Determination of Residual Stresses from the Barkhausen Noise Voltage Signal

Mechanical and heat treatment affects microstructure, hardness, and residual stresses in the surface layer. Micromagnetic examination of the material can determine the correlation between the changes in microstructure or hardness and permeability and electrical conductivity of the material. With a defined analysis frequency fa and by monitoring the Barkhausen noise variations, the depth properties of the material can be estimated. The Barkhausen noise is captured as voltage signal by the detection coil. Processing voltage signals enables to determine a characteristic that can be used as reference when evaluating the condition of the material. In our research, we used the Ck60 carbon steel specimen in three state, determined by heat treatment, that differ in microstructure, microhardness, and residual stresses. We found that the microstructure, microhardness and residual stresses of the surface layer affect the captured Barkhausen noise voltage signals, i.e. the calculated RMS values of the voltage signals and the signal intensity.