Influence of initial texture on formability of aluminum sheet metal by crystal plasticity FE simulation

摘要

Plastic anisotropy (earring) inherent in textured aluminum sheet metal is investigated based on the crystal plasticity and using the dynamic explicit finite element program developed. By means of X-ray technique, texture analyses are carried out for sheet metals of Al-2.5% Mg aluminum alloy A5052 obtained at different annealing temperatures. The corresponding orientation distribution function (ODF) representations show clearly the characteristic feature of rolling textures and their transition from brass to cube before and after annealing, respectively, which are accountable for the occurrence of earrings. By employing the texture coefficients an analytical expression for the orientation distribution function (ODF) is reconstructed making use of the computer algebraic language Mathematica 5.0, which makes it possible for the integration over volume element in Euler angular space to be performed at high numerical precision, yielding an alternative form of ODF in terms of discretized Euler angles set. For the polycrystal model, the materials are described using the rate-dependant crystal plasticity where each material point in the sheet is assumed to be a polycrystalline aggregate of a large number of FCC grains with each grain modelled as an FCC crystal with 12 distinct slip systems. The modified Taylor theory of crystal plasticity is used with initial textures employed as input and their evolution taken into consideration during large plastic deformations. The numerical simulation of anisotropy (earring) has been performed for the above treated aluminum sheet metals to demonstrate the effect of initial texture of materials on their plastic anisotropy and formability.