A New Method of Manufacturing Hollow Shafts via Flexible Skew Rolling

The existing rolling process of large and long axle parts, such as the cross wedge rolling (CWR) process, requires special molds and larger equipment. Flexible skew rolling (FSR) hollow shafts with mandrel is a near net-shape rolling technology which can achieve the diversified production of rolled parts without special molds. It has significant advantages such as small equipment tonnage, small die size, low rolling load, simple process adjustment, and especially suitable for multi-variety and small-batch production. This paper proposes hollow train shafts formed by FSR with mandrel. Reasonable parameters were selected for experiments, and the forming process was calculated by finite element (FE) software. The experimental results are consistent with the simulation results, indicating that the FE model is reliable. The rolling force and rolling torque are analyzed by simulation. Finally, the microstructure of different positions of the rolled-piece is analyzed, and the microstructure of the rolled part is refined. It is provide a feasible scheme for the rolling of large hollow shaft parts.

Research into the Effect of Speed Mismatch during Continuous Rolling on the Process Parameters

The paper analyzes the influence of tension (dam) on the technological parameters of the rolling process (spreading, force and rolling torque). For the analysis, a model of continuous rolling in three adjacent stands was developed, using the Deform 3D software. The adequacy of the model was confirmed by comparing the experimental data from the small-section wire mill 150 and the simulation results. The error in determining the forming was 0.4%, and in determining the power parameters was 11%. Further, a computational experiment was planned, to identify the effect of mismatched of rolling speeds on technological parameters. According to the results of calculations, graphs of changes in technological parameters were constructed. It is established that, even small deviations of rolling speed from the matched mode lead to significant changes in technological parameters.

The mechanical parameters modeling of heavy steel plate snake/gradient temperature rolling with the same roll diameters

The grains in the center of the heavy steel plate can be refined by the snake/gradient temperature rolling, and the deformation penetration, the microstructure, and the properties of the steel plate will be improved. The existing rolling mechanical models are not suitable for the snake/gradient temperature rolling, so it is necessary to establish the mechanical parameters model of the snake/gradient temperature rolling to instruct production. The yield criterion of rolled material was modified based on the idea of equivalent flow stress. The element stress analyses were carried out based on the uniform normal stress and nonuniform shear stress in the vertical sides of each slab. Then the equilibrium equation of the unit pressure based on the slab method was established on this basis. The deformation region was divided into three layers (the top layer, the bottom layer, and the central layer) and maximum four zones (back slip zone, front slip zone, cross shear zone, and reverse deflection zone) according to the temperature distribution and position of the neutral point, and then the 12 zones were formed during the snake/gradient temperature rolling. The boundary conditions of the existence of the back slip zone, the front slip zone, and the cross shear zone were established according to the relationship between the threading angle and the neutral angle. The accurate mechanical parameters model of the rolling force and rolling torque of the snake/gradient temperature rolling with the same roll diameters was set up on this basis. The ANSYS software has been used in the rolling process simulation by many scholars, and the calculating precision has been verified. So the rolling processes were simulated by the ANSYS software to validate the model precision. The results show that the maximum relative deviation of the rolling force analytic model is less than 7% compared with the numerical method, and the maximum relative deviation of the rolling torque analytic model is less than 11% compared with the measured results. The mechanical parameters model can accurately predict the rolling force and rolling torque during the snake/gradient temperature rolling with the same roll diameters, so as to provide a theoretical basis for the design of rolling mill and the setup of the process parameters.

The analytic study on the heavy steel plate snake rolling with the different roll diameters

The deformation in the inner region along the thickness of the heavy steel plate can be improved by snake rolling method. Then the microstructure and property will be refined and the crack in the inner region may be avoided. So the in-depth research on snake rolling method mechanics parameter modeling should be conducted to guide production. The rolling deformation zone will be divided into back slip zone, cross shear zone, front slip zone and reverse deflection zone according to the direction of the friction during the snake rolling process. The four zones may not exist at the same time. The boundary conditions of existence of the back slip zone, cross shear zone and front slip zone were established by calculating the position of neutral point by a special method. The calculating models which were used to calculate the snake rolling mechanical parameters including the rolling force and rolling torque were setup. The calculated models of unit compressive pressure in the four zones were setup by the slab method, and at this basis, the accurate calculating models of the rolling force and rolling torque were setup according to the composition of the rolling deformation zone and the boundary condition. The mechanical parameters were calculated by the analytic method and the numerical method, and the relative deviation is less than 5% which can satisfy the industrial requirement. The present analytical model can predict the characteristics during snake rolling easily and quickly and it is also suitable for online control applications.

The Analytic Study on the Heavy Steel Plate Snake Rolling with the Same Roll Diameters

The deformation in the inner region along the thickness of the heavy steel plate can be improved by snake rolling method. Then the microstructure and property will be refined and the crack in the inner region may be avoided. Therefore, the in-depth research on snake rolling method mechanics parameter modeling should be conducted to guide production. A snake rolling process with the same roll diameters and different angular velocity was conducted in this paper. The rolling deformation zone will be divided into back slip zone, front slip zone, cross shear zone, and reverse deflection zone according to the direction of the friction during the snake rolling process. The four zones may not exist at the same time. The boundary conditions of existence of the back slip zone, front slip zone, and cross shear zone were established according to the relationship between threading angle and neutral angle. The calculating models which were used to calculate the snake rolling mechanical parameters including the rolling force and rolling torque were set up. The calculated models of unit compressive pressure in the four zones were set up by the slab method, and on this basis the accurate calculating models of the rolling force and rolling torque were set up according to the composition of the rolling deformation zone and the boundary condition. The mechanical parameters were calculated by the analytical method and the numerical method, and the relative deviation is less than 6% which can satisfy the industrial requirement. The present analytical model can predict the characteristics during snake rolling easily and quickly and it is also suitable for online control applications.

Analysis of Efficiency of Roll Pass Design Options for Roughing Stands of Section Rolling Mill

The analysis of two roll pass design options of ten roughing stands atOJSC “MMK” 370 rolling mill has been performed. The usage of a new form of the roll grooves will allow achieving higher durability of the rolls. Lesser rolls consumption will allow saving up to 800K rubles annually. More uniform load distribution by the stands will reduce the possibility of main mill lines equipment breakdowns due to the jumps of rolling torque in the most loaded non-equiaxial stands. Better contact conditions and higher billet stability at the input into equiaxial grooves will reduce the amount of metal clogging. Moreover, a changed strain diagram – with higher roll pass design efficiency factor – will increase the roll out of foundry production defects.

Design of a Spherical Robot With Cable-Actuated Driving Mechanism

This paper presents the kinematics and dynamics of a spherical robot with a mechanical driving system that consists of four cable-actuated moving masses. Four cable-pulley systems control four tetrahedrally-located movable masses and the robot functions by shifting its center of mass to create rolling torque. The cable actuation decreases overall mass and, therefore, allow for less energy expenditure, as compared to other moving mass mechanisms that translate the masses by powered-screws. Additionally, the design allows the center of mass for the static (spherical shell, electronics, motors etc.) and dynamic mass (moving masses) to be at the geometric center at any given time, therefore has potential for tumbleweeding when needed. The derived equations of motion are verified by means of simulations.

The Effect of Low Deformation Asymmetric Rolling on Microstructure and Texture of the Polycrystalline Copper

In the most recent years the asymmetric rolling (AR) attracts attention of researchers and technologists. This process can improve some technological parameters (e.g. modification of rolling torque and load, power requirements, etc.) as well as provide the possibility of grain refinement in a relatively inexpensive way. Most of the reports concerning microstructural changes produced by AR refer to high deformations imposed in highly asymmetric conditions. However, such rolling conditions are difficult to control, so there are no prospects to their quick industrial implementation. The present paper refers to relatively low deformation and low asymmetry rate, that is much more interesting for the industry. It was shown that bending of the rolled band (important disadvantage of the AR technology) can be controlled by adjusting of the amount of deformation and asymmetry. It was also shown that ca. 30% reduction in thickness during cold rolling, together with a relatively low asymmetry, reduces significantly the grain size and produces a more fragmented microstructure inside grains of the polycrystalline copper comparing to the symmetric rolling (SR). The material hardness after AR is higher than after the SR. Moreover, the crystallographic texture asymmetry, expressed by its rotation around the transverse direction, is observed in the AR material.

New Numerical Solution of von Karman Equation of Lengthwise Rolling

The calculation of average material contact pressure to rolls base on mathematical theory of rolling process given by Karman equation was solved by many authors. The solutions reported by authors are used simplifications for solution of Karman equation. The simplifications are based on two cases for approximation of the circular arch: (a) by polygonal curve and (b) by parabola. The contribution of the present paper for solution of two-dimensional differential equation of rolling is based on description of the circular arch by equation of a circle. The new term relative stress as nondimensional variable was defined. The result from derived mathematical models can be calculated following variables: normal contact stress distribution, front and back tensions, angle of neutral point, coefficient of the arm of rolling force, rolling force, and rolling torque during rolling process. Laboratory cold rolled experiment of CuZn30 brass material was performed. Work hardening during brass processing was calculated. Comparison of theoretical values of normal contact stress with values of normal contact stress obtained from cold rolling experiment was performed. The calculations were not concluded with roll flattening.

Calculation of Axial Rolling Torque in Radial-Axial Ring Rolling Process

The importance of the axial rolling torque to design equipment and process is described. On the basis of the established formula of axial rolling force, the formula of axial rolling torque is derived by using the moving volume theory of energy method. The influence of processing parameters on the axial rolling torque is investigated. It is found that the axial rolling torque increases with the increase of the outer diameter of ring, and the axial rolling torque decreases with the increase of the inside diameter of ring. The greater the feed in axial direction, the greater the axial rolling torque. The correctness of the formula is verified by calculating actual examples.