Quantifying Hole-Edge Crack of Bolt Joints by Using an Embedding Triangle Eddy Current Sensing Film

Abstract

Hole-edge crack quantification of bolt joints is critical for monitoring and estimating structural integrity of aircraft. The paper proposes a new triangle eddy current sensor array for the purpose of increasing the level of quantifying hole-edge crack parameters, especially, the crack angle. The new senor array consists of triangular coils instead of planar rectangular coils. The configuration of the novel sensor array, including the excitation current directions and the excitation winding shape, is optimized by simulation. The ability of the proposed sensing film to identify the crack parameters has been verified by finite element simulations and experiments. Results shows that triangular coils with same current directions in circumferentially adjacent coils and opposite current directions in axially adjacent coils achieve better performance in sensor linearity and resolution compared to rectangular coils. In addition, it has also been proved that the sensing film has a good potential to identify the crack depth and length.

Computation of Eigenvalues and Eigenfunctions in the Solution of Eddy Current Problems

“…What poses a real challenge is the determination of complex eigenvalues when the region under consideration consists of several sub-regions (containing conductive material or air). Such a situation occurs when modeling disks [ 8 , 9 , 10 , 11 ], tubes [ 12 , 13 , 14 , 15 , 16 ], rods [ 17 , 18 ], materials with a defect [ 19 , 20 , 21 , 22 , 23 , 24 ], and wherever there are edges [ 25 , 26 , 27 , 28 , 29 ] or discontinuities [ 30 , 31 , 32 ] ( Figure 1 ). Determination of the eigenvalues then boils down to finding complex roots of the appropriate complex function.…”

Multisensor Inspection of Laser-Brazed Joints in the Automotive Industry

“…ECT has been broadly applied for contactless measurements on electrically conducting parts including metals [25,26], composites [27], and even some fibers [28,29]. The method is well suited for cracks detection [30,31] as well as to perform coating thickness [32] and conductivity measurements [33] which are related to bulk grain size and porosity.…”