PSI - Issue 84

L. Pisani et al. / Procedia Structural Integrity 84 (2026) 1144–1150 L. Pisani et al. / Structural Integrity Procedia 00 (2026) 000–000

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Fig. 3 Representation of Barkhausen Noise signal

Internal mechanical stresses significantly influence the Barkhausen effect through magnetoelastic coupling (or magnetostriction), which alters how magnetic domains respond to an external magnetic field. This behaviour is the basis for using Magnetic Barkhausen Noise (MBN) analysis as a non-destructive testing method to evaluate stress. Internal stress modifies the energy landscape for the magnetic domains and their walls, impacting their movement: • Domain Wall Movement: Stresses act as additional “pinning sites” or modify existing ones, making the movement of domain walls more difficult or forcing them into a specific orientation; • Domain Orientation: In materials with positive magnetostriction (like most steels and iron), domains tend to align their magnetization parallel to the direction of tensile stress and perpendicular to compressive stress. In this work the considered MBN measurement is the integral representing the overall magnitude or energy of the magnetic Barkhausen signal. It will be denoted by INT while reporting experimental results. For materials with positive magnetostriction, like low carbon steels, the Barkhausen signal's primary characteristics, namely its amplitude (intensity) and distribution (timing of the noise peaks, change predictably with the type and magnitude of stress, provided the sensor is aligned correctly. In particular, in case of tensile stress the domain walls move more easily along the stress direction, increasing the signal amplitude and energy. In case of compressive stress, the domain wall movement is restricted or redirected perpendicular to the stress direction and a decrease in signal amplitude and energy is observed.

Fig 4: MBN INT signal at incremental stress (MPa). Low carbon rebar steel (left), high strength harmonic steel (right).

Opposite behaviour is observed in case of pearlitic steels / high eutectoid steels like harmonic steel normally used for pre- and post-tensioning. For these steels, having negative magnetostriction, the signal decreases with the increment of the applied load. R.Rautiohao et Al.(1994); Neslušan et al (2019)