基于数值模拟的支架成形工艺与排样设计

以翼子板下支架为研究对象,利用冲压成形分析软件AutoForm通过对冲压负角的检查确定产品冲压方向;通过成形极限数值分析确定冲压工艺方案,在AutoForm中仿真预测板料成形过程的减薄、拉裂和起皱等缺陷。在成形仿真分析基础上进行冲压排样分析设计,通过试冲表明产品的尺寸精度和表面质量符合设计要求。     

汽车覆盖件冲压回弹仿真的研究

为了解决汽车覆盖件冲压成形过程中的回弹问题,以板料冲压成形有限元理论和仿真方法为基础,对某汽车U形梁采用板料成形仿真软件Dynaform,在计算机上模拟冲压成形及回弹的过程,预测出实际的模具制造过程中可能出现的回弹量,通过将仿真结果与实验对比,说明了仿真设计方法的实用性,从而总结出控制回弹的措施.     

金属板料单点增量成形厚度减薄率的预测与控制

金属板料单点增量成形过程中成形区域厚度减薄率过大是影响成形极限的一项重要因素,预测成形区域壁厚是控制减薄率的重要方法。选取1060铝板,对单点增量成形过程中的壁厚变形过程进行分析,利用Abaqus有限元分析软件,建立单点增量成形有限元模型,利用仿真结果拟合出精度较高的壁厚预测公式,分析工具头直径、层间距、进给速度、板料厚度、成形角度等工艺参数对减薄率的影响规律,并通过试验验证有限元模拟的正确性,并提出通过改变成形轨迹控制减薄率的方法。结果表明:拟合出的壁厚预测公式所求得壁厚值比正弦定理所求得的壁厚值更接近实验值;壁厚减薄率值随着工具头直径、成形角度和板料厚度的增大而增加,随层间距的增加而减小,进给速度对减薄率影响不显著,成形角度是影响减薄率的最重要因素;采用压入点均布的成形轨迹可有效减小减薄率。     

锆合金薄板冲压工艺的多种群社会群体算法优化

为了减小锆合金薄板冲压成形件的最大减薄率、提高冲压成形件质量,提出了基于多种群社会群体算法的冲压工艺优化方法。介绍了冲压件的3维尺寸和锆合金材料力学参数,以有限元仿真的方式确定了锆合金冲压成形的缺陷。选择冲压速度、压边力、模具间隙作为优化参数,以减小冲压件的最大减薄率为目标建立了优化模型。使用智能神经网络建立了输入参数与输出参数的回归模型,并对回归效果进行了检验。分析了社会群体优化算法的多样性缺陷,在算法中加入了多种群机制和多知识来源机制,提出了多种群社会群体优化算法。使用多种群社会群体算法求解优化模型,得到了工艺参数的优化值。依据优化参数生产了10个冲压试制件,经测量冲压试制件的最大减薄率均值为7.916%,明显小于优化前的最大减薄率10.746%,说明经过优化明显减小了锆合金冲压件的最大减薄率。10个试制件的最大减薄率标准差仅为0.652%,说明生产过程稳定。     

影响轧制差厚板冲压成形性能的几何参数研究

轧制差厚板的出现使得汽车行业能够获得更轻的车身重量以及更低的生产成本。为了推动轧制差厚板的应用进程,需要对其冲压成形性能进行深入研究。对轧制差厚板方盒形件进行了冲压成形仿真,以进料量之差、最大厚度减薄率以及厚度过渡区中心移动量为评价标准,分析了不同板厚比及厚度过渡区位置对差厚板成形性能的影响。研究结果表明:板料厚度差越小,过渡区越接近薄侧端部,差厚板的冲压成形性能越好。     

基于Autoform的轿车引擎盖板冲压成形仿真的研究

介绍了轿车引擎盖零件冲压成形仿真的研究背景,详细论述了板料冲压成形数值模拟的理论和主要步骤.以典型轿车引擎覆盖件为研究对象,以三维成形分析软件Autoform为平台,研究了板科与凸模、凹模的摩擦、压边力、拉深筋等因素对成形性能的影响.通过Autoform的成形仿真预测板料成形过程中减薄、拉裂、起皱等缺陷,分析产生缺陷的原因,进而优化板料成形工艺参数.     

汽车覆盖件冲压成形仿真的应用与研究

介绍了汽车覆盖件冲压成形仿真的研究背景,详细论述了板料冲压成形数值模拟的理论和流程.在Dynaform中对汽车右侧壁上外板进行了冲压成形过程的仿真,通过对仿真结果进行分析,提出了改进工艺参数的措施,有利于优化冲压成形的过程和结果.     

高强钢板热力耦合冲压成形数值模拟北大核心

以热冲压成形中常用的简单工件U型件为研究对象,采用有限元分析软件进行数值模拟,通过建立U型件热力耦合冲压成形有限元模型,研究改变板料初始成形温度、成形速度和保压时间等对板料成形性能的影响机理。探讨热冲压成形过程中协同控制板料初始成形温度、成形速度和保压时间等关键工艺参数的变化,确定优化方案,得到符合生产实际需求的工件。     

高强钢板热力耦合冲压成形数值模拟

以热冲压成形中常用的简单工件U型件为研究对象,采用有限元分析软件进行数值模拟,通过建立U型件热力耦合冲压成形有限元模型,研究改变板料初始成形温度、成形速度和保压时间等对板料成形性能的影响机理。探讨热冲压成形过程中协同控制板料初始成形温度、成形速度和保压时间等关键工艺参数的变化,确定优化方案,得到符合生产实际需求的工件。     

基于Dynaform的汽车覆盖件冲压成形仿真的研究

介绍了汽车覆盖件冲压成形仿真的研究背景,详细论述了板料冲压成形数值模拟的理论和主要步骤.在Dynaform中对汽车行李箱门板进行了冲压成形过程的仿真,证明了仿真设计方法具有实用性,通过反复模拟,找出了合理的工艺参数,有利于优化冲压成形的过程及其结果.     

An analysis of hemispherical punch stretching by the energy method

An approach using the energy method in which the total deforming region is divided into several sections of different geometric shapes is suggested for the analysis of axisymmetric sheet metal forming with friction boundary condition. The corresponding solutions are found through optimization of the total energy dissipation with respect to some parameters assumed in the velocity field as well as in the corresponding geometric profile. Computations are carried out for hemispherical punch stretching of normal anisotropic work-hardening materials for several lubrication conditions. The punch load vs stroke relation, geometric configuration and strain components are determined from the computation. The comparison of the computed results with finite element solutions and corresponding experiments shows good agreements of solutions in load vs stroke, deformed profiles and strain distribution for various lubrication conditions. It is thus shown that the present simple approach can be effectively employed for the analysis of axisymmetric sheet metal working processes.     

虚拟凸模速度对冲压仿真结果的影响

通过对典型冲压件冲压过程中凸模速度参数对仿真结果的影响(包括对单元等效应力、厚向应变的影响)的分析,讨论了不同的参数值对仿真结果的影响,为在不同的仿真条件下合理选择这些参数提供了依据。     

铝合金阶梯形件粘性介质压力成形的研究

通过压缩试验得到了粘性介质的应力－－应变关系、压力衰减随冲头加载速率及时间变化的规律。采用有限元软件DEFORM分析了在不同压边力下分别用钢凸模和粘性介质成形铝合金阶梯形件的工艺过程。结果显示，采用VPF可以提高板料的成形性。根据模拟结果，采用VPF成功地制备了阶梯形件，这表明有限元法对VPF试验具有很好的指导意义。     

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.     

Numerical simulations on reducing the unloading springback with multi-step multi-point forming technology

Multi-point forming (MPF) is an innovative flexible manufacturing technology for three-dimensional sheet metal forming. It replaces the conventional solid dies with a set of height-adjustable discrete punches, called the “punch group”. A set of punches can construct various three-dimensional curved surfaces freely and conveniently, through adjusting the relative position of each punch. MPF technology not only saves a significant amount of money and time in the design, manufacture, and adjusting of the dies but it can also be applied to change the deformation path and to improve the forming quality. Unloading springback is an inevitable phenomenon in sheet metal forming using MPF. To control and reduce springback, numerical simulations for the MPF process and the unloading springback are carried out using the explicit-implicit coupled finite element method. Subsequently, influencing factors such as thickness, deformation amount, and material properties of MPF springback are researched to investigate the MPF springback tendency. Next, the multi-step MPF technology is introduced to reduce MPF springback. Based on numerical simulation analysis, it is obviously validated that the unloading springback is decreased when the multi-step MPF method is applied. Finally, it is verified that the equidifferent deformation path and small deformation amount of each forming step can improve the workpiece stress state and minimize the unloading springback effectively by an evaluation result of the deformation path effect on the multi-step MPF.     

薄板件台阶孔冲压冷锻组合工艺的数值模拟

针对构想的一种薄板件台阶孔冲压冷锻组合工艺,应用金属塑性加工有限元模拟的关键技术,包括几何模型、材料断裂破坏、网格划分等,用DEFORM-3D软件对此种薄板件台阶孔的冲压冷锻组合变形进行数值模拟。得到了工件材料的等效应力、应变分布,速度场和力—行程曲线。提出细观变形过程可分为冲头小直径处冲孔、冲头大直径处压凹和闭式模锻三个阶段的认识,分析组合工艺特点和材料成形性能。用料厚为2.35 mm的AL-1100铝板材料进行工艺试验,获得了清晰的台阶孔形状,验证了数值模拟的认识。     

基于厚度梯度准则的薄板成形极限图建立方法

介绍一种预测薄板成形极限的新准则——厚度梯度准则,该准则基于薄板颈缩时沿垂直于颈缩方向的厚度梯度分布存在极值RC。在薄板成形过程中,当板面内的厚度梯度值小于临界厚度梯度值RC时,认为薄板发生颈缩。基于厚度梯度准则,结合对IF钢成形极限试验的有限元仿真,计算获得其成形极限图,计算结果与试验数据吻合较好。将厚度梯度准则与有限元方法相结合,可在已知薄板单拉性能参数的条件下计算获得其成形极限图。     

Influence of blank profile on the V-die bending camber process of sheet metal

The finite element simulation is now widely used in the design of stamping tools. A trial and error procedure has been replaced by a simulation in which defects associated with sheet forming processes are predicted and evaluated. This paper aims to clarify the process conditions of the V-die bending of a sheet metal. It provides a model that predicts not only the correct punch load for bending, but also the precise final shape of the products after unloading. An incremental elastic-plastic finite element computer code, based on an updated Lagrangian formulation, was developed to simulate the V-die bending of sheet metal. In particular, the assumed strain field (ASF) element was used to formulate the stiffness matrix. The r-minimum technique was used to deal with the elastic-plastic state and solve contact problems at the tool-metal interface. A series of experiments were performed to validate the formulation in the theory, leading to the development of the computer codes. The predicted punch load in the finite element model agrees closely with the experimental results. The whole history of deformation and the distribution of stress and strain during the forming process were obtained by carefully considering the moving boundary condition in the finite element method .A unique feature of this V-die bending process is the camber after unloading. The computer code successfully simulates this camber. The simulation was performed to evaluate the effects of the size of the blank on the camber process. The results in this study clearly demonstrate that the computer code efficiently simulated the camber process .     

Springback prediction of high-strength sheet metal under air bending forming and tool design based on GA�CBPNN

Based on orthogonal test for air bending of high-strength steel sheets, 125 values of sheet thickness (t), tool gap (c), punch radius (r), ratio of yield strength to Young??s modulus (?? _y /E), and punch displacement (e) are used to model the springback for air bending of high-strength sheet metal using the genetic algorithm (GA) and back propagation neural network (BPNN) approach, where the positive model and reverse model of springback prediction are established, respectively, with GA and BPNN. Adopting the ??object-positive model?Creverse model?? learning method, air bending springback law is studied with positive model and punch radius is predicted by reverse model. Manifested by the experiment for air bending forming of a workpiece used as crane boom, the prediction method proposed yields satisfactory effect in sheet metal air bending forming and punch design.     

Numerical simulation of electric hot incremental sheet forming of 1050 aluminum with and without preheating

Incremental sheet forming (ISF) consists of deforming the sheet, through a spherical punch, punctually and progressively until it reaches the desired geometry. Compared to the conventional process, the ISF can achieve much higher levels of formability. But the stresses and residual strains are often pushed to the limit on the path, producing a piece with brittle behavior, which is not desirable for applications in engineering. To work around this inconvenience, one solution would be to perform the conformation at high temperatures, a process known in engineering as hot forming. This study aims to evaluate the behavior of the state of stresses and strains in the hot incremental sheet forming of 1050 aluminum alloy, with and without pre-heating, using the finite element method. This behavior has been studied by numerical simulation, using the software RADIOSS, which has a suitable formulation for inserting the effects of temperature and strain rate in the material. The results show a decline in the forces for electric hot incremental sheet forming preheated (EHISFP) compared to the electric hot incremental sheet forming (EHISF). Moreover, for these same cases, there was a gain in relation to the geometric precision on average more than 4%.