Application of a Preisach-type hysteresis model to the magnetic evaluation of material degradation

Preisach-based magnetic characterization is applied as a non-destructive method to evaluate material degradation due to metal fatigue. At predetermined interruptions of the cyclic mechanical loading a set of first order symmetric and a set of second order minor magnetisation loops are measured and analysed using both the classical and the moving Preisach model. The evolution of microstructure dependent magnetic features such as the Preisach distribution function, the mean-field parameter k and the local coercive field distribution Q(c)(h(c)) is monitored: k increases and the peak value of Q(c) decreases with the number of stress cycles. Moreover, for both parameters the rate of change is higher during the last 10% of the fatigue lifetime.