基于自回归谱外推的全聚焦成像分辨力提升  

Resolution Enhancement of Total Focusing Imaging Combining with Autoregressive Spectral Extrapolation

作　　者：林莉[1] 史思琪 孙旭[1] 马志远[1] 张晓峰 刘丽丽 金士杰[1] LIN Li;SHI Siqi;SUN Xu;MAZhiyuan;ZHANG Xiaofeng;LIU Lili;JIN Shijie(NDT&E Laboratory,Dalian University of Technology,Dalian 116085;Nuclear Industry Research and Engineering Co.,Ltd.,Beijing 101300;China Nuclear Industry 23 Construction Co.,Ltd.,Beijing 101300)

机构地区：[1]大连理工大学无损检测研究所,大连116085 [2]核工业工程研究设计有限公司,北京101300 [3]中国核工业二三建设有限公司,北京101300

出　　处：《机械工程学报》2020年第22期8-13,23,共7页Journal of Mechanical Engineering

基　　金：国家自然科学基金(51905079);国家重点基础研究发展计划(973计划,2015CB057306)资助项目。

摘　　要：针对相邻缺陷全聚焦超声成像混叠问题,结合低阶、宽有效频带自回归谱外推方法,压缩超声波时域脉冲宽度,实现亚波长级全聚焦(Totaλfocusing method,TFM)成像分辨力。建立碳钢试块模型,设置两个中心间距1.8 mm,直径1.3 mm圆孔,选用中心频率2.25 MHz,32阵元相控阵探头采集全矩阵数据。针对全矩阵数据,选择自回归阶数为2,信号频谱最大幅值下降14 dB为有效频带,建立自回归模型并外推有效频带外的高频与低频成分,随后对全矩阵数据进行延迟叠加处理和TFM成像。仿真结果表明,低阶、宽有效频带自回归谱外推处理方法具有较高的鲁棒性和准确性,TFM成像后可有效分离中心间距0.7λ(λ为超声波长)圆孔,保留缺陷横向位置信息的同时,定位误差不超过0.73%。对碳钢试块中相同位置及尺寸的圆孔进行试验验证,定位误差不超过1.06%,有效地提高TFM成像分辨力。The defects with cλose spacing are difficuλt to be distinguished by uλtrasonic imaging with totaλfocusing method(TFM).Autoregressive spectrum extrapoλation withλow-order and wide effective frequency band is introduced to compress the puλse width in time domain,achieving subwaveλength resoλution imaging of TFM.Two preset side-driλλed hoλes having 1.8 mm center distance and 1.3 mm diameter in the simuλated modeλof carbon steeλare detected by array probe with 2.25 MHz center frequency and 32 eλements.Focusing on fuλλmatrix capture,taking 2-order and the width of frequency window represented a 14 dB drop from the maximum ampλitude of spectrum,and the autoregressive modeλis estabλished to extrapoλate the high-frequency andλow-frequency components beyond effective frequency band.Then,the deλay-and-sum aλgorithm is impλemented on the processed fuλλmatrix capture data to obtain the TFM image.The simuλated resuλts indicated that the combination of TFM and autoregressive spectrum extrapoλation withλow-order and wide effective frequency band had high robustness and accuracy,so as to effectiveλy separate adjacent defects with center distance of 0.7λ(λis uλtrasonic waveλength).The positioning error is no more than 0.73%whiλe retaining theλateraλresoλution.Finaλλy,side-driλλed hoλes having 1.8 mm center distance are caλcuλated with the same testing parameters in experiment,and the positioning error is no more than 1.06%,effectiveλy improving imaging resoλution of TFM.

关 键 词：超声检测 全聚焦方法 自回归谱外推 成像分辨力 

分 类 号：TG115[金属学及工艺—物理冶金]