STP496

    Influence of Specimen Design in Plane Strain Fracture Toughness Testing

    Published: Jan 1971


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    Abstract

    The influence of specimen design on plane strain fracture toughness (KIc) was studied by fracturing 2219-T87 aluminum and 5Al-2.5Sn ELI titanium alloy single-edge notched bend (SENB), single-edge notched tension (SENT), compact tension (CT), and surface flawed (SF) specimens at 72 F (295 K) in laboratory air, at -320 F (78 K) in liquid nitrogen, and at -423 F (20 K) in liquid hydrogen. Specimen thickness for all SENB, SENT, and CT specimens except titanium/room air specimens was approximately 2.5(KIcys)2 in. Specimen thickness for SF specimens ranged from 2.5(KIcys)2 to 0.25(KIcys)2. Relative orientations of crack propagation and rolling directions were identical in all specimens of a given alloy. For aluminum alloy specimens having thicknesses of 2.5(KIcys)2, SENB, SENT, and SF specimen tests yielded consistent fracture toughness values at all test temperatures whereas CT specimen tests always yielded lower fracture toughness. For titanium alloy specimens having thicknesses of 2.5(KIcys)2, SENB, SENT, CT, and SF specimen tests yielded consistent fracture toughness values at -423 F (20 K); at -320 F (78 K), fracture toughness values from SF specimen tests were significantly greater than those obtained from tests of other specimen types; at 72 F (295 K) no valid fracture toughness data were obtained. Both aluminum alloy SF specimen tests yielded consistent fracture toughness (KIE) values when both flaw depth and distance between flaw tip and back specimen face exceeded 0.5(KIEys)2.

    Keywords:

    aluminum alloys, titanium alloys, fractures (materials), toughness, fracture strength, bending, tension tests, fracture tests, failure, stresses, cracking (fracturing), cryogenics, liquid hydrogen, liquid nitrogen, aerospace engineering


    Author Information:

    Hall, LR
    Senior specialist engineer, The Boeing Company, Seattle, Wash.


    Paper ID: STP26928S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP26928S


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