TY - JOUR
T1 - A reverse time migration-based multistep angular spectrum approach for ultrasonic imaging of specimens with irregular surfaces
AU - Yang, Xiongbin
AU - Wang, Kai
AU - Xu, Yanfeng
AU - Xu, Lei
AU - Hu, Wenxiang
AU - Wang, Hao
AU - Su, Zhongqing
PY - 2020/12
Y1 - 2020/12
N2 - We develop a new ultrasonic imaging framework for non-destructive testing of an immersed specimen featuring an irregular top surface and demonstrate its capability of accurately depicting the lower surfaces of multiple damages hidden in the specimen. Central to the framework is a multistep angular spectrum approach (ASA), via which the forward propagation wavefields of wave sources and backward propagation wavefields of the received wave signals are calculated. Upon applying a zero-lag cross-correlation imaging condition of reverse time migration (RTM) to the obtained forward and backward wavefields, the image of the specimen with an irregular surface can be reconstructed, in which hidden damages, if any and regardless of quantity, are visualized. The effectiveness and accuracy of the framework are examined using numerical simulation, followed with experiment, in both of which multiple side-drilled holes, at different locations in aluminum blocks with various irregular surfaces, are characterized. Results have proven that multiple damages in a specimen with an irregular surface can be individually localized, and the lower surface of each damage can further be imaged accurately, thanks to the RTM-based algorithm in which multiple wave reflections from the specimen bottom are taken into wavefield extrapolation. The proposed imaging approach presents higher computational efficiency, compared to conventional RTM, and enhanced imaging contrast over prevailing total focusing methods.
AB - We develop a new ultrasonic imaging framework for non-destructive testing of an immersed specimen featuring an irregular top surface and demonstrate its capability of accurately depicting the lower surfaces of multiple damages hidden in the specimen. Central to the framework is a multistep angular spectrum approach (ASA), via which the forward propagation wavefields of wave sources and backward propagation wavefields of the received wave signals are calculated. Upon applying a zero-lag cross-correlation imaging condition of reverse time migration (RTM) to the obtained forward and backward wavefields, the image of the specimen with an irregular surface can be reconstructed, in which hidden damages, if any and regardless of quantity, are visualized. The effectiveness and accuracy of the framework are examined using numerical simulation, followed with experiment, in both of which multiple side-drilled holes, at different locations in aluminum blocks with various irregular surfaces, are characterized. Results have proven that multiple damages in a specimen with an irregular surface can be individually localized, and the lower surface of each damage can further be imaged accurately, thanks to the RTM-based algorithm in which multiple wave reflections from the specimen bottom are taken into wavefield extrapolation. The proposed imaging approach presents higher computational efficiency, compared to conventional RTM, and enhanced imaging contrast over prevailing total focusing methods.
KW - Angular spectrum approach (ASA)
KW - Irregular surface
KW - Nondestructive testing (NDT)
KW - Reverse time migration (RTM)
KW - Ultrasonic imaging
UR - http://www.scopus.com/inward/record.url?scp=85089075681&partnerID=8YFLogxK
U2 - 10.1016/j.ultras.2020.106233
DO - 10.1016/j.ultras.2020.106233
M3 - Journal article
C2 - 32771810
AN - SCOPUS:85089075681
SN - 0041-624X
VL - 108
JO - Ultrasonics
JF - Ultrasonics
M1 - 106233
ER -