Roll Torque Research Articles

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.

Investigation of cavity filling in profile ring rolling process for T-shape ring

In this paper, key parameters affecting the cavity filling in single and double T-shape profile rings are comprehensively investigated via numerical and experimental analysis. A three-dimensional finite element model was developed in Abaqus\Explicit to assess the influence of crucial ring rolling process parameters, including feed speed, main roll rotational velocity, the existence and the absence of axial rolls on the cavity filling of single and T-shape rings and the main roll torque. Besides, a ring rolling machine was built to conduct practical experiments and validate the numerical evaluation, while for the first time, the role of the axial roll and the main roll torque on the quality of the cavity filling is experimentally evaluated. Power requirements and the final ring profile geometry were obtained by the simulation method, and the results were confirmed by the experiments. The results showed that axial rollers significantly reduced the cavity filling rate, and in contrast, the effect of mandrel feed speed and the main roll rotational velocity was much lower. Also, the axial forces were considerably less than the radial forces. However, the rolling operation was done in both radial and axial directions. The existence of axial rolls had an intensive effect on the process’ required power, as a result the main roll torque increased more than three times in case of applying axial rolls, compared with not considering them. Severe effects of axial rollers on increasing force and decreasing cavity filling rate can be attributed to frictional forces between the ring and axial rolls, restricted ring motion, which has to be compensated by a higher torque of the main roll. When the axial rolls are used, the material flow in the ring’s height direction is restricted. Therefore, the material cannot move easily to form the profile. All experimental and simulation results, including mandrel force, cavity filling, and ring profile geometry, were in good agreement, and in all cases, the simulation error was less than 10%.

Methods for online measurement and control of section deviations during hot rolling of wire rod and bars

In the joint project PIREF, the metal forming group of the University of Duisburg-Essen has collaborated with the University of Applied Sciences Ruhr-West Mülheim (Ruhr), the University of Siegen, EMG Automation GmbH and SMS group GmbH to develop sensors, for an online measurement of material velocity and cross section as well as control models for the rolling process of wire rod and bars. The University of Duisburg-Essen provided a metal forming process model for the rolling process to assess the influencing parameters on the rolled section precision. A technique was found to segregate height- from width- influencing parameters from a measured cross-sectional area and actual roll gap. With this measuring technology and with help of the process model, rules for control of the rolling process to achieve close tolerances were obtained. The modelling was accompanied by rolling trials on a laboratory rolling mill at the University of Duisburg-Essen, where a typical Round-OvalRound pass sequence was used for validation of the rolling model concerning lateral spread, inlet and outlet velocity as well as rolling force and torque calculation. The present paper shows how the material flow and the distribution of the velocity in the roll gap can be described. In subsequent rolling of bar and rod in a continuous rolling mill the dimensions can be influenced by application of longitudinal stresses and screwdown. The application of stress can be achieved by an inter-stand velocity mismatch. With the developed models the necessary velocity mismatch can be calculated.

Influence of a Gap in a Mill Stand’s Drive Line on the Elastic Torque

The elastic torque in a section of the drive line with a gap is determined for a mill stand, in the case of variable external rolling torque. A correction factor is introduced to take account of the gap.

Producing 3D friction loads by tracking the motion of the contact point on bodies in mutual contact

We outline a phenomenological model to assess friction at the interface between two bodies in mutual contact. Although the approach is general, the application inspiring the approach is the discrete element method. The kinematics of the friction process is expressed in terms of the relative 3D motion of the contact point on the two surfaces in mutual contact. The model produces expressions for three friction loads: slide force, roll torque, and spin torque. The cornerstone of the methodology is the process of tracking the evolution/path of the contact point on the surface of the two bodies in mutual contact. The salient attribute of the model lies with its ability to simultaneously compute, in a 3D setup, the slide, roll, and spin friction loads for smooth bodies of arbitrary geometry while accounting for both static and kinematic friction coefficients.

Comparative Study of Superelastic Ti–Zr–Nb and Commercial VT6 Alloy Billets by QForm Simulation

A comparative simulation of hot radial shear rolling (RSR) of billets made of a superelastic Ti–Zr–Nb and a commercial VT6 alloy was performed using the QForm finite element modeling program. Rolling in 48 modes with a variable feed angle and elongation ratio at 4 levels and initial rolling temperature at 3 levels was investigated for each alloy. The Ti–Zr–Nb alloy rheology during hot deformation was determined experimentally by hot upset forging and imported into the QForm program. The presence of maxima on the flow curves at the initial stage of deformation, which are absent in the VT6 alloy, is revealed. Simulation results are presented in the form of fields of the stiffness coefficient, strain rate intensity, cumulative strain degree in the maximum reduction section depending on the rolling mode. General regularities of the Ti–Zr–Nb and VT6 behavior in RSR are similar. The gradient of the fields studied decreases, and the roll pressure and torque increase with an increase in the feed angle and elongation ratio. The initial rolling temperature does not significantly affect the deformation pattern, but it significantly affects the roll pressure and torque. At the same time, the experimental alloy demonstrated the greater tendency to localize deforming forces in the near-contact zone and to increase the gradient of stress-strain state parameters over the billet section. The study of the tightening shape and depth of rolled billet ends showed that the Ti–Zr–Nb alloy has a 3.5–9.6% greater tightening depth. It is shown that experimental alloy rolling requires 1.6–2.4 times higher roll pressure and torque as compared to the commercial alloy.

Coupled Vibration Characteristics Analysis of Hot Rolling Mill with Structural Gap

It is important to study the vibration of rolling mills to improve the stability of rolling production. A dynamic rolling process model is established by considering the elastic recovery of the exit strip and the influence of multiroll equilibrium, and the accuracy of the model is verified by experimental data. On this basis, based on the distribution of friction force in the deformation zone, the rolling force and rolling torque are nonlinearized. In addition, a rolling mill structure model is established by considering the structure gap and a piecewise nonlinear horizontal‐vertical‐torsional vibration model of the rolling mill is established by combining the structure model and dynamic rolling process model. Finally, the amplitude‐frequency characteristics of the work roll under different external excitation amplitude and the dynamic bifurcation characteristics of the work roll under different gaps are analyzed. The study indicates that, by reducing excitation amplitude and structure gap, the system vibration can be reduced. The research results can provide a theoretical reference for further exploration of the coupling vibration of hot rolling mills.

A novel yield criterion and its application to calculate the rolling force of a thick plate during hot rolling

In order to solve the problem of establishing the rolling force model, which is caused by the nonlinear Mises specific plastic power, a novel yield criterion, called mean slope yield criterion, is constructed by averaging the slopes of yield loci of the Tresca criterion and Mises criterion. The yield criterion is a linear combination of the principal stress components, and its locus on the π-plane is an irregular dodecagon which intersects the Mises circle. For verification, the yield criterion was rewritten by introducing the Lode stress parameter and compared with the experimental data, and a good consistency is achieved. Meanwhile, a three-dimensional velocity field whose horizontal component satisfies the elliptic distribution from the entrance to the exit is proposed. Based on these achievements, the energy analysis of the velocity field is carried out with the derived yield criterion, and the expression of the internal deformation power is derived. Also, the friction power and shear power are derived in terms of the velocity field. Ultimately, the analytical solutions of rolling torque, rolling force, and the stress state coefficient are obtained through the minimization of the total power. By comparison, it is shown that the theoretical rolling torques and rolling forces coincide well with the measured ones since both the maximum errors are only 13.77%.

Comparative study of superelastic Ti–Zr–Nb and commercial VT6 alloy billets by QForm simulation

A comparative simulation of hot radial shear rolling (RSR) of billets made of a superelastic Ti–Zr–Nb and a commercial VT6 alloy was performed using the QForm finite element modeling program. Rolling in 48 modes with a variable feed angle and elongation ratio at 4 levels and initial rolling temperature at 3 levels was investigated for each alloy. The Ti–Zr–Nb alloy rheology during hot deformation was determined experimentally by hot upset forging and imported into the QForm program. The presence of maxima on the flow curves at the initial stage of deformation, which are absent in the VT6 alloy, is revealed. Simulation results are presented in the form of fields of the stiffness coefficient, strain rate intensity, cumulative strain degree in the maximum reduction section depending on the rolling mode. General regularities of the Ti–Zr–Nb and VT6 behavior in RSR are similar. The gradient of the fields studied decreases, and the roll pressure and torque increase with an increase in the feed angle and elongation ratio. The initial rolling temperature does not significantly affect the deformation pattern, but it significantly affects the roll pressure and torque. At the same time, the experimental alloy demonstrated the greater tendency to localize deforming forces in the near-contact zone and to increase the gradient of stress-strain state parameters over the billet section. The study of the tightening shape and depth of rolled billet ends showed that the Ti–Zr–Nb alloy has a 3.5–9.6 % greater tightening depth. It is shown that experimental alloy rolling requires 1.6–2.4 times higher roll pressure and torque as compared to the commercial alloy.

Analysis of Rolling Force for Extra-Thick Plate with CA Criterion

In order to solve the nonlinear integral difficulty of the Mises yield criterion, a linear yield criterion, called the collaborative approximation (CA) yield criterion, is proposed by the collaborative control method. According to the approximation method, the mathematical expression of the CA yield criterion is derived as a linear function of the three principal stresses. The theoretical results based on the yield criterion in the form of the Lode parameter are verified with the classical test data, and a good agreement is found. Meanwhile, for the purpose of proving the effectiveness of the yield criterion, its specific plastic power is derived and applied to establish the rolling force model of an extra-thick plate. In the modeling, the internal power of plastic deformation is obtained by using the derived specific plastic power, while the shear power dissipation and the frictional power dissipation are obtained by using the methods of strain vector inner product and average velocity integration. Then, the analytical solution of the rolling force is obtained and then extended to the one accounting for the temperature rise. The maximum errors of the predicted rolling torque and rolling force without considering the temperature rise are 12.72% and 11.78%, respectively, while those considering the temperature rise decrease to 3.54% and 5.23%, respectively. Moreover, the influence of relative reduction, friction factor, surface temperature, and the temperature rise of the workpiece on the theoretical results is discussed.

Calculating Power Parameters of Rolling Mill Based on Model of Deformation Zone with Four-Roll Passes

Making “digital twins” for rolling processes and mill equipment should begin with the development of mathematical models of the deformation zone. The deformation zone of two-high flat mill rolling have been studied in detail, relevant models are available in many academic papers. However, the same cannot be said about the most complex deformation zones in stands with multi-roll gauge. Therefore, the task of their reliable mathematical description is of immediate interest. The development of mathematical models is necessary for the design of new wire mills and rolling-drawing units. The combination of rolling in stands with multi-roll gauge and drawing is a promising direction in the production of wire from difficult-to-form steels and alloys. Digital models for pressure-based metal treatment are also necessary for calculating the rolling-mill power parameters during the development of new assortments at the operating mills. The models of deformation zones present the basis for developing the multivariable control systems of process conditions of continuous mills. This research is devoted to the study of the deformation zone and the development of a procedure for calculating the power parameters of rolling in a stand with four-roll passes. The solution of these challenges is given using the example of an operating five-stand wire mill. The authors analysed the known analytical dependencies for calculating the rolling mill force and torque. A mathematical model of the deformation zone and a program for calculating the power parameters have been developed. The paper compares the results obtained from calculations based on analytical dependence and on modelling. A comparison with the experimental parameters obtained at the mill is given. The authors assess the feasibility of using the known formulas and analyse the impact of the front and rear tensions on the power parameters of rolling mill. The problem of developing an automatic tension control system for continuous mills with multi-roll groove is substantiated.

Analysis of asymmetrical rolling of strip considering two deformation region types

Analytical models of two deformation region types considering the percentages of three regions in the plastic deformation zone are proposed for analyzing asymmetrical rolling of strip and used to calculate the critical speed ratio, three region percentages, roll force, and roll torque. The effective range of speed ratio on thickness reduction increases with increasing critical speed ratio. When the deformation region type is backward-slip zone + cross-shear zone + forward-slip zone (B+C+F), with increasing speed ratio, the thickness reduction in asymmetrical strip rolling increases evidently, but remains unchanged when the critical speed ratio is exceeded, where the deformation region type is backward-slip zone + cross-shear zone (B+C). It is achievable to increase thickness reduction by increasing the roll force and front tension, which can not only increase the reduction rate, but also increase the critical speed ratio. The effect of asymmetrical rolling on thickness reduction is enhanced with decreasing of the roll force and front and back tension because of the increasing cross-shear zone percentage.

Analysis of asymmetrical rolling of strip considering percentages of three regions in deformation zone

An analytical model based on slab method considering the percentages of three regions in deformation zone is proposed for analyzing asymmetrical rolling of strip and used to calculate the percentages of three regions, the roll force, and roll torque. The asymmetrical rolling is more effective in reduction than the symmetrical rolling due to the existence of cross-shear zone. The percentage of cross-shear zone increases with the increasing of speed ratio and friction coefficient and decreasing of back and the front tensions, thickness of the strip, and roll force. With increasing of the percentage of cross-shear zone, the contribution ratio of reduction increases. The proposed model has good accuracy for the analysis results are in good agreement with the results measured in experiments.

Flight Stability Control Mechanism Of Ski Jumping In Lateral Wind Environment

Wind is not only closely associated with the discussion of fairness in ski jumping, but also very important to flight safety. Flight stability is essential for performance and safety in ski jumping, and mainly involved several factors, such as environmental wind and flight posture. However, the flight stability control mechanism of ski jumping in lateral wind environment remains unclear. PURPOSE: To determine the flight stability control mechanism of ski jumping in lateral wind environment. METHODS: The aerodynamic characteristics of ski jumping during flight under different lateral wind and yaw angles are predicted by numerical simulation of computational fluid dynamics , and the effects of the above two elements on flight stability are compared and analyzed. The jumper and skis were regarded as a multi-body system, and partially averaged Navier-Stokes turbulence model was used to simulate aerodynamic characteristics of the system based on a general flight attitude and then the forces and torques were obtained. The lateral wind speed involved in the numerical prediction includes 1.5 m/s,3 m/s, 4.5m/s and 7.5m/s, and the flight yaw angle involved includes 2.5°, 5° and 7.5°. RESULTS: When lateral wind speed is small (less than 3m/s), yaw force, yaw torque and rolling torque are small and almost negligible, and when lateral wind speed is larger than 4.5m/s, yaw force, yaw torque and rolling torque are more obvious. When wind speed is 4.5m/s and 7.5m/s, yaw force, yaw torque and rolling torque are 9.5 N and 26.3 N, 2.3 Nm and 6.3 Nm, 2.8 Nm and 7.8 Nm, respectively. When yaw angles are 2.5 °, 5 ° and 7.5 °, yaw force, yaw torque and rolling torque are 6.8 N, 12.9 N and 21.9 N, 2.5 Nm, 5.0 Nm and 6.8 Nm, 2.7 Nm, 5.7 Nm and 8.3 Nm, respectively. When wind speed is 4.5 m/s and yaw angle is 2.5 °, yaw force, yaw torque and rolling torque results of these two conditions are close to each other. Similarly, When wind speed is 7.5 m/s and yaw angle is 7.5 °, yaw force, yaw torque and rolling torque results of these two conditions are close to each other. CONCLUSION: The larger lateral wind can have a significant adverse effect on flight stability control of ski jumping, but it is possible to compensate or even eliminate this adverse effect by taking the appropriate flight yaw angle. Supported by the National Natural Science Foundation of China (Grant No. 11802068).

Mathematical modeling of closure behavior for a centrally elliptical void in thick slab

To investigate the evolution behavior of a centrally elliptical void in thick slab during rolling, a critical criterion for closing a central elliptical void is established through the energy analysis. According to the condition of volume constancy, a triangular velocity field embedding an elliptical void is established. Based on the velocity field, the minimum value of rolling energy rate, composed of shear energy rate and cracking energy rate, is calculated. According to the balance principle of energy rate, the expression of relative stress factor is obtained. Then, a mechanical criterion for void closure is derived from the basis of extreme condition, and the effects of void size, aspect ratio, geometrical shape parameter, thickness-to-radius ratio, and the relative reduction on the void closure are analyzed. Several rolling processes with different elliptical voids under seven aspect ratios are simulated by the finite element method (FEM), and the evolution characteristic of the void is revealed. The analytical results based on the mechanical criterion and those by the FEM are compared. It is shown that the two prediction results are in good agreement, and a flat void is easier to be closed than a sharp one. Also, the simulated rolling force and torque are obtained through the FEM model, and the comparison result confirms the validity of the upper bound solution. Finally, a rolling experiment with a prefabricated void is carried out to check the reliability of the closure criterion, and a good consistence is also found. In addition, the shortage of the present investigation based on 2D simulation for assessing the mechanical criterion is discussed as a prospect of the future research.

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.

Performance Improvement and Parameter Influence of Thread Shaft by Axial Self-infeed Rolling Process

The rolling process is an important processing technology for improving the performances of thread shaft. In this paper, the axial self-infeed rolling process is investigated. The principle of the axial self-infeed rolling process is introduced and the performances of the formed thread shaft with copper T2 are evaluated. In addition, the major diameter of the formed thread shaft and the rolling torque during the axial self-infeed rolling process are studied. The hardness of the formed thread shaft with copper T2 is improved 74.2% and the microstructure is fibrous tissue in the bottom of the tooth groove. The size of the blank has greater impact on the major diameter and the forming torque than the rotating speed of the blank.

A first step towards an in-line shape compensation for UHSS roll forming

Roll forming is an important sheet metal forming process and is being used increasingly in the automotive industry for the manufacture of structural and crash components from Advanced High Strength Steel (AHSS) and Ultra High Strength Steel (UHSS). In AHSS and UHSS, the material properties can change from coil to coil or within the same coil and this can lead to varying part quality in roll forming. The effect of changes in material properties on part quality depends on the geometry of the part being formed as well as on the process parameters. There is a strong interest in developing in-line shape compensation for roll forming, and this will only be possible if the relationship between part quality, material properties, process- and part shape- parameters is understood.In this paper, the effect of material properties and both process and geometrical parameters on longitudinal bow is analysed. A new technique is introduced for the identification of variations in the longitudinal bow in a roll formed component based on roll load and torque measurements as well as process parameters and part geometry.

Upper bound analysis of wire flat rolling with experimental and FEM verifications

In this paper, an upper bound analysis is developed to calculate the rolling torque in the wire flat rolling process. Streamlines are defined parametrically in the deforming region and the formulation of the admissible velocity field are developed. The internal and frictional power terms are obtained from the upper bound solution. Through the analysis, the rolling torque is obtained. Furthermore, the effects of the roll speed, wire diameter, and reduction in height on the rolling torque are studied. In addition, the experimental and numerical investigations are performed to verify the proposed theoretical model. A very good agreement is obtained between the analytical results with those from the simulation and the experiment.

A New Data-driven Roll Force and Roll Torque Model Based on FEM and Hybrid PSO-ELM for Hot Strip Rolling

In this paper, a new Extreme Learning Machine (ELM) regression model of roll force and roll torque based on data-driven is proposed. The three-dimensional elastic-plastic finite element model (FEM) is established to solve the roll force and roll torque under different parameters (including rolling reduction rate, roll radius, rolling speed, average width of strip, entry temperature of strip). The regression model of ELM optimized by Particle Swarm Optimization (PSO) is established through using the datasets obtained by FEM. The PSO-ELM model prediction values of roll force and roll torque are compared with the single ELM and PSO-SVM model, and the error results of the prediction values are analyzed. The error results fully verify the feasibility and accuracy of the PSO-ELM model proposed. It is found that the new data-drive model of roll force and roll torque is simple in structure and it can make up for the deficiency of traditional mathematical mechanism model in dealing with nonlinear problems. The research result reveals that PSO-ELM method is suitable for parameters prediction and model optimization in strip rolling process.