Effect of deformation in bending on magnetic Barkhausen noise in low alloy steel

The influence of bending deformation on magnetic Barkhausen noise (MBN) was studied in low alloy steel. The peak height of the rectified MBN profile was observed to increase systematically with increasing tensile strain until the onset of plastic deformation. Increasing compressive strain initially produced a reduction in peak height, but more complex behaviour was observed at larger values. In particular, broadened profiles were produced under compression, which may indicate the presence of two or more overlapping peaks. As confirmed by X-ray diffraction measurements, one effect of plastic deformation is to leave a residual compressive stress on the tension side of the specimen and a residual tensile stress on the compression side. Measurements of residual stress were correlated with MBN peak height, to the extent that both quantities show functional forms similar to the theoretical relationship between residual stress and the bending moment applied prior to unloading.