EVALUATION OF HIGHT PURITY ALUMINIUM AFTER ASYMMETRIC ROLLING AT AMBIENT AND CRYOGENIC TEMPERATURES

<p class="AMSmaintitle"><span lang="EN-US">Ultrafine grained materials are capable of superplastic elongation at strain rates faster than those currently employed for commercial superplastic forming operations. However, such operations require the material in the form of thin sheets. Asymmetric rolling (ASR), as one of severe plastic deformation (SPD) methods, was used to make ultra-fined grain materials with enhanced performance. This work show effect of the deformation paths on micro-hardness and mechanical properties changing during asymmetric rolling of pure aluminium. In our case, the asymmetric condition was introduced by using different diameters with a ratio of upper and bottom roll 2,4. The thickness of samples was reduced about 20% - 40% at ambient temperature and at cryogenic temperature. Asymmetric rolling at cryogenic temperature (ASR-C) provides greater strength tensile properties than rolling at ambient temperature (ASR-A). </span></p>

Dynamic FE Analysis for Reducing the Flat Areas of Formed Shapes Obtained by Roll Bending Process

Roll bending is a continuous forming process where plates, sheets, beams, pipes, and even rolled shapes and extrusions are bent to a desired curvature using forming rolls. Over the years, with the advantages such as reducing setting up time, the cost in tooling investment and equipment, the roll bending process was fundamental for manufacturing cylindrical shapes. However, the process always leaves a flat area along the leading and trailing edges of the workpiece. Therefore, accuracy could be a challenge when the part to be produced is large and made of high strength steel. There are several methods to minimize the flat area. Among them, for the asymmetrical configuration, moving slightly the bottom roll along the rolling direction may have the highest effect. On the other hand local adjustment of the bottom roll location is also important for providing the pressure needed for gripping and carrying the workpiece through the rolls. Then by optimizing the vertical displacement of the bottom roll one can minimize the span of flat areas. The main objective of this research is to assess 3D dynamic Finite Element (FE) model with Ansys/LS-Dyna for the simulation and analysis of the deformation of the workpiece during the manufacturing of cylindrical parts. Various dynamic simulations based on 3D element are performed to provide better understanding of the whole deformation history and to establish the relationship between the location of the bottom roll and the end shapes of the formed cylinders. The results from FE simulations are then compared with corresponding experimental results from an industrial roll bending machine in order to improve the quality of the final shape.

Factors Affecting Curling in Rolled Sheet

The influence of several rolling parameters on curling during the rolling of sheet was investigated. The material studied was primarily 0.5 in. thick 2024 aluminum. The factors studied were different top and bottom roll diameters, differential strength through the thickness of the sheet, lubrication, roll-table height, reduction ratio, temperature, roll speed, and a beveled leading edge. The sheet curled toward the smaller roll, away from the better lubricated side, toward the strong side if one side was stronger than the other, and up when the entrance roll table was too high. Curling increased for greater reductions (under the conditions studied) and also increased slightly with increasing temperature. Curling was not sensitive to roll speed or a beveled leading edge. The curling observed can generally be explained on the basis of a shear in the roll gap because of different locations of the neutral points along the arcs of contact for the two rolls. Curling observed when one side of the sheet is significantly softer than the other appears to be due to greater elongation of the soft side during rolling.