Inspection of Surface-Breaking Cracks on Steel Wire Rods Using Active Induction Infrared Thermography

In this study, an active induction infrared thermography is developed and applied to detect surface-breaking cracks on steel wire rods, which are frequently made by the rolling process in the manufacturing factory, using the thermal response of surface cracks to an impulsive excitation of electromagnetic induction. Artificial cracks, 20µm wide and 10 mm long along the axial direction with nine different depths ranging from 20µm to 100µm by increments of 10 µm, are machined by laser on two types of steel wire rods (Φ5.5 mm and Φ13 mm) to investigate the detection capability of the induction infrared thermography equipment. All artificial cracks are successfully detected from thermal images, and it is concluded that the active induction thermography is a fast and low-cost method to inspect the surface micro-cracks of steel wire rods that could not be detected and visualized by other nondestructive methods.