The effects of periodic overloads on plastic zone and fatigue crack growth in Al 2024 –T4 using modified Wheeler model

In this paper, the effects of periodic tensile overload onfatigue crack growth rate in CT specimens made of 2024–T4 aluminum alloy were investigated by using the modifiedParis low as well as model proposed by Wheeler. Retardedcrack length following overloads were studied numericallyand validated by experimental results. The coincidencebetween numerical and experimental data in tensileoverload mode, would indicate that the model has highdelicacy. The results depict that there is a direct relationshipbetween the tensile overload and reduction in crack growthrate. However considering the larger radius of plastic zoneat the crack tip and also the residual stresses generated inthe process of applying three overloads on a specimen, leadto more than 26,000 cycles delayed loading in crack growth.The results show that when the sequence between periodicoverloads is a half of delayed cycles in single overload, thecrack growth rate is in its minimum scale.