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    Use of Portable/in situ Stress-Strain Microprobe System to Measure Stress-Strain Behavior and Damage in Metallic Materials and Structures

    Published: 01 January 1997

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    A novel portable/in situ Stress-Strain Microprobe (SSM) system was used to measure true-stress/true-plastic-strain (σtp) behavior of several met llic materials, welds, and their heat-affected-zones (HAZs) in various metallurgical and damage conditions. The SSM system utilized an automated ball indentation (ABI) technique to measure elastic modulus, yield strength, σtp curve, strength coefficient, strain-hardening-exponent (uniform ductility), and to estimate fracture toughness (from the ABI-measured flow properties) in carbon steels, stainless steels, nickel alloys, aluminum alloys, titanium alloys, zirconium alloys, etc. Numerous ABI tests were also conducted on several nuclear pressure vessel steels (NPVSs) in the unirradiated, neutron irradiated, and post-irradiated thermally-annealed conditions. For all these test materials and conditions, the ABI-derived results were in good agreement with those from conventional standard test methods. Furthermore, the nondestructive ABI test results rigorously indicated the various levels of neutron-embrittlement damage and the percentage of ductility recovery following thermal annealing of the NPVS specimens. In situ/nondestructive structural applications of the SSM system and its ABI technique have been demonstrated by testing a circumferentially welded stainless steel pipe and a full-thickness section of a nuclear pressure vessel (using 90° V-blocks and magnetic mounts for temporary attachment of the SSM testing head to the pipe and the steel section, respectively). All SSM localized tests were computer-controlled and conducted in less than 2 minutes per ABI test; depending on the desired strain rate. Example test results on metallic structural components and samples are presented in this paper.


    nondestructive, in situ, structural integrity, ball indentation, partial unloading, welds, heat affected zone, yield strength, flow properties, metals

    Author Information:

    Haggag, FM
    President, Advanced Technology Corp., Oak Ridge, TN

    Wang, JA
    Research Scientist, Oak Ridge National Laboratory, Oak Ridge, TN

    Sokolov, MA
    Research Scientist, Oak Ridge National Laboratory, Oak Ridge, TN

    Murty, KL
    Professor, North Carolina State University, Raleigh, NC

    Committee/Subcommittee: E08.04

    DOI: 10.1520/STP11894S