Mapping Stress as a Function of Depth at the Surface of Steel Structures Using a Frequency Dependent Magnetic Barkhausen Noise Technique

Profiling of stress as a function of depth is an important tool for nondestructive evaluation and can be used to prevent catastrophic failures in structures. In this work, the underlying theory of a new model for the depth profiling of stress in ferromagnetic structures based on the magnetic Barkhausen method is investigated and commented upon. In the model, a ferromagnetic structure is divided into layers of different stress states. By analysis of the constituent equations it was found that the measured Barkhausen voltage increases as the frequency span increases, for both the one- and the two layer cases. It was also found that two layers with the same amplitude of Barkhausen emission at the origin can be approximated as one layer, provided that the upper and lower depths, as well as the frequency range are identical.