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

Abstract

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, H_p(y), and its gradient K. The H_p(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 H_p(y) and K was studied. It shows that the H_p(y) varied intensively and changed its polarity when crack initiated in the stress concentration area. The maximum gradient, K_max, 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.

Keywords::

• stress concentration
• metal magnetic memory
• fatigue damage
• magnetic flux leakage
• ferromagnetic steel

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China [grant numbers 51135004 and 50905052] and Program for New Century Excellent Talents in University of Ministry of Education of China [grant number NCET-12-0837].