锅炉受热面小径管周向缺陷磁致伸缩导波检测试验研究

Experiment Research on Circumferential Defect Detection of Longitudinal Guided Wave Based on Magnetostrictive Effect

针对受热面小径管周向缺陷检测问题,本文设计了纵向磁致伸缩导波传感器,并将其应用于受热面小径管的无损检测.通过分析小径管中纵向导波模态传播特性,选取了130 kHz和250 kHz L（0,2）模态对小径管进行检测.通过比较两个不同尺寸永磁铁构成的偏置磁路对传感器性能的影响,优化选择了尺寸为20×20×10 mm的磁铁.在此基础上,在受热面小径管中进行了纵向导波无损检测试验研究.结果显示,L（0,2）模态可以有效检测小径管内外壁周向缺陷,用中心频率为130 kHz和250 kHz传感器对0.5 ～2 mm深度周向缺陷检测时发现,缺陷波包幅值随缺陷深度的增加而增加,为实际检测小径管提供依据.

A nondestructive examination methold using longitudinal ultrasonic guided wave was used to detect the circumferential defect in heating surface small diameter tube. Theoretical analysis of the propagation characteristics of longitudinal guided wave in small diameter tube was made,130 kHz and 250 kHz L（0,2） modes were selected for detection. By comparing the influence of biasing magnetic circuit of two permanent magnets with different sizes on the sensor performance,the optimal selection of the magnet dimensions is 20 × 20 × 10 mm. Based on above resuls,nondestructive examination for small diameter tube using longitudinal ultrasonic guided waves was conducted. Results show that, L（0,2） mode can effectively detect the small diameter tube defects in the inner and outer circumferential wall. Sensors with the center frequency of 130 kHz and 250 kHz were adopted to detect 0.5 to 2 mm defect of tube, the amplitude of the defect wave packet increased with increasing depth. Above study may provide a certain foundation for the actual detection of small diameter tubes.