High-efficiency method for diffusion velocity of eddy current in metallic plates

Pulsed eddy current has been extensively utilized in metal industry for non-destructive testing due to its distinctive benefits, including fast response, good penetration ability and lift-off tolerance. Eddy current diffuses in a complicated manner, with the diffusion velocity fluctuating over spatial and temporal dimensions. Gaining a comprehensive view of the diffusion velocity field enhances physical insights into pulsed eddy current detection. An explicit analytical equation for calculating the time domain magnetic vector potential in metal plates through inverse Laplace transform is derived, which employs an innovative and more efficient method to calculate the root of the phase term. It shows advantages in terms of speed compared with the traditional inverse Fourier transform. A novel whole-field gradient method is proposed for diffusion velocity field calculation, which divides the whole diffusion process into three stages. This method greatly improves computational efficiency over the previous point-tracing method by calculating the gradient of eddy current contours to obtain the overall velocity field in a single step, rather than tracking individual points. The calculated results align with the phenomena observed in numerical simulations. Additionally, the proposed method has been used to analyze the relationship between the properties of the planar conductor, probe lift-off, and the diffusion velocity field.