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Sensors 2016, 16(9), 1512;

Optimization and Validation of Rotating Current Excitation with GMR Array Sensors for Riveted Structures Inspection

Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA
Author to whom correspondence should be addressed.
Academic Editor: Vittorio M. N. Passaro
Received: 1 August 2016 / Revised: 12 September 2016 / Accepted: 13 September 2016 / Published: 16 September 2016
(This article belongs to the Section Physical Sensors)
Full-Text   |   PDF [5725 KB, uploaded 16 September 2016]   |  


In eddy current non-destructive testing of a multi-layered riveted structure, rotating current excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. However, when used with linear array sensors, the exciting magnetic flux density ( B x ) of the orthogonal coils is not uniform over the sensor region, resulting in an output signal magnitude that depends on the relative location of the defect to the sensor array. In this paper, the rotating excitation coil is optimized to achieve a uniform B x field in the sensor array area and minimize the probe size. The current density distribution of the coil is optimized using the polynomial approximation method. A non-uniform coil design is derived from the optimized current density distribution. Simulation results, using both an optimized coil and a conventional coil, are generated using the finite element method (FEM) model. The signal magnitude for an optimized coil is seen to be more robust with respect to offset of defects from the coil center. A novel multilayer coil structure, fabricated on a multi-layer printed circuit board, is used to build the optimized coil. A prototype probe with the optimized coil and 32 giant magnetoresistive (GMR) sensors is built and tested on a two-layer riveted aluminum sample. Experimental results show that the optimized probe has better defect detection capability compared with a conventional non-optimized coil. View Full-Text
Keywords: eddy current; non-destructive testing; giant magnetoresistive sensor; optimization eddy current; non-destructive testing; giant magnetoresistive sensor; optimization

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Ye, C.; Udpa, L.; Udpa, S. Optimization and Validation of Rotating Current Excitation with GMR Array Sensors for Riveted Structures Inspection. Sensors 2016, 16, 1512.

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