Use of Precracked Specimens in Stress Corrosion Testing of High Strength Aluminum Alloys

Abstract

Abstract Resistance to stress corrosion cracking of 10 high strength aluminum alloys in a variety of heat treatment conditions has been measured using precracked double cantilever beam (DCB) specimens. A new technique is described, and stress corrosion crack growth rates for the alloys tested are presented as a function of the plane-strain stress intensity KI. Crack growth rates for alloys in the T3 and T6 tempers showed both KI-independent and KI-dependent behavior, whereas alloys in the more resistant tempers showed only KI independent behavior over the KI range studied. Double cantilever beam specimen data correlated with established trends from smooth specimens tested by alternate immersion in 3.5% NaCl solution. From the crack growth rate data and the speed and simplicity with which it is obtained, it is concluded that the DCB specimen will be highly useful for (1) comparing and rating alloys, (2) developing new alloys and heat treatments, (3) comparing the effects of environments, (4) achieving or ensuring product uniformity, and (5) studying mechanisms of cracking.