A POLYCRYSTAL MODEL TO EVALUATE MECHANICAL PROPERTIES OF ASYMMETRICALLY ROLLED AL SHEETS

Abstract

The asymmetric rolling process (ASR) differs from conventional rolling (CR) through the use of different roll circumferential velocities. Using proper parameters, asymmetric rolling imposes intense shear deformations across the sheet thickness, leading not only to the occurrence of shear texture, but also to grain refinement [1]. Some shear texture components are known to improve plastic strain ratio values, and consequently formability. In Simoes et al. [4], a AA1050-O sheet was asymmetrically rolled and annealed. Shear texture was obtained, as opposed to typical gamma-fiber texture obtained on sheets rolled through the conventional process. Shear tests were used to evaluate strength and formability. A polycrystal plasticity model, as formulated by Gambin [2] and implemented by Alves de Sousa [3], was employed to evaluate texture evolution and to give a sounding theoretical basis for the improved mechanical properties on sheets after the process. For FCC materials, this approach avoids the uniqueness issue related to the choice of the set of active slip systems by applying a regularized Schmid Law. Consequently, it generates yield surfaces with smooth corners where the normal vector is always uniquely defined. In the following sections, implementation guidelines are given. The accuracy of simulation results and the advantages of the asymmetric rolling process, when compared to conventional rolling, are the main topics of discussion.