SEDL / STP / STP651-EB / STP26546S

Effect of Specimen Width on Fracture Toughness of Ti-6A1-4V Plate

Hall, GS
Senior research engineer, manager-commercial sales development, and director, Metallurgy and Research, RMI Company, Niles, Ohio

Seagle, SR
Senior research engineer, manager-commercial sales development, and director, Metallurgy and Research, RMI Company, Niles, Ohio

Bomberger, HB
Senior research engineer, manager-commercial sales development, and director, Metallurgy and Research, RMI Company, Niles, Ohio

Pages: 19    Published: Jan 1978

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Abstract

From a group of 96 specimens ranging in thickness from 15 to 38 mm (0.60 to 1.50 in.), a regression equation was obtained for Ti-6A1-4V plate relating the fracture toughness, KQ, of 205-mm (8-in.) wide specimens to the variables of specimen thickness and fracture toughness, KQ, for 76-mm (3-in.) width. The fracture toughness value of Ti-6A1-4V plate can be increased appreciably in thin specimens by using an oversized width specimen. The magnitude of this toughness increase diminishes as the thickness increases and approaches 38-mm (1.5-in.). Oversizing the specimen results in a significant reduction in the stress at instability at 2 percent crack extension. The specimen strength ratio, R^sc, essentially remains the same while K^max and the P^max/P^Q ratio increase.

Crack-growth-resistance curves constructed from load versus crack-opening-displacement curves for the two different width specimens are similar. This indicates the fracture behavior is the same and not altered with increased specimen width. Furthermore, K values for oversized specimens can be calculated from the loads at the appropriate crack extension in smaller standard size specimens, and vice versa.