Roll Bending Research Articles

Analytical and Finite Element Analysis of the Rolling Force for the Three-Roller Cylindrical Bending Process

In the roll bending process, the rolling force acting on the roller shafts is one of the most important parameters since, on the one hand, it determines the process settings including the pre-loading, and, on the other hand, its distribution and size may affect the integrity of both the bending system and the final product. In this study, the three-roller bending process was modeled using a two-dimensional plane–strain finite element method, and the rolling force was determined as a function of plate thickness, upper roller diameter, and yield strength for various API steel grades. Based on the numerical simulation results, a critical bending angle of 41° was identified and the rolling systems were divided into two categories, of less than or equal to, and greater than 41°, and an analytical model for predicting the maximum rolling force was developed for each category. To determine the optimal pre-tensioning force, two optimization formulations were proposed by minimizing the maximum equivalent stress and the absolute maximum displacement. The rolling forces predicted by the analytical models were found to be in good agreement with the numerical simulation results, with relative errors generally less than 10%. The predictive analytical models developed in this study capture well the complex deformation behavior that occurs during the roll bending process of steel plates, providing guidelines and predictions for industrial applications of this process.

RETRACTED: Shi et al. Effect of Final Rolling Temperature on Microstructures and Mechanical Properties of AZ31 Alloy Sheets Prepared by Equal Channel Angular Rolling and Continuous Bending. Materials 2020, 13, 3346

The journal retracts the article, “Effect of Final Rolling Temperature on Microstructures and Mechanical Properties of AZ31 Alloy Sheets Prepared by Equal Channel Angular Rolling and Continuous Bending” [...]

Microstructure evolution and springback behavior in single-pass roll bending of magnesium alloy plates

Using magnesium alloy plates instead of high-strength steel and titanium alloys in roll-formed parts significantly improves the lightweight, damping, and heat dissipation properties of automotive components. This paper employs finite element simulation combined with experimental methods to perform single-pass roll bending of AZ31B magnesium alloy plates at angles of 0°-15°, 0°-25°, and 0°-35°. Measured the springback angle and microhardness at the bends, and used optical microscopy (OM) and electron back scatter diffraction (EBSD) to analyze the microstructural characteristics, texture, and orientation evolution at the bend during the roll bending process. The results indicate that during roll bending, the inner bend area has significantly more twins than the outer area, with more pronounced grain refinement on the inner side. {10-12} tensile twins mainly coordinate plastic deformation, with some {10-12}-{10-12} tensile twin variants present. The inner bend area's texture shifts from ND to TD direction, strengthening the TD direction texture, while the outer area retains typical rolling texture. The prismatic slip in the inner region of the bend changes from hard to soft orientation. The inner region is mainly coordinated plastic deformation by prismatic slip, while the outer region is mainly coordinated by basal slip. As single-pass roll bending angles increase, the increase in twin boundaries and low-angle grain boundaries (LAGBs) significantly reduces the springback angle. Additionally, grain refinement and increased geometric necessary dislocation density lead to higher microhardness.

Effect of ultrasonic vibration on the roll bending deformation behavior of ultra-thin-walled corrugated sheets

The ultra-thin-walled corrugated sheet is a crucial component of metal honeycomb structures. Due to the size effect, the traditional roll bend forming process often leads to significant dimensional deviations in ultra-thin-walled corrugated sheets. To address this issue, an ultrasonic vibration-assisted roll bend forming process was proposed. First, an ultrasonic vibration-assisted roll bend forming device was designed, which had a special drive roller structure that can alter the original axial direction of ultrasonic vibration to produce a radial vibration with an amplitude of 0–2 µm. Under the high-frequency impact and acoustic softening effect of ultrasonic vibration, the ultra-thin-walled corrugated sheets formed numerous plastic penetration zones. As a result, the influence of individual grain heterogeneity was weakened and the stress distribution states underwent an interchange. Therefore, the ultra-thin-walled corrugated sheets demonstrated improved edge length uniformity, increased hardness in the deformed areas, reduced surface roughness, and decreased springback angle. However, excessive ultrasonic amplitude resulted in severe thinning or even rupture. Ultimately, high-quality ultra-thin-walled corrugated sheets were successfully fabricated using pure titanium foil with a t/d of 5.4 and an ultrasonic amplitude of 1.6 μm.

Roller Position Design in the Roll Bending Process of a Non-Uniform Curvature Profile

Roller Position Design in the Roll Bending Process of a Non-Uniform Curvature Profile

Springback characteristics and influencing laws of four-axis flexible roll bending forming for aluminum alloy.

This study aims to solve the problem of springback control of aluminum alloy components in the rolling process, and the method of combining experiment and simulation is adopted. Firstly, a series of aluminum alloy samples are designed, and the four-axis flexible bending machine is used for precision roll bending. Secondly, the three-dimensional (3D) shape change data of the workpiece before and after roll bending is monitored and recorded in real-time by a high-precision 3D scanner. Meanwhile, aiming at different rolling process parameters of each group (including roll bend speed, feed rate, pre-deformation amount, mold curvature radius, and other factors), advanced finite element software is used to carry out detailed simulation and calculations. In addition, the coincidence is compared and analyzed between the actual experiment results and the simulation prediction. The stress-strain distribution and springback evolution of aluminum alloy during roll bending are described accurately. The experimental and simulation results show that the springback rate of aluminum alloy fluctuates in the range of 5% to 15% after four-axis flexible roll bending, and the specific springback value is influenced by various process parameters. For example, under the premise of keeping other conditions unchanged, when the roll bending speed is increased from 30mm/s to 60mm/s, the springback rate shows an upward trend of about 3%. By increasing the feed rate by 20%, an average decrease of about 7% in springback quantity is observed. It can be seen that the increase in roll bending speed can aggravate the springback phenomenon, and the appropriate increase in feed rate can play a certain role in restraining the springback. Further analysis shows that the choice of the mold curvature radius and pre-deformation amount also has a decisive influence on the springback characteristics. There is a nonlinear relationship between the two parameters and the amount of springback. Changing these two parameters in a specific range can effectively regulate the springback effect.

Research and application of the flatness target curve discrete dynamic programming based on two-dimensional decision making

The flatness target curve (FTC) is a fundamental process model in cold rolling flatness control, which directly affects the quality control effect of the strip. The accurate and efficient setting of the flatness target curve is the key to ensuring continuous rolling and is a common problem faced by various production companies. This paper establishes a discrete dynamic planning (DDP) setting method for FTC with two-dimensional decision-making. To quantitatively analyze the roles of the coefficients in the FTC, the preprocessing process is established using standardized processing methods and statistical analysis methods. The flatness target curve discrete dynamic programming (FTC-DDP) is based on Bellman optimization theory with a dual structure of local and system decision-making. The decision-making functions are established based on the effect of each coefficient on FTC geometric characteristics. The concepts of “curvature factor” and “wedge factor” are innovatively proposed to obtain the decision-making value functions. The regression analysis establishes the solution equations of even number coefficients, odd number coefficients, and gain coefficients, respectively. Roll bending and tilting roll analyze the FTC’s ability to correct flatness defects. Meanwhile, utilizing a 1450 mm five-stand six-roll cold rolling mill, it is verified that FTC-DDP can quickly and accurately set the FTC, which provides an effective solution for obtaining high-precision and high-quality cold-rolled strips. Application results show that FTC-DDP can reduce the difficulty of setting up FTC by more than 70 %, reduce the setup time to milliseconds, and improve the setup accuracy by more than 50 %.

Research Progress and Prospect on Profile Roll Forming Methods and Equipment

Abstract: In recent years, with the development of aerospace, automotive, rolling stock, shipbuilding, military weapons and other industries, the demand for bent and rolled parts is increasing, and the requirements for roll forming accuracy are growing. With the rapid development of coal power, hydropower, nuclear power, wind power, and petrochemical industries, the design and research on roll bending machine and the profile roll forming methods have come into focus. The purpose of this study is to summarize the classification and characteristics of roll bending equipment, analyze the reasons that affect the accuracy of profile bending, and propose specific solutions. This paper summarizes the research status and patents on the existing roll bending equipment, introduces its structural characteristics, differences, and molding effects, and focuses on the difficulties, optimization, and improvement methods of roll bending molding. In this paper, the mechanical structures of the existing roll forming equipment have been analyzed and compared, the effects of different roll forming equipment on the profile bending results have been determined, and the reasons affecting the bending accuracy have been pointed out. By summarizing the patents and research on profile roll forming methods and equipment, the current situation and future research prospects of roll forming equipment are discussed. The roll forming equipment is divided into a roll bending machine, a CNC roll bending machine, and a flexible roll bending machine. Each design can meet different profile processing needs. From the design point of view, the optimization under the given processing profile can achieve relatively high processing accuracy. However, the processing of different profiles will still produce geometric defects, and there is some space for improvement in the structure of roll forming equipment, the materials of processing rollers, and the NC interactive system. Thus, further research on profile roll forming is needed in the future.

Estimation of pipe wall thickness variation during bending rolling

Abstract. The presented work examines the process of bending pipes using the cold rolling method. The main pa-rameters of bending that affect the change in wall thickness during the deformation process are analyzed. The influence of changing the shape of the cross-sectional shape, the increase in the pipe diameter, and the displacement of the neutral layer of bending, is identified. Theoretical values of thickening and thinning of the pipe wall are presented depending on the bending parameters. The authors provide theoretical and experimental data to assess the wall thickness variation. Data on the wall thickness of a bent pipe fitting with a diameter of 57 mm were obtained using two methods. The first method involves indirect measurements using an ultrasonic thickness gauge, while the second method involves direct measurements using a micrometer. A comparative analysis showed that the actual measurements of the wall thickness of the bent pipe fitting align with the theoretical values. Due to methodological discrepancies in the thickness measurements, it is recommended to use direct physical measurements to obtain more accurate results

A multi-stand work roll bending and shifting approach for profile contour and flatness control of electrical steel in multi-width schedule-free rolling using NSGA-II algorithm

To overcome the severe uneven work roll wear and uneven deformation of the wide-width electrical steel in the SFR (Schedule-Free Rolling) is an effective way to organize production flexibly and maximize production efficiency in hot rolling. In order to meet the increasingly stringent requirements of PCFC (Profile Contour and Flatness Control) of multi-width electrical steel in hot rolling, the collaborative control strategy of multi-stand work roll bending and shifting for profile and flatness of electrical steel in multi-width SFR was developed using NSGA-II approach. The work roll wear prediction model, thermal crown model, and strip crown model were established based on on-site measured data. Combining the work roll wear characteristics with principle, the mathematical model for work roll shifting considering multi-width was established. The main parameters of the multi-width work roll shifting strategy are obtained using the multi-objective NSGA-II algorithm. On this basis, a multi-stand collaborative control strategy, including rolling contour, short stroke roll shifting, and work roll bending, in the downstream stands during multi-width SFR was proposed. The industrial application of the developed control strategy shows that can prominently enhance the PCFC capability of electrical steel, which the uneven wear contour can be reduced.

Microstructure evolution and twinning behavior of AZ31 magnesium alloy sheets with bimodal texture during cold deep-drawing deformation

Cold deep drawing experiments were conducted on AZ31 magnesium (Mg) alloy sheets with bimodal texture, which were prepared by the newly developed equal channel angular rolling and continuous bending and subsequent annealing (ECAR-CB-A) process. The results showed that the sheet could be successfully deep-drawn at a limiting drawing ratio (LDR) of 1.6, and the forming performance was better than that of the as-rolled base-texture sheet at room temperature. The microstructure after deep-drawing deformation was investigated by X-ray diffraction (XRD), optical microstructure (OM), and electron backscatter diffraction (EBSD). A large number of {10−12} extension twins (ETs) are observed in the outer shoulder region. Due to the bimodal texture, the activated {10−12} ET variants and the basal slip within the matrix have a higher Schmid Factor (SF) value when the outer shoulder region is under radial tensile stress, this enables the shoulder of the drawn cup to maintain good deformability. In addition, some {10−11} contraction twins (CTs) and {10−11}-{10−12} double twins (DTs) can be observed in this region, which is activated by the local strain accommodation between the twins and the slip systems, and the multiaxial stress. Due to different stress conditions, the volume fractions of {10−12} ETs in the inner shoulder region are less than that in the outer region. The stress concentration caused by {10−11}-{10−12} DTs that occurred in the edge region is the reason for the fracture of the drawn cups at a drawing ratio(DR) of 1.7.

Research and application of roll bending method for welded pipe with large length and small diameter to thickness ratio

Research and application of roll bending method for welded pipe with large length and small diameter to thickness ratio

Asymmetric Shape Control Ability and Mutual Influence of the S6-High Cold Rolling Mill

The control of the asymmetric shape of strips has always been an important and difficult part of the production of cold rolling strips. In this paper, the S6-High cold rolling mill is taken as the research object. A finite element model of this mill is constructed using ABAQUS 2022 software, and a multistage working condition simulation analysis is carried out. The independent effects of asymmetric Intermediate Roll Bending (IRB) and asymmetric Intermediate Roll Shifting (IRS) on the strip shape are investigated by constructing an asymmetric convexity evaluation index. The equivalent relationship between the asymmetric roll bending and the asymmetric roll shifting was determined by analysing the coupling effect of the benchmark bending and shifting rollers on their asymmetric shape control characteristics. The on-site application shows that optimizing the amount of preset asymmetric shape control can significantly improve the asymmetric situation of the shape, providing theoretical guidance for the asymmetric shape control of the S6-High cold rolling mill.

Calculation method and analysis of residual stress in the strip bending roller straightening process

Taking thin gauge strip as an example, the deformation process of metal strip in bending roll straightening was studied. Based on the theory of discrete, curvature integral and elastic–plastic mechanics, the strip travel trajectory of the bending roll straightening process is analyzed, and the numerical analytical calculation method of the continuous straightening process of the strip bending roll is established. The results are verified by establishing MARC finite element simulation and designing straightening experiment. The effects of yield strength, plastic rate and bending amount on residual stress after straightening were studied. In the straightening process, with the increase of the amount of bending roll, the residual strain converges to the region Γ, and with the increase of the yield strength, the region Γ decreases. With the increase of the yield strength, the amount of bending roll and the plastic rate, the wave height increases. The results of the calculation of residual stress, finite element simulation and experiment are close and the trend is consistent. The results show that the logic of the calculation method is reasonable, and the prediction error is within the scope of engineering application, which is helpful to the realization of process intelligence in the process of bending roller straightening.

Wind turbine load optimization control and verification based on wind speed estimator with time series broad learning system method

AbstractWith the rapid development of wind power, the power performance and mechanical load characteristics of wind turbine are simultaneously considered and focused. Normally, wind turbine senses the incoming flow characteristics through the nacelle mounted anemometer, due to the inability to perceive the characteristics of wind speed in advance, the control strategy makes the wind turbine itself to be at a passive state during the operation process. In this paper, a wind turbine mechanical load optimization control strategy based on an accurate wind speed estimator with time series Broad Learning System Method (BLSM) is designed, simulated and also verified. Firstly, the basic control theory of the BLSM and also a mechanical load optimization controller is designed. Then the OpenFAST is used to conduct a full‐life cycle simulation comparison study on mechanical load characteristics of wind turbine before and after the implementation of the optimization control strategy. Finally, a field empirical mechanical load test is performed on the wind turbine, which is configured with BLSM mechanical load optimization control technology. The findings indicate that the implementation of this control strategy can significantly mitigate the ultimate and fatigue loads of wind turbines, particularly the fatigue loads of tower base tilt and roll bending moments, with a reduction rate of approximately 6.2% and 4.3%, respectively.

Insights into microstructure evolution and fracture mechanisms of welded joints of high strength steel patchwork components

The hot roll bending patchwork components of B1500HS uncoated ultra-high strength steel processed at industrial scale were welded with filler wire. The microstructure, grain orientation, mechanical properties and fracture behavior of the joint were investigated. The results showed that the weld metal (WM) was mainly composed of lath martensite and lower bainite (LB). Various microstructure appeared in different positions of the HAZ, among which martensite-austenite (M-A) constituents in the incompletely quenched zone and tempered martensite (TM) in the tempered zone were the key factors determining the performance of the joint. The welded joint exhibited complex structure and anisotropic mechanical response due to the decarburization and rolling texture of the original base material (BM). In the tempered zone, lath merge and boundaries disappear lead to the annihilation of dislocations, carbide precipitation leads to reduction of mobile dislocations, and recrystallization and recovery eliminate work hardening. The reduction of the effect of dislocation strengthening results in the formation of a softening belt at 6 mm from the center of the weld, with a minimum hardness of 266 HV. The tensile strength of the joint in the rolling direction (RD) was 983 MPa, and the fracture occurred in the softening belt. Both brittle and ductile fracture features were observed. The reason why the fracture occurs in the high temperature tempered zone instead of the incompletely quenched zone was the difference in the effect of “constraint strengthening”. Fracture occurred through delamination cracking along the “weak interface” owing to precipitated high-hardness cementite particles and the unfavorably oriented ferrite cleavage planes.

Moisture‐Driven Cellulose Actuators with Directional Motion and Programmable Shapes

The hygroscopic motion of plants has inspired the development of moisture‐activated soft actuators. These actuators driven by ambient moisture sources are of great research interest in robotics and self‐regulating textiles. However, these actuators often have slow motion and can only perform bending and twisting motions. Herein, a cellulose film‐based fast‐morphing and motion‐programmable soft actuator is presented that can generate caterpillar‐like movement. The cellophane films reported here bend almost instantaneously under changing humidity, with a large bending curvature, high repeatability, and negligible hysteresis. Different actuation modes are studied using both coated and uncoated cellophane films. The uncoated cellophane film can continuously move on a moist substrate through autonomous bending–rolling–flipping (or oscillating) cycles. A facile strategy is used here to control the rolling direction and facilitate the flipping motion by offsetting its center of gravity during deformation by adding appropriate weights on the end of the actuator. The coated cellophane film is used to fabricate motion‐programmable actuators through heat‐laminating. Several actuator structures are designed and fabricated and their diverse moisture‐induced motions are demonstrated.

Online Partition-Cooling System of Hot-Rolled Electrical Steel for Thermal Roll Profile and Its Industrial Application

The shape and convexity are crucial quality assessment indicators for hot-rolled electrical steel strips. Besides bending rolls, shifting rolls, and the original roll profile, the thermal roll profile also plays a significant role in controlling the shape and convexity during the hot-rolling process. However, it is always overlooked due to its dynamic uncertainty. To solve this problem, it is necessary to achieve online cooling-status control for the local thermal expansion of rolls. Based on the existing structure of a mill, a pair of special partition-cooling beams with an intelligent cooling system was designed. For high efficiency and practicality, a new online predictive model was established for the dynamic temperature field of the hot-rolling process. An equivalent treatment was applied to the boundary condition corresponding to the practical cooling water flow. In addition, by establishing the corresponding target distribution curve for the partitioned water flow cooling, online water-flow-partitioning control of the thermal roll profile was achieved. In the practical application process, a large number of onsite results exhibited that the predicted error was within 5% compared to the experimental results. The temperature difference between the upper and lower rolls was within 5 °C, and the temperature difference on both sides of the rolls was controlled within 0.7 °C. The hit rate of convexity (C40) increased by 33%. It was demonstrated that the partition-cooling processes of hot rolling are effective for the local shape and special convexity. They are able to serve as a better control method in the hot-rolling process.

Few-shot regression with differentiable reference model

Precise control models of industrial manufacturing are essential for high-quality products. In specific industrial fields, there usually exist certain theoretical results and analytical reference models. Due to the diversity of the control input and complex coupling effect on results, the analytical reference model often has strong assumptions and simplified conditions, so that the error can be large. However, it can characterize the overall trend of the real control curve. Deep learning is a promising solution for precise control model, but the huge data demand hinders its application. To this end, we propose a novel few-shot regression framework based on a differentiable reference model, where the gradient of reference model is used as the prior of the function fitter. We implement the framework on a neural network, named Gradient Guided Network, GGN, achieving accurate regression with few samples. Experimental results of sinusoidal regression and roll bend forming problem demonstrate the effectiveness and superior performance compared with meta learning methods. In addition, by combining the trend of the theoretical reference model with real data, our method also achieves better results than the reference model.

Effective Strains Determination in Continuous Constrained Double Bending with Active Friction Forces

In this work, a new process for severe plastic deformation (SPD) with active friction forces - CCDB Conform R3D2, a variation of the so-called "active bending", which is a continuous two-stage bending in calibers with small relative bending radius, is analyzed. A mechanical scheme of a device for realization of the process with a bending roller is proposed, based on a developed 3D virtual tool for its realization. Using CAD/CAE software 3D simulation, two virtual solutions of the process were compared, differing in terms of the location of the bending roller relative to the axes of the feeding and output rolls. The distribution and magnitude of the effective strains in the volume of the deformed long workpiece in the two bending stages at small relative bending radiuses were analyzed. An analytical expression is developed to determine the effective strains achieved in the SPD operation by constrained continuous bending in calibers with grooved rolls. The strain calculation methodology is based on the results obtained by simulation modelling of the CCB Conform R3D2 process in trapezoidal calibers with a bending roller located above and below the rolls line.