Characterisation of stress concentration of ferromagnetic materials by metal magnetic memory testing

The relationship between the degree of stress concentration and the Hp(y) signals of metal magnetic memory was investigated by tension-tension fatigue tests. Sheet specimens of 45CrNiMoVA steel were machined and two types of notches were cut into them to obtain two stress concentration factors. During the testing process, Hp(y) signals were collected from three measured lines on the specimen surface. In the absence of a precut notch, the Hp(y) signal curve of a measured line at the central position was linear. However, the Hp(y) signal curves of measured lines near a precut notch or across a notch showed a distribution of abnormal magnetic peaks. The magnetic gradient K of the abnormal magnetic peaks was found to increase as the stress concentration factor increased. This feature could potentially be used to characterise the degree of stress concentration of ferromagnetic materials.