In-Situ Magnetic Barkhausen Noise Measurements to Identify Elastic-Plastic Deformation and Failure in Different Steels

Plastic processing operations of ferromagnetic materials may cause significant mechanical stress, which has a strong impact on its final magnetic behavior. In this paper, the magneto-mechanical correlations between the stress-strain behavior and magnetic Barkhausen noise emission in three typical steels subjected to uniaxial tension were studied comparatively, the tensile damage and fracture morphology of each sample was identified by magnetic measurements and scanning electron microscopy. The results show that the characteristics values of Barkhausen noise envelope can be approximated by a parabolic function of the carbon content experimentally and theoretically. In the elastic region, the Barkhausen noise response exhibits progressive growth with increasing strain, and reaches saturation at a critical point for the stress-induced magnetic anisotropy. However, once plastic deformation occurs, the Barkhausen noise signal intensity appears a downward trend until specimen failure, because the increasing dislocation tangles further hinder the domain wall motion. According to the mapping of Barkhausen noise eigenvalues, the location of tensile cracking is determined with a very satisfactory agreement. This indicates that the magnetic Barkhausen noise technique can be used for the nondestructive quantitative evaluation of elastoplastic deformation and failure location of ferromagnetic products.