VARIATION OF COERCIVITY OF FERROMAGNETIC MATERIAL DURING CYCLIC STRESSING

The relationship between coercivity and the number of stress cycles is reported in this paper. The linear relation between coercivity and the logarithm of the number of stress cycles was confirmed in load controlled fatigue tests, for both pre-strained and unprestrained specimens. It is believed that the dislocation activity is the main factor changing the magnetic properties of a ferromagnetic material under fatigue, rather than other microstructures and internal stress. As a result, a theoretical model was developed to explain the correlation between the coercivity and the number of stress cycles. The model is based on domain wall dislocation interaction and the strain-dislocation relation. We predict the relation between magnetic properties and the stage of fatigue life as Hc-Hc(0)= b ln(N), where Hc - Hc(0) is the change in coercivity, N is the number of stress cycles and b is a constant.