STP1072: Influence of Thermal Conditioning Media on Charpy Specimen Test Temperature

    Nanstad, RK
    consultant, Oak Ridge National Laboratory, Oak Ridge, Tennessee

    Swain, RL
    consultant, Oak Ridge National Laboratory, Oak Ridge, Tennessee

    Berggren, RG
    consultant, Oak Ridge National Laboratory, Oak Ridge, Tennessee

    Pages: 16    Published: Jan 1990


    Abstract

    The Charpy V-notch (CVN) impact test is used extensively for determining the toughness of structural materials. Research programs in many technologies concerned with structural integrity perform such testing to obtain Charpy energy vs temperature curves. American Society for Testing and Materials Method E 23 includes rather strict requirements regarding determination and control of specimen test temperature. It specifies minimum soaking times dependent on the use of liquids or gases as the medium for thermally conditioning the specimen. The method also requires that impact of the specimen occur within 5 s of removal from the conditioning medium. It does not, however, provide guidance regarding choice of conditioning media. This investigation was primarily conducted to investigate the changes in specimen temperature which occur when water is used for thermal conditioning. A standard CVN impact specimen of low-alloy steel was instrumented with surface-mounted and embedded thermocouples. Dependent on the media used, the specimen was heated or cooled to selected temperatures in the range-100 to 100°C using cold nitrogen gas, heated air, acetone and dry ice, methanol and dry ice, heated oil, or heated water. After temperature stabilization, the specimen was removed from the conditioning medium while the temperatures were recorded four times per second from all thermocouples using a data acquisition system and a computer. The results show that evaporative cooling causes significant changes in the specimen temperatures when water is used for conditioning. Conditioning in the other media did not result in such significant changes. The results demonstrate that, even within the guidelines of E 23, significant test temperature changes can occur which may substantially affect the Charpy impact test results if water is used for temperature conditioning.

    Keywords:

    acetone, air, charpy V-notch, cooling rate, evaporation, methanol, nitrogen gas, oil, thermal conditioning, water


    Paper ID: STP24146S

    Committee/Subcommittee: E28.94

    DOI: 10.1520/STP24146S


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