扩散场扇扫重建格林函数实现近表盲区缺陷检测

Defect detection in near-surface blind zone using Green’s function reconstruction of diffuse field sector scanning

2020年5月12日定稿摘要针对结构近表盲区缺陷检测难题,发展了一种扩散声场扇扫重建格林函数的超声检测方法。在对扩散场扇扫重建格林函数理论分析的基础上,通过5 MHz超声相控阵探头对铝块近表盲区缺陷进行了检测实验并对影响成像结果的延时时间、时间窗宽和扫查方式进行了分析。结果显示,该方法可以有效检测铝块近表1.5~3 mm的盲区缺陷;扇形扫查方式的有效扩散时间较全矩阵捕获方式延长0.5 ms以上;在有效扩散时间内,随着延时接收时间和时间窗宽的增加,成像质量得到提高。本研究工作为超声检测近表盲区缺陷提供了一种有效可行的新方法。

Aiming at the problem of defect detection in the near-surface blind zone of structure,the detection method for reconstruction of Green’s function by sector scanning of diffuse field was developed.Based on the theoretical analysis of the reconstruction Green’s function of diffuse field sector scanning,a 5 MHz ultrasonic phased array probe is utilized to test the near-surface defects of an aluminum block and the delay time,time window length and scanning method that affects the imaging results were analyzed.The result shows that this method can effectively detect defects from 1.5 mm to 3 mm in the near-surface blind zone of the aluminum block.The effective diffusion time of the sector scanning mode is longer than the full matrix capture mode by more than 0.5 ms.In particularly,within the effective diffusion time,as the delayed reception time and the time window length increase,the imaging quality is improved.This research work provides an effective and feasible new method for ultrasonic detection of defects in the near-surface blind zone.