Magnetic Barkhausen emission technique for evaluation of residual stress alteration by grinding in case-carburised En36 steel

The effect of residual stress changes caused by grinding on the magnetic Barkhausen emission (MBE) has been studied in case-carburised En36 steel. Both high and low frequency MBE measurements were made on specimens with case-depth of 0.55 and 0.8 mm subjected to varying level of grinding damage. The high frequency MBE profile shows single peak while the low frequency MBE profile shows two peaks. The first peak is not affected by grinding damages. But, the second peak increases and shifts to lower field systematically indicating the changes in microstructure and residual stresses. Both high and low frequency MBE measurements have been correlated to residual stress (RS)-depth profile measured using X-ray diffraction method. The high frequency MBE indicates the changes in surface RS, but does not indicate changes in RS at depths >10 (mu)m. The low frequency MBE profile indicates the changes in RS below the surface.