Evaluation of applied and residual stresses in case-carburised En36 steel subjected to bending using the magnetic Barkhausen emission technique

The effect of applied and residual stresses on the magnetic Barkhausen emission (MBE) profile has been studied in case-carburised En36 steel specimens with 0.65 and 0.95 mm case-depth. The initial MBE profile shows two peaks in lower case-depth specimen and only single peak in higher case-depth specimen. The MBE peaks gradually increase in height with applied tensile stress. Under compression, the first peak in lower case-depth specimen disappears and the dominant second peak decreases in both case-depth specimens. However, after unloading from higher stress levels, the MBE profiles show different behaviour. In lower case-depth specimen, on tensile side, the first peak disappears and the second peak decreases with pre-stress level. On compressive side, the first peak increases while the second peak decreases with pre-stress level. In higher case-depth specimen, on both tensile and compressive sides, the MBE peak decreases with pre-stress, but to different extent. These variations in MBE peaks are correlated with residual stress redistribution in the near-surface and subsurface regions.