低阶扭转模态电磁声阵列传感器研制及其在厚壁小径管中的试验研究

Array of Fundamental Torsional Mode EMATs and Experiment in Thick-wall Pipe with Small Diameter

管道检测是发电厂热力设备安全的重要问题,由于高温以及检测区域的限制,常规无损检测方法很难满足电站管道检测要求。低阶扭转T(0,1)模态导波,由于其非频散特性,对管道缺陷大范围检测十分有效。为在管道中实现非接触激励T(0,1)模态,设计并研制了一种电磁声阵列传感器。利用所研制的电磁声阵列传感器,实现了厚壁小径管中T(0,1)模态激励和接收。通过优化电磁声阵列传感器各元件间不同连接方式可知,当各元件并联连接时,不仅提高了所激励信号的能量,还抑制了其它模态产生。同时测试了电磁声阵列传感器的频率特性,并对有周向人工缺陷的样管进行检测。试验结果表明,该电磁声阵列传感器可以实现对样管中周向缺陷的检测与准确定位,为在管道中激励接收T(0,1)模态并实现非接触检测缺陷奠定了基础。

Pipe inspection is an important issue from the perspective of power plant thermal equipment safety. It is difficult to inspect pipe with the conventional non-destructive methods, because of a high temperature and a limited accessibility in the region. The fundamental torsional guided wave is very effective for long range crack of pipe inspection, because of its non-dispersive characteristics. In order to generate non-contact T（0,1） mode, array of fundamental torsional mode electromagnetic acoustic transducers（EMATs） is designed and developed. Using the transducer, T（0,1） mode is generated and detected in the thick-wall pipe with small diameter. By optimizing the element connections of array of EMATs, when the elements are connected in parallel, the generated signal energy not only can be improved, but also other modes can be inhibited. Meanwhile, the frequency response characteristic is tested and the artificial defect along the circumferential direction of the sample pipe is detected. The transducer can achieve identification and accurate location of crack in the circumferential direction of the sample pipe. This proposed method provides a certain foundation for generation and detection T（0,1） mode and non-contact detection of cracks in the pipe.