiment, the echo signal is not only independent of the wave packet, but also has the largest peak ratio coefficient when the 5MHz K1 piezoelectric ultrasonic oblique probe is used to detect the anti-corrosion coating, which is the best detection condition for judging whether the anti-corrosion coating has peeling defect or not. The maximum critical value method is used to quantify and locate the exfoliation of the anticorrosive coating, and the precision increases with the increase of the peeling length of the anticorrosive coating. It provides the basis for the engineering realization of detecting the anti-corrosion coating peeling defect in pipeline by ultrasonic guided wave.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB553

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