Transient crack growth behavior in aluminum alloys C415-T8 and 2519-T87

摘要

This research focused on the creep crack growth characteristics of two creep-brittle aluminum-copper alloys in sheet form, 2519-T87 (2.921 mm) and its chemical variant C415-T8 (2.286 mm), at 135 and 150℃. Transient crack growth behavior duringwhich the creep crack growth rate does not correlate with K was observed in both aluminum alloys. By utilizing a transition time, tg, concept, the data obtained under transient crack growth conditions were separated from the quasi-steady-state crackgrowth data. In the quasi-steady-state regime, the creep crack growth rates were shown to best correlate with the stress intensity factor; K, for both alloys and test temperatures. The window for steady-state crack growth in creep-brittle materials isdemonstrated to be very narrow, and the proposed condition for steady-state crack growth behavior is that Vc/V≤0.50 and that Vc/ V changes by less than 100% over a crack extension of 0.5 mm. K/r{sub}c{sup}q is investigated as a crack tip parameterapplicable to both transient and steady-state crack growth conditions; however, the experimental difficulties in determining the creep zone size were encountered and are discussed in the paper.