A review of three magnetic NDT technologies

Magnetic Barkhausen Noise and hysteresis loop in commercial carbon steel : influence of applied tensile stress and grain size

The dependence of Barkhausen noise on elastic and plastic deformations, achieved in tension and in compression, has been investigated both in Armco iron and a low carbon steel These materials exhibit quite different behaviours, especially with regard to the effect of plastic deformation: a tensile plastic deformation (>1%) induces a marked increase in Barkhausen noise for Armco iron while it induces a steep decrease in the low carbon steel The comparison between the tensile and compressive behaviours, as well as between the elastic and plastic regimes of deformation enables us to attribute these effects to two underlying mechanisms, ie effect of residual internal stresses through magneto-elastic coupling and dislocation–domain wall interaction In Armco iron, the latter mechanism seems to have the strongest influence on the Barkhausen noise, while in the low carbon steel the influence of residual internal stresses prevails

On the role of residual internal stresses and dislocations on Barkhausen noise in plastically deformed steel

The characteristics of the Barkhausen noise phenomenon are investigated for various crystalline microstructures of plain steels. The measurements of the magnetic Barkhausen noise (MBN) and of the acoustic Barkhausen noise (ABN) are performed using the same magnetisation rate for different materials, specially developed to provide fully reproducible experimental conditions. The MBN fingerprints of single constituent steels (ferrite, pearlite and martensite) are first studied. Then, examples of MBN characteristics for more complex microstructures are presented. The results concerning single constituent steels are discussed in terms of shape, amplitude and position of the MBN and ABN fingerprints, taking into account two main aspects: the elementary Barkhausen events (sources), linked to the interaction of the magnetic domain microstructure with the crystalline microstructure, and the propagation of the electromagnetic waves in the material as well as its detection at the pick-up coil, both strongly influencing the frequency spectrum of the detected signal. This approach enables us to get a better understanding of the dependency of Barkhausen noise on the crystalline microstructure, which is then used to explain the characteristics of MBN observed for more complex microstructures.

Barkhausen noise from plain carbon steels: analysis of the influence of microstructure

The aim of this study is to predict residual stress and hardness of a case-hardened steel samples based on the Barkhausen noise measurements. A data-based approach for building a prediction model proposed in the paper consists of feature generation, feature selection and model identification and validation steps. Features are selected with a simple forward-selection algorithm. A multivariable linear regression models are used in predictions. Throughout the selection and identification procedures a cross-validation is used to guarantee that the results are realistic and hold also for future predictions. The obtained prediction models are validated with an external validation data set. Prediction accuracy of the prediction models is good showing that the proposed modelling scheme can be applied to prediction of material properties.

Quantitative prediction of residual stress and hardness in case-hardened steel based on the Barkhausen noise measurement

Characterization of pure iron and (130 p.p.m.) carbon–iron binary alloy by Barkhausen noise measurements: study of the influence of stress and microstructure

Barkhausen noise is generated by the irreversible and discontinuous motion of Bloch walls induced by an external magnetic field or a mechanical stress. These wall motions depend on the magnetic structure of the material (magnetocrystalline anisotropy for instance) and on the microstructural flaw density and distribution within the crystal. Barkhausen noise allows to characterize the microstructural state of ferromagnetic materials The aim of this work is to study the influence of various metallurgical and crystallographic parameters on the Barkhausen noise. High purity iron is studied as a reference material and is used to prepare carbon iron binary alloys (130 and 400 ppm) Characterization tests are carried out with an alternating magnetic field to reach one state of saturation to the other in the sample. The transducer used is a coil surrounding the sample. This transducer converts the variations of magnetic flow during magnetization in an electrical voltage. The signal is then amplified and fi...

C. Gatelier-Rothéa

Papers

Characterization of pure iron and (130 p.p.m.) carbon–iron binary alloy by Barkhausen noise measurements: study of the influence of stress and microstructure

Role of microstructural states on the level of barkhausen noise in pure iron and low carbon iron binary alloys