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In this paper, a method is presented in which that the diffuse field information of Lamb waves is used to realize the full focal imaging of the defect that is near the transducer array. The near distance means that the defect is located in the near field of ultrasonic phased array and satisfies the near field calculation formula. Near field acoustic information of the defect is obscured by the nonlinear effects of early time saturation present in a directly acquired ultrasonic inspection. The approach proposed here is to recover near filed information through cross-correlation of diffuse fields. The diffuse field is generated through multiple scattering and reflection effects after sufficiently long time transmission of ultrasonic signal in a bounded medium. The near field information is implicitly contained throughout the diffuse field. By cross-correlating the diffuse fields of ultrasonic responses recorded at two monitoring points, the Green's functions between the two points is recovered and the direct response between them is obtained. This idea is applied to the full matrix capture of ultrasonic phased array in which the full matrix is formed by sequential acquisition of responses for each transmitter-receiver pair. A virtual array of emitters and receivers is therefore established. Typically, phase delays are used in post-processing to achieve advanced imaging. Here an undelayed full matrix of inter-element responses is reconstructed through cross-correlation of a later time diffuse full matrix. In order to evaluate the applicability of the method for ultrasonic non-destructive testing, the process of full matrix reconstruction is demonstrated experimentally on an aluminium plate containing the near field defect. Combining the full focal imaging, it is shown that a hybrid full matrix formed through a temporally weighted sum of coherent and reconstructed matrices reduces the background noise and allows the effective imaging of near field defect by direct contact experimental measurements. However, the near field defect is hidden by the region of artificial noise in conventional coherent capture images. The proposed imaging method presents a theoretical guidance for detecting and imaging near field defect in plate-like configurations by using the Lamb wave nondestructive testing method.
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Keywords:
- diffuse field /
- cross-correlation /
- Lamb waves /
- total focusing imaging
[1] Holmes C, Drinkwater B W, Wilcox P D 2004 Insight 46 677
[2] Holmes C, Drinkwater B W, Wilcox P D 2008 Ultrasonics 48 636
[3] Jiao J P, Chang Y, Sun X R, He C F, Wu B 2015 J. Nanjing Univ. 51 72 (in Chinese) [焦敬品, 常予, 孙欣荣, 何存富, 吴斌 2015 南京大学学报 51 72]
[4] Hunter A J, Drinkwater B W, Wilcox P D 2008 IEEE Trans. Ultrason. Ferroelectr. Freq. Control 55 2450
[5] Labyed Y, Huang L 2012 IEEE Trans. Ultrason. Ferroelectr. Freq. Control 59 2186
[6] Poli P, Pedersen H, Campillo M 2012 Geophys. J. Int. 188 549
[7] Froment B, Campillo M, Roux P 2011 Compt. Rend. Geosci. 343 623
[8] Chi J, Li X L, Gao D Z, Wang H Z, Wang N 2017 Acta Phys. Sin. 66 194304 (in Chinese) [迟静, 李小雷, 高大治, 王好忠, 王宁 2017 66 194304]
[9] Liu C X, Cheng C F, Ren X R, Liu M, Teng S Y, Xu Z Z 2004 Acta Phys. Sin. 53 427 (in Chinese) [刘春香, 程传福, 任晓荣, 刘曼, 滕树云, 徐至展 2004 53 427]
[10] Potter J N, Wilcox P D, Croxford A J 2018 Ultrasonics 82 44
[11] Potter J N, Croxford A J, Wilcox P D 2014 Phys. Rev. Lett. 113 144301
[12] Weaver R, Lobkis O 2002 Ultrasonics 40 435
[13] Snieder R, Slob E, Wapenaar K 2010 New J. Phys. 12 063013
[14] Chehami L, Moulin E, Rosny J D, Prada C, Matar O B, Benmeddour F, Assaad J 2014 J. Appl. Phys. 115 104901
[15] Sun F, Zeng Z M, Jin S J, Chen S L 2013 J. Sys. Simul. 25 1108 (in Chinese) [孙芳, 曾周末, 靳世久, 陈世利 2013 系统仿真学报 25 1108]
[16] Li G F, Li J, Gao D Z, Wang N 2016 Acta Acust. 41 49 (in Chinese) [李国富, 黎洁, 高大治, 王宁 2016 声学学报 41 49]
[17] Yang Y, Xiao L, Qu W Z, Lu Y 2017 Ultrasonics 81 187
[18] Li J, Li G F, Gao D Z, Wang N 2017 Acta Acust. 42 143 (in Chinese) [黎洁, 李国富, 高大治, 王宁 2017 声学学报 42 143]
[19] Zhang J, Drinkwater B W, Wilcox P D, Hunter A J 2010 NDT & E Int. 43 123
[20] Zhang J, Drinkwater B W, Wilcox P D 2011 NDT & E Int. 44 361
[21] Rodriguez S, Deschamps M, Castaings M, Ducasse E 2014 Ultrasonics 54 1880
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[1] Holmes C, Drinkwater B W, Wilcox P D 2004 Insight 46 677
[2] Holmes C, Drinkwater B W, Wilcox P D 2008 Ultrasonics 48 636
[3] Jiao J P, Chang Y, Sun X R, He C F, Wu B 2015 J. Nanjing Univ. 51 72 (in Chinese) [焦敬品, 常予, 孙欣荣, 何存富, 吴斌 2015 南京大学学报 51 72]
[4] Hunter A J, Drinkwater B W, Wilcox P D 2008 IEEE Trans. Ultrason. Ferroelectr. Freq. Control 55 2450
[5] Labyed Y, Huang L 2012 IEEE Trans. Ultrason. Ferroelectr. Freq. Control 59 2186
[6] Poli P, Pedersen H, Campillo M 2012 Geophys. J. Int. 188 549
[7] Froment B, Campillo M, Roux P 2011 Compt. Rend. Geosci. 343 623
[8] Chi J, Li X L, Gao D Z, Wang H Z, Wang N 2017 Acta Phys. Sin. 66 194304 (in Chinese) [迟静, 李小雷, 高大治, 王好忠, 王宁 2017 66 194304]
[9] Liu C X, Cheng C F, Ren X R, Liu M, Teng S Y, Xu Z Z 2004 Acta Phys. Sin. 53 427 (in Chinese) [刘春香, 程传福, 任晓荣, 刘曼, 滕树云, 徐至展 2004 53 427]
[10] Potter J N, Wilcox P D, Croxford A J 2018 Ultrasonics 82 44
[11] Potter J N, Croxford A J, Wilcox P D 2014 Phys. Rev. Lett. 113 144301
[12] Weaver R, Lobkis O 2002 Ultrasonics 40 435
[13] Snieder R, Slob E, Wapenaar K 2010 New J. Phys. 12 063013
[14] Chehami L, Moulin E, Rosny J D, Prada C, Matar O B, Benmeddour F, Assaad J 2014 J. Appl. Phys. 115 104901
[15] Sun F, Zeng Z M, Jin S J, Chen S L 2013 J. Sys. Simul. 25 1108 (in Chinese) [孙芳, 曾周末, 靳世久, 陈世利 2013 系统仿真学报 25 1108]
[16] Li G F, Li J, Gao D Z, Wang N 2016 Acta Acust. 41 49 (in Chinese) [李国富, 黎洁, 高大治, 王宁 2016 声学学报 41 49]
[17] Yang Y, Xiao L, Qu W Z, Lu Y 2017 Ultrasonics 81 187
[18] Li J, Li G F, Gao D Z, Wang N 2017 Acta Acust. 42 143 (in Chinese) [黎洁, 李国富, 高大治, 王宁 2017 声学学报 42 143]
[19] Zhang J, Drinkwater B W, Wilcox P D, Hunter A J 2010 NDT & E Int. 43 123
[20] Zhang J, Drinkwater B W, Wilcox P D 2011 NDT & E Int. 44 361
[21] Rodriguez S, Deschamps M, Castaings M, Ducasse E 2014 Ultrasonics 54 1880
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