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Application of the J Integral to Crack Initiation in a 2024-T351 Aluminum Alloy,
NAVAL RESEARCH LAB WASHINGTON D C
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The J integral has been successfully applied as a fracture initiation criterion for 2024-T351 aluminum alloy. A heat-tinting technique was used for quantitative measurement of crack extension at selected points on the load-deflection curve. In three-point bend tests incorporating six specimen configurations the critical J values JIc at the onset of crack movement differ by at most 15 percent and yield a mean KIc value of 30.9 plus or minus 1.2 ksiin. superscript 12. The relationship between instantaneous J value and crack extension is independent of initial crack length over the range of crack sizes investigated. J-integral values associated with maximum load 5 to 15 percent crack growth, unlike JIc, show a strong dependence on specimen thickness. Author
APPROVED FOR PUBLIC RELEASE