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.
Highlights
College of Aerospace Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China; COMAC Shanghai Aircraft Design & Research Institute, Shanghai 201210, China
Compared to Model 2, the inducted voltage of S2 in Model 1 changes little until the crack is at C4 and C5, which indicates that the rectangular exciting coil deteriorates the crack angle identifying ability of the triangular sensing coil
The induced voltage of the S1 changes little when the crack is at C1–C3, though there is much Eddy current (EC) flowing in the radial direction shown in the cloud picture in Figure 10, which contributes to the increasing induced voltage at a macroscopic level
Summary
College of Aerospace Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China; COMAC Shanghai Aircraft Design & Research Institute, Shanghai 201210, China. 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. In addition to the bolt-loosening failure, there are three typical hole-edge failure modes: shear failure, tensile failure and bearing failure [2,3]. According to the characteristics of structural force, the crack distribution of three failures along the circumferential angle of the bolt hole is obviously different (shear failure [30◦ , 60◦ ], tensile failure [75◦ , 105◦ ] and bearing failure [−15◦ , 15◦ ]), which can be used to distinguish failure modes by crack angle
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