Finite Element Modeling of Shear Strain in Rolling with Velocity Asymmetry in Multi-Roll Calibers

Abstract

Severe plastic deformation is now recognized the most efficient way of producing ultrafine grained metals and alloys. At the present time a lot of severe plastic deformation methods have been proposed and developed. They differ in the deformation schemes. Unlike such severe plastic deformation methods as high pressure torsion and equal-channel angular pressing, rolling with the velocity asymmetry is a continuous process. It helps to solve the problem of the limited length of manufactured bars with semi ultrafine structure. Rolling process with roll velocity asymmetry generates high shear strain necessary for obtaining ultrafine structures of the processed material. A new process of asymmetric rolling of profiles in multi-roll passes has been developed. This process can be used for production of high-strength profiles such as circles, hexagons, wire rods, etc. Compression of the bar in multi-roll passes can be done not only from two, as usual, but from three or four sides. In case of a multi-crimped bar, a uniform compression scheme with large hydrostatic pressure is created in the deformation zone. It enhances the ductility of the material and allows increasing the strain intensity. Simulation in DEFORM 3DTM proved that the process of asymmetric rolling in multi-roll calibers allows to obtain higher values of shear strain and strain effective.

FE Simulation of the Stress-Strain State during Shear-Compression Testing and Asymmetric Three-Roll Rolling Process

“…Previously [12]- [13] it was found that to obtain a high uniform shear strain through the bar thickness during asymmetric three-roll rolling process is necessary: 1) very high contact friction; 2) high elongation ratio; 3) speed ratio of rolls should be equal to elongation ratio per pass. Schematic illustration of the asymmetric threeroll rolling process in a stand with two three-roll calibers located very close to each other is shown in Fig.…”

“…Contrary to other SPD methods such as high pressure torsion and equal channel angular pressing, the asymmetric rolling allows to provide the possibility for overcoming the limitation of producing UFG materials with large dimensions due to its continuous feature [8]- [9]. Among the asymmetric rolling processes, the differential speed rolling in which the speeds of the rolls are different, is considered to be the most effective for achieving UFG structure of materials [10]- [13]. Better mechanical properties of wire rod, round bars and hexagonal profiles can be achieved due to large plastic deformation in asymmetric three-roll rolling process.…”

Finite Element Analysis of Symmetric and Asymmetric Three-roll Rolling Process

“…On the basis of the finite element simulation it was stated that with reduction Research of influence of different technological factors on metal elongation, shear strain and strain effective in a single three-roll caliber was performed in [11]. One of the problems of asymmetrical three-roll rolling is bending of the bar at the exit from the deformation zone what makes its threading into the next pass more difficult.…”

Heat transfer modeling in asymmetrical sheet rolling of aluminium alloys with ultra high shear strain

“…It is well known that shear strain plays a critical role in the grain refinement of aluminium alloys processed by asymmetric rolling [11][12][13][14][15]. The strength of the material continuously increases with increasing the applied shear strain.…”