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Model based laser-ultrasound determination of hardness gradients of gas-carburized steel.

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Title: Model based laser-ultrasound determination of hardness gradients of gas-carburized steel.
Authors: Singer, F.1 f.singer@isat-coburg.de, Kufner, M.1
Source: NDT & E International. Jun2017, Vol. 88, p24-32. 9p.
Subjects: Laser ultrasonics, Hardness, Carburization, Carbon steel, Rayleigh waves, Interferometers
Abstract: Gas carburizing is a common industrial process utilized for case hardening of low carbon steels. However, there is a lack of non-destructive evaluation systems for the measurement of hardness-depth profiles. We propose a novel measurement method for the determination of hardness-depth profiles of two-step gas carburized steel specimens. The method is based on the measurement of broadband laser excited Rayleigh waves. Rayleigh waves were generated by a pulsed Nd: YAG laser in the thermoelastic regime and measured with a heterodyne Mach-Zehnder interferometer in the near-field. From two measurements with different source to receiver distances the dispersion diagrams were calculated by means of the phase spectral analysis method. In order to simulate the observed dispersive behavior of the Rayleigh waves, first the two-step gas carburizing process was simulated using solutions of the diffusion equation. The resulting continuous hardness profile was then discretized into up to 100 layers. Thereafter the Rayleigh wave dispersion diagram was calculated from the discretized stack of layers using a delta-matrix formulation of the Thomson-Haskell transfer matrix method. In order to obtain best fitting hardness profiles, the simulated dispersion diagrams were fitted to measurements with a curve fitting algorithm. Comparison of the Rayleigh wave inversion method with destructively obtained Vickers hardness profiles shows good quantitative agreement. [ABSTRACT FROM AUTHOR]
Copyright of NDT & E International is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
An: 122106753
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  Data: Model based laser-ultrasound determination of hardness gradients of gas-carburized steel.
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  Data: <searchLink fieldCode="AR" term="%22Singer%2C+F%2E%22">Singer, F.</searchLink><relatesTo>1</relatesTo><i> f.singer@isat-coburg.de</i><br /><searchLink fieldCode="AR" term="%22Kufner%2C+M%2E%22">Kufner, M.</searchLink><relatesTo>1</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22NDT+%26+E+International%22">NDT & E International</searchLink>. Jun2017, Vol. 88, p24-32. 9p.
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  Data: <searchLink fieldCode="DE" term="%22Laser+ultrasonics%22">Laser ultrasonics</searchLink><br /><searchLink fieldCode="DE" term="%22Hardness%22">Hardness</searchLink><br /><searchLink fieldCode="DE" term="%22Carburization%22">Carburization</searchLink><br /><searchLink fieldCode="DE" term="%22Carbon+steel%22">Carbon steel</searchLink><br /><searchLink fieldCode="DE" term="%22Rayleigh+waves%22">Rayleigh waves</searchLink><br /><searchLink fieldCode="DE" term="%22Interferometers%22">Interferometers</searchLink>
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  Label: Abstract
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  Data: Gas carburizing is a common industrial process utilized for case hardening of low carbon steels. However, there is a lack of non-destructive evaluation systems for the measurement of hardness-depth profiles. We propose a novel measurement method for the determination of hardness-depth profiles of two-step gas carburized steel specimens. The method is based on the measurement of broadband laser excited Rayleigh waves. Rayleigh waves were generated by a pulsed Nd: YAG laser in the thermoelastic regime and measured with a heterodyne Mach-Zehnder interferometer in the near-field. From two measurements with different source to receiver distances the dispersion diagrams were calculated by means of the phase spectral analysis method. In order to simulate the observed dispersive behavior of the Rayleigh waves, first the two-step gas carburizing process was simulated using solutions of the diffusion equation. The resulting continuous hardness profile was then discretized into up to 100 layers. Thereafter the Rayleigh wave dispersion diagram was calculated from the discretized stack of layers using a delta-matrix formulation of the Thomson-Haskell transfer matrix method. In order to obtain best fitting hardness profiles, the simulated dispersion diagrams were fitted to measurements with a curve fitting algorithm. Comparison of the Rayleigh wave inversion method with destructively obtained Vickers hardness profiles shows good quantitative agreement. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of NDT & E International is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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      – Type: doi
        Value: 10.1016/j.ndteint.2017.02.006
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 9
        StartPage: 24
    Subjects:
      – SubjectFull: Laser ultrasonics
        Type: general
      – SubjectFull: Hardness
        Type: general
      – SubjectFull: Carburization
        Type: general
      – SubjectFull: Carbon steel
        Type: general
      – SubjectFull: Rayleigh waves
        Type: general
      – SubjectFull: Interferometers
        Type: general
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      – TitleFull: Model based laser-ultrasound determination of hardness gradients of gas-carburized steel.
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            NameFull: Singer, F.
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              M: 06
              Text: Jun2017
              Type: published
              Y: 2017
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              Value: 88
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