Quantitative prediction of textures in aluminium cold rolled to moderate strains

Two aluminium plates with different hot band textures were cold rolled to moderate thickness reductions (55 and 60%). The formation of a rolling texture was analyzed quantitatively by focusing on crystallographic fibers in the orientation distribution function. These measurements served to test several polycrystal plasticity theories that rely on different assumptions on how individual grains perceive the macroscopically exerted load. It was found that N-site models in which each grain interacts with a specific neighborhood, yield improved predictions of rolling textures compared to ‘full constraints’ and ‘relaxed constraints’ Taylor models. The β-fiber representing stable lattice orientations was reproduced satisfactorily by the N-site models but none of the models captured the behavior of grains initially oriented near {0 0 1}〈1 0 0〉. The latter is perhaps attributable to the fact that the continuum theories evaluated do not account for the fragmentation mechanisms active in such grains

Comparison of two grain interaction models for polycrystal plasticity and deformation texture prediction

The reader is briefly reminded that there are no models, yet available, capable of truly quantitative deformation texture predictions for arbitrary strain paths, although such models are clearly needed for accurate finite element (FE) simulations of metal forming processes. It is shown that for cold rolling of steel, the classical models (full-constraints and relaxed constraints Taylor, self-consistent) are clearly outperformed by new 2-point or n-point models, which take grain-to-first-neighbour interactions into account. Three models have been used: the 2-point “Lamel”-models (two variants) and the micromechanical finite element-model developed by Kalidindi et al. (J. Mech. Phys. Sol. 40 (1992) 537). Extensive comparisons of the results of the Lamel-model with experimental data has been published before (by Delannay et al. (J. Phys. IV France 9 (1999) 43) and van Houtte et al. (Textures and Microstuctures 31 (1999) 109). Emphasis of the present paper is a confrontation of the Lamel model with the micromechanical finite element-model. It was found that for the case study at hand, the solutions of each model can be regarded as approximations of the solutions of the other. It is, however, believed that the FE-model would really be able to produce reference results (macro and micro deformation textures) if more elaborate meshes are used that describe the microstructure more closely

Special issue in honor of Lallit Anand

10.1016/j.ijplas.2010.06.001International Journal of Plasticity2681071-1072IJPL

A disclination-based model for grain subdivision

Grain subdivision under cold rolling of fcc polycrystals is modelled by formulating evolution equations for the statistically stored dislocation densities (cell structure), the propagating partial disclination dipole densities, and the immobile partial disclination densities (cell block structure) at the slip system level. The development of the mean cell and cell block sizes and of the mean misorientations across the cell block boundaries (cbb) is predicted for several grain orientations. Two types of grain subdivision were distinguished, cube, rolling direction (RD)- and transverse direction (TD)-rotated cube oriented grains showed a finer subdivision and nearly no spread of misorientation between the cbb families, while Goss, brass and S-oriented grains showed a coarser subdivision and a significant spread of the misorientations. Copper oriented grains exhibit an intermediate behaviour. The predictions of the model for the evolution of the cell and cell block sizes are in reasonable agreement with experimental results

Modelling of the evolution of dislocation sheets during strain-path changes and their influence on the Bauschinger effect of B.C.C. polycrystals

An extension of a full-constraints Taylor model is presented which captures substructural dislocation features, e.g. cell boundaries and cell-block boundaries. This allows coupling the anisotropy due to slip processes, texture and substructure. The extended Taylor model is used to study the dislocation sheets during reverse tests. The evolution of these structures in crystals with stable/unstable orientation is discussed in the context of the Bauschinger effect observed during reverse tests