Charpy Impact Tests Near Absolute Zero

    Volume 19, Issue 1 (January 1991)

    ISSN: 0090-3973

    CODEN: JTEOAD

    Page Count: 7


    Tobler, RL
    MetallurgistCryogenic Materials Group Leader, National Institute of Science and Technology, Materials Reliability Division, Boulder, CO

    Reed, RP
    MetallurgistCryogenic Materials Group Leader, National Institute of Science and Technology, Materials Reliability Division, Boulder, CO

    Hwang, IS
    ResearcherGraduate StudentAssociate Professor, Massachusetts Institute of TechnologyMassachusetts Institute of Technology, CambridgeCambridge, MAMA

    Morra, MM
    ResearcherGraduate StudentAssociate Professor, Massachusetts Institute of TechnologyMassachusetts Institute of Technology, CambridgeCambridge, MAMA

    Ballinger, RG
    ResearcherGraduate StudentAssociate Professor, Massachusetts Institute of TechnologyMassachusetts Institute of Technology, CambridgeCambridge, MAMA

    Nakajima, H
    ResearcherDivision Chief, Superconducting Magnet Laboratory, Division of Thermonuclear Fusion Research, Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Ibaraki,

    Shimamoto, S
    ResearcherDivision Chief, Superconducting Magnet Laboratory, Division of Thermonuclear Fusion Research, Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Ibaraki,

    (Received 13 November 1989; accepted 29 May 1990)

    Abstract

    We review Charpy impact testing at extreme cryogenic temperatures, especially at liquid helium temperature (4 K), considering methods of testing and calibration, thermal behavior during the various stages of testing, and correlations between Charpy absorbed energy and quantitative toughness parameters. Because of the very low specific heats of metals near absolute zero, any surface condensation of gases, convective or conductive heat transfer, or plastic deformation during a test will cause the specimen temperature to rise rapidly. Consequently, valid impact tests of alloys at 4 K can not be performed according to the procedure outlined in ASTM Methods E 23-88. During Charpy tests, the temperature of austenitic steel specimens, initially at or near 4 K, may in fact rise outside the cryogenic regime. Fracture does not occur at the intended temperature, but at an uncontrolled temperature, since materials with different work hardening rates heat differently. In view of the temperature rise variability and scatter in measurements and property correlations, we conclude that it is not possible to accurately estimate the 4 K fracture toughness of ductile steels, or rank them properly, using Charpy tests.


    Paper ID: JTE12527J

    DOI: 10.1520/JTE12527J

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    Author
    Title Charpy Impact Tests Near Absolute Zero
    Symposium , 0000-00-00
    Committee E28