Multiple cracks detection and visualization using magnetic flux leakage and eddy current pulsed thermography

•Detection and visualization of multiple cracks using electromagnetic non-destructive evaluation.•Artificial and natural multiple cracks are visualized by 3D leakage magnetic field imaging and eddy current pulsed thermography.•Comparison of magnetic flux leakage and eddy current pulsed thermography with simulation and experiments.•Discussion on Probability of Detection and potential new sensing structure are provided.

This paper investigates two non-destructive evaluation methods, magnetic flux leakage (MFL) and eddy current pulsed thermography (ECPT), for both artificial and natural multiple cracks (MC) detection and visualization. The detection capability and characteristics of MC visualization are verified and compared through simulations and experiments. Results show that, MFL testing reflects the surface shapes and orientations of MC by 3D magnetic field imaging. However, it is unable to evaluate the depth of artificial MC and detailed surface shapes of natural MC due to limitations of sensor array spatial resolution. ECPT shows more capability in MC visualization in detail from thermal images. The obtained thermal image sequences from ECPT demonstrate rich transient and pattern information to evaluate MC geometrical features. After discussion of the two methods with the probability of detection (POD) analysis, a promising new sensing structure which potentially combines both advantages of them is proposed to enhance the NDE performance for MC evaluation.