[3] [3] Broberg P. Surface crack detection in welds using thermogra-phy[J]. NDT & E International, 2013, 57: 69-73.

[7] [7] YANG Ruizhen, HE Yunze. Logarithmic analysis of eddy current thermo-graphy based on longitudinal heat conduction for subsurface defect evaluation[J]. Infrared Physics & Technology, 2014, 67: 467-472.

[9] [9] HE Y, TIAN G Y, PAN M, et al. An investigation into eddy current pulsed thermography for detection of corrosion blister[J]. Corrosion Science, 2014, 78: 1-6.

[10] [10] XU Changhang, ZHANG Wuyang, WU Changwei, et al. An improved method of eddy current pulsed thermography to detect subsurface defects in glass fiber reinforced polymer composites[J]. Composite Structures, 2020, 242: 112145.

[11] [11] YANG Z W, YAN H P, LI Y, et al. A novel inclined excitation method for crack detection of non-ferromagnetic materials using eddy current thermography[J]. Strength of Materials, 2019, 51(4): 558-568.

[13] [13] Barakat N, Mortadha J, Khan A, et al. A one-dimensional approach towards edge crack detection and mapping using eddy current thermography[J]. Sensors and Actuators A: Physical, 2020, 309: 111999.

[14] [14] Tsopelas N, Siakavellas N J. Experimental evaluation of electromagnetic-thermal non-destructive inspection by eddy current thermography in square aluminum plates[J]. Ndt & E International, 2011, 44(7): 609-620.

[15] [15] TIAN Guiyun, GAO Yunlai, LI Kongjing, et al. Eddy current pulsed thermography with different excitation configurations for metallic material and defect characterization[J]. Sensors, 2016, 16(6): 843.

[16] [16] ZHAO Jian, GAO Bin, Woo W L, et al. Crack evaluation based on novel circle-ferrite induction thermography[J]. IEEE Sensors Journal, 2017, 17(17): 5637-5645.

[17] [17] LIU Zewei, GAO Bin, TIAN Guiyun. Natural crack diagnosis system based on novel L-shaped electromagnetic sensing thermography[J]. IEEE Transactions on Industrial Electronics, 2019, 67(11): 9703-9714.

[18] [18] Hansen K A, Weisberg E C. Asymmetric induction work coil for thermoplastic welding: US, US5444220 A[P]. 1994-12-05

[19] [19] ZHU Z Q, PANG Y, Howe D, et al. Analysis of electromagnetic performance of flux-switching permanent-magnet machines by nonlinear adaptive lumped parameter magnetic circuit model[J]. Transactions on Magnetics, 2005, 41(11): 4277-428.