补偿回弹的冲压件模具设计方法

回弹是金属板料冲压中的主要缺陷之一,它可以通过修正模具形状加以解决.基于对经过成形--回弹的有限元数值模拟,提出一种循环位移补偿回弹修正模具型面的方法.它基于对经过成形--回弹有限元数值模拟得到的成形工件与目标工件多次循环比较,用成形工件结点回弹位移修正实验模具形状,直到利用修正的模具能够换获得满意的工件为止.利用此方法对一小型三维铝合金板料冲压工件的冲压模具设计过程进行了数值模拟,结果表明,通过两次修正的模具可获得满意工件.并根据模拟得到的型面制作模具进行了实冲实验,证明此补偿回弹的模具修正法是有效的.     

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。     

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。     

基于数值模拟的板料冲压成形回弹补偿方法

板料冲压中的回弹误差可以通过修正模具形状得到解决。基于冲压及回弹数值模拟,以控制系统、傅立叶变换及传递函数为理论基础,提出了一种模具回弹补偿的修正算法并开发了springbackcom系统。该方法通过两组小量变化的模具及其数值模拟得到回弹前后冲压件,建立模具形状传递函数,修正模具形状。利用此方法对某车引擎盖冲压过程进行了数值模拟及回弹补偿的实例验证,分析结果证明此回弹补偿方法是有效的,具有工程实用价值。     

高强度钢板汽车A柱回弹控制与工艺优化

以NUMISHEET’96标准考题模型S_Rail对高强度钢板材料B410LA进行模拟分析,确定了凸模圆角半径与压边力变化对B410LA板料成形回弹的影响,根据模拟结果优化了A柱的冲压工艺。经检验,生产的零件回弹控制效果良好,优化后的生产工艺可行。     

Rapid design of corner restraining force in deep drawn rectangular parts

With the development of finite element method and computer technology, the complete modeling of the forming of a 3D sheet metal part is becoming realistic. However, an accurate 3D simulation is usually too time-consuming to be used in the early stage of design. One solution is to model the straight side of a 3D part as a plane strain problem and the corner section as an axisymmetric problem. Unfortunately, the axisymmetric solution often over-predicts the severity of the deformation at the corner and leads to a very conservative design. In this study, a modified axisymmetric model with a center offset is proposed to predict tearing failure in the corner sections of 3D parts. The proposed offset is found to be a function of the center strains, failure height, and tooling/process parameters, including tooling geometry, material properties, friction coefficient, and restraining force provided by the binder. Finite element analyses of both 3D and 2D axisymmetric models for square and rectangular cup forming are utilized to verify the proposed concept and to define the function. Excellent predictions of the failure heights are obtained. The proposed model enables engineers to rapidly specify the right amount of the restraining force in the corner section based on the desired center strains and forming depth. A detailed design algorithm is provided.     

Finite element simulation of the manufacturing process chain of a sheet metal assembly

An increasing number of components in automotive structures are today made from advanced high strength steel (AHSS). Since AHSS demonstrates more severe springback behaviour than ordinary mild steels, it requires more efforts to meet the design specification of the stamped parts. Consequently, the physical fine tuning of the die design and the stamping process can be time consuming. The trial-and-error development process may be shortened by replacing most of the physical try-outs with finite element (FE) simulations of the forming process, including the springback behaviour. Still it can be hard to identify when a stamped part will lead to an acceptable assembly with respect to the geometry and the residual stress state. In part since the assembling process itself will distort the components. To resolve this matter it is here proposed to extend the FE-simulation of the stamping process, to also include the first level sub-assembly stage. In this study a methodology of sequentially simulating each step in the manufacturing process of an assembly is proposed. Each step of the proposed methodology is described, and a validation of the prediction capabilities is performed by comparing with a physically manufactured assembly. The assembly is composed of three sheet metal components made from DP600 steel which are joined by spot welding. The components are designed to exhibit severe springback behaviour in order to put both the forming and subsequent assembling simulations to the test. The work presented here demonstrates that by using virtual prototyping it is possible to predict the final shape of an assembled structure.     

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。     

Three-dimensional sheet metal continuous forming process based on flexible roll bending: Principle and experiments

To effectively manufacture three-dimensional sheet metal parts with various curvatures produced in small batch quantities, continuous sheet metal forming, a new flexible forming technology is being developed. This process employs an upper flexible roll and two lower flexible rolls as a forming tool, and the shape of a flexible roll can be changed in vertical direction. With the rotation of flexible rolls, the sheet metal is bent in longitudinal and transverse directions simultaneously and is formed continuously. In the present study, the three-dimensional surface of formed part is described by sweep surface based on the characteristic of the forming process and the arc-length parametric equation for describing continuous forming part is developed. The three-roll bending deformation of sheet metal in longitudinal direction is analyzed and the longitudinal curvature equation of the formed part is derived. The shape of flexible roll axis controlled at a number of points is represented by the cubic spline curve and the transverse curvature of the formed part after springback is then calculated piecewise. Typically experiments for forming concave shape surface and saddle-type surface have been performed, the experiment results are measured and analyzed by a binocular stereo vision measurement system, it is demonstrated that the formed surfaces are in good agreement with the desired shapes and the presented equations are useful for the continuous forming process design.     

双曲度覆盖件多点成形中回弹的数值模拟

以双曲度覆盖件为模型,采用显-隐式求解方法对其多点成形过程和卸载回弹过程进行数值模拟计算。讨论了压边力、板料厚度、型面曲率半径(中心弧高)和屈服强度对双曲度回弹的影响规律,得出了回弹趋势和回弹分布。这些结果对于制定合理的冲压工艺方案,并在多点成形过程中研究回弹的控制方法,具有重要的指导意义。     

板材多点成形中回弹的数值模拟及补偿研究

回弹是板材多点成形中一个必须解决的问题。利用有限元软件LS-DYNA对板材冲压成形的回弹进行数值模拟,采用动态显式算法模拟板材成形过程,隐式算法模拟卸载回弹过程。对不同曲率半径、不同屈服强度的圆柱面成形件进行数值模拟,分析得出回弹趋势和回弹分布,提出通过修正基本体群成形面来补偿回弹的方法,并用B样条曲线拟合生成的曲面。经过两次补偿,成形件精度提高,证明该方法可以很好地补偿多点成形中的回弹。研究结果对于减小因回弹带来的误差,提高成形件的成形精度具有十分重要的意义。     

空调后板冲压成形的回弹翘曲研究

采用CAE分析以及试验相结合的方法,建立加筋后空调后板冲压成形及回弹的有限元数值模型,研究后板在冲压成形过程中的回弹问题,得到加强筋的形状、位置、尺寸等对成形效果的影响规律。提出该后板的加筋设计规范,依据设计规范,加筋后的后板回弹较小,满足实际生产要求。     

板料弯曲回弹的有限元模拟影响因素研究

阐述了板料成形数值模拟中回弹问题的研究历史和发展现状,分析了塑性弯曲加工中工件发生弯曲回弹的原因、特点及有限元模拟过程的影响因素,总结了回弹模拟的算法,从成形过程模拟和回弹计算两方面系统分析了影响回弹模拟准确性和收敛性的主要因素及改进方向,讨论了模具设计中回弹的补偿算法 ,并提出了当前控制回弹的基本方法     

板料成形FE中网格节点重构参数曲面的方法研究

有限元模拟成形仿真的结果,可以帮助设计开发者正确选择冲压工艺参数和模具形状及材料特性等。在对模拟进行后处理过程中,往往必须了解由有限元节点构成的参数曲面的性质,为后续回弹分析及毛坯设计提供重要支持。如何应用变形后的节点阵构成光顺的几何曲面是问题的关键。文章给出了由节点序列散点构成非均匀B样条光顺曲面的实际算法,并开发了应用程序。对散乱点数据构成曲面进行了系统的阐述,所开发的方法已经用于板料成形仿真中FE网格节点重构曲面。     

Springback prediction for incremental sheet forming based on FEM-PSONN technology

In the incremental sheet forming (ISF) process, springback is a very important factor that affects the quality of parts. Predicting and controlling springback accurately is essential for the design of the toolpath for ISF. A three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the process and the simulated results were compared with those from the experiment. The springback angle was found to be in accordance with the experimental result, proving the FEM to be effective. A coupled artificial neural networks (ANN) and finite element method technique was developed to simulate and predict springback responses to changes in the processing parameters. A particle swarm optimization (PSO) algorithm was used to optimize the weights and thresholds of the neural network model. The neural network was trained using available FEM simulation data. The results showed that a more accurate prediction of springback can be acquired using the FEM-PSONN model.     

Comparison of Material Models for Spring Back Prediction in an Automotive Panel Using Finite Element Method

Springback is a crucial factor in sheet metal forming process. An accurate prediction of springback is the premise for its control. An elasto-plastic constitutive model that can fully reflect anisotropic character of sheet metal has a crucial influence in the forming simulation. The forming process simulation and springback prediction of an automobile body panel is implemented by using JSTAMP/LS-DYNA with the Yoshida-Uemori, the 3-parameter Barlat and transversely anisotropic elasto-plastic model, respectively. Simulation predictions on spingback from the three constitutive models are compared with experiment measurements to demonstrate the effectiveness and accuracy of the Yoshida-Uemori model in characterizing the anisotropic material behavior of sheet metal during forming. With an accurate prediction of springback, it can provide design guideline for the practical application in mold design with springback compensation and to achieve an accurate forming.     

多点技术在飞机板类部件制造中的应用

多点技术是一种机电一体化的柔性制造技术,其核心是高度由计算机控制的基本体单元。多个基本体单元紧密排列在一起,构成型面可变的多点模具,用于板类零件成形。由于多点模具型面可由计算机任意调整,可代替传统模具用于不同形状的飞机板类部件的对压成形、蒙皮拉形等。基本体单元按照一定距离排列在一起,构成多点柔性工装,不仅可用于飞机大型板类零件成形后的测量、切割等操作的支撑与定位,还可用于飞机部件的柔性装配过程。应用多点技术,可以实现飞机板类部件生产过程的数字化。     

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。     

蒙皮件多点拉形过程中成形缺陷的数值模拟

多点拉形是一种将柔性制造技术和计算机技术结合为一体的先进制造技术。文章基于动力显式有限元算法,从板厚、材质、变形程度和塑性指数等工艺参数入手,对球形和鞍形件的多点拉形过程进行数值模拟。研究表明,正确的选择工艺参数可以减轻或消除压痕缺陷。同时利用显-隐式算法,分析了板材厚度和成形件目标曲率半径对回弹的影响,得到了回弹的趋势和分布规律,即回弹量与板材厚度成反比,与成形件的曲率半径成正比。研究结果对蒙皮件多点拉形技术的实际应用具有一定的参考价值。     

可重构柔性模具蒙皮包覆拉形仿真系统开发

针对飞机蒙皮拉伸成形工艺中的包覆成形方式,基于有限元软件PAM-STAMP 2G平台,利用其二次开发工具Stamp Tool Kit,开发蒙皮拉形工艺仿真专用系统.将复杂的前置处理过程进行封装,可方便地对带弹性挚层的可重构柔性模具蒙皮拉形包覆成形过程进行弯曲、成形、切边及回弹过程模拟.系统实现了对飞机蒙皮拉形成形质量的预测,有较强的实用性和可靠性.针对所开发的系统,研究了不同挚层厚度对抑制成形板料表面压痕的规律,发现对于可调钉柱其截面尺寸为30 mm×30 mm的柔性模具,垫层厚度大于等于25 mm时可达到很好抑制表面缺陷的目的.