Adjacent Rolls Research Articles

Process design for flexible T-profile-rolling of tailored thickness stringers with different cross sections

A new process, called flexible T-profile-rolling, is being developed to produce T-profiles with variable thickness distribution in longitudinal direction by flexible rolling. These tailored thicknesses allow for load-adapted and weight-optimised design of stringer profiles for aircrafts. The new process can replace the chemical milling currently used in the production of stringers and enables a more environmentally friendly and resource-saving production of the thickness changes. In order to achieve uniform thicknesses in the web and flange of the T-profile, a new rolling stand with rolls inclined against the T-profile and varying roll radii was developed. However, the varying roll radii cause different longitudinal strains in the profile cross-section due to the varied contact areas between the roll and the rolling stock, resulting in unwanted profile bowing. This bowing depends on the profile dimensions, as the adjacent roll radii vary over the profile cross-sections.This paper demonstrates the effects of profile dimensions on deflection through numerical investigations with different web heights, flange widths and thickness reductions. A straightening method is presented to obtain straight profiles as a function of the profile dimensions. The results show that this process can produce almost straight T-profiles with variable thicknesses for different cross section dimensions.

МІНІМІЗАЦІЯ МІЖКЛІТЬОВОГО НАТЯГУ НА БЕЗПЕРЕРВНИХ СТАНАХ ЗА ЯКІРНИМИ СТРУМАМИ ЕЛЕКТРОПРИВОДІВ ПРОКАТНИХ КЛІТЕЙ

In the conditions of continuous rolling of graded profiles with no or too little metal deflection between adjacent rolling cages, the most promising is tension regulation based on information about the armature currents of the main electric drives. The effectiveness of the method of minimizing the tension of graded rolled products based on information about the armature currents of the main electric drives was investigated. The method is based on the hypothesis of the constant ratio of the armature current of the drive of the next cage to the armature current of the drive of the previous cage in the free rolling mode. The method involves predicting the free-rolling current in rolling electric drives based on information about the free-rolling current in the electric drives of previous cages. The study is based on a complex model of the process of continuous bar rolling in four finishing cages of a small-grade mill with individual electric drives equipped with subordinate speed control systems. Given the fundamental impossibility of approbation of the proposed method by the methods of an industrial experiment, verification of its operability requires computer simulation modeling. The created computer model allows for adequate simulation of the operation of the control system in the conditions of rolling in a continuous group of cages with an accuracy that is sufficient for conclusions about the effectiveness of its operation. According to the results of the study of the control system by means of computer simulation, the effectiveness of its work was proven, in particular, the reduction of the specific tension in all intercell spaces of the finishing group of roll stands to an acceptable level of 10 N/mm2 and a significant narrowing of the range of changes in the width of the finished rolled product.

Mathematical Modeling and Finite Element Analysis of Residual Stress (RS) Field after Multipass Ultrasonic Surface Rolling

In order to achieve the change rule of the induced residual stress (RS) field after multipass ultrasonic surface rolling (USR), a mathematical model of the induced residual stress (RS) field after multipass ultrasonic surface rolling is first established. Then, the coupling mechanisms of the RS field after dual-pass USR and multipass USR are analyzed, respectively. Subsequently, a finite element (FE) model is established, and the influence of the interval between two adjacent rolling paths LS is investigated. Finally, both the mathematical model and the FE model are experimentally verified. The results show that both the mathematical model and the FE model can predict the RS field after multipass USR. Two adjacent RS fields will couple with each other in their overlapping regions. For a relatively small interval LS, the RS field after multipass USR can be fully coupled, so as to form a uniform compressive RS layer. In this study, when LS = 0.05 mm, the values of the surface compressive RS, the maximum compressive RS, the depth of the maximum compressive RS, and the depth of the compressive RS layer reach 426.71 MPa, 676.54 MPa, 0.05 mm, and 0.54 mm, respectively.

Tailoring the microstructure and mechanical properties of Cu–Fe alloy by varying the rolling path and rolling temperature

Cu–Fe alloys are expected to be extensively used in electronics, transportation and machinery industries due to the extraordinary mechanical properties and functional properties. To optimize rolling process and the final properties of Cu–Fe plates. The effect of rolling path, rolling temperature and thickness reduction on microstructure evolution, mechanical and electrical properties of Cu–Fe alloy are carefully investigated. The results shown that the thickness reduction has a significant effect on mechanical properties of Cu–Fe alloy. The yield strength of Cu–Fe plates with 20% thickness reduction is more than 2 times higher than that of homogenized ingot. While the yield strength increases gradually as further increasing the thickness reduction. Rolling temperature is an important parameter determining the strength-ductility balance. The strength of plate rolled with 80% thickness reduction at 400 °C is similar to that of the plates in cold-rolled state, and the ductility is higher than that for the plates in the cold-rolled state. Further investigation reveals that the formation of heterogeneous structure characterized with recrystallized-fine grains embedded in deformed-coarse grains is responsible for the observed extraordinary mechanical properties. Rolling path could also affect the microstructure evolution and formability of the plates. For plate rolled with route 1 (unidirectional rolling), a stronger Copper-type texture with two Brass-type textures are observed. For plate rolled with route 2, where the rolled plate is rotated to 90° with respect to previous rolling direction between adjacent rolling passes, only Brass-type texture is generated. A rolling-path dependent edge-crack behavior is observed during rolling. Edge cracks are generated during rolling with route 2, while the edge cracks are not observed for plates rolled with route 1. Factors affecting the edge-cracks behavior are also discussed.

Macro-superlubricity in sputtered MoS2-based films by decreasing edge pinning effect

AbstractTo date, MoS2 can only be achieved at microscale. Edge pinning effect caused by structure defects is the most obvious barrier to expand the size of structural superlubricity to macroscale. Herein, we plan to pin edge planes of MoS2 with nanospheres, and then the incommensurate structure can be formed between adjacent rolling nanoparticles to reduce friction. The sputtered MoS2 film was prepared by the physical vapor deposition (PVD) in advance. Then enough Cu2O nanospheres (∼40 nm) were generated in situ at the edge plane of MoS2 layers by liquid phase synthesis. An incommensurate structure (mismatch angle (θ) = 8°) caused by MoS2 layers was formed before friction. The friction coefficient of the films (5 N, 1,000 r/min) was ∼6.0×10−3 at the most. During friction, MoS2 layers pinned on numerous of Cu2O nanoparticles reduced its edge pinning effect and decreased friction. Moreover, much more incommensurate was formed, developing macro-superlubricity.

Development and Application of Asynchronous Roll Shifting Strategy of Double Attenuation Work Roll in Hot Rolling

In view of the problems of the violent crown fluctuation and unstable shape control in the endless rolling production line, the field measurement results show that the abnormal crown fluctuation is related to the shifting limit position of the work roll after the uneven wear occurs. For this reason, the asynchronous roll shifting strategy is developed, which has double attenuation of roll shifting amplitude and roll shifting step. By coupling the roll wear contour model, the roll thermal contour model and the rolls-strip integrated model, the strip crown calculation model of the whole rolling unit is established, and the causes of abnormal crown fluctuation are revealed theoretically. In addition, the simulation analysis of the important parameters of asynchronous roll shifting strategy of double attenuation working roll is made by using this model. The number of strips in a roll shifting cycle is found to be too large or too small, which is not benefited by the control of the strip crown stability due to the influence of roll wear and roll thermal crown. A rolling unit has many shifting cycles. When the roll shifting amplitude at the end of a rolling unit is smaller, which can make the amplitude difference between adjacent roll shifting cycles greater, it is easier to avoid the uneven edge wear area and to control the strip crown stability. The industrial test shows that the maximum crown fluctuation in a rolling unit decreases by 21.05%, and the maximum crown fluctuation of adjacent strips decreases by 28.57%, which significantly improves the stability of crown control.

A Study on Bearing Dynamic Features under the Condition of Multiball–Cage Collision

Cage stability directly affects the dynamic performance of rolling bearing, which, in turn, affects the operating state of rotating equipment. The random collision between the rolling elements and the cage pocket is the main reason for cage instability. In this paper, from the perspective of the relative sliding velocity between the rolling elements and the bearing raceway, the interactions of the rolling elements and the cage pockets were analyzed, and the four zones with different collision features were defined. On this basis, and on the basis of the bearing dynamics model, the interaction of two adjacent rolling elements and the cage pockets in the a’–b’ area is discussed, and the peak impact force of the adjacent two balls and the cage pockets was investigated in terms of the rotation speed, radial load, acceleration/deceleration, and materials. When the ball runs close to the loaded zone, the probability of multiball random collision increases, which leads to an increase in the cage instability. At the entrance of the loaded zone, the peak impact force has the greatest impact on the cage stability during the acceleration process. Compared to the radial load applied to the bearing, the peak impact force is more sensitive to the bearing speed changes. The multiball collision analysis method provides a new idea for the research of cage stability.

Relaminarization of spanwise-rotating viscoelastic plane Couette flow via a transition sequence from a drag-reduced inertial to a drag-enhanced elasto-inertial turbulent flow

Direct numerical simulation of spanwise-rotation-driven flow transitions in viscoelastic plane Couette flow from a drag-reduced inertial to a drag-enhanced elasto-inertial turbulent flow state followed by full relaminarization is reported for the first time. Specifically, this novel flow transition begins with a drag-reduced inertial turbulent flow state at a low rotation number $0\leqslant Ro \leqslant 0.1$ , and then transitions to a rotation/polymer-additive-driven drag-enhanced inertial turbulent regime, $0.1\leqslant Ro \leqslant 0.3$ . In turn, the flow transitions to a drag-enhanced elasto-inertial turbulent state, $0.3\leqslant Ro \leqslant 0.9$ , and eventually relaminarizes at $Ro=1$ . In addition, two novel rotation-dependent drag enhancement mechanisms are proposed and substantiated. (1) The formation of large-scale roll cells results in enhanced convective momentum transport along with significant polymer elongation and stress generated in the extensionally dominated flow between adjacent roll cells at $Ro\leqslant 0.2$ . (2) Coriolis-force-generated turbulent vortices cause strong incoherent transport and homogenization of significant polymer stress in the bulk via their vortical circulations at $Ro=0.5 - 0.9$ .

Dynamic analysis of the center position control and design of disturbance observers during annealing and pickling

In this study, we propose a new center position controller (CPC) to control the center position error (CPE) of the steel strip during the annealing and pickling processes. The model of the nonlinear CPC system is described for two adjacent rolls and extended to multifeed rolls. We derive a linearized discrete state equation for the multi CPC and analyze its characteristics. A simulator of the CPC system that includes rollers, actuators, and plant data is developed to test the dynamics of the CPC. In addition, a disturbance observer with a low pass filter Q(s) is designed to minimize the effects of various disturbances. The order and time constant of the filter are selected in consideration of the order of the system and the response of the actuator. Results of the offline tests show that the CPE is greatly decreased by the proposed control technology.

A research on the time-varying stiffness of the ball bearing considering the time-varying number of laden balls and load distribution

In response to the fact that not all rolling balls are laden when the angular contact ball bearing working under the condition with certain combined loads especially when the axial preload is not large enough, an analytical method for the determination of the time-varying stiffness of angular contact ball bearing considering the effect of time-varying number of laden balls and load distribution is proposed in this paper. According to the definition of the stiffness, the time-varying stiffness under different sets of combined loads is obtained by the implicit function derivation method. Only the principal diagonal elements of the stiffness matrix are studied for the sake of simplicity. Several numerical examples are simulated and the simulation results indicate that the time-varying number of laden balls and load distribution have a significant effect on the stiffness. The period of the time-varying stiffness is consistent with the time required for the cage to rotate the angle between the adjacent rolling balls. The calculation of the ball bearing quasi-static model and the analytical method for the determination of the stiffness is verified by the existing references.

Effect of deformation routes on the microstructures and mechanical properties of the asymmetrical rolled 7050 Aluminum alloy plates

Asymmetric rolling (ASR) with three different deformation routes and conventional symmetric rolling (CR) were carried out in 7050 Al alloy plates, so as to study the influence of deformation route on the strain distribution, microstructural evolution and mechanical properties. The results show that the ASR process introduces much more effective strain throughout the thickness, resulting in severe deformation or microstructural evolution and improving the alloy's ductility compared to CR deformed samples, irrespective of the deformation routes. Among the three ASR deformation routes, the ASR-R process can introduce highest strains to improve the through-thickness deformation homogeneity, subsequently amount of finer subgrains can be observed in the wider shear band zones due to the intersection of shearing patterns of adjacent rolling passes. Although the strengths of the ASR-processed plates are almost similar, their tensile elongations are obviously affected by the deformation routes, especially the ASR–R route contributes to ~ 23% elongation, which would be mainly responsible by the grain refinement, homogeneous distribution of microstructure and fragmentation of coarse constituent particles.

DNA Bending through Roll Angles Is Independent of Adjacent Base Pairs.

We have studied DNA bending for a wide range of DNA sequences by two-dimensional adaptive umbrella sampling simulations on adjacent roll angles. Calculated free energy surfaces are largely additive and can be well approximated by the sum of the one-dimensional free energy surfaces. Cooperativity between adjacent roll angles was found to be negligible: less than 1.0 kcal/mol and a small fraction of the overall bending energy. Our calculations validate the assumptions underlying many popular coarse-grained models for DNA bending, and demonstrate their theoretical validity for investigating DNA bending.

Simulations of DNA Bending using Adaptive Umbrella Sampling on Roll Angles

Many proteins bend DNA significantly upon binding. To simulate this bending within the time scales accessible to molecular dynamics, we used adaptive umbrella sampling on the roll angles. We studied the inherent flexibility of bare DNA by simulating dodecamers with varying sequences and made comparisons to the worm-like chain model. Simulations of bare DNA were also performed to assess the co-operativity of the bending of adjacent roll angles. A study of DNA bending by the archaeal DNA packaging protein Sac7d will be presented as well.

Taking into account the possibility of rolled strip breaking in simulation model of electric drives of two adjacent rolling mills of cold rolling train

The simulation model of electric drives of two adjacent rolling mills is developed, which takes into account the possibility of rolled strip breaking. The model is designed to study electromechanical transition processes in these actuators at emergency operation.

Simplification of Dynamic Capacity and Fatigue Life Estimations for Oscillating Rolling Bearings

A Dynamic capacity for oscillating rolling bearings was published in 1968 and correlated with available laboratory fatigue life data. That development of the Dynamic Capacity extended the classic fatigue life theory of Lundberg and Palmgren (1947 and 1952) to oscillating rolling bearings. The calculation of the Dynamic Capacity is simplified as a modification of present ABMA and ISO load rating and life standards for continuously rotating rolling bearings. The simplified formulas agree with the Harris, 1991, text book formulation for oscillation amplitudes (greater than the critical amplitude) which cause an overlapping of stressed contact areas by adjacent rolling elements. Oscillation amplitudes less than the critical amplitude result in separate, discrete contact areas on each raceway. Use of the Harris equations will lead to overestimation of the fatigue for oscillation amplitudes which are less than the critical amplitude.

Flow in a double-film-fed fluid bead between contra-rotating rolls Part 1: equilibrium flow structure

In multiple-roll coaters thin liquid films are transferred from roll to roll by means of liquid ‘beads’ which occupy the small gaps between adjacent rolls. Double-Film-Fed (DFF) beads are those which feature two ingoing films instead of the usual one, and arise in the intermediate stages of certain types of roll coater. One of the ingoing films, h1, is supplied from the previous inter-roll gap while the other, h2, ‘returns’ from the subsequent gap. Such a flow is investigated here under the conditions of low flow rate, small capillary number and negligible gravity and inertia, using lubrication theory and finite element analysis. The thickness of film h1 is fixed independently, while that of h2 is specified as a fraction, ζ, of the film output on the same roll. This simple approach allows a degree of feedback between the output and input of the bead, and enables one to simulate different conditions in the subsequent gap. Predictions of outgoing film thicknesses made using the two models agree extremely well and show that, for each value of ζ < 1, one outgoing film thickness decreases monotonically with speed ratio, S, while the other features a maximum. Good agreement is also seen in the pressure profiles, which are entirely sub-ambient in keeping with the small capillary number conditions. The finite element solutions reveal that in the ‘zero-flux’ case (when ζ = 1) the flow structures are very similar to those seen in an idealized cavity problem. In the more general (ζ < 1) situation, as in single-film-fed meniscus roll coating, several liquid transfer-jets occur by which liquid is conveyed through the bead from one roll to the other. The lubrication model is used to calculate several critical flow rates at which the flow is transformed, and it is shown that when the total dimensionless flow rate through the bead exceeds 1/3, the downstream flow structure is independent of the relative sizes of the ingoing films.

Interface instability in the bulk processing of 2223 BSCCO powders

Abstract Interface instability (or “sausaging”) has been a major problem in the oxide powder-in-tube tape-rolling process. The fast Fourier transform of core instabilities are first performed to study the rolled tapes and to obtain quantitative information on the wavelengths and magnitudes of the non-uniform profiles. The existing experimental observations are also re-examined and summarized. Treating this problem as the bimaterial interface instability, both bifurcation analysis and finite-element modelling are applied to study the influences of roll-gap geometry, packing fill factor and clad material properties on the instability wavelength and magnitude. Good correlations between theoretical results and experimental observations are found. The critical wavelength/current core thickness ratio λ∗/ d c is found to be sensitive to the fill factor only, and insensitive to the reduction/pass ratio, and the core and clad material properties; that is, the relative tape geometry is the single dominating factor that affect the normalized critical wavenumber λ∗/d c. Consistent with experimental observations, a smaller reduction/pass ratio, a higher initial core porosity, a higher hardening clad material and a larger core fill factor can reduce the normalized instability magnitude Δv/d c (i.e. the instability magnitude/current core thickness ratio) at the same tape reduction strain level. The results suggest that the reason for the much smaller interface variation magnitude with a small reduction/pass ratio (i.e. 5% per pass) compared with a large reduction/pass ratio (i.e. 25% per pass) is not because the small reduction/ pass ratio can eliminate or delay the interface instability initiation; it is, however, most probably caused by the random disruption of the interface by the many rolling steps with critical wavelengths very close to each other between adjacent rolling steps.

Fast modelling of roll stack behaviour for control applications

A fast model of roll stack deformation is presented. Appropriate simplified structural models are chosen by careful consideration of the application of general theories. Discretization of continuous variables allows the use of matrix-based weighting functions in describing component deformation and leads to a vectorized solution. All model non-linearities are considered, with particular attention given to the variable region of contact between adjacent rolls in the stack. A novel and efficient ‘binary choice matrix’ method is developed to describe the uncertainty in defining this region. This leads to a more efficient solution than previously published related models. Opportunities for future extensions are discussed.

Mathematical model of the transfer of the excitation of vibration between adjacent rolling stands of a continuous group

In this study the bar is replaced by a system with a continuous distribution of mass. The mathematical description of this system should be an element of the model of continuous rolling mills and can be investigated only in conjunction with rolling mills.

A new mechanism of small-scale transition in a plane mixing layer: core dynamics of spanwise vortices

We present a new mechanism of small-scale transition via core dynamics instability (CDI) in an incompressible plane mixing layer, a transition which is not reliant on the presence of longitudinal vortices (‘ribs’) and which can originate much earlier than ribinduced transition. Both linear stability analysis and direct numerical simulation are used to describe CDI growth and subsequent transition in terms of vortex dynamics and vortex line topology. CDI is characterized by amplifying oscillations of core size non-uniformity and meridional flow within spanwise vortices (‘rolls’), produced by a coupling of roll swirl and meridional flow that is manifested by helical twisting and untwisting of roll vortex lines. We find that energetic CDI is excited by subharmonic oblique modes of shear layer instability after roll pairing, when adjacent rolls with out-of-phase undulations merge. Starting from moderate initial disturbance amplitudes, twisting of roll vortex lines generates within the paired roll opposing spanwise flows which even exceed the free-stream velocity. These flows collide to form a nearly irrotational bubble surrounded by a thin vorticity sheath of a large diameter, accompanied by folding and reconnection of roll vortex lines and local transition. We find that accelerated energy transfer to high wavenumbers precedes the development of roll internal intermittency; this transfer, inferred from increased energy at high wavenumbers and an intensification of roll vorticity, occurs prior to the development of strong opposite-signed (to the mean) spanwise vorticity and granularity of the roll vorticity distribution. We demonstrate that these core dynamics are not reliant upon special symmetries and also occur in the presence of moderate-strength ribs, despite entrapment of ribs within pairing rolls. In fact, the roll vorticity dynamics are dominated by CDI if ribs are not sufficiently strong to first initiate transition; thus CDI may govern small-scale transition for moderate initial 3D disturbances, typical of practical situations. Results suggest that CDI constitutes a new generic mechanism for transition to turbulence in shear flows.