筒形件磁脉冲辅助冲压成形数值模拟

针对磁脉冲辅助冲压成形过程,提出了基于ANSYS平台的有限元分析程式,通过编制用户子程序,采用重启动分析法,建立了冲压预成形过程显式求解和瞬态磁脉冲成形"松散"耦合分析之间的动态连接,并用于5052-O铝合金圆筒形拉深件磁脉冲辅助冲压成形过程的有限元仿真研究。结果表明,所建立的有限元分析方案,能实现圆筒形件磁脉冲辅助冲压成形连续变形过程的模拟,板坯变形信息体现了准静态冲压变形和高速率磁脉冲成形之间的耦合。有限元模拟结果与实验吻合较好。     

Experimental and numerical investigation of laminated steel sheet in V-bending process considering nonlinear visco-elasticity of polymer layer

Laminated steel sheet consists of two steel sheets and a polymer layer which bonds them. During forming process, mechanical properties of polymer layer significantly influence the shape of final product. In this study, a continuum model in which nonlinear visco-elasticity is taken into account has been developed for polymer layer of laminated steel sheet and implemented in a commercial finite element program by material subroutines. Lap-shear test and T-peel test have been conducted to obtain parameters of this continuum model. Two different methods are compared to establish a better method for modeling the polymer layer deformation in lap-shear test simulation. One is cohesive zone element and the other is contact method. In order to assess calculation efficiency, both explicit and implicit procedures are used to simulate lap-shear test, and T-peel test is simulated by implicit procedure to evaluate accuracy. The result indicates that cohesive element is easier to solve convergence problem and implicit procedure may save much simulation time. T-peel test data can be used to describe the normal mechanical behavior of polymer layer in an acceptable range. Finally, V-bending forming process has been studied to investigate the effect of polymer layer on the springback and final deformation shape through experiment and numerical simulation. The result indicates that the comparison between numerical simulation and experiment is in good agreement. The finite element model can accurately predict the final shape after bending and springback.     

OPTIMIZATION OF AUTOBODY PANEL STAMPING PROCESS BASED ON DYNAMIC EXPLICIT FINITE ELEMENT METHOD

1.IntroductionItiswellknown,sheetmetalformingprocessexperiencesverycomplicateddeformationeffectedbyprocessparameterssuchasdiegeometry,theblankshapeandposition,theblank-holderforce,frictionandlubricationandsoon.Traditionally,theoptimumconditionforstampingprocessparametersisdeterminedbyintuitionandexperiencecalledknow-howtechniques,withtrial--and--error,andthereisnogoodwaybuttomakeexpensiveandtime-consumingmodificationstothetoolsandtodeterminetheprocessparametersexperimentally.Internationalsever…     

汽车轮毂件冲压成形断裂分析

板料冲压过程是一个非常复杂的塑性成形过程,许多因素都直接或间接影响着成形的结果.以Forge2D软件为平台,采用弹塑性有限元法对某一汽车轮毂零件的成形过程进行数值模拟,揭示零件冲压过程中板料的变形行为,预测冲压过程中可能出现的各种工艺缺陷,例如坯料的局部减薄和破裂,并以模拟结果为依据提出改进工艺参数的办法,优化工艺参数,可以减少调试和修模的次数,以此实现降低模具费用、缩短制模时间、提高产品成品率和材料利用率,最终达到减少产品成本的目的.在此基础上,对3种冲压工艺方案分别进行了数值模拟,对比研究了各方案的成形特点,得出了较好的成形工艺参数方案.     

基于ABAQUS药芯铝焊丝铝带成型过程的仿真研究

在对显式动力学有限元方法的概念、基本理论和应用范围进行了阐述的基础上,通过ABAQUS有限元仿真软件,在Explict显式动力学模块中,对4047铝药芯焊丝轧制过程中4047铝带成型过程进行了模拟仿真.比较不同铝带速度下铝带成型质量.比较不同质量缩放因子下仿真结果稳定的4047铝合金的成型质量,择优选出成型质量最好、运算速度最快的质量缩放因子.比较不同上下轧辊轴线距离时4047铝合金成型质量,得出了当上下轧辊的距离为4047铝带厚度时其成型质量最佳.     

半球形凸模拉深过程的动力显式有限元分析

本文基于连续介质力学及有限变形理论 ,建立了用于三维板料成形过程分析的有限元模型 ,开发了动力显式算法的板料成形过程模拟的有限元分析程序DESSFORM3D。采取集中质量矩阵 ,用动力显式积分的方法 ,使位移计算显式化 ,避免了由材料、几何、边界条件等高度非线性因素引起的计算收敛问题。对半球形凸模拉深过程进行模拟计算 ,并把模拟结果与实验结果进行对比 ,验证了软件的计算结果     

Industrial applications of sheet stamping simulation using new finite element models

The paper is aimed to present industrial applications of sheet stamping simulation using new finite element formulations developed in the International Center for Numerical Methods in Engineering in Barcelona. Theoretical formulation is briefly reviewed. Both continuum and shell elements have been considered. The new shell elements developed are based on a geometrically exact shell model treating the shell as one-director Cosserat surface. The formulation of the continuum elements employs the multiplicative decomposition of the deformation gradient tensor into its elastic and plastic parts. The new finite element models have been implemented in the in-house explicit dynamic code STAMPACK. A number of practical problems of sheet metalforming have been solved with the program. Some of the problems, namely stamping of a kitchen sink, hydraulic forming of an aeronautical part and stamping of a food can, have been presented in the paper. The examples give an idea of practical information that can be obtained from the computer simulation of a forming process. The results confirm a good behaviour of the formulation and program used in the industrial applications.     

金属板材成形中拉深损伤模拟的两种求解方法

讨论用数值模拟预测板材成形中发生拉深损伤破坏的两种不同的求解方法。第一种是采用完全耦合的弹塑性破坯模型的动力显式数值方法。基于状态参量的不可逆热力学过程 ,完全耦合的本构方程考虑各向同性强化和拉深。这些已引入有限元软件ABAQUS/E用于对金属成形的模拟。在数值技术方面 ,隐式积分方法被用来对本构方程的局部时间积分 ,动力显式技术用于求解总体平衡方程。第二种方案是采用简化的损伤模型的方法 ,被称为逆法 (InveseApprch)。I.A被限定在考虑各向同性强化和损伤的塑性全量理论基础上的简单的本构关系。做比例加载和临界损伤达到以后的损伤饱和假定 ,可以得到损伤演化方程的封闭解。这两种损伤模型在编程中的实施采用两种方式 :计算中考虑或不考虑损伤作用 ,也就是耦合的或非耦合的计算。文中给出一些算例来说明每种损伤模型的优点     

Elastic-plastic finite element analysis of automotive body panel stamping processes using dynamic explicit time integration scheme

In this article, the elastic-plastic finite element formulations using dynamic explicit time-integration schemes are proposed for numerical analysis of automotive body panel stamping processes. A general formulation of finite element simulation for complex sheet forming processes with arbitrarily shaped tools is briefly introduced. In finite element simulation of automotive body panel stamping processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. For analyses of more complex cases with larger and more refined meshes, the explicit method is more time effective than the implicit method, and it has no convergency problem and has the robust nature of contact and friction algorithms, although the implicit method is widely used because of excellent accuracy and reliability. The elastic-plastic scheme is more reliable and rigorous, while the rigid-plastic scheme requires short computation time. The performance of the dynamic explicit algorithms is investigated by comparing the simulation results of forming of complex-shaped automotive body parts, such as a fuel tank and a rear hinge, with the experimental results. It has been shown that dynamic explicit schemes provide quite similar results to the experimental results. It is thus shown that the proposed dynamic explicit elastic-plastic finite element method enables an effective computation for complicated automotive body panel stamping processes.     

高强度钢板拉深模具结构有限元分析与试验研究

高强度钢板在汽车车身结构中的广泛应用,对冲压成形工艺和模具的设计带来了诸多问题和挑战。文章针对高强度钢板DP600的拉深成形过程,基于LS-Dyna和MSC.Marc有限元软件,采用动力算法和静力算法相结合的方法,对拉深模具结构在冲压过程中的应力应变状态进行了有限元分析,得到了模具结构上任意位置应力和应变随冲压行程的变化规律。同时,利用自主开发的冲压模具结构应力应变状态的试验测量系统,在MTS试验机上完成了相应的冲压拉深实验和模具变形测量。实验测量结果与数值计算结果吻合较好。提出的研究方法对进一步开展高强度钢冲压模具的受力分析和设计优化提供了保证。     

Study of dynamic explicit analysis in sheet metal forming processes using faster punch velocity and mass scaling scheme

A finite element formulation using dynamic explicit time integration scheme is developed for numerical analysis of autobody panel stamping processes. The lumping scheme is employed for the diagonal mass matrix and linearizing dynamic formulation. A contact scheme is developed by combining the skew boundary condition and direct trial and error method. To investigate the effects of punch velocity, various values of punch velocity are used for numerical analysis. The mass scaling scheme is introduced for economic analysis. To investigate the effects of mass scaling, various mass scalings are used. Computations are performed for analysis of complicated autobody panel stamping processes including the formation of an oilpan and a fuel tank.     

用动态显式有限元法对板材成形进行计算机模拟

介绍了动态显式有限元法的原理和特点 ,总结讨论了国际现有各种商用有限元软件的情况。采用显式有限元软件 L S- DYNA3D对板材零件冲压过程进行计算机模拟分析 ,预测冲压过程中可能出现的各种工艺缺陷 ,例如坯料的起皱、局部减薄和破裂 ,并以模拟结果为依据提出改进模具和工艺参数的办法 ,优化工艺参数 ,可以减少调试和修模的次数 ,以此实现降低模具费用、缩短制模时间、提高产品成品率和材料利用率 ,最终达到减少产品成本的目的。     

环件轧制过程的显式有限元模拟分析

用于金属成形模拟的有限元方程的求解方法 ,主要有隐式和显式积分两种方法。对于复杂的三维变形分析 ,如环件轧制 ,隐式方法需要很长的运行时间。而利用显式方法 ,可以达到很好的效果。本文利用Abaqus /Ex plicit通用有限元程序对径向环轧进行了模拟。     

Quasi-static implicit and transient explicit analyses of sheet-metal forming using a C three-node shell element

A three-node isoparametric shell element well suited for extensive non-linear analyses is developed and used for the simulation of sheet-metal forming processes. Two computational strategies based on this element are presented: a quasi-static implicit one based on an updated lagrangien formulation with a consistent tangent stiffness matrix and a transient explicit one where the diagonal mass matrix is used to compute the nodal acceleration vector. The anisotropic elastic-plastic constitutive equations are treated using a rotated frame subjected to follow the anisotropy axes. Two numerical examples are presented and the two computational strategies are compared.     

Efficient numerical prediction of residual stress and deformation for large-scale laser shock processing using the eigenstrain methodology

Laser shock processing (LSP) is an effective but costly process for inducing compressive residual stresses and deformation that are primarily applied in the aerospace industry. Accurate modeling of the LSP process with optimization is helpful to reduce development time and cost, but the simulation time is computationally expensive due to the long duration to capture the transient response of the material for each shock. In the present research, the eigenstrain modeling method is developed to predict the effect of large-scale LSP more efficiently compared with previous methods. In the developed eigenstrain-based method, residual stress and deformation fields are analyzed elastically using the simulated eigenstrain as initial strain, which is incorporated into the model by thermal expansion with a predefined unit temperature field and different anisotropic thermal expansion coefficients. For the large-scale LSP application, the eigenstrain in one representative cell identified through an explicit analysis is proposed as an approximation of the actual full eigenstrain field for efficient prediction. The predictions are verified by the predicted results from the explicit/implicit method for laser peening (LP) and the pure explicit method for laser peen forming (LPF) and are also validated by the experimental results of a single LP surface treatment of Ti6Al4V and a LPF bending of 1060 pure aluminum plates. Compared with the previous methods, the eigenstrain modeling method is proved to be effective and much more computationally efficient.     

多通管挤压胀形过程的分析与计算

挤压力、胀形力和平衡力三者之间的最佳匹配关系是多通管超高压挤压胀形工艺中的关键问题 ,提出并采用“应变样条”法建立了这 3个成形力间的数学表达式。同时 ,根据多通管挤压胀形双重非线性的变形特点 ,建立了动力分析有限元模型 ,采用自行开发的程序软件 (SMFT) ,模拟分析和计算了这 3个力的大小及相互匹配关系对挤压胀形的影响     

Large deformation finite element analysis of strain localization in fine-blanking process

In this study, an updated Lagrangian large deformation finite element method is developed for solving the metal forming problems with an incrementally objective mid-interval integration algorithm. A numerical simulation of fine-blanking process is hence performed to predicate the strain localization and to investigate the failure mechanism of fine-blanking process. Using the numerical result, The stress and strain fields developed in the fine-blanking process as well as the large deformation elasto-plastic finite element implementation for solving axisymmetric strain localization problems are discussed.     

金属管接头复合成形过程有限元模拟及实验研究

针对凸筋类金属管接头提出了一种新的管接头复合成形工艺：“缩口－轴压－胀形”复合成形工艺,分析了该复合成形的工艺特点,利用刚塑性有限元方法对复合成形过程进行了模拟,得出了不同时刻的网格变形图和等效应变的等值线分布图,讨论了缩口半锥角和摩擦因子对成形极限的影响,将刚塑性有限元计算的结果与实验结果进行了比较,并得出了一些对生产实际有价值的结论     

显式动力学有限元法分析板宽对板带轧制压力分布的影响

显式动力学有限元法是分析大型接触问题的有效方法 ,近年来在分析板料成形及碰撞冲击问题方面得到了广泛的应用。本文介绍了显式动力学有限元法的特点及在板带轧制过程分析中的研究状况 ,阐述了其基本理论 ,并采用显式动力学有限元法模拟了板带轧制过程 ,模拟计算出的变形区轧制压力分布与实验结果吻合较好。     

Research on formability of 5052 aluminum alloy sheet in a quasi-static–dynamic tensile process

In order to establish the efficacy of electromagnetically assisted sheet metal stamping (EMAS), the formability of 5052 aluminum alloy sheet in a quasi-static–dynamic tensile process is experimentally investigated using a combined quasi-static tension and the pulsed electromagnetic forming (EMF) method. Data on the formability of aluminum alloy 5052-O employing this combined loading method is compared with data for traditional quasi-static tensile tests. Results show that the formability of aluminum alloy sheet undergoing a quasi-static–dynamic tensile process is dramatically increased beyond that exhibited in quasi-static tensile tests, and a little higher than or at least similar with that obtained in the fully dynamic EMF process. The forming limits of aluminum samples with both low and high pre-strain levels are almost similar in quasi-static–dynamic tensile process, which makes it possible stretching the sheet to a higher quasi-static pre-strain level without weakening its total quasi-static–dynamic formability. This would enable the use of a quasi-static pre-form fairly close to the quasi-static material limits for design of an EMAS process in manufacturing large aluminum alloy shell parts.