Behaviour Analysis of Pre-Fatigue Damaged Aluminum Alloys Under High-Velocity and Quasi-Static Tension

The following interesting facts are experimentally found. In high velocity tensile loading, the mechanical properties of pre-fatigued Al alloys decrease remarkably, for A2219P-T87 and A7075P-T7351, although they do not decrease for A6061P-T6. In low velocity tensile loading, they do not decrease so clearly even in strongly pre-fatigued materials for all of these three Al alloys.The difference in the sensitivity to high-velocity loading is analyzed from the standpoint of the mechanism of strengthening, that is, precipitation strengthening for the first two alloys and solid solution strengthening for the last one. In conclusion, this difference should be attributed to the effect of dynamic stress concentration in the neighbourhood of precipitates for 2219 and 7075 alloys. On the other hand, no dynamic stress concentration takes place for solid solution strengthened 6061 alloy, under high velocity tension.Theoretical analysis of dynamic stress concentration at the neibourhood of precipitates located in matrix by incident stress wave caused by dynamic tension was made based upon a proposed Dynamic Stress Concentration Fracture model.