SEDL / STP / STP590-EB / STP33945S

Investigation of R-Curve Using Comparative Tests with Center-Cracked-Tension and Crack-Line-Wedge-Loaded Specimens

Wang, DY
Senior engineer, Douglas Aircraft Co., McDonnel Douglas Corporation, Long Beach, Calif.

McCabe, DE
Senior research metallurgist, Armco Steel Corporation, Middletown, Ohio

Pages: 25    Published: Jan 1976

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Abstract

This paper provides a comparison of the crack-line-wedge-loaded (CLWL) and center-cracked-tension (CCT) test methods for determining R-curves on a number of high-strength aluminum sheet alloys. In general, R-curves were reasonably close, differing only by amounts which could be explained by differences in testing procedure and in crack driving force curve. Gross stress, Kc, and crack length at instability were predicted satisfactorily for CCT panels from CLWL R-curves. The test results for CCT specimens show that consistent Kc values are obtainable from specimens of various widths provided that the net-section stress at failure is below general yielding.