Electromagnetic Nondestructive Evaluation of Surface Decarburization on Steels : Feasibility and Possible Applications

Structural Characteristics at Surface and Barkhausen Noise in Aisi 4340 Steel After Grinding

“…of the noise signals connected with the magnetic domain wall movement and with the nucleation of the domains themselves, In materials with positive magnetostriction (like steels) Barkhausen noise increases or decreases by increasing tensile or compressive residual stresses respectively [1,2], Calibration curves of BN versus stress are given in the bibliography [1]; these curves are valid only for specific structures, Effects of microstructure and intergranular impurity segregation, due to tempering, on BN have been examined by Kameda et at. [3,4,5]; the dependence of BN on surface decarburation has been considered by Mayos et al [6], who have resolved the contributions to BN of pearlite and of ferrite; effects of subboundary formation and of dislocation density have been analysed by Klesnil et al [7] and by Kronrnuller [8], From a comparative study of the effects on BN of tensile stresses, precipitates and dislocations, Buttle et al [9] have drawn the conclusion that for practical 256 P. GONDI ET AL monitoring by BN of stressed regions allowance has to be made for accompanying variations of the local microstructure.…”

Assessment of Microhardness Profile in Grinding Using Barkhausen Noise Technique at Various Analysis Parameters

“…Augustyniak et al [9] analyzed the impact of variation in magnetizing frequency over BN amplitude while evaluating the time and space distribution of magnetic flux density. Mayos et al [10][11][12] investigated changes in magnetic properties of Barkhausen emission at different frequencies while assessing surface decarburization in steels at different depths.…”