Roll Torque Research Articles

Slab Analysis of Ring Rolling Assuming Constant Shear Friction

In this article, an analytic solution for ring rolling process based on the slab method theory is presented, in which the non-uniformity of the normal and shear stresses across the section of the deforming material throughout the plastic region is considered. The friction factor multiplied by the shear yield strength (s = mk) is used to present friction between the main roll and the ring. The influence of the process parameters such as friction factor, feed speed, main roll rotational speed, and radii of the main roll and mandrel on process outputs is investigated. Complete expressions for the ring rolling pressure, force, and torque are obtained, and the position of neutral point is predicted. Comparison of the analytic results of this model with the experimental results of other investigators and FEM analysis show that they are in good agreement.

Simulation of Torque during Rod Rolling of HC SS316 at Low Strain Rate Using “Phantom-Roll” Method

Rolling torque for a seventeen passes, 125 x 125 mm HC SS316 billets rolled to a 16 mm diameter rod have been simulated. Torque calculations based on pressure exerted by the metal on the rolls and the area of contact during longitudinal rolling were obtained using the temperature values derived using the “Phantom Roll” method. Investigations were carried out for four different starting mean rolling temperatures between 988 0 C and 1191 0 C and at four different strain rates of 0.4s -1 , 0.8s -1 , 1.2 s -1 and 1.6s -1 . Results obtained showed that for all cases, rolling in grooved rolls required higher torque compared to rolling in flat rolls. In general, it was observed that torque value increased as starting temperature decreases and for each set of starting temperatures, the torque value increases with temperature. In all cases, the torque values for grooved rolls were higher than those for flat rolls. This was due to the higher frictional effect, occasioned by the larger contact area between roll and stock. Results obtained also revealed an inverse relationship between strain rate and torque.

Finite Element Simulation of the Hot-Rolling Process of Titanium Alloy Bar

In order to overcome the drawbacks in the process of the titanium alloy, the authors propose to produce this kind of bar by Y-type rolling mill. The deforming process of titanium alloy has been simulated dynamically using MSC.Marc finite element software. The stress, strain, temperature and residual stress distributions of deformation area have been analyzed. The rolling force and torque have been obtained. The model could provide the foundation for further theoretical research and engineering application of titanium alloy bar rolling process.

The effects of rolling method changes on productivity in thick plate rolling process

We present a draft schedule scheme to estimate the productivity in thick plate rolling process. Dependency of design force, design torque and maximum bite angle of a rolling mill on the reduction ratio models were fully considered in the draft schedule scheme. Roll force and torque equations used in the reduction ratio models were verified by comparing the measurements with the predictions. Using the draft schedule scheme, we examined the influence of rolling method changes on the productivity (i) material position after the broadside passes, (ii) material position after the longitudinal passes and (iii) the number of turn, i.e., number of times that slab (material) is rotated by 90 degree, before the broadside and/or longitudinal passes begin. Results reveal that the number of turn gives the major influence on productivity. Rolling time can be minimized if material positions after the broadside and longitudinal passes are not fixed in advance.

Approach to evaluate the rolling mill capacity in a plate rolling process

This study presents an approach to evaluating the rolling mill capacity from the viewpoints of productivity and revamping cost when a plate mill is upgraded. In this light, a concept is proposed of a ‘characteristic length’, defined as the ratio of the design torque of the drive motor over the design force of the rolling equipment (structure of the rolling mill). A draft schedule algorithm for the plate rolling process is also presented, which consists of a force–thickness relation at each pass, and a roll force and torque prediction model. Using the draft schedule algorithm linked with the characteristic length, a series of plate rolling analyses was performed to examine the productivity of a plate mill while varying: (i) the design force of the rolling equipment; (ii) the design torque of the drive motor; (iii) both its design force and torque; and (iv) the strength of the slab. In addition, as a practical example, the proposed approach has been applied to three actual plate mills in Korea, China, and Russia. The results reveal that upgrading the design torque is the most efficient method from the viewpoint of productivity and revamping cost. It was also found that a critical characteristic length exists in which productivity cannot be increased any further, even though the rolling mill capacity has been upgraded further. Hence, this critical characteristic length can be used as an index to avoid the overcapacity problem of a plate mill when it is revamped.

Development and validation of a numerical model for sheet metal roll forming

The latest trends in the automotive industry towards fuel efficient, lightweight and sustainable transport have increased the use of Ultra High Strength Steels in the body in white of the vehicles. However, the formability of these steels is poor at room temperature and new geometrical errors appear when they are formed using conventional forming processes. In this context, the conventional roll forming process is a very interesting process to form these new materials. Since the yield strength of these materials is higher, the risk of appearance of not desired longitudinal plastic strains decreases. On the other hand, using these materials higher spring back occurs in the profile and higher forces and amounts of energy are needed. The Finite Element simulation is a powerful tool to optimise the process and understand the complex behaviour of the strip during the roll forming processes. In the present work, a Finite Element model has been developed to model the roll forming process. Experimental tests have been performed using different Ultra High Strength Steels and the roll load, the roll torque, the longitudinal strain and the spring back of the profile have been measured experimentally. Finally, the validation of the finite element model has been made comparing numerical and experimental results.

Linear Integral Analysis of Bar Rough Rolling by Strain Rate Vector

A new linear integral method for bar hot rolling on roughing train was obtained. First, for plastic deformation energy rate, equivalent strain rate about Kobayashi's three-dimensional velocity field was expressed by two-dimensional strain rate vector; then, the two-dimensional strain rate vector was inverted into inner product and was integrated term by term. During those processes, boundary equation and mean value theorem were introduced; for friction and shear energy dissipation rate, definite integral was applied to the solution process. Sequentially, the total upper bound power was minimized, and the analytical expressions of rolling torque, separating force, and stress state factor were obtained. The calculated results by these expressions were compared with those of experimental values. The results show that the new linear integral method is available for bar rough rolling analysis and the calculated results by this method are a little higher than those of experimental ones. However, the maximum error between them is less than 10%.

Effects of friction on roller expanded tube–tubesheet joint strength

Roller expansion of new tubes in enlarged heat exchanger tubesheet holes requires higher rolling torques which may result in over-thinning of the tube wall. This affects adversely the tube–tubesheet joint strength, which is measured in terms of residual contact pressure between the expanded tube and tubesheet. The axial force required to cause the mechanical failure of the tube–tubesheet joint has therefore been considered as an indication of the integrity of the joint. This force is influenced by several parameters such as the type of tube and tubesheet materials, the initial clearance and coefficient of friction. In the present work, an axisymmetric finite element (FE) model is used to evaluate the combined effects of friction between tube and tubesheet, initial clearance and tube material strain hardening on the strength of the tube–tubesheet joint. The FE results show that the increase in friction between tube and tubesheet results in higher residual contact stress and lower cutoff clearances. The residual contact stress also increased linearly with increasing tube material strain hardening level for all friction coefficients.

On the stability and control of unicycles

A mathematical model of a unicycle and rider, with a uniquely realistic tyre force and moment representation, is set up with the aid of multibody modelling software. The rider’s upper body is joined to the lower body through a spherical joint, so that wheel, yaw, pitch and roll torques are available for control. The rider’s bandwidth is restricted by low-pass filters. The linear equations describing small perturbations from a straight-running state are shown, which equations derive from a parallel derivation yielding the same eigenvalues as obtained from the first method. A nonlinear simulation model and the linear model for small perturbations from a general trim (or dynamic equilibrium) state are constructed. The linear model is used to reveal the stability properties for the uncontrolled machine and rider near to straight running, and for the derivation of optimal controls. These controls minimize a cost function made up of tracking errors and control efforts. Optimal controls for near-straight-running conditions, with left/right symmetry, and more complex ones for cornering trims are included. Frequency responses of some closed-loop systems, from the former class, demonstrate excellent path-tracking qualities within bandwidth and amplitude limits. Controls are installed for path-following trials. Lane-change and clothoid manoeuvres are simulated, demonstrating good-quality tracking of longitudinal and lateral demands. Pitch torque control is little used by the rider, while yaw and roll torques are complementary, with the former being more useful in transients, while the latter has value also in steady states. Wheel torque is influential on lateral control in turning. Adaptive control by gain switching is used to enable clothoid tracking up to lateral accelerations greater than 1 m s −2 . General control of the motions of a virtual or robotic unicycle will be possible through the addition of more comprehensive adaptation to the control scheme described.

Effect of Scale on Coefficient of Friction in Hot Sheet Rolling of Steel

The effect of scale on coefficient of friction in hot rolling was investigated by changing the scale thickness of Si–Mn steel, using the simulation testing machine developed by the authors. The simulation testing machine for the evaluation of the lubrication behavior consisted of a main stand, a substand, a furnace and a tension device. The rolling force and the rolling torque were measured and the coefficients of friction were calculated by changing the scale thickness, the reduction and the emulsion concentration. The scale thicknesses were obtained by the control of the flow rate of Ar gas and the heating time at 800°C in the image furnace. The experiments were carried out at constant rolling conditions of a velocity ratio of 20, a rolling speed of 50 m/min and a furnace temperature of 800°C at the rolling reductions of 0.3, 0.5 and 1.0 mm. The colza oil was used as the base oil. The emulsion concentrations were 0.1 and 3.0 mass%. At an emulsion concentration of 3 mass%, the coefficient of friction at rolling reductions of 0.3 and 0.5 mm remains constant above 60 μm, whereas below 60 μm it increases with decreasing scale thickness. The coefficient of friction at a rolling reduction of 1.0 mm remains constant above 110 μm, whereas below 110 μm it increases with decreasing scale thickness. At an emulsion concentration of 0.1 mass%, the coefficient of friction at a rolling reduction of 0.3 mm increases with increasing scale thickness above 60 μm, whereas below 60 μm it increases with decreasing with scale thickness. The coefficient of friction at a rolling reduction of 0.5 mm increases with increasing scale thickness above 110 μm, whereas below 110 μm it increases with decreasing with scale thickness. The coefficient of friction at a rolling reduction of 1.0 mm remains constant above 110 μm, whereas below 110 μm it increases with decreasing scale thickness. The increase in the coefficient of friction for the specimens with a thinner layer of scale is due to the formation of white zones in which the scale is removed from the interface between scale and steel. For these specimens, the ratio of the Fe3O4 layer of the scale surface is higher and the black layer is observed on the roll surface after rolling.

Numerical Investigation of Roll Torque Induced by Solid Rocket Motor Internal Flow

In order to understand the mechanism of the large roll-torque generation in the operating solid rocket motor with axially-slotted propellant grain and the narrow nozzle submergence region, fully three-dimensional Navier-Stokes numerical simulations have been conducted. The several grain configurations are computed and it is found that there are at least two groups of quasi-steady state solutions, one shows large roll torque, and the other shows small one. From the present simulation results, it is observed that the large roll torque is generated due to the interaction of the circling flow around the nozzle inlet with the slot jet exhausting out from the slot end into the aft-end cavity. Although the roll torque evaluated from the computation is one-order higher than that observed in the real fight, the present simulation serves the insight into the qualitative mechanism of the real roll torque generation.

Investigation of Single Pass Shape Rolling Using an Upper Bound Method

This paper presents a generalized analytical upper bound method for the study of external shape, pressure, and torque in the single pass rolling of shaped sections. Generalized kinematically admissible velocity fields have been calculated from an assumed deforming geometry, in turn mathematically developed from a new parameterization of curves for the stream line flow of the material. An upper bound on rolling power was established based on the calculated velocity fields. Unknown variables in the velocity field were determined by minimizing rolling power with respect to unknown velocity field variables, yielding an upper limit to the actual power required as well as rolling pressure and torque. As an applied example, the single oval-to-round and rectangle-to-diamond roll passes have been chosen and analyzed. Velocity fields and power relations were obtained for each pass and computer analysis was carried out to analyze and simulate the process of shape rolling. External shape, average roll torque, and rolling pressure data from the analysis were compared with other worker’s analytical solutions, numerical analyses, and experimental data. The results were found to be in good agreement with previous research and the method was shown to be quicker and easier to use.

A finite deformation method for discrete modeling: particle rotation and parameter calibration

We present a finite deformation method for 3-D discrete element modeling. In this method particle rotation is explicitly represented using quaternion and a complete set of interactions is permitted between two bonded particles, i.e., normal and tangent forces, rolling and torsional torques. Relative rotation between two particles is decomposed into two sequence-independent rotations, such that an overall torsional and rolling angle can be distinguished and torques caused by relative rotations are uniquely determined. Forces and torques are calculated in a finite deformation fashion, rather than incrementally. Compared with the incremental methods our algorithm is numerically more stable while it is consistent with the non-commutativity of finite rotations. We study the macroscopic elastic properties of a regularly arranged 2-D and 3-D lattice. Using a micro-to-macro approach based on the existence of a homogeneous displacement field, we study the problem of how to choose the particle-scale parameters (normal, tangent, rolling and torsional stiffness) given the macroscopic elastic parameters and geometry of lattice arrangement. The method is validated by reproducing the wing crack propagation and the fracture patterns under uniaxial compression. This study will provide a theoretical basis for the calibration of the DEM parameters required in engineering applications.

An approach to simulate cold roll‐forging of turbo‐engine thin compressor blade

PurposeStudying manufacturing process of compressor blade can reduce the production cost and time in aircraft turbo‐engine industries. In the cold roll‐forging of thin compressor blades, the elastic behavior of machine structure and rolls is considerable due to the higher volume of roll separating force. Owing to this kind of elastic deformation during rolling, the adjusted gap between the rolling dies is increased and this causes unexpected flow of material, shape and thickness. The purpose of this paper is to present a new approach for simulation of cold rolling of thin blades and studying the effect of elastic behavior of the machine structure as well as rolls deflection on the material flow and roll separating force.Design/methodology/approachIn this paper, the process has been investigated using experimental test and simulation by introducing a new approach in a decision‐making flowchart. Instead of simulating of the entire system structure, a couple of virtual deformable rolls are suggested. The specifications of these rolls are selected to behave elastically during rolling same as whole roll stand. In addition, the thickness values are compared in both experiment and simulation. Also, the roll separating force is compared with and without using this approach.FindingsA decision‐making algorithm has been presented that can be used to study the process. This finding provides the basis to investigate the effect of elastic deformation of machine structure and rolls on dimensional accuracy and roll force.Originality/valueResult of this work can promote the position of simulation of the thin rolled sections to an extent more compatible with reality. For instance, the amount of increased gap between two dies during rolling can be estimated accurately. Also the influence of this gap on final blade thickness and the roll force and on the roll torque can be investigated by this approach.

Methodology for draft schedule design of plate rolling process with peening effect considered

We propose an approach for designing a draft schedule applicable to thick plate rolling. In the proposed approach, the peening effect, i.e. thick material is rolled with a small reduction ratio, is considered fully in computing roll force and torque. To determine an initial draft schedule, we calculate material thickness at each pass and total number of passes by taking the smallest of the critical reduction ratios (reduction ratio by maximum reduction increment, reduction ratio assigned in designing a plate mill, reduction ratios by allowable roll force and roll torque). To make a final draft schedule, we then propose two ways (thickness ratio correction (TRC) method and reduction ratio correction (RRC) method) that redistribute reduction ratios predetermined in the initial draft schedule. The proposed approach has been applied to POSCO No. 2 Plate Mill. Results reveal that the reduction ratios are determined by allowable roll torque if the material being rolled is relatively thick, but reduction ratios are decided by roll force as the material thickness being rolled decreases. It has been found that the thickness ratio correction method is useful when a heavy reduction ratio is necessary in the later part of the rough rolling sequence, and obtaining a uniform microstructure over material thickness during rolling is important. Meanwhile, the reduction ratio correction method is effective if surface defect generation on the material during rolling is a concern.

Analysis of Rolling Pressure in Asymmetrical Rolling Process by Slab Method

The plane strain asymmetrical rolling was analyzed using slab method. The contact arc was replaced by parabola, and the constant surface friction status was adopted during the analysis. The deformation area was divided into three zones according to the direction of the friction. Then, the three zones were studied, respectively. A rolling force model and a rolling torque model were developed based on the analysis, and they were used to analyze the influence of asymmetrical rolling factors on deformation area and unit pressure if they had good precision which was determined by comparing the calculated results with the measured ones.

FINITE ELEMENT ANALYSIS OF DEFORMATION CHARACTERISTICS IN HEAVY SLAB ROLLING

Plastic deformation that occurs in a heavy slab during plane-strain rolling was investigated by the finite element analysis. A cylindrical pore was assumed to be located along the transverse direction of a slab. The effective strain was found to be the largest at the sub-surface layer and the smallest at the middle layer, where the shear strain developed the least. Pore closure was most difficult at the middle layer. This is where hydrostatic stress in addition to effective strain developed the least. Rolling torques, rolling forces and pressure distributions at the roll/slab interface were investigated as well, under various conditions.

Rolling Temperature for Steel Hot Flat Rolled at Low Strain Rates

Different methods of obtaining averages have been used to determine mean rolling temperatures from measured temperatures of various specimens during roll contact in hot flat rolling. The obtained mean rolling temperatures were used in turn in hot rolling simulation programs based on Sims, and Bland and Ford’s theories for calculating rolling loads and torque during hot flat rolling of steels at low strain rates (0.08 – 1.5 s-1). The hot rolling Bland and Ford’s (HRBF) Theory and Sim’s Theory gave similar results when any of the averaging methods of temperature is used to calculate rolling load and torque at high strain rates (1.5 –500s-1). However at low strain rates HRBF gave closer approximations to experimental results. Comparing the results with experimental values, the harmonic mean was found to give the best mean rolling temperature for hot flat rolling simulation at low strain rates compared to geometric mean, arithmetic mean and root mean square.

Effect of Pass Reduction on Rolling Parameters Using Reverse Sandwich Model Integrated into the Hot Rolling Bland and Ford’s Theory

Hot flat rolling simulation by use of the Bland and Ford’s cold rolling (HRBF) theory confirmed the reverse sandwich effect in selected carbon steels at low strain rates. The Reverse Sandwich Model (RSM) was subsequently integrated into the HRBF theory for load and torque estimation. In this work, the effect of pass reduction on rolling temperature distribution, yield stresses and rolling load were studied for AISI Type 316 stainless steel (HCSS316). For this new simulation, at low and high strain rates, results showed that the ratio of experimental to calculated roll load and torque were higher at lower reduction than at higher reduction. These results confirmed excess load and torque in the hot rolling of HCSS316 at low reductions. This is in agreement with results obtained using Sim’s theory, HRBF theory and the RSM.

Dynamic Model of the BYQ-3 Spherical Robot

Based on the motion analysis,the integral dynamics model of the BYQ-3 spherical robot is introduced through the Kane equation modeling method with the characteristics of vector operation,and the simulation and experiment research are implemented. The angular velocity,angular acceleration,centroid velocity and acceleration of the spherical shell,framework and weight pendulum are defined,respectively,and the generalized rate,partial velocity,partial acceleration,generalized inertial force and generalized active force of the spherical shell,framework and weight pendulum are derived,respectively. Then,the integral dynamics model of the BYQ-3 spherical robot is proposed on the basis of derived formula above. The integral dynamics model is revised through the designed model of the moment of friction torque of the rotating joint and the couple moment of rolling torque between the ground and the spherical shell. In conditions of the line motion of which the longitude axis is parallel with the ground,the simulation is presented on the basis of revised integral dynamics model,and moreover,the open motion control experiment is also presented by using the BYQ-3 spherical robot. The results of the simulation and experiment show that considering the frication factors among the system,the integral dynamics model of the BYQ-3 spherical robot is effective.