An upper bound method for analysis of three-dimensional deformation in the flat rolling of bars

A new upper bound method for the analysis of three-dimensional deformation in the flat rolling of bars is proposed. In the conventional upper bound method, stress distribution is not calculated. Hence, a new method of calculating stress distribution is proposed in which the hydrostatic stress in each element and the contact stress on the contact surface between material and roll in each element are calculated. In the conventional upper bound method, the structure of the computer program also depends highly on the kinematically admissible velocity fields assumed. Hence, a new method of analysis in which the structure of the computer program depends minimally on the kinematically admissible velocity fields assumed is proposed. In the analysis of strip rolling, the calculated roll force and roll torque agree with the roll force and roll torque calculated from Sims’ slab method. In the analysis of the flat rolling of bars, the calculated width spread agrees with the width spread obtained by experiments reported in the literature. The effects of a reduction in thickness, roll radius, material width-to-height ratio, front tension, back tension, and front and back tensions on the width spread, forward slip, roll force and roll torque are demonstrated. Hence, the validity of the new upper bound method is confirmed.     

An approximate method for a three-dimensional analysis of rolling

A theory, based on the extremum principle for rigid perfectly plastic materials, is given for the analysis of three-dimensional deformation in rolling. Theoretical solutions are obtained for single-pass rolling in terms of sideways spread, roll torque and the location of neutral points. The results on spread and roll torque showed excellent agreement with those found by experiments in the literature.     

Simplified theories of flat rolling—II. Comparison of calculated and experimental results

A simplified inhomogeneous solution for the roll pressure has been used as the basis for computing consistent precise estimates of roll force and roll torque from the theory of cold flat rolling. The accuracy of the new method is established in this paper by re-analysing previous data for the rolling of prestrained copper, data for the rolling of annealed mild steel and results for the rolling of low carbon steel with lubrication. Both Swift's stress-strain law and a polynomial function are used to represent the experimental yield data for the rolled materials.     

Modified slab analysis of asymmetrical plate rolling

In this paper the general case of asymmetrical plane strain rolling due to unequal roll diameter, unequal surface speed of the rolls and different contact friction is considered. An analytical model based on the slab method of analysis was used and further developed to obtain the characteristics of asymmetrical sheet rolling and to predict strip curvature. This method describes an enhancement to the rolling theory where friction becomes an integral part of deformation mechanics in the roll gap. To verify the validity of the proposed analytical model, the analytical rolling force, torque and curvature were compared with experimental and analytical results of other investigators. Very good agreements are found. Capability as well as the simplicity of the proposed model in predicting more accurate theoretical results for the rolling force, torque and curvature makes it suitable for the online control application.     

Simulation of T-section profile ring rolling by the 3-D rigid-plastic finite element method

The three-dimensional rigid-plastic finite element method is used to simulate the open pass profile ring rolling of a T-shaped section from an initially rectangular cross-section. Because the ring rolling process is incremental and the deforming region is restricted to the vicinity of the roll gap, only a ring segment spanning the roll gap is analysed in order to save computation time. As the thickness of the ring is reduced, the mesh system is progressively modified to treat profile development more effectively. Roll separating force, strain distribution, strain rate distribution and cross-sectional configuration of the deformed ring are calculated. Comparisons between computation and experiment show good agreement in roll separating force and cross-sectional configuration of the deformed ring.     

Numerical simulation and experimental study on geometry variations and process control method of vertical hot ring rolling

The accurate geometry and effective control during the ring rolling process are the prerequisites for the ring products’ precise forming. In this paper, the interaction modes and rules between ring and rolls in vertical hot ring rolling (VHRR) process are analyzed, and the change laws of the ring’s geometry are studied. Based on the ABAQUS/Explicit software and its subroutine VUAMP, the finite element (FE) model of the VHRR process with measurement and control is established. Then, the ring rolling process of a groove-section profile ring is simulated. During the simulation, the ring’s outer diameter, roundness error, and the stability of the rolling process are detected in time, and the close-loop control of feed plan of the drive roll and measuring roll are also employed. The results obtained show the following: (1) Four feed stages are divided by means of a step-down feed movement, that is, bite stage, main rolling stage, precise forming stage, and sizing stage. (2) At bite and main rolling stages of the VHRR process, the ring’s center swings in a spiral line, and the rolling process is unstable, the ring’s roundness becomes worse, while the process is entering the precise forming stage, by means of the guide roll, the rolling process becomes steady and the ring’s roundness tends to be better. (3) The measuring roll contacts with the ring at the main rolling stage, afterwards, it is pushed back at the precise forming stage by ring’s growth. When the measuring roll meets the desired displacement value, a stop feeding command will be fed back, and the ring rolling process enters the sizing stage. At the sizing stage, the ring’s outer diameter still increases a little. (4) A series of VHRR experiments are conducted, and FE results are in good agreement with experimental results. The absolute errors of the ring’s outer diameter and the roundness are within 1 mm. The research results of this paper have practical significance to guide the VHRR production.     

Study on the improved accuracy of strip profile using numerical formula model in continuous cold rolling with 6-high mill

The quality requirements for thickness accuracy in cold rolling continue to become more stringent. In cold rolling mill, it is very important that the rolling force calculation considers rolling conditions. The rolled strip thickness was predicted using calculated rolling force. However, the prediction of strip thickness in cold rolling is very difficult; in particular, for 6-high mill with shifted intermediate roll (IMR), the accuracy of thickness is not good. In this study, to improve the accuracy of rolled strip thickness, the roll gap flattening can be given based on Hertz contact theory, with contact between rolls and the smooth cylindrical rolls for the rolling elastic deformation. Also, the distribution of the roll gap flattening may be calculated using the contact force of unit transverse length. The strip profile at the continuous cold rolling is calculated by using the numerical analysis model considering the initial strip profile before cold rolling. Hence, we propose that the numerical model can predict the rolled strip profile more quickly and accurately and be applicable to the field. The results of the proposed numerical model were verified by FE-simulation and cold rolling experiments of 6-high mill with five stands.     

花键冷滚压成形力测试与分析

根据花键冷滚压加工原理,按机床受力,将加工过程中的滚压力分为主轴转矩和径向进给力两部分。设计测试方案,用计算机数据采集系统测得了主轴转矩和径向进给力在滚压过程中的实时变化曲线,分析了它们的变化特征,得出压入阶段结束时滚压力取最大值。对不同的工艺参数进行实验,得到了工艺参数对最大滚压力的影响规律。     

芯辊进给速度对环件冷轧工艺的影响规律

环件冷轧是一种先进的塑性加工工艺,而其中芯辊的进给速度对环件冷轧工艺有重要影响。本文针对环件冷轧工艺的特点,以数值仿真法为主要研究方法,以有限元分析软件ABAQUS为平台,利用弹塑性动态显式有限元法对环件冷轧变形过程进行了三维数值模拟,研究揭示了矩形截面环件开式冷轧工艺中总压下量不变时芯辊进给速度对轧制力、轧制力矩和环件轴向宽展的影响规律,并分析了进给速度与环件咬入之间的关系。结果表明:进给速度相对较小时,环件的宽展以及鱼尾形状系数随进给速度的增大而急剧减小,端面变得平整;当进给速度进一步增大时,环件宽展以及鱼尾形状系数变化不大;进给速度对鱼尾形状系数的影响主要取决于进给速度对环件外层附近金属的轴向流动的影响;随着芯辊进给速度的增大,轧制力和轧制力矩也相应增大,因此对轧环机力能参数的要求也提高;芯辊进给速度的增大不利于环件的咬入。     

材料参数对环件冷辗扩工艺的影响规律研究

基于ABAQUS软件环境,采用弹塑性动态显示有限元法,通过三维数值模拟研究揭示了几个重要的材料参数(硬化指数、屈服强度和弹性模量)对环件冷辗扩过程中环件端面质量、轴向宽展、辗扩力、辗扩力矩以及金属流动特性的影响规律,并从金属塑性成形原理和塑性加工力学等角度对这些规律进行了合理的解释,从而获得了何种材料性能适应冷辗扩成形的认识,为环件冷辗扩在实际应用中材料和设备的选择提供了依据,对揭示冷辗扩成形机理也具有十分重要的意义。     

Three dimensional thermal mechanical coupled simulation during hot rolling of aluminium alloy 3003

Rolling passes of a pass schedule supplied by an aluminium company and containing reliable measured data of roll load and torque is considered. Percentage reductions range from 6% to 20% and are analysed by a commercial thermo-mechanical coupled FEM program FORGE3 V5.3. An inverse analysis method is adopted to match the calculated rolling force and torque with the measured rolling force and torque by treating the friction law and the friction coefficient as free parameters. Three widely accepted friction laws are investigated; Tresca friction, Coulomb friction and viscoplastic friction. The use of viscoplastic friction is shown to yield both more reliable and more accurate results than other models. Significantly the friction coefficient can be traced to remain constant throughout the pass schedule of the breakdown rolling. The contact pressure distribution is then studied with different thickness reductions and compared with published experimental results. The predicted and experimental agreement is such that the load calculation can be regarded as satisfactory. Acceptable agreement is also obtained with the measured torque values. The distribution of equivalent strain, temperature and the stress in the roll gap and the lateral profile are discussed.     

超大型环件径轴向轧制过程稳定性与圆度自适应控制方法研究

超大型环件径轴向轧制过程失稳、失圆等异常状态常导致轧环终止和产品质量波动。提出了轧环过程稳定性和圆度自适应控制方法,从历史数据中归纳人工控制经验知识,建立了基于锥辊转速模糊调节的轧制稳定性控制方法,制定了基于导向力反馈的轧制圆度控制策略。运用ABAQUS有限元软件和子程序二次开发,设计了轧环过程稳定性和圆度自适应控制子程序,建立了16 m超大型环件轧制过程控制有限元模型,仿真分析了锥辊转速模糊调节、导向力反馈以及基于限幅滤波的锥辊转速模糊调节+导向力反馈综合控制下的轧环过程偏移量和圆度误差变化规律,结果表明该方法与常规规划控制相比,环件偏移量减小了48.3%,圆度误差减小了61.8%。     

An experimental determination of the roll pressure distributions in cold rolling

The paper describes the design of transducers and experiments to measure the pressure distribution in the roll gap during cold metal rolling. Results are presented for aluminium, copper and mild steel. The pressure distributions obtained experimentally conform to cold rolling theory in certain circumstances, but there are notable exceptions. The experiments indicate that there is no sticking between the specimen and rolls.     

An application of fuzzy inference for studying the dependency of roll force and roll torque on process variables in cold flat rolling

In this work, the roll force and roll torque in a cold flat rolling process are modelled using first order Takagi–Sugeno fuzzy models. The fuzzy models predict the most likely lower and upper estimates of the roll force and roll torque. Although the fuzzy models can be based on the experimental data, in the present work, the required data is generated by radial basis function neural networks. The neural networks, in turn, are trained by a finite element method-based code. It is demonstrated that the coefficients of the linear crisp function used to represent the output variables in the fuzzy inference system can be used for assessing the sensitivity of these variables with respect to the process variables. An algorithm to detect and suppress the outliers in the data is proposed. The effectiveness of the proposed algorithm is demonstrated through an example.     

Simulation of ring rolling using a rigid-plastic finite element model

This paper describes details of a finite element model for analysing three-dimensional flow in the roll gap during radial ring rolling between plain cylindrical rolls. The model considers such factors as curvature of the workpiece, unequal roll diameters and the fact that the inner roll or mandrel is unpowered. The results of the analysis compare favourably with experimental observations. Fishtailing is predicted satisfactorily, also the form of the pressure distribution in the roll gap, which shows twin peaks under some rolling conditions. The method has the merits of easy handling and short calculation time. It should be a useful aid to the design of ring rolling and other asymmetric rolling processes.     

Multi-factor coupling system characteristic of the dynamic roll gap in the high-speed rolling mill during the unsteady lubrication process

In the present work, a multi-factor coupling dynamic model of a rolling mill system for a dynamic roll gap during an unsteady lubrication process was developed on the basis of the rolling theory, lubrication and the friction theory, and the mechanical vibration theory. The multi-factor coupling model of interfacial film binding was coupled with the rolling force model, dynamic roll gap interface friction model and work roll movement model. The corresponding distributions of friction and pressure at varying surface roughness and times were systematically analyzed during the unsteady mixed lubrication process. The effects of the main processing parameters on the critical speed and amplitude for self-excited vertical vibration were investigated.     

复合轧环机液压系统动态分析与优化研究

介绍了HHRM200型复合轧环设备液压系统的构造及其工作原理,并基于AMESim软件建立其仿真模型,利用批运行的方法确定了二通插装阀中难以确定的最大流量系数,研究了整个环件轧制过程中复合轧环设备液压系统的动态特性,且依靠优化算法对液压系统PID控制器参数进行优化,优化后的参数使位置偏差对时间的积分值降低了40.2%。最后,进行了复合轧制实验,验证了利用该参数建模所得主轧辊定位精度的可靠性。该研究为复合轧环机液压系统的设计、调试提供参考依据,有一定的实用价值。     

A comparison of methods to estimate the roll torque in thin strip rolling

An energy balance method is used to calculate the roll torque associated with non-circular thin strip rolling and the results for the torque are compared with the moments of the forces exerted on the roll by the strip. An example is given in which the results of the two methods are quite different. This probably indicates that the axis of the roll is not at the point about which the moment is taken. The energy balance method is also used to estimate the torque associated with circular arc rolling. The results are compared with those calculated with Hill's formula in one example and, in another example, the comparison is made between the results from the energy method formulated in this paper and a commercial package which also uses both an energy method and Hill's formula.     

Modeling of on-line measurement for rolling the rings with blank size errors in vertical hot ring rolling process

The size errors of the ring blanks have a considerable effect on the vertical hot ring rolling process and the ring products’ dimensional precision. In this paper, the geometric relationship between the ring’s outer diameter and the measuring roll’s displacement is studied, and then, the influence of the blank size errors on this geometric relationship is analyzed. Subsequently, a modeling method of the measurement model for vertical hot ring rolling process is proposed, that is, the ring’s outer diameter can be measured indirectly through the relations of the ring’s outer diameter with respect to the measuring roll’s displacement and the ring blank’s outer diameter. Using this modeling method, the on-line measurement model of a certain type of vertical hot ring rolling mill was established, and the verification experiments were also conducted. The experiments showed that this on-line measurement model could calculate the ring’s outer diameter precisely, and the absolute errors of the formed rings were less than ±1.5 mm. The research results of this paper have general significance for the on-line measurement and process control of vertical hot ring rolling process.     

万能凸度轧机中间辊偏移板形调控能力分析

1420单机架万能凸度轧机(Universal crown mill,UCM)轧制极薄带时,中间辊偏移对正向轧制与负向轧制时工作辊弯辊、中间辊弯辊及中间辊窜辊的板形调控特性存在一定的影响,从力学角度分析辊系的受力状态,并运用LS-DYNA有限元软件建立显示动力学模型,定量计算中间辊不偏移轧制与正向偏移轧制及负向轧制时各板形调控手段的调控特性。计算结果显示轧机中间辊不偏移时,工作辊弯辊力与带钢凸度呈线性关系,随着工作辊弯辊力的增大,带钢凸度减小;当中间辊偏移时,工作辊弯辊调控功效要大于中间辊不偏移时,且正向轧制的弯辊调控功效要优于负向轧制;中间辊弯辊调控特性表现出与工作辊弯辊相似的变化趋势。不同中间辊窜辊的板形调控能力变化不大,不偏移轧制与负向轧制调控能力基本相同,正向轧制在窜辊量为15~30 mm范围内,其调控能力好于另外两种轧制工况。