Date(s) - 9 Apr 2014
1:10 PM - 2:00 PM
3043 ECpE Building Addition
Title: Detection of sub-surface stresses in ferromagnetic materials using a new Barkhausen noise method
Speaker: Orfeas Kypris, ECpE Graduate Student
Adviser: David C. Jiles, Palmer Endowed Department Chair; Anson Marston Distinguished Professor
Abstract: Barkhausen jumps are discontinuous changes in magnetization which occur in a ferromagnetic material subjected to a time-varying magnetic field. These local magnetization changes, also termed Barkhausen jumps, give rise to an electromagnetic noise-like signal which can be detected using an induction coil. Owing to the coupling between magnetic and mechanical properties of ferromagnetic materials, the Barkhausen signal can reveal the stress state of the specimen under test. This allows for a powerful non-destructive evaluation method, which has been used to determine average stresses in a structure. Compared to other stress evaluation methods such as hole drilling and sectioning, and even XRD combined with electropolishing, it offers the advantage of being entirely nondestructive, rapid and cost- effective. However, the inability to extract depth-dependent information has previously imposed a limitation on its popularity. In previous work, we developed a parametric frequency domain model [1-2] which expresses the measured Barkhausen signal in terms of the contributions from different depths inside the material. This method can be used for the non-destructive evaluation of sub-surface stresses in ferromagnetic materials; particularly in assessing the structural health of aerospace components, thus making it possible to prevent catastrophic failures and loss of life.