SEDL / STP / STP559-EB / STP38593S

More on Specimen Size Effects in Fracture Toughness Testing

Kaufman, JG
Manager and senior engineer, Alcoa Laboratories, Aluminum Company of America, Alcoa Center, Pa.

Nelson, FG
Manager and senior engineer, Alcoa Laboratories, Aluminum Company of America, Alcoa Center, Pa.

Pages: 12    Published: Jan 1974

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Abstract

A new study of the effect of specimen size on the results of plane-strain fracture toughness tests of a relatively tough aluminum alloy, 2219-T851, suggests that an increase in specimen size requirements may be necessary to assure size-independent test results. Specifically, it appears that the crack length limit should be increased to 5(K^Ic/σ^YS)², which has the effect of keeping the maximum nominal net-section stress below two thirds of the yield strength. The current limit on thickness could be maintained at 2.5 (K^Ic/σ^YS)², although there is some evidence that it might be relaxed further. Additional work is needed to check the generality of these suggestions for other materials, as well as the possibility that if W/B=2 and a=B ⋝ 5(K^Ic/σ^YS)², K^max, may be useful as an engineering estimate of K^Ic.