In-situ springback compensation in incremental sheet forming

Limited geometric accuracy in incremental sheet forming is a major obstacle for its wide adoption in industry. This paper develops a generic methodology, suitable for arbitrary part geometries and various ISF processes, for addressing one of the main causes of geometric inaccuracy, i.e., in-process springback. The methodology consists of three main elements: determination of key control points to treat geometric complexity, simplified simulation models to predict springback offline, and in-situ toolpath modification during forming. It is shown experimentally that the method provides an efficient and robust solution for various geometries with negligible setup cost.     

A 3D forming tool optimisation method considering springback and thinning compensation

In this paper, an enhanced numerical method for forming tool design optimisation in three-dimensional (3D) sheet metal forming applications is presented. The applied procedure enables a determination of appropriate forming tool geometry so that the manufacture of a sheet metal product inside specified tolerances would be ensured. In addition to the springback that occurs in the formed part after removal of the forming tools, the impact of the thinning of the sheet metal during the forming process is considered in the method, and both effects are correspondingly compensated for an iterative procedure. Computational efficiency in the E-DA-3D method is achieved mainly because the improved accuracy of the communicated data established corresponding interrelations between the discretised topologies used in the definition of the prescribed product geometry, the current tool geometry, and on this basis actually computed product geometry which is achieved by means of additional point topology mappings. The potential and effectiveness of the method is demonstrated by considering two cases of the forming tool design optimisation that are also experimentally validated.     

基于位移回弹补偿原理的汽车加强板回弹补偿研究

回弹问题一直是汽车覆盖件冲压成形中的一大难题,而回弹补偿是控制回弹量的一种有效途径。本文以某汽车加强板为例,进行全工序仿真模拟和回弹分析,利用位移回弹补偿原理对拉延型面和整形型面进行回弹补偿,并将回弹补偿后的工艺数模再次进行回弹分析,验证回弹补偿结果是否满足设计产品的精度要求,为控制汽车高强板的回弹提供依据。     

Prediction and inline compensation of springback in roll forming of high and ultra-high strength steels

With the rising interest in lightweight construction, the usage of high and ultra-high strength steels has increased remarkably during the last years. Unfortunately, these steel grades show more springback than mild steels do, which leads in consequence to lower dimensional accuracy. To improve the bended part’s geometry considerable trial-and-error work is necessary since the influence of different bending-parameters (e.g. the bending radius, sheet thickness, yield strength, Young’s modulus, the material’s strain hardening coefficient, …) on the amount of springback is still unknown. The aim of the paper at hand is therefore the investigation of springback for different parameter combinations. Furthermore, an online calibration system for occurring springback during roll forming is presented to compensate springback independent of material or process parameters.     

炉具前面板的回弹补偿分析

利用模具型面补偿的方法控制回弹,是模具生产中常用的控制回弹的方法。以炉具前面板为例,采用模具型面补偿的方法对其回弹进行了控制。利用此种方法设计出的零件已投入实际生产,实践证明：采用模具型面补偿的方法进行回弹控制是切实可行的。     

一种基于能量法的冲压回弹预测补偿算法

冲压零件的回弹会严重影响零件的形状和尺寸精度。通过对模具型面进行调整,从而去除回弹造成的形状误差是目前常用的一种手段。但是这种方法的模具型面设计工作量很大。文章在能量法的基础上,提出了一种预测任意截面形状的回转体零件回弹量的算法。该算法具有较快的计算速度,适用于多次迭代的补偿计算。利用该算法对半球形零件的拉深回弹进行了预测,所得结果与实验结果吻合较好。在此基础上,提出了一种位移调整的算法,通过在回弹预测量的反方向对模具型面进行补偿,可以自动获得补偿后的模具型面。实际计算结果表明,该算法具有较快的迭代速度,对一般形状的回转体零件可以在2次迭代后获得较高的零件精度。     

汽车覆盖件回弹逆向补偿过程中回弹量的精确计算

提出应用CAE仿真计算获得汽车覆盖件在自身重力作用下带来的变形量,采用在冲压件上悬挂砝码的方法来近似验证重力仿真计算的精度,并在二维弧形件和三维门内板零件上验证了仿真分析的准确性。然后通过强制变形仿真方法将扫描数据与模具型面模型优化对齐,应用网格映射方法建立节点映射关系并通过三角形形函数插值计算出投影点的坐标值,之后通过偏置的方法对扫描数据进行相应的修正,获得准确的回弹变形网格模型,提高逆向补偿的精度。     

模面几何修正的回弹补偿方向分析

精确回弹预测的目的是通过数值回弹模拟来修正模面,使得回弹后零件与设计的产品一致,因此,在回弹预测的基础上进行基于数值模拟或逆向工程的模面补偿和工艺调整,甚至修改成形方案和模具结构,仍然是当前降低回弹的主要措施。文章对模面几何补偿方法进行了阐述,对其应用特点、精度和效率进行了系统的对比分析,结果表明,在以转动为主导回弹的情况下,法向补偿具有很高的精度,但运行计算时间较长;在回弹存在大平移的情况下,连线方向补偿则精度较高,且算法简单;而Z向反向补偿法虽然具有算法简单、计算效率高的优点,却不能很好地对模面进行修正。     

轮罩拉深成形的回弹补偿模拟分析

针对轮罩的回弹会严重影响零件的形状和尺寸精度的问题,提出了通过模具补偿降低轮罩回弹的方法。在对轮罩成形进行回弹仿真分析的基础上,根据回弹变形后的形状与期望形状的偏差对初始模具型面进行修正,使得冲压件过正成形,对覆盖件进行回弹补偿。回弹补偿模拟分析结果表明,一次补偿后回弹量得到明显改善,回弹量控制在0.65mm以内,减少回弹量56个百分点,满足了工程设计要求,大大减少了反复试模、修模的工作量,降低了冲压件的制造成本,缩短了新产品的开发周期。     

Mechanisms for controlling springback and strength in heat-assisted sheet forming

The recently developed multi-step sheet forming technology with inductive in-situ heating serves to increase the productivity and to reduce costs compared to hot stamping with furnace heating. The paper reveals the mechanisms for the flexible setting of geometric and mechanical properties such as the bending angle and strength in terms of a closed loop control. The air and die bending as representative forming processes are analyzed with respect to the mechanisms overbending, springback and thermal distortion by experimental, numerical, and analytical investigations. The mechanisms for controlling strength in carbon steels by grain refinement, grain growth and cooling rate are described.     

基于回弹补偿的模具型面设计方法研究

模具型面的回弹补偿是冲压模具设计中的难题。首先阐述了模具型面回弹补偿理论,提出一种利用有限元数值模拟技术进行模具型面回弹补偿设计的方法;然后以某工业螺旋叶片为研究对象,结合实冲试验验证了回弹数值模拟预测的精度;最后通过对叶片初始模具型面的两次补偿,得到了满足叶片成形精度要求的模具CAE型面,并将叶片模具型面CAE模型转化为CAD模型,实现了基于回弹补偿的模具型面“CAD→CAE→CAD”双向集成设计。     

基于迭代式回弹补偿的触发弹簧片折弯模具设计

回弹是金属板材折弯成形过程中需要考虑的主要问题之一。采用传统的工艺控制方法只能在一定程度上减少回弹量,通过回弹补偿则能更好地解决回弹问题。利用Dynaform有限元分析软件对某触发弹簧片的折弯成形过程进行了仿真分析和回弹预测,并根据回弹预测结果分别进行两次回弹补偿。最后将回弹补偿得到的模具型面应用于折弯模具设计。试验结果表明,通过两次回弹补偿修正得到的模具可制得符合精度要求的折弯件,从而证明通过迭代式回弹补偿解决弯曲回弹问题是有效的。     

汽车车门玻璃导轨件冲压成形回弹补偿研究

回弹是板料成形中不可避免的现象,有效减小回弹量是制造合格零件的保证。利用软件Dynaform对汽车车门玻璃导轨的成形过程和回弹进行了数值模拟,并对回弹产生的原因进行了合理的分析。对于零件中回弹量较大的位置,利用节点对称的方法对模具型面进行了针对性的补偿,并利用Dynaform对零件的成形质量进行了有效验证。回弹量由0.67 mm降到0.3 mm以下,降低了近60%,模拟结果表明此方法可以有效控制回弹。     

基于AutoForm的汽车顶盖冲压回弹补偿研究

为解决冲压成形的零件与原产品数据偏差较大的难题,提供了2种回弹补偿方式,即AutoForm迭代补偿与几何补偿,以某车型顶盖为研究对象,分别对2种补偿方式重构的型面进行全工序CAE分析,对比其回弹结果。AutoForm迭代补偿在全夹持状态下,局部区域的回弹量超过3 mm,几何补偿方式在补偿量为6 mm时,全夹持状态下回弹量在1.5 mm以内,说明AutoForm迭代补偿不宜用于自由回弹量大的零件,采用几何补偿可以提高回弹补偿的准确性。三坐标检测试制首件的尺寸符合率为85.2%,模具状态研配到与数值模拟边界条件一致时,尺寸符合率可达96.5%,验证了几何补偿方式的有效性。     

整体壁板时效成形模具回弹补偿的工艺研究

时效成形是解决整体高筋壁板成形、提高零件制造精度和使用寿命的有效工艺方法,但由于具有回弹量大,且模具型面难以确定和修正的特点,限制了其在国内工程化的应用。该文针对小曲率、小变形整体壁板的时效成形,通过时效成形基础试验,研究其回弹规律,并应用几何补偿算法,进行模具型面的回弹补偿计算。实验验证表明,零件外形曲面误差小于1mm,筋条处的误差小于0.5mm,证明该回弹规律及补偿算法具有有效性和准确性。     

框肋零件弯边回弹补偿系统的开发与应用

针对框肋零件弯边回弹问题,基于CATIA V5平台,利用其二次开发工具CAA,开发了框肋零件弯边离散与信息提取模块、弯边重构模块;开发了基于知识库展现于Web浏览器的弯边回弹预测与补偿模块.工艺设计人员可以直接在CATIA环境与Web浏览器中,快速实现框肋零件弯边的回弹补偿.应用所开发的系统,对某一典型框肋零件弯边进行回弹补偿,并采用试验验证.     

Variable blankholder force in U-shaped part forming for eliminating springback error

Springback is the main defect in U-shaped part forming, which can badly affect the shape of a part. Applying reasonable variable blankholder force in the forming process is one of the useful methods to solve this problem, but determination of the curve of blankholder force vs. punch displacement is still difficult. A method is advanced in this paper to control the forming process of a U-shaped part, by which a reasonable blankholder force curve can be easily gained. Comparing with constant blankholder force, higher forming quality can be obtained in both avoiding cracking and improving dimension accuracy. The benchmarks of the 2D draw bending problem in NUMISHEET’93 has been utilized to validate the method by FEM, and good results of springback elimination have been obtained.     

Development of an incremental rolling process for the production of defined riblet surface structures

Viscous drag reduction on fan, compressor and turbine blades may be achieved by employing a riblet surface structure. Such a structure assists in increasing efficiency and in reducing energy consumption in flow applications. In order to produce riblet surface structures industrially, a new and incremental rolling process is being developed and investigated. The process design is being determined by common airstream requirements as well as the forming mechanisms that are predominant during the rolling process. Based on this principle, the required shape of the structured rollers is being developed. Research is focused on the feasibility of manufacturing small riblet structures at a size of a few hundred microns. Experimental production of different riblet geometries made from Ti-6Al-4V (WL 3.7164) provides some initial insights with respect to feasibility, shape accuracy, surface quality, and micro structure.     

基于ABAQUS的筋板件时效成形型面回弹补偿算法

基于回弹预测与控制的模具型面补偿,是时效成形工艺研究亟待解决的关键问题。该文根据回弹补偿原理,提出了基于零件形状虚拟迭代修复的时效成形模具型面回弹补偿修正算法的思路。以2A12铝合金筋板件蠕变时效成形过程为研究对象,利用ABAQUS有限元分析平台,在筋板件时效成形及回弹模拟分析的基础上,实现了该过程模具型面的回弹补偿优化设计。研究结果表明,提出的型面补偿算法具有良好的收敛性,数值模拟结果验证了该算法的可行性。     

厚板滚弯回弹计算新方法

理论分析表明板材弯曲时后继变形中弹性变形所占比例较大,对于Q235而言,其比例达到了10％.新的回弹计算方法考虑了板材后继变形中弹性变形.将文献回弹公式、新的回弹公式与实际使用的经验公式和数值模拟进行对比,对比结果表明：新的回弹公式介于模拟结果与经验公式之间,更接近于经验公式,并且误差在10％以内,成形内半径越大,新旧方法之间的差距越大,新方法的优势越明显.