Stress dependence of the spontaneous stray field signals of ferromagnetic steel

• Published in: NDT & E international : independent nondestructive testing and evaluation 2009-06, Vol.42 (4), p.323-327
• Main Authors: Dong, Lihong, Xu, Binshi, Dong, Shiyun, Song, Li, Chen, Qunzhi, Wang, Dan
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Effective magnetic field; Elastic deformation; Exact sciences and technology; Materials science; Materials testing; Physics; Plastic deformation; Spontaneous stray field signal; Stress
• ISSN: 0963-8695; 1879-1174
• DOI: 10.1016/j.ndteint.2008.12.005

Measuring spontaneous stray field signals provides a promising tool to analyze the stress in ferromagnetic materials. However, strong initial stray field signals on the surface of ferromagnetic materials originating from various manufacturing processes can disturb stress-induced stray field signals. Consequently, it is necessary to conduct a study that will clarify the stress dependence of spontaneous stray field signals by eliminating initial random signals. In the present work, the focus is placed on sheet specimens that have a clean initial magnetic state by means of vacuum heat treatment. Measurements of the normal component H p( y) signals of stray field were performed during the whole tensile test. The results showed that the stress-induced H p( y) signal curve had good linearity after loading, i.e., the slope coefficient K s increased continuously in the elastic deformation stage but decreased slightly during the plastic deformation stage. This phenomenon was discussed and explained from both the stress-induced effective magnetic field and residual compressive stress viewpoints.