自适应解卷积方法抑制管道TOFD周向扫查盲区  

Reducing dead zone for TOFD circumferential scan of pipeline by the adaptive deconvolution method

作　　者：金士杰[1] 张波[1] 王志诚 孙旭[1] 林莉[1] Jin Shijie;Zhang Bo;Wang Zhicheng;Sun Xu;Lin Li(NDT&E Laboratory,Dalian University of Technology,,Dalian 116085,China)

机构地区：[1]大连理工大学无损检测研究所,大连116085

出　　处：《仪器仪表学报》2022年第5期227-234,共8页Chinese Journal of Scientific Instrument

基　　金：国家自然科学基金(51905079);辽宁省“兴辽英才计划”项目(XLYC1902082)资助。

摘　　要：利用超声衍射时差法(TOFD)沿管道外表面实施周向扫查时,受管道曲率和直达纵波脉冲宽度共同影响,在近表面区域形成分层盲区。本文采用自适应解卷积方法,选取与混叠信号主频接近的子带直达纵波信号作为参考信号,进行解卷积与自回归谱外推处理,拓宽有效频带范围,实现时域信号脉冲压缩,并结合周向扫查图像中端点衍射波确定缺陷深度。实验结果表明,对于外壁半径100.0 mm、壁厚30.0 mm,以及外壁半径148.0 mm、壁厚27.0 mm的碳钢管道,在中心频率5 MHz、探头中心距87 mm的检测条件下,自适应解卷积方法能够将管道近表面分层盲区范围减少约60%,且到直达纵波声线距离不小于4.0 mm缺陷的深度定量误差不超过10.6%。同常规频谱分析方法和自回归谱外推方法相比,自适应解卷积方法具有更优的盲区抑制效果,且能够准确定量前者难以检测的缺陷,测量误差不超过5.8%。When the circumferential scan is performed along the outer surface of pipeline by the ultrasonic time-of-flight diffraction(TOFD)technique,the layered dead zone is generated in the near-surface area due to the influence of the pipe curvature and the pulse width of direct longitudinal wave(DLW).In this article,the adaptive deconvolution method is applied to perform deconvolution and autoregressive spectrum extrapolation by selecting the sub-band DLW,whose main frequency is close to that of the overlapped signals,as the reference signal,realizing the extension of effective frequency band and the pulse compression of time-domain signal.Meanwhile,the defect depths are determined according to the tip-diffracted waves in circumferential scan images.Experimental results show that the range of layered dead zone is reduced by about 60%under the condition of 5 MHz central frequency and 87 mm probe center separation(PCS)for the carbon steel pipelines with 100.0 mm outer wall radius and 30.0 mm wall thickness,and with 148.0 mm outer wall radius and 27.0 mm wall thickness by the adaptive deconvolution method.When the distances from defect tips to the ray path of DLW are no less than 4.0 mm,the measurement error of the depths for the defect is within 10.6%.Compared with the conventional spectrum analysis method and the autoregressive spectrum extrapolation method,the adaptive deconvolution method has better performance in reducing dead zone and can accurately quantify the defects being difficult to detect with measurement error within 5.8%.

关 键 词：超声衍射时差法 管道 周向扫查 盲区 自适应解卷积 

分 类 号：TH142[一般工业技术—材料科学与工程] TB553[机械工程—机械制造及自动化]