Magnetic incremental permeability as indicator of compression stress in low-carbon steel

Abstract

The field dependences of the signal of induction transducer U~(H), proportional to the magnetic incremental permeability, were obtained on plastically deformed samples of low-carbon steel subjected to compression in the range of elastic deformation. It was found that the greater the relative elongation of the samples, the greater the magnetic fields in which maxima in the U~(H) curves are observed. The additional elastic compression results in the presence of three maxima in the U~(H) curves instead of two. These maxima are associated with the displacement of 90° and 180° domain walls. Most likely, for small values of compressive stresses in the samples, the third maximum in the U~(H) curves was not visible because of its close position to the maximum in the negative field. Fittings by pseudo-Voigt functions were carried out to determine the fields corresponding to three maxima. A new approach was proposed for the evaluation of internal stresses via determination of the fields of two maxima in the U~(H) curve associated mainly with the displacement of 90° domain walls.