EVALUATION OF RESIDUAL STRESS AND TEXTURE IN FERROMAGNETIC CRYSTALLINE MATERIAL BY BARKHAUSEN NOISE MEASUREMENTS

Abstract The Barkhausen noise (BN), induction rate, dB/dt, and hysteresis loop of 50% cold rolled polycrystal-line permalloy, annealed and tensile strained mild steel have been measured simultaneously. The peak of the BN amplitude distribution of the permalloy shifted toward lower amplitude and the total number of Barkhausen pulses decreased as the specimen cut angle respect to the rolling direction increased due to the increased number of impassable defects caused by the reduction in the driving force of domain wall. The two peaks in the rectified BN envelope of annealed mild steel specimen at the knee regions of hysteresis curve was accounted for the acceleration and deceleration of domain wall movement due to nucleation and annihilation of new reverse domain. As the residual strain increased from 6.7%, the BN envelope changed to the single peak at the coercive field due to the increased interactions with dislocations during irreversible wall displacement. The hysteresis loss and the BN energy in the cold-rolled permalloy and strained mild steel specimens decreased with the specimen angle and residual strain due to the increase in the number of impassable defects. The rapid increase in the hysteresis loss and the decrement of the BN energy up to 6.7% residual strain was explained in terms of the decrease in the energy for domain nucleation and annihilation.