Strip Layer Method for Analysis of the Three-Dimensional Stresses and Spread of Large Cylindrical Shell Rolling

As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a...     

模拟板带轧制三维变形的流面条元法

提出模拟板带轧制过程三维变形的一种新的数值方法——流面条元法。沿着金属的流动轨迹,将变形区划分为若干流面(曲面)条元,为方便分析和计算,又将其映射为平面条元。横向位移和高向位移的纵向分布被分别构造为四次曲线和二次曲线,其横向分布均用三次样条插值函数表示,高向分布均用二次曲线拟合。根据塑性力学流动理论,分析推导了变形区三维变形和应力的数学模型。与曾经提出的流线条元法相比,考虑了应力与变形沿高向的不均匀分布,实现了精确的三维分析和计算。仿真实例表明,该方法和模型符合实际,为板带轧制过程的三维力学仿真提供了一个新的实用工程数值方法。     

Stream surface strip element method for simulation of the three-dimensional deformations of plate and strip rolling

A new method—the stream surface strip element method (SSSEM)—for simulating the three-dimensional deformations of plate and strip rolling process is proposed. The rolling deformation zone is divided into a number of stream surface (curved surface) strip elements along metal flow traces, and the stream surface strip elements are mapped into the corresponding plane strip elements for analysis and computation. The longitudinal distributions of the lateral displacement and the altitudinal displacement of metal are constructed respectively to be a quartic curve and a quadratic curve, the transverse distributions of them are expressed as the third-power spline function, and the altitudinal distributions of them are fitted to be a quadratic curve. Based on the flow theory of plastic mechanics, the three-dimensional deformations and stresses of the deformation zone are analyzed and formulated. Compared with the streamline strip element method, the SSSEM considers the uneven distributions of stresses and deformations along altitudinal direction, and realizes an accurate three-dimensional analysis and computation. The simulation examples indicate that the method and the model of this paper are in accord with facts, and provide a new reliable engineering-computation method for the three-dimensional mechanics simulation of plate and strip rolling process.     

带材轧制过程应力及变形的计算机仿真

用三次样条流线条元法分析带材的三维塑性变形,用分割模型影响系数法分析辊系的弹性变形,用BP神经网络方法对轧后带材板形进行模式识别,将三者联立,对900 mm HC轧机冷轧带材轧制过程进行了计算机仿真,得到了较为详细的应力及变形的仿真结果。仿真实例表明,提出的方法和模型符合实际,对三维轧制理论、板形理论及控制技术的发展有重要意义。     

Coupled dynamic modeling of rolls model and metal model for four high mill based on strip crown control

The crown is a key quality index of strip and plate,the rolling mill system is a complex nonlinear system,the strip qualities are directly affected by the dynamic characteristics of the rolling mil.At present,the studies about the dynamic modeling of the rolling mill system mainly focus on the dynamic simulation for the strip thickness control system,the dynamic characteristics of the strip along the width direction and that of the rolls along axial direction are not considered.In order to study the dynamic changes of strip crown in the rolling process,the dynamic simulation model based on strip crown control is established.The work roll and backup roll are considered as elastic continuous bodies and the work roll and backup roll are joined by a Winkler elastic layer.The rolls are considered as double freely supported beams.The change rate of roll gap is taken into consideration in the metal deformation,based on the principle of dynamic conservation of material flow,the two dimensional dynamic model of metal is established.The model of metal deformation provides exciting force for the rolls dynamic model,and the rolls dynamic model and metal deformation model couple together.Then,based on the two models,the dynamic model of rolling mill system based on strip crown control is established.The Newmark-β method is used to solve the problem,and the dynamic changes of these parameters are obtained as follows:(1) The bending of work roll and backup roll changes with time;(2) The strip crown changes with time;(3) The distribution of rolling force changes with time.Take some cold tandem rolling mill as subject investigated,simulation results and the comparisons with experimental results show that the dynamic model built is rational and correct.The proposed research provides effective theory for optimization of device and technological parameters and development of new technology,plays an important role to improve the strip control precision and strip shape quality.     

Three-dimensional FE analysis of ring rolling by employing thermal spokes method

This paper investigates the performance of the “Thermal Spokes Method” in modeling the effect of the guide rolls on the ring rolling process. If the guide rolls are not included FE, simulation encounters problems such as tilting of the ring and process instability. Thermal spokes are introduced to withstand any unwanted moment of the resultant rolling forces at the roll gap and to maintain the ring in a centralized location in the mill. By employing the thermal spokes method, much closer predictions for the lateral spread and flow patterns are calculated. This method is able to predict the tilting of the ring with respect to the stiffness of the elements of the adjustment mechanism. It is also possible by this method to predict the point at which the ring changes its support from one guide roll to another one and to study the deformation mechanism outside the roll gap. To verify the validity of the proposed method, the predicted results from this method are compared with some available references. Since the proposed method considers the effect of the guide rolls and consequently offers much closer predictions, it is a very suitable method for ring rolling simulations.     

Continuous-forming method for three-dimensional surface parts combining rolling process with multipoint-forming technology

Flexible rolling is a novel forming process for three-dimensional surface parts, which combines the rolling process with multipoint-forming technology. This process employs a pair of forming rolls as a forming tool. By controlling the gap between the upper and lower forming rolls, residual stress caused by the longitudinal non-uniform elongation of sheet metal makes the sheet metal generate three-dimensional deformation. In this paper, the improvement of the process is introduced that the middle curve radius of the roll gap is much larger than the transverse curvature radius of the forming surface in the forming process. The forming roll rotates around its own axis easily because of the small bending deformation which is suitable for producing three-dimensional surface parts including the wide sheet metal with a relatively small transversal curvature radius. The forming principle is set forth, and corresponding formulations are presented. Finite element analysis model is established, and spherical and saddle surface are simulated. The forming precision and the causes of the shape errors are analyzed through simulated results. The experimental equipment is designed and their experimental results are obtained. Simulation results are in well agreement with the experimental results, which verifies the feasibility of using simulation to guide the experiment. The results of both numerical simulations and experiments show that the proposed process is a feasible and effective way of forming three-dimensional surface parts.     

板带四辊轧机的三维振动特性

针对轧机振动传统的一维或二维的解析模式,给出1 580 mm四辊轧机振动的三维(空间)振动解析模式及其振动特性-固有频率和振型。在四辊轧机振动解析中被忽略的“不得已”间隙,必须在辊系结构予以考虑。利用修正三维多物体传递矩阵法辅之有限元法对轧机轧辊进行包含3个位移3个转角6个自由度的三维振动数值解析。数值模拟结果显示,四辊轧机考虑阻尼作用后的固有频率(复频率虚部)与现场测试频率基本吻合;“不得已”间隙导致轧机系统出现危险低频率,且振型为含有水平、交叉及摇摆等包含多个单一振型的复合振型。     

复杂断面型钢辊弯成形数值模拟

以结构分析有限条法为基础,引用固体力学有限形变理论的更新拉格朗日法（Updated-Lagrange法）,建立了弹塑性大变形样条有限条模型,并将其用于模拟一种复杂断面型钢多道次辊弯成形全过程。分析了带材的变形特点,获得了带材变形空间曲面形状,以及纵向薄膜应变和应力分布。算例表明,变形带材的角部和边缘部位是变形剧烈区域,带材上靠近轧辊前部位出现纵向拉应变峰值。沿变形带材宽度方向,离带材中心线越远变形越剧烈。     

DSC-element method for free vibration analysis of rectangular Mindlin plates

A novel DSC-element method is proposed to investigate the free vibration of moderately thick plates based on the well-known Mindlin first-order shear deformation plate theory. The development of the present approach not only employs the concept of finite element method, but also implements the discrete singular convolution (DSC) delta type wavelet kernel for the transverse vibration analysis. This numerical algorithm is allowed dividing the domain of Mindlin plates into a number of small discrete rectangular elements. As compared with the global numerical techniques i.e. the DSC-Ritz method, the flexibility is increased to treat complex boundary constraints. For validation, a series of numerical experiments for different meshes of Mindlin plates with assorted combinations of edge supports, plate thickness and aspect ratios is carried out. The established natural frequencies are directly compared and discussed with those reported by using the finite element and other numerical and analytical methods from the open literature.     

20辊轧机轧件截面形状与边部减薄预报软件开发

利用接触元双坐标法（CEM）建立了双AS—U—Roll系统森吉米尔轧机轧制过程中轧件及辊系变形行为的CEM函数矩阵,并开发了SM4SM软件。该软件能够很好地预报各种轧制条件下轧件截面形状、轧件边部减薄、轧制力、轧辊挠曲等功能。文中应用SM4SM,分析了第一中间辊锥角、锥度长度和窜辊长度对轧件截面形状和轧件边部减薄控制的影响。研究结果对冷轧过程控制轧件板形和边部减薄具有重要的参考价值。     

Shape control of alloy steel rolled by sendzimir mill

In order to improve quarter waves occurred in the wide and thin gauged alloy steel rolled by 20-high sendzimir mill, a computer simulation based on the divided element method and an actual cold rolling experiment were carried out. Quarter waves were simulated by elastic deformation analysis of rolls considering bending deformation of back up rolls and the effect of control actuators on controllability of quarter waves were analyzed. Computer simulation showed that control actuators such as shifting of the 1st intermediate roll and crown adjustment of As-U-Roll in back up rolls were not effective to control quarter waves and that changing taper mode (both length and magnitude) at the barrel-end taper radius of the 1st intermediate roll was rather very effective. From an actual rolling experiment it was verified that quarter waves could be reduced remarkerably by changing taper mode of the 1st intermediate roll.     

基于流面条元法的四辊热带钢连轧机整机仿真

用流面条元法分析带材的三维塑性变形，用影响系数法分析辊系的弹性变形，将二者联立，组成板形和板凸度的分析和计算模型，对1450mm四辊热带钢连轧机的轧制过程进行了仿真，仿真结果与实测结果吻合良好，为四辊热带钢连轧机板形分析与控制的仿真提供了模型和方法。     

Roll-pressure distribution and coefficient of friction in hot rolling by caustics

The optical method of reflected caustics was employed to investigate the variation of the coefficient of friction in the roll gap during strip rolling. Experiments have been carried out on an experimental rolling mill, using lead at room temperature, to obtain quantitative information about pressure distribution and friction, relevant to hot rolling, i.e. when frictional effects are pronounced. The rolls were made of Plexiglas. The normal and tangential pressure distribution and thence the coefficient of friction along the arc of contact at the outer edge of the strip were calculated from the caustic curves formed due to elastic deformation of the rolls, although the rolled strip was deformed plastically.An almost linear decrease of the friction coefficient from a maximum value, at the entry plane to the roll gap. to zero at the neutral plane and then a parabolic, tending to linear, increase of it, towards the exit plane, were predicted, in contradiction to what is up-to-now accepted in the praxis, that the friction coefficient remains constant during hot rolling.     

STUDY ON STRIP AND ROLL DEFORMATION COUPLING OF COLD STRIP ROLLING ON 4-H MILL

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六辊CVC轧机辊系变形的有限元分析

建立了运用有限元软件ANSYS求解具有特殊辊廓曲线和辊间接触状态的六辊CVC轧机辊系三维弹性变形的有限元模型，合理解决了对辊间接触压扁变形的建模问题，实现了对较复杂变形的求解。以国内某1420冷轧机组为研究对象，结合现场实际数据，运用有限元软件ANSYS求解六辊CVC轧机的辊系三维弹性变形，计算结果与实测数据吻合较好。     

六辊CVC宽带轧机轧辊接触压力横向分布特性的计算机仿真

用条元法分析带材的三维塑性变形,用影响系数法分析辊系的弹性变形,将二者联立,对1850mm六辊CVC轧机冷轧带材轧辊接触压力的横向分布进行了计算机仿真。结果表明,CVC中间辊横向移动、工作辊弯和中间辊弯辊等手段,对轧制压力的横向分布影响很大,对辊间压力的横向分布也有明显影响。在各种情况下,辊间压力都呈S形分布。     

Research on forming precision of flexible rolling method for three-dimensional surface parts through simulation

Flexible rolling is a novel forming process for three-dimensional surface parts using a pair of bendable rolls. By controlling the distribution of the gap between the upper and lower forming rolls in the rolling process, the sheet metal is nonuniformly thinned in the thickness direction and the longitudinal elongation is different in the width direction of the sheet metal, which makes the sheet metal deform in rolling direction. With the rotation of the bendable rolls, the sheet metal is deformed consecutively and a three-dimensional surface part could be obtained. A small experimental device has been designed. Finite element analysis (FEA) model is established. Spherical surface and saddle surface are simulated, and their experimental results are presented. The major purpose of the present work is to analyze the forming precision of flexible rolling and the reasons for the shape errors through simulated and experimental results. The results demonstrate that the proposed process is a feasible and effective way of forming three-dimensional surface parts.     

多道次直缝焊管连续成型有限条分析

采用基于Updated-Lagrangian法的大变形样条有限条法,分析直缝焊管多道次连续成型过程的纵向薄膜应变和位移。模拟结果表明,变形带材的边缘是变形剧烈的部位,必须严格控制带材边缘纵向应变。多道次连续成型时,带材变形应先逐渐增大,然后逐渐减小,以保证成品质量。     

Buckling and vibration of stiffened plates subjected to partial edge loading

The buckling and vibration characteristics of stiffened plates subjected to in-plane partial and concentrated edge loadings are studied using finite element method. The initial stresses are obtained considering the pre-buckling conditions. Buckling loads and vibration frequencies are determined for different plate aspect ratios, edge conditions and different partial non-uniform edge loading cases. The non-uniform loading may also be caused due to the supports on the edges. The analysis presented determines the stresses all over the region for different kinds of loading and edge conditions. In the structural modelling, the plate and the stiffeners are treated as separate elements where the compatibility between these two types of elements is maintained. The vibration characteristics are discussed and the results are compared with those available in the literature. Buckling results show that the stiffened plate is less susceptible to buckling for position of loading near the supported edges and near the position of stiffeners as well.