Visualization of hidden cracks under corrosion layer in steel structures via eddy current pulsed thermography: Simulation and experiment

Abstract

Cracks in steel structures are usually covered by corrosion material and become a hidden hazard to the safety of the structures. It is significantly hard to detect this kind of hidden cracks because of the serious interference form the corrosion layer. This study aims to evaluate the effectiveness of eddy current pulsed thermography (ECPT) in visualizing such hidden cracks and to conduct an in-depth investigation into the inspection mechanism. A simulation model is constructed to analyze electromagnetic and thermal response in the inspected object, which helps to determine the specific thermal features caused by hidden cracks and to clarify the inspection mechanism. Experiments were implemented to verify the effectiveness of ECPT and to confirm thermal features caused by hidden cracks at the inspected surface. Simulation and experimental results show that specific thermal features caused by hidden cracks provide a means of recognizing the hidden cracks from the inspection results. Experimental results also verify that ECPT presents good applicability for specimens with various corrosion severity and for cracks with various orientations. Without need of additional preprocessing of the corroded surface, this work provides a non-contact, instant and intuitive way to visualize the hidden cracks covered by corrosion in steel structures.