Some fundamental considerations for the control of residual flatness in tension levelling

Tension levelling is a process used in the steel industry in order to remove any shape defects present in temper rolled strip. It is generally the final process before the cold rolled product is despatched to the customer, and therefore plays an important rôle in delivering the desired material properties and the product standards required.

In this paper a designed factorial analysis has been employed in order to study the effect that tension levelling process parameters have on the shape characteristics of the levelled product. These characteristics include residual flatness (longitudinal curvature or longbow), centreline elongation and residual (or internal) stress imbalances; criteria which determine whether the customer accepts the material or not. It has been identified that in a basic five-roll leveller the final, adjustable roll wrap angle, has the most significant influence on these characteristics in over 70% of cases. It has also been determined that final flatness is dictated by many second-order process interactions.     

Computer aided development of the levelling technology for flat products

The computer aided development of the levelling technology for flat hot rolled products is the main aim of this work. Accuracy of the numerical simulations is important when they are used to develop a real manufacturing technology. The nonlinear combined hardening model was selected to capture the influence of the Bauschinger effect that plays an important role during low cyclic deformation that is characteristic for levelling. The model identification procedure on the basis of cyclic tension/compression tests combined with inverse analysis is described first. Application of the developed model to design efficient leveller setups is presented in the second part of the paper.     

流线形拉深件冲压工艺分析及有限元数值模拟优化

利用Dynaform软件模拟流线形铝制品零件的拉深成形过程，得出冲压成形的FLD图，并优化板料形状和工艺参数避免产生缺陷。分析了成形工艺参数对成形质量的影响，制定了铝制品零件的冲压工艺方案。实际生产的产品无缺陷，满足质量要求。     

Analysis of the levelling process based upon an analytic forming model

Roller levelling is a complex forming process to minimize flatness imperfections and residual stresses by repeated forming of a sheet.At the Institute for Metal Forming and Metal Forming Machine Tools at the University of Hanover an analytic forming model is being developed which analyses the levelling process with sufficient precision in a shorter time than is possible with the finite element method (FEM).With this analytic forming model, the states of multiple forming under bending conditions during the levelling process can be investigated. The residual stresses and the residual bend of the sheet metal are calculated. Additionally, the forces acting on the rollers during levelling are determined. The controlling system assures setting of rollers automatically.     

板料成形数值模拟进展

在给出板料成形的典型成形过程、物理过程与力学模型的基础上，评述了板料成形数值模拟的发展历史和最新进展，包括成形过程与成形缺陷模拟发展，常用材料模型与壳体模型，接触摩擦处理及汽车覆盖件成形应用，文末指出了该领域的发展趋势。     

变断面矫直机的控制原理

本文提出的变断面矫直机的控制原理,成功地应用在我国第一台电子计算机控制的2800mm变断面矫直机上,并取得了比较满意的矫直效果,从而证明所提出的控制原理及工艺是正确的,可以推广到工业生产中去。     

变压边力对矩形件成形性能的影响

起皱和断裂是板料成形过程的主要失效模式 ,合理控制成形过程中压边力 ,可以消除这些缺陷 ,提高成形性能。本文通过对随位置变化的变压边力作用下的矩形盒拉深过程进行数值模拟 ,研究各部位压边力变化对整体成形性能影响、及其影响范围 ,为分块压边圈的压边力的调整提供一定的依据。     

板材多工步成形中切边工序的数值模拟技术研究

切边在板材多工步成形中一般是获得成品的最后一个工序。成形过程中 ,由不均匀塑性变形产生的残余应力在切边时的释放 ,会造成零件应力应变场的重新分布 ,因此本文建立了简化的线弹性切边卸载模型 ,基于静态隐式算法 ,在复杂蒙皮拉形数值模拟系统STRETCHFORM基础之上 ,开发了板材多工步成形中切边工序的计算模块 ,用以计算零件在切边后应力应变场的变化情况。本文还详细研究了切边求交、单元的取舍判断、畸变判断和局部调整、新旧单元系统的变形场信息传递等算法     

数值模拟在板料冲压加工中的应用

介绍了板料冲压加工有限元数值模拟的常用软件 ,以汽车覆盖件 (盒形件 )为例 ,详细介绍了建模方法、参数设置和模拟过程。分析了常见成形缺陷 (起皱和拉裂 )的产生原因 ,介绍了利用 .din格式文件的多工序拉伸模拟法和确定复杂零件毛坯形状的反向模拟法 ,论述了采用自适应网格再划分技术以提高计算精度和效率、通过适当布置拉伸筋调控板材流速以确保复杂冲压件成形质量等问题     

金属板料渐进成形工艺过程有限元模拟

介绍了金属板料分层渐进成形过程有限元模拟。在金属板料渐进成形过程中,材料的弹塑性变形十分复杂,影响成形过程的因素很多,同时各个工艺参数对成形过程的影响又很难确定。为此,根据金属板料分层渐进成形为多工步成形的技术特点,建立一种有限元模拟方案,对板料渐进成形过程进行了模拟分析。     

基于PAM-STAMP2G的回弹自动补偿功能的模具设计

回弹是钣金零件成形过程中很常见的现象,并直接影响产品质量,传统解决回弹的方法是采用"试错法"来解决模具回弹补偿问题。文章提出了基于PAM-STAMP2G回弹自动补偿功能的模具设计方法,以解决模具回弹补偿问题,并通过一个叶片零件回弹自动补偿问题,验证了此回弹自动补偿方法的正确有效性。     

国产三重辊式冷板矫平机的研制

为提高冷轧板的矫平质量 ,研制了 2 1辊三重辊式矫平机。介绍了该机的主要技术参数、设备结构特点及主要优点。使用结果表明 ,该机不仅可提高产品合格率 ,矫平质量完全可替代进口产品 ,而且其成本仅为进口产品的 1/ 3。     

板料成形过程数值模拟与实测比较研究

采用板料成形过程数值模拟技术,模拟了某汽车覆盖件拼焊板的拉延成形工序,结合试模情况,测量了试模拉延件的边缘进料量、厚度,并与模拟结果进行了比较,在验证模拟结果可靠性的基础上,评判试模的基本工艺参数,指导模具的调试工作,同时,还对工序件的回弹问题进行了分析,得到了合理的计算结果,对如何更好地应用成形过程模拟技术,合理分析成形过程中存在的问题,解决成形缺陷的工艺方案等问题有一定的参考作用。     

Failure Analysis of a Sheet Metal Blanking Process Based on Damage Coupling Model

In this paper, a blanking process of sheet metal is studied by the methods of numerical simulation and experimental observation. The effects of varying technological parameters related to the quality of products are investigated. An elastoplastic constitutive equation accounting for isotropic ductile damage is implemented into the finite element code ABAQUS with a user-defined material subroutine UMAT. The simulations of the damage evolution and ductile fracture in a sheet metal blanking process have been carried out by the FEM. In order to guarantee computation accuracy and avoid numerical divergence during large plastic deformation, a specified remeshing technique is successively applied when severe element distortion occurs. In the simulation, the evolutions of damage at different stage of the blanking process have been evaluated and the distributions of damage obtained from simulation are in proper agreement with the experimental results.     

矩形盒拉延件的压边力计算研究

压边力是板料拉延成形过程的重要工艺参数之一,合理控制压边力的大小,可避免起皱或破裂缺陷,采用多点压边的压边力控制拉延过程,可提高成形极限及提高拉延件质量,文章对矩形盒形拉延件分段压边的压边力随凸模行程(时间)变化曲线的计算提出了见解,为实现拉延过程中变压边力控制提供了一定的依据。     

基于有限元分析的覆盖件拉延筋设计与优化

结合等效拉延筋模型，采用基于有限元逆算法的三维有限元分析软件，对汽车后窗内板的拉延成形进行模拟。在确定合理的等效拉延筋阻力后，通过适当的优化算法对拉延筋的真实几何结构进行优化设计。并通过UG二次开发技术，获取优化的拉延筋几何参数和位置，在拉延件上生成真实的拉延筋模型。     

用动态显式有限元法对板材成形进行计算机模拟

介绍了动态显式有限元法的原理和特点 ,总结讨论了国际现有各种商用有限元软件的情况。采用显式有限元软件 L S- DYNA3D对板材零件冲压过程进行计算机模拟分析 ,预测冲压过程中可能出现的各种工艺缺陷 ,例如坯料的起皱、局部减薄和破裂 ,并以模拟结果为依据提出改进模具和工艺参数的办法 ,优化工艺参数 ,可以减少调试和修模的次数 ,以此实现降低模具费用、缩短制模时间、提高产品成品率和材料利用率 ,最终达到减少产品成本的目的。     

浅析U形件回弹

回弹是冷冲压成形过程中不可避免的物理现象,一直是影响、制约模具和制件质量的重要因素。回弹给模具设计和制造带来了很大的困难,常常需要采用反复试模、修模及成形后人工矫正的方法才能制造出符合要求的制件。通过分析金属板材弯曲回弹的现象、影响因素,总结了控制弯曲回弹的具体措施和方法,解决了实际生产中的问题。     

基于Dynaform的板材成形变压边力数字模拟研究

利用板材成形CAE分析软件Dynaform研究压边力对大型板材拉延成形性能的影响.模拟结果表明,合适的变压边力能够降低成形后的局部变薄率,改善成形后的回弹量.     

基于遗传算法和神经网络技术的板料拉深成形参数优化

结合数值模拟和人工神经网络技术．建立了板料拉深成形的加工参数（压边力和冲压速度）与其成形质量之间的映射关系，既保证了精度，又减少了数值模拟次数。在神经网络建模的基础上，利用遗传算法对板料拉深成形的加工参数进行了优化，通过实例可以看出，该方法具有较好的优化结果。