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

Abstract

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 (Bx) 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 Bx 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.

Metrology and Measurement Systems

“…1). An analytical mathematical model of a rectangular coil ES SECP is obtained on the basis of the mathematical model of a thin rectangular loop (4), (5), by additional integration over the cross-sectional area at a constant current density in it. In particular, in expressions ( 4) and ( 5),…”

“…A number of authors have proposed the creation of a uniform, initially given tangential EMF of excitation [1][2][3][4][5][6] in order to improve the selectivity and ensure the uniform sensitivity of surface eddy current probes (SECPs). Excitation systems (ESs), generating uniform configurations of EMFs in the testing zone are discussed in those works.…”

Cold-Rolled Strip Steel Stress Detection Technology Based on a Magnetoresistance Sensor and the Magnetoelastic Effect

“…Detection capability of sensors using the magneto-resistor has significantly improved since the giant magneto-resistive effect was first discovered in (Fe/Cr)N multilayer film material in 1988 [ 19 ]. Many detection technologies based on the magneto-resistive sensor have been applied successfully [ 20 , 21 , 22 , 23 , 24 ], making possible the direct detection of weak changes in magnetic induction caused by magnetoelastic effect.…”

Studying the computational resource demands of mathematical models for moving surface eddy current probes for synthesis problems

“…Rotational excitation field was generated in [8] by means of a system of rotating orthogonal coils. First, an optimized distribution of ECD was calculated which provides uniform sensitivity to flaws regardless of their orientation in space and then the coil with uneven winding was designed.…”