Simulation of the ductile tearing for two grades of 2024 aluminum alloy thin sheets
Résumé
The purpose of this work is to develop a finite-element simulation of ductile tearing tests carried out on aerospace aluminum alloys using continuum damage mechanics. The model is applied to two similar 2024 alloy thin sheets containing different amounts of intermetallic particles. The materials are characterized using small specimens (smooth and notched bars, Kahn specimens) and large M(T) panels. Observations show that, in severely notched samples, crack initiation is “flat” whereas crack propagation is “slanted”. The simulation is based on an extension of the Rousselier model which includes the description of plastic anisotropy and void nucleation around second phase particles. The model parameters are adjusted in the case of the material containing the lowest amount of intermetallic particles to represent continued crack propagation as well as the overall plastic behavior, without modeling the fact that the crack is slanted. The model is adjusted on small specimens and the transferability of the model is checked on M(T) panels. It is shown that such large panels present a certain amount of buckling despite the use of an anti-buckling device. Apart from buckling, prediction of load and crack advance is good. The transfer of the model parameters to the material containing the highest amount of particles is made by modifying the mesh size according to the ratio of the particle mean spacing as the materials have very similar behaviors. This methodology is shown to be satisfactory. Finally, the model is used as a numerical tool to investigate the effects of plastic hardening, prestraining and plastic anisotropy on crack growth resistance.