Abstract :
[en] The effect of triaxiality on the evolution of damage in Al-2024 aluminum cylindrical
specimens is studied in this work. Uncoupled and coupled damage models, all of them explicitly
dependent on triaxiality, are assessed and compared. These models are characterized by tensile
tests on cylindrical specimens without notches, to obtain the material parameters for each model.
The capability of each model to predict fracture when different positive triaxial conditions evolve
is then evaluated through tensile tests on notched cylindrical specimens. In particular, the damage
index, evaluated at the fracture strain level, is compared with the experimental results validating the
models. Moreover, the triaxiality evolution in the different specimens is studied in order to assess
its effect on damage, demonstrating that the fracture strain decreases at greater triaxiality values.
Observations through scanning electron microscopy confirm this pattern; i.e., an increase in triaxiality
reveals a shift in the fracture mechanism from a more ductile condition in the original specimens to a
more brittle one as the notch radius decreases. In addition, bilinear damage evolution is proposed to
describe the physical behavior of the material when the Lemaitre coupled model is considered. In
such a case, special attention must be devoted to the material characterization since coupling between
hardening material parameters and damage affects the results.
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