STP1220: Further Studies of a Modified-Charpy Specimen for Lower-Bound Toughness

    Bonenberger, RJ
    Graduate research assistant and professor, University of Maryland, College Park, MD

    Dally, JW
    Graduate research assistant and professor, University of Maryland, College Park, MD

    Pages: 13    Published: Jan 1995


    Abstract

    A low cost method for determining the lower-bound fracture toughness with a modified-Charpy specimen is described in this paper. The oversized Charpy specimen is face grooved to enhance constraint, and strain gages are used during the impact loading to record the strain-time history at a point near the crack tip. A dynamic photoelastic analysis is employed to determine a suitable relation between the strain and the stress intensity factor Ki during the impact period. Strain-time traces from several specimens are used to develop a master strain-time curve representative of the material considered (A533-B reactor grade steel). This curve is converted to a Ki-t curve using the relation developed from the dynamic photoelastic study. The time corresponding to crack initiation, determined from the original strain gage records, permits the determination of the dynamic initiation toughness Kid, which is a good approximation of the lower-bound toughness.

    Keywords:

    Charpy specimen testing, fracture, fracture toughness (lower bound), impact testing, dynamic photoelasticity, steel (reactor grade)


    Paper ID: STP14600S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP14600S


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