Barkhausen Emission Measurement

The Barkhausen noise method is a prominent tool for assessing residual stresses in ferromagnetic structures in a non-destructive manner. Detection of unwanted residual stress in load bearing components has become vital in aerospace applications where the failure of parts can have catastrophic consequences. Load bearing parts are usually made of high strength materials such as steels and therefore magnetic methods can be used to to evaluate their mechanical condition. While the Barkhausen noise technique has been used successfully for determining surface stresses, a major challenge is to extract depth dependent information and thus create stress-depth profiles, which are essential in assessing shot peening quality. Currently, the destructive process of electropolishing is used to remove surface layers of material, followed by x-ray diffraction stress analysis. We are developing a new frequency-dependent model for Barkhausen emissions based on the skin effect, in order to uncover the stress-depth profiles of steel components. By conceptually dividing a steel specimen into layers, and assigning uniform material properties to each layer, we are able to derive a system of integral equations that describe the attenuation of Barkhausen signals with frequency and distance.

Project participants: Orfeas Kypris, Ikenna Nlebedim, David Jiles