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Abstract: Rolling is the most appropriate process to produce a severe plastic deformation in the sheet or plate type of materials. Compared to symmetric rolling, asymmetric rolling is more efficient in producing plastic deformation since it develops additional shear strain for a given reduction in thickness. In the present investigation, various asymmetric rolling processes were analyzed by the rigid-viscoplastic finite element method. The results of the analyses were compared to each other in terms of plastic deformation: effects of asymmetries due to the differences in size, rotational speed and frictional condition between upper and lower rolls. Rolling pressure distribution, rolling force and rolling torque were also compared. [Copyright &y& Elsevier]

Abstract: Rolling is an effective method used to impose a large amount of plastic deformation to metallic materials in a form of sheet. As the plastic deformation increases at appropriate temperatures, the grains become smaller in size and the mechanical properties of the sheet are improved. A recent study found that the grains of magnesium alloy AZ31 sheets are recrystallized and reduced to 3μm in diameter by a differential speed rolling at an elevated temperature. The present study analyzed the thermo-mechanical processes occurring in the sheet during differential speed rolling by the rigid-thermoviscoplastic finite element method. Findings include a significant increase of plastic deformation by severe shear deformation, a notable increase of temperature by plastic deformation as well as by friction, and an incredible decrease of rolling force by low hydrostatic stress in magnitude at the deformation zone. [Copyright &y& Elsevier]

Abstract: Rib-web type aerospace and aircraft components in general have small fillet and corner radii with zero draft angles. In precision forging of such a component, the preform should be designed with a great care in order to produce appropriate metal flows. An improper preform invokes defects of underfilling and folding in the component with excessive stresses and wears in the forging equipments and dies. In the present study, it was attempted to design the preform for precision forging of an asymmetric rib-web component by predicting metal flows with the rigid-plastic finite element analysis. It was found that the key to the preform design is a proper distribution of the material, which was successfully achieved by a thorough investigation of metal flow and volume change from the result of the finite element analysis. [Copyright &y& Elsevier]

Abstract: Deformation mechanics of differential-speed rolling with a high speed ratio between the upper and lower rolls, which was found to be effective in producing very fine-grained microstructure in Mg–3Al–1Zn sheets, has been investigated by means of the rigid-plastic finite element method. The shear strain (3.1) takes a great portion of the total effective strain (∼3.5) in average. The magnitude of total effective strain is equivalent to that obtained by equal channel angular pressing on rods after 3–4 passes. [Copyright &y& Elsevier]

In the present investigation, it was attempted to design the rolling pass schedule for a thick plate of 0.1C–1.5Mn–0.25Si with the objective of the austenite grain refinement. As the method of approach for the design, a mathematical modeling technique was proposed which consists of a recrystallization model and a flow stress model. The validity of this coupled model was examined by comparing with continuous and discontinuous compression tests under various conditions. The coupled model was incorporated with the finite element method to establish a systematic design methodology for the rolling pass schedule toward the refinement of austenite grains. Two pass schedules were obtained and discussed in the paper with regard to rolling pass time, average grain size, grain size deviation in thickness, etc. [Copyright &y& Elsevier]