Numerical analyses of surface roughness during bending of FCC single crystals and polycrystals

Bending is a common strain path observed in various metal forming operations. In this paper, a rate-dependent crystal plasticity model is incorporated into the commercial software LS-DYNA to analyze the effect of five common Face Centered Cubic (FCC) crystal orientations on the surface roughness developed during bending. Single crystals and polycrystals are modeled and the developed surface roughness is quantified. The models treat single crystals as a range of orientations that lie within 10 degrees of the specified orientation, mimicking the many subgrains that form during the deformation of aluminum single crystal. Polycrystals are treated in the same fashion but instead contain a mix of specified orientations of different texture components of rolled aluminum sheets. Second derivative surface roughness calculations are done both perpendicular and parallel to the bend axis. The simulations reveal that the presence of the Brass and S orientations greatly increases surface roughness. Surface roughness is seen to correlate well with a lack of strain accommodating capability of texture.