Stress concentration impact on the magnetic memory signal of ferromagnetic structural steel

A novel method for quantitatively evaluating the impact of stress concentration on the magnetic memory signal of ferromagnetic structural steels was proposed. A theoretical model was established to illustrate the impact of stress concentration and microdefects on the normal component of surface magnetic signals, Hp(y), and its gradient K. The Hp(y) signals of the notched sheet specimens with different stress concentration factors were measured throughout the tension–tension fatigue tests, and the variation in measured Hp(y) and K was studied. It shows that the Hp(y) varied intensively and changed its polarity when crack initiated in the stress concentration area. The maximum gradient, Kmax, was used to indicate the stress concentration degree, which was found to be theoretically exponential increasing with an increase in the crack length. The research provides the potential possibility of quantitative inspection on stress concentration and microdefects for ferromagnetic structural steels.