基于罚函数法和Backofen模型的刚粘塑性有限元列式推导

讨论了刚粘塑性有限元法,对其基于罚函数法和Backofen模型的求解列式进行了详细的推导.     

刚粘塑性有限元数值模拟中粘性系数的获取方法

以塑性元件和粘性元件并联的模型为基础,研究材料粘性系数的获取方法,给出了一些材料的粘性系数和影响因素之间的关系曲线,为模拟研究中粘性系数的获取提供一种方便有效的方法.     

有限元方法在金属塑性成形中的应用

有限元法是应用于金属塑性成形数值模拟中的一种有效的数值计算方法.详细介绍了弹塑性、刚塑性、粘塑性3种有限元法.刚塑性有限元法适用于大塑性变形,包括板带、型钢轧制和环件轧制的模拟分析等.弹塑性有限元法在金属塑性成形数值模拟中应用最广.与刚塑性方法相比,弹塑性有限元法还能有效处理卸载问题,计算残余应力和应变.而粘塑性有限元法适用于金属热变形或强化不显著的软金属变形.同时,结合国内外最新的具体实例说明了这些方法在金属塑性成形领域中的具体应用,展望了有限元方法在金属塑性成形中的发展.     

轴对称件扭压成形的粘塑性有限元分析

运用体积微可压缩法的三维刚粘塑性有限元方法.对轴对称体的扭压成形变形规律进行了模拟分析.结果表明:与一般镦粗成形相比,扭压成形具有可促使变形均匀、增加变形量等优点.     

盒形件拉延成形的刚塑性有限元数值模拟

本文采用刚塑性有限元理论，开发了一个二维数值模拟程序系统，对盒形件拉延成形中的法兰变形区进行了较全面的数值模拟，研究了冲压成过程中法兰变形区的金属流动规律。     

金属塑性成形三维有限元模拟软件3D - PFS的开发

金属塑性成形过程的三维有限元模拟仿真是否有效的关键在于快速适用的算法和有效的模拟系统.介绍了自主开发的三维刚塑性/刚粘塑性有限元模拟分析软件3D-PFs的组成及关键技术问题的处理,并给出了计算实例.结果表明:利用该系统可实现对体积和板料成形过程的模拟分析,获得成形过程中材料在模腔中的流动情况及成形规律,该系统是研究金属塑性成形的有效工具.     

刚/粘塑性圆板的强迫振动

本文用分离变量方法分析刚／粘塑性圆板的强迫振动问题,给出了该板强迫振动时的挠度与内力解。     

刚／粘塑性梁的强迫振动

本文依据粘塑性梁强迫振动的非齐次方程与非线性本构方程,提出采用分离变量的位移方法求解,获得该问题的应力和位移解.     

直齿圆柱齿轮精锻过程的三维刚塑性有限元模拟

对空心直齿圆柱齿轮的精锻成形过程进行三维刚塑性有限元模拟.通过有限元模拟分析,深入揭示直齿圆柱齿轮精锻过程的金属流动规律和变形力学特征,对直齿圆柱齿轮精锻工艺和模具设计具有重要的指导意义.     

超塑性充模胀形的有限元模拟

以跟踪最大应变速率单元并使之维持最佳应变速率的方法确定超塑性充模胀形的最佳加压规范；用大变形刚粘塑性有限元法模拟了恒压和最佳加压规范下的超塑性充模胀形过程，并对比二者的结果，同时分析了ｍ值对胀形的影响。     

Rigid body considerations for non-linear finite element analysis

The purpose of the paper is to demonstrate how the concept of rigid body motions can be employed to derive the external stiffness matrix for an initially stressed finite element. Such a matrix is as important as the elastic and geometric stiffness matrices. It can be used not only in an eigenvalue analysis for testing the zero energy modes of a finite element under initial loadings, but for calculating the element forces in a step-by-step non-linear analysis. The two-dimensional beam element presented in this paper serves as a vehicle to demonstrate the concept involved. The principle of virtual work in its updated Lagrangian form has been adopted as the method of formulation. Several examples are provided to illustrate the adequacy of the present approach.     

Hot deformation behavior and finite element simulation of hot isostatic pressed Mo-50Cu composite

Journal of Materials Science - The characterization of hot deformation behavior and determination of hot processing parameters of Mo-50Cu composites were studied by the isothermal compression tests...     

A stable finite element simulation of convective transport

A finite element simulation of the equations of momentum and energy transport in fluids has been implemented with triangular elements. An attempt is made to single out the reasons for numerical instabilities reported by other investigators for convection–diffusion transport operations in fluid mechanics when the ratio of the convective to the diffusive terms, measured by the Reynolds and Peclét numbers, is of the order of a hundred. To this end, the equations are solved for several problems to permit a direct comparison with results of other formulations. It is shown that the appearance of instability can be delayed by a proper choice of boundary conditions, and its intensity can be reduced through the use of triangular finite elements. Results agree very well with theoretical solutions for particular test problems including flows with large convection effects, large dissipation effects and fluids with temperature dependent properties.     

Thinning analysis for hot forming of single-piece hemispherical dish end using finite element simulation and its empirical modeling

Hot forming is an important forming method for production of small and medium sized single-piece pressure vessel dish ends. Thinning of the blank material with increased degree of forming is quite obvious. Present work shows finite element (FE) analysis of hot forming of single-piece hemispherical dish end (SPHDE) for predicting maximum thinning of blank during forming. Thinning analysis is performed for SPHDE of two different ferrous material grades SA-387 Gr22 and SA-516 as per ASME, Section II, Part A (2004). Percentage thinning results of FE analysis are verified with the practical material thinning data. Based on the thinning analysis, empirical relation for calculation of percentage thinning as a function of different dish ends′ geometry parameters is proposed. Empirically predicted percentage thinning is observed to be in good agreement with practical and FE simulation results. Thinning results obtained based on proposed FE simulation and empirical model can be helpful to design engineer in selecting thickness of developed blank considering thinning allowance for hot forming of SPHDE. Thinning analysis data can be used for optimizing the dish end geometrical parameters for minimum thinning during forming.     

有限元简化模型应用于超声换能器模拟分析

依据有限元方法的基本物理思想,在某些不需要计算辐射声场的准确声学参数和波束特性的工程应用方面,对流体模型进行充分简化,提出了简化模型处理的有效方法,利用该方法对超声换能器进行模拟分析,并进行了样品的制作和测试,实测结果与模型简化分析处理的结果基本一致。可以证明,用该方法进行换能器的优化设计是可行和高效的。     

Finite element simulation of the steel plates hot rolling process

In this paper we discuss our finite element procedure for simulating the hot rolling of flat steel products. We couple an Eulerian rigid‐viscoplastic model of the steel plates deformation to a Lagrangian elastic model of the rolls deformation. This latter model incorporates the bending deformation of the work rolls supported by the back‐up rolls and the flattening of the contact areas (Hertz problem) via an enhanced beam model. The finite element model is validated comparing its predictions with actual industrial measurements and then it is used to analyse different rolling set‐ups. Copyright © 2001 John Wiley & Sons, Ltd.     

Fragmentation algorithm for finite element failure simulation and analysis

An algorithm which combines the techniques of numerical analysis and numerical simulation in the study of transient dynamic structural response is proposed. This is achieved by incorporating the ability to create new surfaces and separate fragments according to a defined failure criterion into a finite element procedure which uses explicit time integration. Thus, the algorithm not only provides accurate prediction of the structural failure and fragmentation pattern, but also evaluates accurate stress, velocity, acceleration and displacement values of each fragmented component. To develop a viable fragmental algorithm, other than the expected modification in storage and node bookkeeping, we found it necessary to introduce an efficient algorithm to handle extremely large displacements resulting from the fracture. In that regard, an updated corotational approach is introduced.     

A micromechanical composite approach for finite element crashworthiness simulation

The present article deals with micromechanical composite modeling. Both analytical and computational micromechanics approaches are described as well as micromechanical modeling of damage. Based on micromechanics of failure theory, a user subroutine including a progressive damage algorithm is programmed for finite element analysis. Three theory-experiment correlations of tubes under a three-point bending test have been carried out using the bi-phase material model developed along with this project. These studies include three-ply schedules.     

A finite element model for plasma simulation in multipoles

A numerical model is proposed to simulate the space-time behaviour of a low-density plasma in a linear multipole. Semi-discrete Galerkin techniques are used in conjunction with triangular finite elements. For both space and time discretizations, special techniques are developed to numerically separate the effect of rapid diffusion along the field lines from the slow perpendicular diffusion. Numerical results are exhibited to show how these techniques succeed in eliminating the problems caused by the strong anisotropy of the diffusion coefficient in the strongly curved and very inhomogeneous multipole configuration.     

Mesh scalability in direct finite element simulation of brittle fracture

A new approach of dealing with mesh dependence in finite element modelling of fracture processes is introduced. In particular, in brittle fracture modelling, the stress concentration is mesh dependent as the results do not stabilise when refining the mesh. This paper presents an approach based on the explicit incorporation of mesh dependence into the computations. The dependence of the relevant stress is quantified on the finite elements at the crack tip upon the element size; when the dependence approaches a power law with the required accuracy, the mesh is called scalable. If the mesh is scalable and the exponent and pre-factor are known, then the results of the computations can be scaled to the size relevant to the scale of the physical microstructure of the material; the latter while not being modelled directly ultimately controls the fracture propagation. To illustrate this new approach, four 2D examples of a single straight crack loaded under tensile and shear tractions applied either to the external boundary or to the crack faces are considered. It is shown that combining the stresses at the crack tip computed using a set of similar meshes of different densities with the crack tip asymptotic allows accurate recovery of the stress intensity factors.