Experimental Analysis of the Piezomagnetic Properties of Ferromagnetic Steels Subjected To Cyclic Tensile Stress

The objective of this research is to investigate the evolution of the piezomagnetic field of 30CrNiMo8 steel under cyclic tensile stress with variable amplitudes and asymmetrical cyclic tensile stress. The piezomagnetic field signal of an initially undemagnetised 30CrNiMo8 steel specimen was recorded simultaneously during the whole loading process. It was found that the magnetic field variation is in contrast to the variation of the applied stress during the elastic stage. However, the magnetic field variation started to be consistent with the variation of the applied stress when approaching and entering the plastic stage. A reasonable explanation was given for understanding this phenomenon. The Villari reversal point and the tail reversal point occurred during the plastic stage, which can be used to characterise the transition state from the elastic to plastic stage. The variations of the Villari reversal point and the tail reversal point under cyclic tensile stress with variable amplitudes were slightly different from those under asymmetrical cyclic tensile stress.