Comparison of different types of focusing probes in pulsed eddy current testing

Pulsed eddy current (PEC) testing has attracted widespread attention because of its unique advantages in detecting local defects in insulated pipes. In this paper, rectangular, U-shaped, and semicircular PEC focusing probes are designed, the magnetic energy utilization efficiency and focusing properties of the developed probes are simulated and compared, and their detection sensitivities are experimentally compared. The magnetic flux through specific surfaces is calculated to find the utilization of magnetic energy by the different probes, and the eddy current dissipation power is used to quantitatively describe the eddy current field focusing properties of various types of probes. The simulation results show that the magnetic field energy utilization efficiency of the semicircular focusing probe is significantly higher than that of the other two probes, but the eddy current field distributions of the three probes are similar, and the focusing properties are not significantly different. The experimental results show that the three types of PEC probes can effectively detect local defects under a certain lift-off. By calculating the detection sensitivity of different probes to defects under different lift-off conditions, it is determined that the detection sensitivity of the semicircular probe is significantly higher than that of the U-shaped probe and rectangular probe. The experimental results are consistent with the numerical simulation results. The research results are conducive to the optimal design of PEC focusing probes for insulated pipes.