大型板材模具设计所需的回弹逆解算法

在分析理想弹塑性材料弯曲回弹的基础上,提出了一种板料弯曲回弹的计算方法,推导出根据板料强度、厚度和最终成形半径直接计算弯曲半径的逆解公式.这一公式对板料成形中模具修正有一定的借鉴作用.     

金属板材回弹与曲率关系的研究

目前主要采用位移量来评估板材冲压后的回弹,这种评估方法不能直接地反映回弹是由于弹性应变能释放而引起的曲率改变的物理本质,从而给回弹补偿和模面修改带来一定的困难。根据塑性弯曲理论,将膜力和弯矩引起的回弹分别用高斯曲率和平均曲率表征,并对双曲率片回弹后的高斯曲率和平均曲率的分布情况进行了分析。实验结果表明,用曲率评估方法可以较好地体现回弹的成因,有助于准确地预测回弹趋势,对实际生产加工中的修模、试模过程具有一定的指导意义。     

板条多点成形中曲率分布及回弹控制的研究

分析了板条在整体模具成形与多点成形过程中的受力状态,指出　整体模具成形和多点成形的实质均为多点弯曲成形;通过有限元分析揭示了采用不同成形方式,如：多点模具成形、多点压机成形和整体模具成形时,板条柱面弯曲曲率分布及回弹规律,从而提出了有效抑制回弹及均布曲率的反复多点成形方法;利用有限元法对反复成形抑制回弹的机理进行了分析,考查了反复成形次数对曲率分布及回弹控制的影响。     

基于曲率的二维弯曲回弹补偿计算方法

传统的回弹补偿主要依靠工作人员的经验根据回弹角进行反复补偿,对于复杂型面没有行之有效的方法.以塑性弯曲理论为基础,用解析法求得回弹后的曲率.根据回弹前后曲率的改变,为模面补偿设计提供了自动计算方法.另外,结合试冲压结果,提出用综合辛卜偿系数来表征回弹在实际生产条件中和理想条件下理论计算结果之间的区别.同时也给出了相应的有限元模拟和物理试验来验证.结果表明,该方法在工业应用方面是可行的,也是足够准确的.     

汽车覆盖件冲压成形回弹补偿问题研究

本文针对回弹对汽车覆盖件冲压成型的影响,提出了汽车覆盖件冲压模具回弹自动补偿的方法;以某保险杠骨架外杠的模具为例进行回弹自动补偿,验证了此方法的正确性,并总结出了汽车覆盖件冲压模具自动回弹补偿的流程。     

基于一步逆成形法弯曲成形回弹的快速模拟

首先阐述了弯曲成形回弹模拟的方法及其一步逆成形法的基本原理。通过采用一步逆成形法来获得弯曲成形后的应力分布,然后利用LS～DYNA隐式求解器对卸载回弹过程进行了模拟。最后将该方法分别应用到无约束圆柱弯曲成形和卡车纵梁弯曲成形的回弹模拟中,并将模拟结果与实验结果进行了比较,比较的结果表明,该方法可以有效地预示出弯曲成形的回弹量。     

基于一步逆成形法弯曲成形回弹的快速模拟

首先阐述了弯曲成形回弹模拟的方法及其一步逆成形法的基本原理.通过采用一步逆成形法来获得弯曲成形后的应力分布,然后利用LS-DYNA隐式求解器对卸载回弹过程进行了模拟.最后将该方法分别应用到无约束圆柱弯曲成形和卡车纵梁弯曲成形的回弹模拟中,并将模拟结果与实验结果进行了比较,比较的结果表明,该方法可以有效地预示出弯曲成形的回弹量.     

铝合金板材冲压成形回弹有限元模拟研究

板料卸载后回弹变形对钣金件的成形精度影响很大。基于Numisheet1993的U形弯曲标准考题,考虑板材与模具间的接触演变过程,建立了一个有限元模型来预测铝合金板材弯曲过程的回弹。模拟中板材本构方程基于更新拉格朗日弹塑性材料模型,压边力采用凸缘边界的等效力表示,卸载过程采用模具反向运动方法。对有限元敏感度分析发现,回弹大小和整体精度受到元素大小、积分点和屈服准则的很大影响。有限元模型通过Numisheet1993和2005的考题进行验证,发现精度达90%以上。通过有限元分析得到了一个优化的模型,提供了一个更加精确的方法,该方法还可减少计算时间。     

板材成形的回弹预测和控制的研究

板材成形的回弹影响产品的品质,对回弹进行准确预测和控制是提高成形精度的关键.从回弹预测和控制两个方面介绍了有关的研究现状,阐述了各种预测和控制回弹方法的优缺点,介绍了华南理工大学模具研究室团队近年在板材成形回弹方面的研究情况.     

管件冲压回弹补偿弯曲模的设计

通过对材料、工艺、模具和设备等方面进行研究分析,介绍了一种可以补偿弯曲回弹,节省模具材料和模具加工费用的可调换式管件弯曲模的结构设计。该弯曲模的应用,一方面确定了角度回弹值Δα,另一方面大量地节约了弯曲模材料和制造费用,对于工厂日常加工和平面弯曲管件的生产,具有显著的经济效益及普遍的实用价值。     

Tooling design in sheet metal forming using springback calculations

A method to design tooling in sheet metal forming using springback calculations is presented. The designed tooling produces a part which matches the desired shape, thereby compensating for springback. To design the appropriate tooling, traction distributions on the sheet in the fully loaded deformed state are computed using the finite element method. The calculated tractions are then used to numerically reproduce springback of the desired part shape by elastic unloading of the part in a reverse manner. The method is examined for materials covering a range of steel strength and hardening, and is found to produce parts with negligible shape error. The success of the tooling design algorithm leads to a proposal for an experimental method to design tooling based on traction distribution measurements.     

冲压成形薄板厚度变化与回弹量工程估算

研究了忽略薄板厚度变化对有限元仿真计算时间和计算结果的影响 ,得到薄板冲压成形过程中压边力和材料特性与薄板回弹量的关系曲线     

板料成形中单元大小对回弹的影响研究

板料成形数值模拟的准确性在很大程度上取决于回弹模拟的精度。本文就 DYNAFORM软件中单元尺寸与回弹模拟计算的关系进行了研究 ,得出了相应的结论。     

Digitized die forming system for sheet metal and springback minimizing technique

The design of the runner and gating systems is of great importance to achieving a successful injection moulding process. The subjects of this study are the finite element and abductive neural network methods applied to the analysis of a multi-cavity injection mould. In order to select the optimal runner system parameters to minimize the warp of an injection mould, FEM, Taguchi’s method and an abductive network are used. These methods are applied to train the abductive neural network. Once the runner and gate system parameters are developed, this network can be used to accurately predict the warp of the multi-injection mould. A simulated annealing (SA) optimization algorithm with a performance index is then applied to the neural network in order to search the gate and runner system parameters. This method obtains a satisfactory result as compared with the corresponding finite element verification.     

铝合金汽车覆盖件冲压成形回弹的仿真研究

简要介绍了用于冲压成形回弹的有限元基本理论,提出了复杂汽车覆盖件成形仿真的模式,并以汽车底座横梁外板为例,利用DYNAFORM软件,对其拉延、切边、冲孔和回弹的过程进行了仿真,通过仿真结果与实验结果的比较,证明了所得到的数值参数和仿真方法能获得比较可靠的仿真结果,对实际生产有一定的指导意义。     

Study on multiple-step incremental air-bending forming of sheet metal with springback model and FEM simulation

A mathematical model of springback radius was developed with dimensional analysis and orthogonal test. With this model, the punch radius could be solved for forming high-precision semiellipse-shaped workpieces. With the punch radius and other geometrical parameters of a tool, a 2D ABAQUS finite-element model (FEM) was established. Then, the forming process of sheet metal multiple-step incremental air bending was simulated with the FEM. The result showed that average errors of the simulated workpiece were +0.68/?0.65 mm, and provided the process data consisting of sheet feed rate, punch displacement and springback angle in each step. A semiellipse-shaped workpiece, whose average errors are +0.68/?0.69 mm, was made with the simulation data. These results indicate that the punch design method is feasible with the mathematical model, and the means of FEM simulation is effective. It can be taken as a new approach for sheet metal multiple-step incremental air-bending forming and tool design.     

Characterising material and process variation effects on springback robustness for a semi-cylindrical sheet metal forming process

Variation in the incoming sheet material and fluctuations in the press setup is unavoidable in many stamping plants. The effect of these variations can have a large influence on the quality of the final stamping, in particular, unpredictable springback of the sheet when the tooling is removed. While stochastic simulation techniques have been developed to simulate this problem, there has been little research that connects the influence of the noise sources to springback. This paper characterises the effect of material and process variation on the robustness of springback for a semi-cylindrical channel forming operation, which shares a similar cross-section profile as many automotive structural components. The study was conducted using the specialised sheet metal forming package AutoForm™ Sigma, for which a series of stochastic simulations were performed with each of the noise sources incrementally introduced. The effective stress and effective strain scatter in a critical location of the part was examined and a response window, which indicates the respective process robustness, was defined. The incremental introduction of the noise sources allows the change in size of the stress–strain response window to be tracked. The results showed that changes to process variation parameters, such as BHP and friction coefficient, directly affect the strain component of the stress–strain response window by altering the magnitude of external work applied to forming system. Material variation, on the other hand, directly affected the stress component of the response window. A relationship between the effective stress–strain response window and the variation in springback was also established.