Naked eye visualization of defects in ferromagnetic materials and components

Abstract

We report a methodology to visualize defects by naked eye using magnetically polarizable nanoemulsions stabilized with different surface active species. The response of the nanoemulsions to the leaked magnetic flux from a defective region is exploited to locate the defect. In the presence of leaked magnetic flux, the nanofluid shows a visually perceivable color change due to the changes in the interparticle spacing within the self-assembled nano-arrays. We discuss the methodologies to detect defect morphologies and the underlying physics. The detection methodologies to quantify the defect shape, location and dimensions are validated in specimens with simulated defects of different geometries. The notable advantage of this technique is that it is simple, user friendly (does not need any processing of electronic data), fast and ideal for inspection of large area surfaces rapidly. This technique is ideal for the detection of surface and subsurface defects such as voids, cracks and inclusions in ferromagnetic materials.