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'ZERO POINT' IN THE EVALUATION OF MARTENS HARDNESS UNCERTAINTY

G. Barbato, G. Brondino, M. Galetto, G. Vicario
  • Abstract:
    The Instrumented Indentation Test is based on simultaneous recording of force and indentation depth, obtained during test cycle. The force-depth curve, describing the indentation pattern, is typically formed by two parts having the “zero-point” in common, i.e. the first contact point between the indenter and the surface of test piece. The zero-point determination is a crucial aspect for Martens Hardness evaluation, so that relevant ISO standard suggests to estimate it by extrapolation of polynomial fitted functions. In this paper a new model, based on a segmented function, is proposed. This approach implies the use of maximum likelihood estimator for parameters determination. The corresponding uncertainty is provided through the covariance matrix of the regression model.
  • Keywords:
    Instrumented Indentation Test, Martens Hardness, Hardness Measurement, Uncertainty in Hardness Measurement, Hardness Standardization.
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  • DOI:
    _unreg_tc5-2002.013

Event details:

  • IMEKO TC:
    TC5
  • Event name:
    Joint International Conference on Force, Mass, Torque, Hardness and Civil Engineering Metrology in the age of globalization
  • Title:
    8th HARDMEKO Conference on Hardness Measurement (together with 18th TC3 Conference on Force, Mass and Torque and 1st TC20 Conference on Civil Engineering Metrology)
  • Place:
    Celle, GERMANY
  • Time:
    24 September 2002 - 26 September 2002