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    STP1256

    Orientation Effects on the Measurement and Analysis of Critical CTOA in an Aluminum Alloy Sheet

    Published: 01 January 1995


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    Abstract

    Fracture tests were conducted on 76.2mm wide, 2.3mm thick middle crack tension (M(T)) specimens machined from 2024-T3 aluminum sheet. The specimens were tested in the T-L orientation and comparisons were made to similar tests conducted in the L-T orientation. Measurement of critical crack tip opening angle (CTOA), applied stress, and crack front shape were made as a function of crack extension. A two-dimensional, elastic-plastic finite element analysis was used to simulate the fracture behavior for both orientations. The results indicate that the T-L orientation had a 10% lower stress at fracture than similar tests conducted in the L-T orientation. Correspondingly, the critical CTOA in the T-L tests reached a constant value of 4.7° after 2–3mm of crack extension and the L-T tests reached a value of 6°. The fracture surface of the T-L specimens were observed to remain flat, while those of the L-T specimens transitioned to a 45° slant fracture after about 2–3mm of crack extension. The tunneling behavior of the two orientations also differed; the T-L specimens reached a deeply tunneled stabilized crack front shape, while the L-T specimens were observed to have only a small amount of tunneling once the crack began to grow on the 45° slant. The two-dimensional, elastic-plastic finite element analysis was able to simulate the fracture behavior for both the T-L and L-T orientations.

    Keywords:

    Fracture, stable crack growth, CTOA, thin sheet, rolling orientation, experimental data


    Author Information:

    Sutton, MA
    Professor, University of South Carolina, Columbia, SC

    Dawicke, DS
    Senior Scientist, Analytical Services and Materials, Inc., Hampton, VA

    Newman, JC
    Senior Scientist, NASA Langley Research Center, Hampton, VA


    Committee/Subcommittee: E08.04

    DOI: 10.1520/STP16387S