MEASUREMENT OF RESIDUAL-STRESS IN STEEL USING THE MAGNETIC BARKHAUSENNOISE TECHNIQUE

Surface residual stresses on a structural beam steel sample were evalu ated using a non-destructive technique based on the measurement of sur face magnetic Barkhausen noise (MEN). MBN measurements were performed using a high resolution probe consisting of a small magnetic read head mounted between the poles of a ferrite U-core magnet. Applied stress magnitudes were correlated to MBN energy levels for calibration purpos es. MBN energy measurements were done at various locations on the stee l sample. The magnitude of the residual stress component along the sam ple beam axis was evaluated across the width of the beam using these c alibration curves. The range of sensitivity of the MBN signal to stres s as defined by the calibration curves was limited by the direction of easy magnetization. The effect of stress on the MBN signal was interp reted in terms of the active 180 degrees domain wall population. The v alidity of the residual stress results was confirmed experimentally us ing conventional methods: cutting and sectioning and hole drilling. Po ssible sources of residual stresses and their distribution on the stru ctural steel specimen are discussed. (C) 1997 Elsevier Science Ltd.