Symmetric and Asymmetric Rolling Pure Copper Foil: Crystal Plasticity Finite Element Simulation and Experiments

A systematic study has been conducted aiming to attain an insight into the influence of coefficient of roll speed asymmetry, crystal orientation and structure on the deformation behavior, and crystallographic orientation development during foil rolling. Simulations were successfully carried out by using crystal plasticity finite element method（CPFEM）,and a novel computational framework is presented for the representation of virtual polycrystalline grain structures. It has been found that asymmetric rolling（ASR） is more efficient in producing plastic deformation since it develops additional shear strain and activity of slip system compared with symmetric rolling（SR）. For ASR, increase in the length of the shear zone, and decrease in the amount of the pressure and roll force would lead to further reduction. The shear strain path in SR and ASR is strictly influenced by the misorientation of neighbor grains, and corresponding {1 1 1} pole figures offer direct evidence of the spread of crystallographic orientation around the normal direction. The activity of slip systems was examined in detail and found that the predicted results are consistent with the surface layer model. The accuracy of the developed CPFEM model is verified by the fact that the simulated results of roll force coincide well with the experimental results.

Analysis on Shear Deformation for High Manganese Austenite Steel during Hot Asymmetrical Rolling Process Using Finite Element Method

Based on the rigid-plastic finite element method（FEM）, the shear stress field of deformation region for high manganese austenite steel during hot asymmetrical rolling process was analyzed. The influences of rolling parameters, such as the velocity ratio of upper to lower rolls, the initial temperature of workpiece and the reduction rate, on the shear deformation of three nodes in the upper, center and lower layers were discussed. As the rolling parameters change, distinct shear deformation appears in the upper and lower layers, but the shear deformation in the center layer appears only when the velocity ratio is more than 1.00, and the absolute value of the shear stress in this layer is changed with rolling parameters. A mathematical model which reflected the change of the maximal absolute shear stress for the center layer was established, by which the maximal absolute shear stress for the center layer can be easily calculated and the appropriate rolling technology can be designed.

Effects of Process-Induced Voids on the Properties of Fibre Reinforced Composites

It is well known that voids have detrimental effects on the performance of composites. This study aims to provide a practical method for predicting the effects of process induced voids on the properties of composites. Representative volume elements （RVE） for carbon fibre/epoxy composites of various fibre volume fractions and void contents are created, and the moduli and strengths are derived by finite element anal- ysis （FEA）. Regression models are fitted to the FEA data for predicting composite properties including tensile, compressive and shear. The strengths of composite laminates including tensile strngth and interlaminar shear strength （ILSS） are calculated with the aid of the developed models. The model predictions are compared with various experimental data and good agreement is found. The outcome from this study provides a useful optimisation and robust design tool for realising affordable composite prod- ucts when process induced voids are taken into account.