This paper puts forward a novel nondestructive method to measure the coating thickness of aeronautical construction materials (e.g. Al, AU4G, Ti and Inox 304L) using the eddy current. First, the forward model of the coupled electric field method was adopted to facilitate the eddy current measurement the coating thickness. The forward model was applied in Matlab simulation. Based on the simulation results, the authors examined the effects of nonconductive coating thickness on sensor impedance component such as amplitude, resistance and reactance. On this basis, an inverse algorithm was developed and coupled with the forward model, and verified through experiments. The results show that our method can measure the coating thickness of aeronautical construction materials rapidly at a high precision. The method has great potential for automated industrial applications.
It is a challenging task to detect the hidden cracks in multilayer riveted structures in a nondestructive manner. This paper puts forward an eddy current nondestructive method for crack detection in such structures based on the electric conductivity of the rivets. Specifically, an eddy current sensor was designed with a ferrite core coil to evaluate the surface and inner defects of different layers. The magnetic phenomena during the detection process was simulated based on the magnetic potential and the scalar electrical potential, and the magnetic potential vector was solved by finite-element method. The proposed method was compared with the eddy current detection method without considering rivet conductivity through an experiment on a three-layer riveted aluminum structure. The length and position of each defect on each layer were changed in the experiment. The results show that the proposed method achieved better accuracy than the contrastive method, and its sensitivity depends on two issues: the position of the defect relative to the separation of the layers and the length of the defect relative to the length of the rivet head. The research results are of great significance for nondestructive testing of multilayer riveted structures in many fields.
In this paper, we have carried out an experimental study of the detection of top rail surface cracks. Firstly, we have highlighted the inability to inspect the entire rail head surface by a single sensor with a single scan. To overcome this inspection inability, we have proposed a multisensor system composed of three differential probes arranged within a specific configuration. The yielded results showed the efficiency and the robustness of the proposed configuration in the detection of cracks regardless its size, orientation and location.
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