Effects of initial overload on the fatigue crack initiation and growth in notched plates

This paper studies the initial overload effects on the stages of the crack initiation and its growth under fatigue loads in v-notched plates. V-notched samples made of aluminum alloy 2024-T3 were overloaded with different values. These specimens went under fatigue loads with various constant amplitudes and their fatigue behaviors were investigated. Numerical analysis in finite element software with a proper crack growth law was used to estimate the crack initiation cycles to reach a specified length and also crack growth rates and propagations. The superposition principle was employed for considering the effects of the applied and residual stresses on the stress intensity factor ranges. For validation, the estimated results were compared with experimental data which showed good agreement. Results show that the crack initiation lives were increased significantly after an overload cycle due to retardation of micro-cracks creation around the notch root. Compressive residual stresses in comparison with the tensile stresses are dominant in the affected area by the overloads.