Effects of Mechanical Scanning Speeds on Eddy-Current Detection of Cavity Defects

This article presents a distributed current-source (DCS) model considering the perturbation of the eddy-current (EC) field and its EC-generated magnetic flux density (MFD) caused by the defect in a moving conductor. The perturbed EC field, which is formulated into two subproblems (with and without a defect) in state space, is iteratively solved for the transient responses of a 3-D EC system and used to analyze the parametric effects on the fine and coarse detection of cavity defects. The DCS model improves the computational efficiency by reducing the solution domain and the number of experiments for parameter optimization, leading to the development of an EC probe consisting of an MFD sensor and a pair of rectangular electromagnets. Experimentally evaluated on a testbed configured on a computer numerical control (CNC) lathe for 2-D area scanning, the findings demonstrate the feasibility of mechanical scanning at a high speed to improve EC detection efficiency.