Volume 6, Issue 3 (May 1978)

    Evaluation of Correction Methods for Determining Load-Independent Knoop Microhardness

    CODEN: JTEOAD

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    Abstract

    The correction methods proposed in the literature for determining load-independent Knoop microhardness were surveyed. The methods were evaluated by using the results from seven samples and two testers. Adding a constant correction factor for each sample to the measured long diagonals to obtain the unrecovered diagonal lengths was found to be quite successful. The correction factor includes terms from elastic recovery, visibility error, and calibration error. This factor, when applied, corrects the elastic recovery in the diagonals and the systematic errors associated with the tester employed, and thus results in Knoop hardness numbers independent of load and tester, which can be taken as the true hardness. The correction factor is load-independent but varies with sample and tester.

    Two methods in the literature, a trial and error approach and an extrapolation technique, were found to work equally well for the seven samples in determining the correction factors and the load-independent hardness numbers. The approach attempting to correct the applied load with a term representing the minimum indenting load proved to be unsatisfactory.


    Author Information:

    Young, CT
    Project metallurgist and directormember of ASTM, Materials and Chemistry Department, Research Laboratories, The Bendix Corporation, Southfield, Mich.

    Rhee, SK
    Project metallurgist and directormember of ASTM, Materials and Chemistry Department, Research Laboratories, The Bendix Corporation, Southfield, Mich.


    Stock #: JTE10945J

    ISSN: 0090-3973

    DOI: 10.1520/JTE10945J

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    Author
    Title Evaluation of Correction Methods for Determining Load-Independent Knoop Microhardness
    Symposium , 0000-00-00
    Committee E04