A material model for warm forming of aluminium sheet


Boogaard, A.H. van den and Bolt, P.J. (2003) A material model for warm forming of aluminium sheet. In: VII International conference on computational plasticity, COMPLAS, April 7-10, 2003, Barcelona, Spain.

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Abstract:A material model has been developed to simulate the warm forming of Al–Mg
sheet. Both the hardening behaviour, including temperature and strain rate effects, and the
biaxial stress–strain response of the sheet are considered. A physically-based hardening model
according to Bergström is used. This model incorporates the influence of the temperature
and strain rate on the flow stress and on the hardening rate based on dynamic recovery. For
deformations at constant temperature and strain rate, the Bergström model reduces to the well
known Voce hardening model. The Bergström/Voce models can be fitted quite well to the results
of monotonic tensile tests of an AA 5754-O alloy.
The biaxial stress–strain response of the material is experimentally determined by uniaxial,
plane strain, simple shear and equi-biaxial stress tests. It is demonstrated that the widely used
Hill ’48 yield locus is inappropriate for simulation of deformation of aluminium. The low Rvalues
for aluminium lead to a significant underestimation of the equi-biaxial yield stress. In
the simulation of the deep drawing of a cylindrical cup this results in a much too thin bottom of
the cup. The Vegter yield criterion is sufficiently flexible to accurately represent the shape of the
yield locus and the anisotropy.
Item Type:Conference or Workshop Item
Engineering Technology (CTW)
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