Alexander Pesin

Influence of Process Parameters on Distribution of Shear Strain through Sheet Thickness in Asymmetric Rolling

Materials with ultrafine grain structure and unique physical and mechanical properties can be obtained by methods of severe plastic deformation, which include asymmetric rolling processes. Asymmetric rolling is a very effective way to create ultrafine grain structures in metals and alloys. Since the asymmetric rolling is a continuous process, it has great potential for industrial production of ultrafine grain structure sheets. Basic principles of asymmetric rolling are described in detail in scientific literature. Focus in the well-known works is on the possibility to control the structure of metal sheets. However the systematic data on the influence of the process parameters (e.g., ratio of rolls velocity mismatch, reduction per pass, friction and diameter of rolls), and the shear strain rate required to achieve a significant grain refinement in asymmetric rolling are lacking. The influence of ratio of rolls velocity mismatch, reduction per pass, friction and the rolls diameter on the distribution of shear strain through the sheet thickness in asymmetric rolling has been studied in DEFORM 2D. The results of the study will be useful for the research of evolution of ultrafine grain structure in asymmetric rolling.

Numerical Study of Grain Evolution and Dislocation Density during Asymmetric Rolling of Aluminum Alloy 7075

The paper gives a mathematical model of grain evolution and dislocation density during asymmetric cold rolling of aluminum alloy 7075 in an SPD mode. Correlations between the effect of equivalent and shear strain on Al 7075 structure are obtained. An agreement of simulation results with experimental data is shown.

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

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.

Numerical Research of Shear Strain in an Extreme Case of Asymmetric Rolling

Considerable shear strain is necessary for manufacture of metallic materials with ultramicrograin structure. For flat rolling shear strain intensity is determined by two components: compression strain and shear strain . The vertical asymmetric sheet rolling process in rolling-drawing mode was investigated with the purpose of shear strain implementation. Calculation results show that during asymmetric rolling mode a vertical cross-section inclination takes place being especially pronounced with the total amount of deformation of 50% and more.

Theoretical Basis and Technology Development of the Combined Process of Asymmetric Rolling and Plastic Bending

The article focuses at technology development of the vertical asymmetric rolling and combined process of vertical asymmetric rolling and plastic bending. It has been shown that vertical asymmetric rolling peculiarity relates to the presence of a mixed zone, in which friction forces on contact roll surfaces are directed are differently. Experimental research showed serious drawbacks in the rolling technology caused by the growth of dynamic loads arising at the moment of plate contact with the bending roller. For solving the problem it was proposed to make the roller position motile to allow its movement along the required trajectory. The application of the motile roller helps to reduce dangerous torque differentiation at working rolls by the value of 1,5-2,5 compared with the rigidly fixed roller. The most effective bending roller trajectory is a second-order curve that is convex parabola.

FE Analysis of the Applicability of the Shear-Compression Testing to the Modeling of the Asymmetric Rolling Process

The mechanism of a severe plastic deformation during asymmetric rolling comes from its large equivalent strain, which is composed of a compressive strain and additional shear strain. Physical simulation of shear strain, which is similar to that occurring in asymmetric rolling processes, is very important for design of technology of ultrafine grain material production. Shear testing is complicated because a state of large shear is not easily achievable in most specimen geometries. Application of the shear-compression testing and specimen geometry to physical simulation of asymmetric rolling is discussed in the paper. The results of the numerical simulation and comparison of the stress-strain state during shear-compression testing and asymmetric sheet rolling are presented. The results of the investigation can be used to optimize the physical simulation of asymmetric rolling processes and for the design of the technology for ultrafine grain material production by means of a severe plastic deformation.

Development of the Technology of Various Large Bodies Manufacturing Based on Combined Methods of Deformation

Metallurgy and heavy engineering construction, which are considered the most energy-intensive industries, place great focus on complex shaped thick-gage plate metal items of equipment with wall thickness exceeding 40 mm and diameter/width of up to 4000 mm. Such items of equipment include large machine parts manufactured by means of hot plate stamping, such as bodies of rotation (for example, the segment of the radial surface of converter shell, the bottom part of degassing unit, etc.) utilized as pressure-operated devices, vessels, tanks and other facilities by metallurgical, petrochemical, oil and gas, and nuclear industries. Presently known manufacturing methods of such items of equipment, for instance, stamping methods, have a number of technological problems. In the present paper, creation and development of the theory and technology of manufacturing different large bodies based on the combination of plate rolling and stamping processes, as well as the combination of asymmetric rolling and plastic bending processes, are proposed. The goal was to develop a cost-effective technology of producing large-size bodies of rotation in the conditions of a thick-plate mill. The rolling of the package forms the basis of the first stage of the new process. The package consists of the upper (punch) base, the lower (matrix) base, and the blank plate situated between them. The economic benefit from installing the developed technology based only on the combination of asymmetric rolling and plastic bending processes was more than 1 million dollars. Casings on two converters were produced and installed in the oxygen-converter plant.

Finite Element Simulation of Shear Strain during High-Ratio Differential Speed Rolling of Aluminum Alloy 5083

High-ratio differential speed rolling (HRDSR) is a process of severe plastic deformation (SPD) that can be used to improve the structure and properties of aluminum alloys. The mechanism of SPD during HRDSR comes from its large equivalent strain, which is composed of compressive strain and additional shear strain. Plastic strain control of aluminum alloys are of importance for improvement of sheet microstructure and properties. This paper presents the results of the finite element simulation of shear strain during high-ratio differential speed rolling of aluminum alloy 5083. Four deformation routes UD, TD, RD and ND were simulated. By the route UD the sheet was not rotated between two deformation steps, while by the other three cases it was rotated with 180° degrees. By the route RD the rotation axis was the rolling direction, by the route TD the transverse direction and by the route ND the normal direction. The effect of rolls velocity ratio, friction coefficient and deformation route on the shear strain and the effective strain of Al 5083 was found. The results of investigation can be used to optimize the high-ratio differential speed rolling process to improve microstructure and mechanical properties of aluminum sheets.

Development of the Technology of Large Bodies Manufacturing Based on Combined Process of Plate Rolling and Stamping

An experimental study of the developed new technologies for obtaining large-sized parts with an elliptical surface has been carried out. The advantages and disadvantages are established, as well as the boundaries of effective applicability of new combined process. Verification of the results of computer simulation based on testing the technology in the conditions of a laboratory rolling mill was performed. Optimal geometric shapes of matrices and punches to produce spherical and elliptical bottoms of various thicknesses and diameters are obtained on a thick plate rolling mill. The methods of correction of the technology for obtaining large-sized parts with an elliptical surface have been developed and tested in laboratory conditions to eliminate the identified shortcomings.

Finite Element Modeling of Influence of Roll Form of Vertical Scale Breaker on Decreased Formation of Surface Defects during Roughing Hot Rolling

During production of rolled steel strips the quality of the surface of finished strips influences steel consumption considerably. The most critical areas for crack formation during rolling are lateral sides of slabs. Deformation behaviors of the slab edge in roughing rolling process were analyzed by the finite element method with Deform-3D. In this study our focus is the analysis of the influence of edger’s form on the possibility to decrease surface cracking during roughing hot rolling.