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Barkhausen Noise

The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform

Toivo Lepistö – 1st expert on this subject based on the ideXlab platform

  • Barkhausen Noise evaluation of fatigue in high strength steel
    International Journal of Materials & Product Technology, 2006
    Co-Authors: Mari Lindgren, Toivo Lepistö

    Abstract:

    The rms value of Barkhausen Noise and residual stresses were followed as a function of the number of loading cycles in alternating bending fatigue of high strength steel. The measurements were carried out in several directions to ensure that changes in the angular anisotropy of Barkhausen Noise could be detected. The Barkhausen Noise amplitude in the loading direction changed only slightly due to cyclic deformation. On the other hand, in other directions, especially in the angle 60° with respect to the loading direction, significant alteration of Barkhausen Noise amplitude as a function of the number of loading cycles was observed. The angular anisotropy of Barkhausen Noise increased as a function of the number of loading cycles. The amount of increase depended on the strain amplitude. The changes in the Barkhausen Noise amplitude could not be explained solely on the basis of changes in residual stresses.

  • On the stress vs. Barkhausen Noise relation in a duplex stainless steel
    Ndt & E International, 2004
    Co-Authors: Mari Lindgren, Toivo Lepistö

    Abstract:

    Abstract Various parameters of a Barkhausen Noise burst were measured under applied stress in prestrained duplex stainless steel specimens. After quenching, the root mean square value of the Barkhausen Noise amplitude was low because of the compressive macroscopic and interphase macrostresses in the ferrite phase. Prestraining increased the amplitude of the Barkhausen Noise in all measuring directions due to reduction of macroscopic compressive residual stress and introduction of tensile interphase microstresses in the ferrite phase. Under applied stress, Barkhausen Noise measured in the loading direction behaved similarly to ferritic steels: Barkhausen Noise increased under tensile stress and decreased under compressive stress. In the direction transverse to the loading axis, the Barkhausen Noise response was anomalous: Barkhausen Noise increased or remained unchanged under macroscopic compressive strain in the transverse direction and decreased under tensile strain in the transverse direction. In unstrained specimens in the loading direction, applied stress vs. Barkhausen Noise showed a linear relation under the applied stress range from −200 to 250 MPa. The stress sensitivity of the Barkhausen Noise was, however, low. In the prestrained specimens, the stress sensitivity was higher than in the unstrained specimens, especially under applied compressive stress.

  • effect of cyclic deformation on Barkhausen Noise in a mild steel
    Ndt & E International, 2003
    Co-Authors: Mari Lindgren, Toivo Lepistö

    Abstract:

    The rms value of the Barkhausen Noise and residual stresses were followed as a function of loading cycles in alternating bending fatigue of mild steel specimens. The measurements were carried out in several directions so that the changes in the angular anisotropy of the Barkhausen Noise and reorientation of the macroscopic easy axis of magnetisation could be detected. In the loading direction the Barkhausen Noise amplitude decreased due to build-up of compressive residual stresses. This was followed by either an increase or a decrease in the Barkhausen Noise amplitude depending on the direction of the initial magnetic easy axis with respect to the loading direction. After the commencement of macroscopic plastic deformation the angular anisotropy of Barkhausen Noise augmented substantially. In the transverse direction to the loading axis Barkhausen Noise decreased in the beginning of loading, reached thereafter a minimum followed by an increase in Barkhausen Noise. When cycling under larger strain amplitudes the loading direction and the direction transverse to the loading axis exhibited least changes as a function of loading cycles compared to other directions. The results indicated that following Barkhausen Noise only in one direction, usually in the loading direction, as a function of loading cycles, may lead to misevaluation of the fatigue damage development. Monitoring of several directions gives much more reliable results and therefore it is highly recommended.

Pirfo S Barroso – 2nd expert on this subject based on the ideXlab platform

  • investigation of shot peened austenitic stainless steel 304l by means of magnetic Barkhausen Noise
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010
    Co-Authors: Xavier Kleber, Pirfo S Barroso

    Abstract:

    Different shot peening conditions were applied to an austenitic stainless steel AISI 304L in order to transform austenite to martensite α′ at different depths. Magnetic Barkhausen Noise measurements performed on this steel reveal a correlation between the strength of the signal and the depth of the treatment. The combined effect of the volume fraction of martensite and the residual stress in martensite determined using X-ray diffraction analysis were found to be responsible for the evolution of the Barkhausen Noise response. Using tensile plastic deformation, the residual stress in martensite was changed, giving rise to a strong increase of the Barkhausen Noise activity. This variation was correlated to a modification of the sign and amplitude of the residual stress in the martensite phase. Directional measurements of the Barkhausen Noise revealed the anisotropy of the residual stresses induced by the tensile plastic deformation. It is concluded that the Barkhausen Noise activity recording could lead to the determination of the residual stresses in martensite induced by shot peening processes.

Mari Lindgren – 3rd expert on this subject based on the ideXlab platform

  • Barkhausen Noise evaluation of fatigue in high strength steel
    International Journal of Materials & Product Technology, 2006
    Co-Authors: Mari Lindgren, Toivo Lepistö

    Abstract:

    The rms value of Barkhausen Noise and residual stresses were followed as a function of the number of loading cycles in alternating bending fatigue of high strength steel. The measurements were carried out in several directions to ensure that changes in the angular anisotropy of Barkhausen Noise could be detected. The Barkhausen Noise amplitude in the loading direction changed only slightly due to cyclic deformation. On the other hand, in other directions, especially in the angle 60° with respect to the loading direction, significant alteration of Barkhausen Noise amplitude as a function of the number of loading cycles was observed. The angular anisotropy of Barkhausen Noise increased as a function of the number of loading cycles. The amount of increase depended on the strain amplitude. The changes in the Barkhausen Noise amplitude could not be explained solely on the basis of changes in residual stresses.

  • On the stress vs. Barkhausen Noise relation in a duplex stainless steel
    Ndt & E International, 2004
    Co-Authors: Mari Lindgren, Toivo Lepistö

    Abstract:

    Abstract Various parameters of a Barkhausen Noise burst were measured under applied stress in prestrained duplex stainless steel specimens. After quenching, the root mean square value of the Barkhausen Noise amplitude was low because of the compressive macroscopic and interphase macrostresses in the ferrite phase. Prestraining increased the amplitude of the Barkhausen Noise in all measuring directions due to reduction of macroscopic compressive residual stress and introduction of tensile interphase microstresses in the ferrite phase. Under applied stress, Barkhausen Noise measured in the loading direction behaved similarly to ferritic steels: Barkhausen Noise increased under tensile stress and decreased under compressive stress. In the direction transverse to the loading axis, the Barkhausen Noise response was anomalous: Barkhausen Noise increased or remained unchanged under macroscopic compressive strain in the transverse direction and decreased under tensile strain in the transverse direction. In unstrained specimens in the loading direction, applied stress vs. Barkhausen Noise showed a linear relation under the applied stress range from −200 to 250 MPa. The stress sensitivity of the Barkhausen Noise was, however, low. In the prestrained specimens, the stress sensitivity was higher than in the unstrained specimens, especially under applied compressive stress.

  • effect of cyclic deformation on Barkhausen Noise in a mild steel
    Ndt & E International, 2003
    Co-Authors: Mari Lindgren, Toivo Lepistö

    Abstract:

    The rms value of the Barkhausen Noise and residual stresses were followed as a function of loading cycles in alternating bending fatigue of mild steel specimens. The measurements were carried out in several directions so that the changes in the angular anisotropy of the Barkhausen Noise and reorientation of the macroscopic easy axis of magnetisation could be detected. In the loading direction the Barkhausen Noise amplitude decreased due to build-up of compressive residual stresses. This was followed by either an increase or a decrease in the Barkhausen Noise amplitude depending on the direction of the initial magnetic easy axis with respect to the loading direction. After the commencement of macroscopic plastic deformation the angular anisotropy of Barkhausen Noise augmented substantially. In the transverse direction to the loading axis Barkhausen Noise decreased in the beginning of loading, reached thereafter a minimum followed by an increase in Barkhausen Noise. When cycling under larger strain amplitudes the loading direction and the direction transverse to the loading axis exhibited least changes as a function of loading cycles compared to other directions. The results indicated that following Barkhausen Noise only in one direction, usually in the loading direction, as a function of loading cycles, may lead to misevaluation of the fatigue damage development. Monitoring of several directions gives much more reliable results and therefore it is highly recommended.