Fracture toughness characterization of several aluminum alloys in semi-brittle fracture |
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Authors: | DL Jones H Liebowitz J Eftis |
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Affiliation: | School of Engineering and Applied Science, The George Washington University, Washington, D.C. 20006, U.S.A. |
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Abstract: | A method has recently been developed for determining a nonlinear fracture toughness parameter defined by the relation where Gc is the critical elastic strain energy rate as defined by Irwin. The term is a function of the nonlinearity of the load-displacement test record and has been evaluated using the three parameter Ramberg-Osgood approach, although other curve fitting techniques could be applied as well. The method is quite straightforward and is applicable to plane stress, plane strain and mixed mode testing although only plane stress conditions are considered in this paper. For the case of a linear load-displacement record and reduces to the linear elastic result.The toughness parameter has been evaluated for a number of high strength aluminum alloys and compared with published Gc values for these materials. The tests were conducted on center-cracked sheets of 2014-T6, 2024-T81, 7075-T6 and 7475-T61 aluminum alloys under conditions of varying specimen geometry and displacement gage length. It was found that the values of obtained from displacement readings with a gage length of 2 in. generally agreed with published values of . The values were found to vary inversely with gage length and a/w ratios. The variation in values for is of the same order of magnitude as the scatter in published values for Gc. However, appears to be less sensitive than Gc to changes in a/w. |
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