Small Crack Growth Behavior in Long Life Regime Of Aluminum Alloy 2017

It is generally known that the fatigue phenomenon of non-ferrous metals such as aluminum alloys are somewhat different from those of carbon steels. For example, it has been said that the knee point of S-N curve and non-propagating cracks do not appear in these metals. However, the exact meaning of these phenomenon still seems ambiguous growth behavior at the apparent fatigue limit (defined for N=2×107) and fatigue strength was investigated using aluminum alloy 2017 (aged and annealed). In annealed and aged aluminum alloys, non-propagating cracks can exist after repetition of (25)×107 stress cycles. This suggests the possibility of existence of fatigue limit even in aluminum alloys.