Experimental and numerical analysis of ratcheting in thin Aluminum alloy 2024-T3 plate in low cycle loading

Accumulation of plastic strain during cyclic loading is one of the main reasons for fatigue failure. In order to predict the fatigue life of plates¡ it is necessary to calculate the accumulated plastic strain and the affecting parameters carefully. In this study¡ a combination of nonlinear isotropic and nonlinear kinematic hardening model (modified Choboche) was implemented in the commercial finite element code of ABAQUS¡ by using a FORTRAN subroutine to calculate the accumulation of strain in samples made from thin plates of aluminum. In this regard experimental¡ strain controlled and stress controlled cyclic tests were carried out¡ and the required coefficients for simulating the hardening behavior of aluminum alloy 2024-T3 were obtained and the accumulation of plastic strain was simulated at different uniaxial loading condition. The comparison of the experimental and the predicted results shows that¡ the determination of optimal coefficients for combined nonlinear isotropic and nonlinear kinematic hardening model (modified Choboche)¡ has an adequate ability to predict the experimental results. The obtained results also show that¡ increasing stress amplitude and mean stress increase the strain accumulation. The results from 4 types of cyclic loading indicate that the stress ratio has a direct influence on the strain rate when the maximum applied cyclic load is kept the same¡ and an increase in stress ratio increases the accumulation of plastic strain. Moreover¡ the rate of strain accumulation at the first cycles is high while it is reduced by increasing the number of cycles.