Thermographic Crack Detection in Hot Steel Surfaces
The detection and characterization of surface cracks in steel specimens prior to damage is a technologically and economically highly significant task and is of utmost importance when it comes to safety relevant structures. In steel production where steel billets at high temperatures have to be inspected while moving a number of well established NDT methods cannot be applied. Laser thermography however is a promising candidate to serve as a fast, non contact and remote tool in this case. We present a study that shows that the crack detection capabilities of laser thermography can be extended also to specimens at high temperature. A combination of inductive and laser heating allows to systematically study the contrast formation as well as the optimization of the important measurement parameters. The experiments are accompanied by FEM simulations that provide a better insight of the physical correlations and support the experimental developments. The aim of these studies is to develop a system with high inspection speed and detection performance to be in line operated under the hostile environment of steel production lines.