Length changes during free end torsion: A rate sensitive analysis

Abstract A rate sensitive crystal plasticity model of the Sachs type is introduced for the simulation of free end torsion testing. The lattice spins are calculated and an example of the rotation field is displayed in Euler space. The orientation stability map (OSM) corresponding to a rate sensitivity of m = 0.125 is presented for the free end torsion of a thin walled tube. The effect of rate sensitivity on the stability of the main ideal orientations is derived. The model is employed to simulate the textures developed and length changes observed in free end torsion. With the aid of a length change map in Euler space and of the cloud model of texture development, lengthening and shortening are explained in terms of the low strain anti-shear and high strain shear-parallel asymmetries of the free end fibres.

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