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    STP1576

    Certified KLST Miniaturized Charpy Specimens for the Indirect Verification of Small-Scale Impact Machines

    Published: 10 February 2015


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    Abstract

    Small specimen test techniques are becoming ever more popular as the need increases to characterize mechanical properties by use of the smallest possible amount of material, because of various restrictions on material availability, irradiation, testing space, and other factors. The National Institute of Standards and Technology (NIST) recently qualified reference miniaturized Charpy V-notch (MCVN) specimens for the indirect verification of small-scale impact testing machines (with capacity in the range 15 J to 50 J and impact velocity around 3.8 m/s). The same materials used for NIST standard verification specimens were evaluated at three energy levels (low, high, and super-high). The miniaturized specimen type investigated is denominated KLST (from the German Kleinstprobe, or “small specimen”). In the first phase of the qualification activity, several instrumented impact tests on miniaturized KLST specimens of low, high, and super-high energy were performed and analyzed at NIST. In this part of the study, which was published elsewhere [Lucon, E., “Certified Miniaturized Charpy Specimens for the Indirect Verification of Small-Size Impact Machines,” Mater. Perform. Character., Vol. 2, No. 1, 2013], the variability of MCVN data was compared to that of full-size Charpy data from the same lot of specimens. Additional aspects were also investigated, such as the influence of shear lip symmetry and specimen full or partial fracture on absorbed energy, and the correlation between miniaturized and full-size Charpy data. In the second phase of the qualification activity, certified values of absorbed energy and maximum force were established for each energy level by means of an international round robin, which involved nine highly qualified laboratories. The results of this round robin, and the outcome of the statistical analyses performed in accordance with ASTM E691-13 (ASTM E691-13: Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method, ASTM International, West Conshohocken, PA) and ISO 5725-2 [ISO 5725-2, 1994, “Accuracy (Trueness and Precision) of Measurement Methods and Results,” International Organization for Standardization, Geneva, Switzerland], are presented in this paper. Complete details are provided by NIST [Lucon, E., McCowan, C., Santoyo, R., and Splett, J., “Standard Reference Materials—Certification Report for SRM 2216, 2218, 2219: KLST (Miniaturized) Charpy V-Notch Impact Specimens,” NIST Special Publication 260-180, National Institute of Standards and Technology, Gaithersburg, MD, 2013], which accompanies the certified KLST.

    Keywords:

    small specimen test techniques, miniaturized Charpy specimens, small-scale impact machines, KLST, instrumented impact tests, international round robin, statistical analyses


    Author Information:

    Lucon, E.
    National Institute of Standards and Technology (NIST), Applied Chemicals and Materials Division, Boulder, CO

    McCowan, C. N.
    National Institute of Standards and Technology (NIST), Applied Chemicals and Materials Division, Boulder, CO

    Santoyo, R. L.
    National Institute of Standards and Technology (NIST), Applied Chemicals and Materials Division, Boulder, CO

    Splett, J. D.
    National Institute of Standards and Technology (NIST), Statistical Engineering Division, Boulder, CO


    Committee/Subcommittee: E10.02

    DOI: 10.1520/STP157620140003