Plastic versus elastic deformation effects on magnetic Barkhausen noise in steel

A study was performed to differentiate the effects of elastic and plastic deformation on magnetic Barkhausen noise (MBN) signals. Linear and angular MBN measurements were made on a number of mild steel plate samples subjected to varying degrees of uniaxial elastic and plastic deformation up to similar to 40% strain. Elastic strain effects on the MENenergy were determined to be far more significant than plastic strain effects. MENenergy increases in the early plastic deformation region were attributed to a slight increase in elastic strain due to work hardening. Magnetic anisotropy studies indicated that elastic strain significantly alters the magnetic anisotropy (alpha) in the sample, but changes the isotropic signal(beta) very little. Plastic deformation has a smaller, but apparently opposite effect, in that it appears to change beta but has little influence on alpha. As plastic deformation levels become large, however, behaviour becomes more complex and is less well understood. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Lid. All lights reserved.