Volume 1, Issue 10 (November 2004)
Overload Effects in Aluminum Alloys: Influence of Plasticity and Environment
This paper presents the behavior of selected aluminum alloys when subjected to a single overload, with an aim to highlight the effects of plasticity and environment. The delaying effect of a single overload is given in terms of number of delay cycles. The delay behavior is systematically compared with the constant amplitude crack growth resistance. It is shown that for most of the studied alloys, a strong parallel can be drawn between the constant amplitude crack growth behavior and the overload induced delay. Delay induced by an overload in vacuum is higher than that in air for the 7075 and the 2024 alloys, compatible with stronger constant amplitude crack growth resistance in vacuum. The influence of the elastic-plastic behavior is stronger in vacuum than in air. In the case of the Aluminum Lithium alloy, delay in air is higher than that in vacuum, which is opposite to the behavior under constant amplitude loading. The basic mechanisms governing crack growth in aluminum alloys and their influence on the delay induced by an overload are revealed. The experimental results are compared with a phenomenological model, taking into account the cyclic plastic behavior of materials.