Influence of Impact-Oscillatory Loading on Fatigue Life of Aluminium Alloy 2024-T351

Dynamic non-equilibrium processes (DNP) caused by impact-oscillatory loading affect the mechanical/structural changes and fatigue life of aluminium alloy 2024-T351 under static tension at a load frequency of 110 Hz. The main patterns of this effect are considered. Dynamic deformation εimp was chosen as the control parameter of DNP. In other words, εimp indicates a sudden increase in the specimen length when an additional impulse load is applied. It has been proven that an increase in εimp causes the occurrence of yield points on static stress–strain diagrams of alloys subjected to impact-oscillatory loading. Ranges of εimp values were found, at which fatigue life of the alloy subjected to DNP under four different modes of cyclic loading can be extended. Loading conditions that do not cause any noticeable DNP effect on the fatigue life of the alloy are analysed, and the reasons for a significant reduction in the fatigue life of the alloy are considered. Aluminium alloy 2024-T351, previously subjected to DNP, was aged in a free state for a long time to extend its cyclic life. The positive effect of DNP and ageing was estimated in this research.