|
|
|
| Time-Domain Analytic Expressions for Pulsed Eddy Current Field of Conductive Plate and Characteristic Quantity for Thickness Measurement |
| Chen Xingle,Lei Yinzhao |
| Beihang University Beijing 100191 China |
|
|
|
|
Abstract This paper solves the pulsed eddy current field in time-domain of the conductive plate induced by falling current,and puts forward a way to obtain the signal characteristic quantity for thickness measurement. Through Laplace transformation and finite Hankel transformation,the series expansions for truncated eddy current field are attained in complex frequency-domain. The inverse Laplace transformation is figured out via residue theorem,and a new method is developed to calculate the eddy current field induced by falling current through the convolution between the time derivative of current and the unit step response of the model. The variations of the eddy current density in the conductor are studied and its relationship with induced voltage is presented. The thickness of the plate can be measured by using the peak time of the differential induced voltage between conductive plate and conducting half-space. Analytic expressions and characteristic quantity are verified through the experiments on aluminium plates.
|
|
Received: 31 December 2011
Published: 11 December 2013
|
|
|
|
|
|
[1] Bowler J, Johnson M. Pulsed eddy-current response to a conducting half-space[J]. IEEE Transactions on Magnetics, 1997, 33(3): 2258-2264.
[2] Ludwig R, Dai X W. Numerical and analytical modeling of pulsed eddy currents in a conducting half-space[J]. IEEE Transactions on Magnetics, 1990, 26(1): 299-307.
[3] de Haan V O, de Jong P A. Analytical expressions for transient induction voltage in a receiving coil due to a coaxial transmitting coil over a conducting plate[J]. IEEE Transactions on Magnetics, 2004, 40(2): 371-378.
[4] Fu F W, Bowler J. Transient Eddy-Current Driver Pickup Probe response due to a conductive plate[J]. IEEE Transactions on Magnetics, 2006, 42(8): 2029-2037.
[5] Jaeger J C. Magnetic screening by hollow circular cylinders[J]. Philosophical Magazine Series 7, 1940, 29(192): 18-31.
[6] Lee K S H, Bedrosian G. Diffusive electro-magnetic penetration into metallic enclosures[J]. IEEE Transactions on Antennas and Propagation, 1979, AP-27(2): 194-198.
[7] Theodoulidis T. Developments in calculating the transient eddy-current response from a conductive plate[J]. IEEE Transactions on Magnetics, 2008, 44(7): 1894-1896.
[8] Dodd C V, Deeds W E. Analytical solutions to eddy-current probe-coil problems[J]. Journal of Applied Physics, 1968, 39(6): 2829-2838.
[9] Theodoulidis T, Kriezis E. Series expansions in eddy current nondestructive evaluation models[J]. Journal of Materials Processing Technology, 2004, 161(1-2): 343-347.
[10] 雷银照. 时谐电磁场解析方法[M]. 北京: 科学出版社, 2000: 181-183.
[11]《现代数学手册》编纂委员会. 现代数学手册#x000b7;经典数学卷[M]. 武汉: 华中科技大学出版社, 2000: 467-489. |
|
|
|
2013, Vol. 28 
