Experimental characterization and theoretical modeling of plastic behavior of rolled metal sheets

Sheet metal forming is an important manufacturing process. Improvement of the forming process for sheet metals has played an important role in the advancement of technology in the twentieth century. The overall objective of the current research is to better understand the effect of rolling on the resultant plastic behavior of sheet metals through a combined experimental and theoretical investigation.; The dissertation consists of three major parts. The emphasis of the first part is on the experimental investigation. A special biaxial loading device and a cruciform specimen were designed to experimentally measure the yield loci of 1100 aluminum sheets corresponding to various rolling conditions. A set of uniaxial tension tests were also performed to determine the plastic properties of the aluminum sheets along various directions with respect to the rolling directions.; In the second part, it is attempted to better understand the cold-rolling process through a micromechanical study. Specifically, the texture development due to cold rolling and the corresponding evolution of yield loci of sheet metals are studied. The dominant deformation mechanism is assumed to be the crystallographic slips in single crystal. The rolling process is simulated as a plane strain compression process with Taylor's microstructural model. The yield loci corresponding to various rolling conditions are determined with the self-consistent method. Results show that these micromechanical models are very successful in predicting the general behavior of sheet metal subject to moderate rolling, but somewhat deficient for deep-rolling conditions probably due to some assumptions underlying the formulations.; In the third part, Hill's 1990 phenomenological yield criterion for in-plane anisotropic sheet metals are evaluated based on both experimentally measured and micromechanically simulated data on the plastic behavior of 1100 aluminum sheet. Through this evaluation, some deficiencies of Hill's model are identified. A modified form is therefore suggested. It is demonstrated that the modified form yields a much better prediction of the plastic behavior of sheet metals without imposing additional mathematical complexities in the characterization of the material parameters in the yield criterion.