基于ABAQUS的马鞍形曲面板材渐进折弯成形研究

为改善大幅面曲面板材成形精度,提出一种渐进折弯成形新方法。以马鞍形曲面成形为例,采用平面应变和Mises各向同性屈服准则,建立基于ABAQUS/ExplicitStandard求解分析平台的板材三维弹塑性渐进折弯成形有限元模型,对板材渐进折弯与回弹全过程进行了数值模拟,结合试验研究,获得最优工艺参数。模拟及实验结果表明:采用曲面凸凹模及优化工艺参数可实现高精度大幅面曲面板材的成形,模拟成形工件的平均误差为+2.1/-1.8 mm,实验测量成形板材曲率与目标模型理论曲率误差较小,模拟结果与实验结果基本吻合,这对曲面冷弯成形技术的应用,具有重要的参考价值和指导意义。     

金属板材数控单点渐进成形加工轨迹优化研究

提出一种对金属板材数控单点渐进成形的加工轨迹优化及成形压头压入点沿工件轮廓均布处理的方法。解决了工件局部的凹陷与破裂问题，提高了板料数控渐进成形的质量。     

应用开放式CNC进行金属板材数控渐进成形加工的研究

金属板材数控渐进成形工艺是目前国际上一种新兴的板材成形工艺。本文将原有使用固定支撑模型的反向加工方式进行改进,应用开放式CNC技术,使用了一种通过上下2系统5轴控制成形方式,构建了改进型的数控渐进成形系统,并通过灵活应用工件测量功能,修改数控程序,调节成形工具的成形轨迹,提高成形零件的加工精度。     

拉形辅助的数控渐进成形试验研究

解决了板材数控渐进成形的厚度减薄严重、加工时间长等缺陷,分析了数控渐进成形和拉形的主要特点,研究了基于数控渐进成形机床伺服托架的拉形辅助的数控渐进成形技术。设计了专用夹具在数控渐进成形机床上实现了一次装夹的混合成形。通过试验分析了两种成形方法对产品厚度及成形时间的影响,结果表明,此混合成形与单一的渐进成形相比,可以有效的减少零件的过度变薄及加工时间,可以突破渐进成形的成形极限角,成形出单一的渐进成形不容易成形的零件。     

成形滾刀的设计和制造

一、成形滚切原理成形(异形)齿轮长期以来一般都进行铣削加工,如图1所示齿轮就难以用滚刀进行滚切,即使用铣刀切削,也必须是组合铣刀,不能单齿切削,如果要滚切成形齿轮,就须找出一种方法,使既能滚切又能成形。从滚切角度讲,滚切是连续的,而实际上若干刀齿之间存在一定的空间距离,成形滚切就是利用了这个间断性,因此成形齿轮滚切的基本原理是工件与刀具的配合运动,利用成形分度铣齿法原理建立刀齿齿形,利用同步转角法的原理来达到成形滚切。     

刀具路径对单点渐进成形的影响

在单点渐进成形技术中,刀具路径是加工时刀具在空间中的运动轨迹。本文使用有限元分析软件ANSYS／LS—DYNA模拟了刀具路径对渐进成形过程的影响。模拟结果表明：当刀具四点压下时,模拟的轮廓曲线对称性最好,底面上凸的幅度较小;同时,板材的最大等效应变和主要变形区节点的塑性应变较小,板材连续逐层变形能力较好。     

基于超声辅助对TA1板材渐进成形性能的研究

钛及其合金因具有小密度、高比强度、且具有较好的生物相容性等优点，被广泛应用各个领域。将超声辅助渐进成形工艺应用到TA1钛合金板材的渐进成形过程当中，利用Abaqus有限元软件模拟超声辅助渐进成形的过程，并分析了在成形过程中成形力减少的原因，研究了不同的振动参数和工艺参数对TA1钛合金板材成形力影响的规律。结果表明，超声振动可显著降低成形过程中的成形力，为超声振动应用于TA1钛合金板材的渐进成形提供了相关依据。对拓展钛合金板材渐进成形工艺应用具有重要意义。     

约束对板材激光直线扫描成形的影响

板材激光弯曲成形是利用激光成形工件的柔性成形技术。以板材激光单次扫描成形过程为研究对象,对板材激光直线扫描成形过程进行了有限元模拟,分析了有约束和无约束情况下板材的变形行为。     

基于量纲分析法的金属板材折弯回弹数学模型

回弹是影响金属板材工件成形精度的一个非常重要因素。准确控制回弹是工件精密成形和模具设计的关键所在。针对用于修正回弹的传统试错法的不足,提出一种基于量纲分析和正交试验相结合的方法来建立金属板材折弯回弹半径数学模型。并讨论回弹数学模型的适用范围。该模型定量求解了板料回弹半径与凸模半径、板材厚度、屈服强度、弹性模量之间的非线性关系。将此应用于折弯凸模的设计制造,且用该凸模多道次渐进成形了一半椭圆形工件,它的平均误差是+0.63/-0.65mm。该制造结果表明,基于量纲分析法和正交试验法建立的板料回弹半径数学模型是合理有效的,该建模方法有助于加快模具设计进程,降低生产成本,为金属板料折弯成形及模具设计提供了一条新的途径。     

金属板材数字化渐进成形技术研究现状

金属板材数字化渐进成形技术是国际上刚刚兴起的一种柔性成形技术。介绍了数字化渐进成形的原理、特点及其工艺过程,综合分析了近年来数字化渐进成形技术的研究成果,重点对渐进成形的工艺规划及成形轨迹的优化、对板材成形性能的影响、成形过程的数值模拟、成形精度等方面进行了较系统的归纳和总结,列举了大量的国内外工艺应用及设备情况,探讨了数字化渐进成形技术的发展趋势和有待进一步研究的若干课题。     

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.     

Analytical modeling and numerical simulation for three-roll bending forming of sheet metal

The three-roll bending forming of sheet metal is an important and flexible manufacturing process due to simple configuration. It is suitable for forming large sheet parts with complex, curved faces. Most researches on roll bending forming of large workpiece are mainly based on experiments and explain the process through macroscopic metal deformation. An analytical model and ABAQUS finite element model (FEM) are proposed in this paper for investigating the three-roll bending forming process. A reasonably accurate relationship between the downward inner roller displacement and the desired springback radius (unloaded curvature radius) of the bent plate is yielded by both analytical and finite element approaches, which all agree well with experiments. Then, the three-roll bending forming process of a semi-circle-shaped workpiece with 3,105 mm (length)?×?714 mm (width)?×?545 mm (height) is simulated with FEM established by the optimum tool and process parameters. Manifested by the experiment for three-roll bending forming of this workpiece, the numerical simulation method proposed yields satisfactory performance in tool and process parameters optimization and workpiece forming. It can be taken as a valuable mathematical tool used for three-roll bending forming of large area sheet metal.     

Modeling and simulation for multiple-step incremental air-bending forming of sheet metal

Based on Hill’s yielding criterion and plane strain condition, the explicit expressions of elastoplastic constitutive model are derived in this paper which takes into account the effects of transverse stress, neutral surface shifting, and sheet thickness thinning on the sheet springback of air-bending. Then, this model is embedded into ABAQUS software platform by means of programming. Finally, 3D ABAQUS finite-element models (FEM), used to form the semiellipse-shaped workpiece with super length and large opening of sheet metal, are established, and the multiple-step incremental air-bending forming and springback processes are simulated. The simulation and experiment results show that the data predicted with the new constructed constitutive model under the plane strain condition are in much better agreement with experimental data than those predicted with the constitutive model built-in ABAQUS. It can be taken as a valuable mathematical tool used for multiple-step incremental air-bending forming simulation of large area sheet metal.     

The study for stability of closed-loop control system based on multiple-step incremental air-bending forming of sheet metal

To solve the springback problem for sheet metal forming, feedback control idea in automatic control theory is introduced to incremental air-bending forming process. The advanced control techniques are used to solve precision forming for workpiece of sheet metal. However, stability, accuracy, and rapidity of closed-loop control can directly affect system normal operation. Aiming to analyze the effect of stability on the quality of the formed workpiece, a closed-loop control system model for incremental air-bending forming is established. The transfer function and characteristic equation of the closed-loop system are solved through theory deduction and minor incremental linearization method. Both simulations with Matlab/Simulink and root locus results show that, as the overall gain is equal to one, the shape of formed part could converge to the target shape at the fastest rate. Finally, a semiellipse-shape workpiece is manufactured with the corrected mold obtained by the closed-loop forming method. The experimental results show that the closed-loop forming way is feasible and the means of correcting the mold parameters by iterative compensation of the stable closed-loop control system is effective. It can be taken as a new approach for sheet metal incremental air-bending forming and mold design.     

金属板料多道次渐进成形过程的数值模拟

介绍了金属板料渐进成形工艺的基本原理.以ANSYS/LS-DYNA为分析平台,构建了板料多道次渐进成形的有限元模型,并以LS-PREPOST和ETA/Post-Processor为后处理平台,得到各道次厚度云图及网格变形图.对半球形制件的三道次成形过程进行了模拟,将模拟结果与实验结果进行比较,证明了模拟的可行性.     

Tool path correction algorithm for single-point incremental forming of sheet metal

There exists some error between the manufactured part shape and the designed target shape due to springback of this part after forming. To reduce the error, an iterative algorithm of closed-loop control for correcting tool path of the single-point incremental forming, based on Fast Fourier and wavelet transforms, has been developed. Moreover, the data of the springback shapes, after unloading, of the sheet metal parts formed with the trial and corrected tool paths, used for iterative correction of tool path in the algorithm, are obtained with finite element model (FEM) simulation. Then, a truncated pyramid-shaped workpiece, whose average errors are +0.183/?0.175 mm, was made with the corrected tool path after three iterations solved by the above algorithm and simulation data. The results show that the tool path correction algorithm with Fourier and wavelet transforms is reasonable and the means with FEM simulation are effective. It can be taken as a new approach for single-point incremental forming of sheet metal and tool path design.     

汽车覆盖件冲压成形仿真研究进展

汽车覆盖件冲压成形仿真技术的发展,突破了原有汽车冲压件模具及工艺设计的设计方法,对保证工件质量、减少材料消耗、缩短产品开发周期、降低制造成本具有重要意义.概述了目前汽车覆盖件冲压成形仿真所涉及到的热点领域,如摩擦与接触、回弹分析、模具系统和工艺参数、材料屈服模型和板料形状设计,讨论了这些领域的研究进展和进一步研究的发展方向.     

基于有限元复杂回转体渐进成形过程研究

数字化渐进成形技术是一种新兴的金属板料柔性成形技术。通过有限元数值对其成形过程模拟,能够对渐进成形的研究起理论指导作用。利用有限元分析软件LS-DYNA对金属板料渐进成形的过程进行了模拟。根据试验特点建立了相关的有限元模型,对其中工具头的运动轨迹和加载方式进行了简化,同时根据实际成形特点建立了边界条件和约束,保证了模拟的真实性,并据此模型分析了成形过程中板料上的应力、应变分布特点。     

考虑接触演变的板材回弹过程建模与优化

回弹是由工件在卸载后的弹性变形引起的。板料成形过程中为了控制成形件的最终形状,必须进行回弹设计优化。准确预测回弹对于板料成形过程的模具设计非常重要。降低回弹模拟结果与试验结果的偏差是设计过程中的难题。基于NUMISHEET’02的自由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回弹。采用一个常规的优化方法对有限元分析中的材料和单元模型进行了分析,研究发现不同模型对回弹结果有较大影响。模拟结果与参考文献中的试验结果比较表明了模型的正确性和可行性。