The measurement of stress in steels of varying microstructure by magnetoacoustic and Barkhausen emission

Abstract

Magnetoacoustic emission (MAE) and Barkhausen emission (BE) have been measured as a function of applied magnetic field and tensile stress from mild-steel samples in a wide range of heat treatments, to develop a technique to measure stress without prior knowledge of the microstructure. The results are supplemented by measurements of magnetic coercivity and mechanical hardness. MAE is found to decrease with increasing applied stress, whereas the variation of BE is more complicated. The amplitudes of both MAE and BE, as well as the coercivity and hardness are also found to depend on the microstructure to varying degrees. Thus in ferritic-pearlitic and ferritic-pearlitic-martensitic steel MAE is much more sensitive to stress than to changes in microstructure, whereas the sensitivity of BE to stress and microstructure is similar. Above 50 MPa MAE is also more sensitive to stress in ferrite containing cementite, whereas BE both lacks a monotonic dependence upon stress and is sensitive to microstructure. In martensite, however, there is no MAE, the BE increasing monotonically with stress. Tempered martensitic structures give a weak MAE signal that is more sensitive to tempering temperature than applied stress, whereas the BE increases with stress for tempers below 500°C and decreases above. The dependence of MAE and BE on magnetic field are discussed in terms of domain-wall nucleation and irreversible motion in ferrite at higher fields, and irreversible wall motion through martensite or pearlite at lower fields. The results imply that MAE can be used alone to measure stress provided the general form of the microstructure is known; otherwise BE can be used as an additional technique to resolve any ambiguity.

Non-destructive monitoring of tensile of mild steel samples by magnetic Barkhausen and ultrasonic methods

“…MAE is associated with the generation of acoustic signals as a result of continuous changes in magnetization and change of magnetostriction in separate areas of the material. The MAE parameters are obtained from the whole volume of material [8,9,[11][12][13]. The third method is ultrasonic.…”

Effect of Different Stages of Tensile Deformation on Magnetic Barkhausen Emission in High Strength Low Alloy Steel

“…The effect of tensile deformation on micromagnetic parameters has been studied by many researchers [8][9][10][11][12][13][14]. Most of these studies have been done only in the elastic region and the obtained relation between magnetic parameters and the applied stress has been used to determine the residual stresses, considering that the residual stress level will not exceed the yield stress of the material.…”

“…Micromagnetic techniques have been considered as a potential non-destructive evaluation (NDE) method for microstructural characterization and stress/strain measurements in ferritic steels [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The effect of tensile deformation on micromagnetic parameters has been studied by many researchers [8][9][10][11][12][13][14].…”

Control of flux in magnetic circuits for Barkhausen noise measurements

“…MBN is known to be affected by material microstructure, and is a candidate for non-destructive evaluation (NDE) applications due to its response to elastic stresses [3][4][5][6][7][8][9][10][11][12][13][14][15].…”