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Frequency domain reverse time migration method is used to reconstruct damages in isotropic and anisotropic plates. Considering multimode overlapping, the Lamb wave signals scattered by the defects may result in artifacts in defect imaging. The scattering signals are thus pre-processed by using a mode separation method based on the vibration symmetry difference between the fundamental guided modes. Based on the multi-element array ultrasonic technique, a numerical study is carried out for defect imaging of aluminum and composite plates by using the frequency reverse time migration method. This paper is organized as follows. Firstly, in order to capture multi-directional information about damages, scattering Lamb wave signals caused by the defects are numerically collected by an annular array of transducers through using the finite element simulation. Secondly, after the pre-processing of mode separation, the separated scattering signals are time-reversed and used to stimulate the corresponding receivers. The Green's function is utilized to back-propagate the scattering Lamb signals in frequency domain, so that the back-propagated acoustic field information of monitored area can be obtained. Finally, the defect images are reconstructed by the cross-correlation between the incident acoustic field and the back-propagated acoustic field. To illustrate the influence of mode separation, the numerical experiments are carried out on an aluminum plate with single defect and on another composite plate with two adjacent identical defects. The reconstructed results from frequency domain reverse time migration method with and without mode separation are compared. The comparison indicates the importance of mode separation. Furthermore, the method is extended to detecting the double adjacent defects with different depths in the composite plate. The imaging result illustrates that the presupposed two adjacent defects with different depths are successfully identified. Numerical results demonstrate that the pre-processing of mode separation helps to effectively remove the artifacts resulting from the multimode interference in the imaging process. The proposed frequency reverse time migration method presents a strong potential for detecting and imaging defects in isotropic and anisotropic plates, which is capable of accurately measuring multi-site defects with information about geometry, size and depth.
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Keywords:
- Lamb wave /
- reverse time migration /
- ring sensor array /
- mode separation
[1] Monkhouse R S C, Wilcox P D, Cawley P 1997 Ultrasonics 35 489
[2] Lin X, Yuan F G 2001 AIAA J. 39 2206
[3] Whitmore N D 1983 1983 SEG Annual Meeting Las Vegas, Nevada, USA, September 11-15, 1983 p382
[4] Arnal B, Pernot M, Tanter M 2010 2010 IEEE Ultrasonics Symposium(IUS) San Diego, USA, October 11-14, 2010 p1039
[5] Anderson B E, Griffa M, Bas P Y L, Ulrich T J, Johonson P A 2011 J. Acoust. Soc. Am. 129 EL8
[6] Fink M 1992 IEEE Trans. Ultrason. Ferr. 39 555
[7] Mller S, Niederleithinger E, Bohlen T 2012 Int. J. Geophys. 2012 128465
[8] Ma F Z, Guo S J, Wang J 2016 Prog. Geophys. 31 741 (in Chinese) [马方正, 郭书娟, 王杰 2016 地球物理学进展 31 741]
[9] Lin X, Yuan F G 2005 Struct. Health. Monit. 4 341
[10] Zheng L, Guo J Z 2016 Acta Phys. Sin. 65 044305 (in Chinese) [郑莉, 郭建中 2016 65 044305]
[11] Xu Y F, Hu W X 2014 Acta Phys. Sin. 63 154302 (in Chinese) [徐琰锋, 胡文祥 2014 63 154302]
[12] Claerbout J F 1971 Geophysics 36 467
[13] Qiu L, Yuan S F, Zhang X Y, Wang Q, Zhang B L, Yang W W 2010 Acta Mater. Compos. Sin. 27 101 (in Chinese) [邱雷, 袁慎芳, 张逍越, 王强, 张炳良, 杨伟伟 2010 复合材料学报 27 101]
[14] Wang Q, Yuan S F, Qiu L, Sun Y J 2008 Chin. J. Sci. Instrum. 29 1816 (in Chinese) [王强, 袁慎芳, 邱雷, 孙亚杰 2008 仪器仪表学报 29 1816]
[15] Rose L R F, Wang C H, Chan E 2015 Wave Motion 58 222
[16] Xu K, Zhou B, McMechan G A 2010 Geophysics 75 61
[17] Zheng Y, Zhou J J 2014 Eng. Plast. Appl. 31 21 (in Chinese) [郑阳, 周进节 2014 工程力学 31 21]
[18] Chan E, Rose L R F, Wang C H 2015 Ultrasonics 59 1
[19] Wang L, Yuan F G 2005 Struct. Health. Monit. 4 3
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[1] Monkhouse R S C, Wilcox P D, Cawley P 1997 Ultrasonics 35 489
[2] Lin X, Yuan F G 2001 AIAA J. 39 2206
[3] Whitmore N D 1983 1983 SEG Annual Meeting Las Vegas, Nevada, USA, September 11-15, 1983 p382
[4] Arnal B, Pernot M, Tanter M 2010 2010 IEEE Ultrasonics Symposium(IUS) San Diego, USA, October 11-14, 2010 p1039
[5] Anderson B E, Griffa M, Bas P Y L, Ulrich T J, Johonson P A 2011 J. Acoust. Soc. Am. 129 EL8
[6] Fink M 1992 IEEE Trans. Ultrason. Ferr. 39 555
[7] Mller S, Niederleithinger E, Bohlen T 2012 Int. J. Geophys. 2012 128465
[8] Ma F Z, Guo S J, Wang J 2016 Prog. Geophys. 31 741 (in Chinese) [马方正, 郭书娟, 王杰 2016 地球物理学进展 31 741]
[9] Lin X, Yuan F G 2005 Struct. Health. Monit. 4 341
[10] Zheng L, Guo J Z 2016 Acta Phys. Sin. 65 044305 (in Chinese) [郑莉, 郭建中 2016 65 044305]
[11] Xu Y F, Hu W X 2014 Acta Phys. Sin. 63 154302 (in Chinese) [徐琰锋, 胡文祥 2014 63 154302]
[12] Claerbout J F 1971 Geophysics 36 467
[13] Qiu L, Yuan S F, Zhang X Y, Wang Q, Zhang B L, Yang W W 2010 Acta Mater. Compos. Sin. 27 101 (in Chinese) [邱雷, 袁慎芳, 张逍越, 王强, 张炳良, 杨伟伟 2010 复合材料学报 27 101]
[14] Wang Q, Yuan S F, Qiu L, Sun Y J 2008 Chin. J. Sci. Instrum. 29 1816 (in Chinese) [王强, 袁慎芳, 邱雷, 孙亚杰 2008 仪器仪表学报 29 1816]
[15] Rose L R F, Wang C H, Chan E 2015 Wave Motion 58 222
[16] Xu K, Zhou B, McMechan G A 2010 Geophysics 75 61
[17] Zheng Y, Zhou J J 2014 Eng. Plast. Appl. 31 21 (in Chinese) [郑阳, 周进节 2014 工程力学 31 21]
[18] Chan E, Rose L R F, Wang C H 2015 Ultrasonics 59 1
[19] Wang L, Yuan F G 2005 Struct. Health. Monit. 4 3
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