Numerical and experimental study of ratcheting in cold expanded plate of Al-alloy 2024-T3 in double shear lap joints

摘要

In this paper strain ratcheting in cold expanded flat plate of Al-alloy 2024-T3 in double shear lap joints was studied both experimentally and numerically. In the experimental part, two types of symmetric strain-controlled and asymmetric stress-controlled cyclic tests were performed. Also, the cold expanded double shear lap joints subjected to cyclic stress-controlled tests. The required parameters for simulating the cyclic plastic behaviour of Al-alloy 2024-T3 were obtained on the basis of the experimental responses. In the numerical part, a combination of nonlinear isotropic and nonlinear kinematic hardening model (Chaboche) was implemented in the commercial finite element code of ABAQUS, using the subroutine UMAT written in FORTRAN. The results of simulations give an accurate prediction of ratcheting for all types of loading. The obtained results show that increasing the mean stress increases the strain ratcheting. It is clearly shown that the cold expansion process decreases the magnitude of strain ratcheting remarkably compared with "as drilled" specimens and the decrease is bigger for larger cold expansion sizes. Also, it is shown that the middle plane has the highest amount of ratcheting compared to the pin entrance plane and exit plane of the plate hole.