Inspection and Visualization Method for the Internal Structure of Spot-Welded Three-Steel Sheet Using Eddy Current Testing

摘要

Spot-welding is widely used to assemble parts, such as those of vehicle bodies. To control the quality, safety and productivity of industrial products, a quick and accurate method of inspecting spot-weld is required. In our previous research, we reported an analysis method of examining the strength of spot welded parts by eddy current test (ETC) using a wide range of frequencies from high to low. In this paper, we report a method of analyzing the internal structure of a spot-weld. Magnetic field change showed a good correlation with the destructive shear test to check joint strength. The depth profile of the welded part was obtained by changing the skin depth using a wide range of frequencies. As the magnetic field strength at each frequency was not constant, they were normalized to create the depth profile. The two-dimensional depth profile was obtained by line scanning, and the three-dimensional depth profile was obtained by surface scanning. The three-dimensional internal structure of the welded part, which is nugget-shaped, was constructed from the volume rendering of the three-dimensional map, and it correlated with the shape obtained by cross-sectional observation.