【作者】 张晓丹；

【导师】 杨理践；

【作者基本信息】 沈阳工业大学 ， 仪器科学与技术， 2017， 硕士

【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。更多还原

【Abstract】 The oil and gas pipeline is often protected by external anticorrosive layer.Anticorrosive layer in the soil is susceptible to corrosion,damage caused by a variety of reasons,and lose the protection effect.Thus resulting in pipeline fracture,or even explosion and other hazards.It causes waste of energy,economic loss,and endangers the safety of people and property.At present,the international use of outer detection methods for the detection of defects in the coating.These methods are to add incentives to the pipeline,artificial in the pipe along the top of the test.This requires a lot of manpower,time,and by terrain and weather and other natural conditions.The ultrasonic guided wave is used to detect the defects of the anticorrosion layer in the pipeline,which avoids the limitation of the natural environment on the detection and saves manpower and material resources.According to the inner detection of anticorrosion layer defects in the pipeline,the propagation mode,path and echo signal energy,wave packet independence of the ultrasonic wave guided by the single-layer steel plate and the double layer board with the intact coating are studied in this paper.The energy attenuation,critical angle and waveform transformation of ultrasonic guided waves propagating in a solid medium are analyzed and studied.Based on the displacement field and stress field of ultrasonic guided waves propagating in a solid medium,the reflection and refraction coefficients of ultrasonic guided waves at the interface between layers are deduced based on the convergence condition at the interface between the two layers of solid dielectric.Nine groups of piezoelectric ultrasonic inclined probes with three different center frequencies and three different K values were used to detect the anticorrosion layer completely stripped of single-layer and double layer plate structure with good anticorrosion layer of the detection.The peak to peak,the packet independence,the energy mean and the peak scale coefficient of the echo signal are analyzed,A method of selecting piezoelectric ultrasonic oblique probe for detecting the anticorrosion layer in pipeline is proposed.Based on the probe selection method,select the 5MHz,K1 piezoelectric ultrasonic oblique probe with anticorrosion layer of steel plate to detect.The maximum critical value defect identification method is used to quantify and locate the peeling of the coating.The experimental results show that the energy of the ultrasonic guided wave echo signal decreases with the increase of probe center frequency and increases with the decrease of probe K value.The energy of the echo signal received when the ultrasonic guided wave propagates in a single plate with a completely stripped anticorrosion layer,is greater than the energy of echo signal detected during it propagates in the double layer of the anticorrosive layer.According to this experiment detected objects 5MHz,K1 piezoelectric ultrasonic diagonal probe is used for detection,the echo signal is not only good in the wave packet,but also has the largest peak scale factor.It is the best way to judge whether the coating has stripping defects with the detection conditions.The maximum critical value method is adopted to quantify and locate the coating peeling,and the accuracy increases with the increase of the peeling length of the coating.The results provide a basis for the engineering realization of the detection of the stripping defects in the pipeline by ultrasonic guided wave.更多还原