STP496: Fracture of Thin Sections Containing Through and Part-through Cracks

    Orange, TW
    Aerospace technologists, Lewis Research Center, National Aeronautics and Space Administration, Cleveland, Ohio

    Sullivan, TL
    Aerospace technologists, Lewis Research Center, National Aeronautics and Space Administration, Cleveland, Ohio

    Calfo, FD
    Aerospace technologists, Lewis Research Center, National Aeronautics and Space Administration, Cleveland, Ohio

    Pages: 21    Published: Jan 1971


    Abstract

    Current fracture mechanics theory is used to illustrate the effects of crack dimensions and material properties on fracture stresses for through-thickness and part-through cracks. The implication of the analysis for leak-before-burst design of pressure vessels is discussed.

    The applicability of plane strain theory to surface cracks in thin metal sections was studied experimentally. Specimens containing surface cracks of various depths and lengths and specimens with through cracks in the same range of crack lengths were tested. Ti-5Al-2.6Sn ELI (0.06 and 0.11 in. (1.6 and 2.9 mm) thick), 2014-T6 aluminum (0.06 in. (1.6 mm) thick), and 2219-T87 aluminum (0.07 in. (1.6 mm) thick) were tested at -423 F (20 K); the 2219-T87 alloy was also tested at +70 and -320 F (300 and 77 K).

    The fracture tests indicate that, when Irwin's plastic zone size is less than about one tenth of the uncracked ligament depth (thickness minus crack depth), surface crack fracture behavior is in agreement with plane strain theory. When the plastic zone is greater than the ligament depth, fracture stresses for surface crack specimens are nearly the same as for specimens with through cracks of the same original length.

    Keywords:

    fracture mechanics, fracture strength, cracking (fracturing), aluminum alloys, titanium alloys, plastic properties, crack propagation, strains, stresses, fracture tests, cryogenics


    Paper ID: STP26929S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP26929S


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