CENTRAL HOLE SIZE INFLUENCES A FATIGUE CRACK BEHAVIOR OF Al7050-T6 ALLOY

This research studied experimentally the behavior of an aluminum alloy 7050 thin plate containing different sizes of circular central holes under thermo-mechanical fatigue crack growth testing. Transient thermal cyclic loading from 50℃ to 200℃ where applied, combined with constant tensile mechanical load at 200 kg at the edge of the plate. Three cases were experimentally tested based on the hole diameter of (1, 2, 3 mm) under the same testing conditions. Results show the increment of central hole diameter makes the crack initiation start earlier and crack growth increases then goes faster. Also, it has increased the stress intensity. The length of the second region of crack propagation related to stress intensity decreased when the hole size increased, and the slope changed too. For that, different Paris laws were obtained based on the central hole size. Accordingly, to these Paris laws, it can be easily informed and analyzed the behavior of any engineering structure made of this type of alloy under the same loading condition and predict its fracture or failure limits or lives.