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.     

塑性有限元在金属体积成形过程中应用的进展

塑性有限元法已经成为研究金属体积成形的重要方法。介绍了刚塑性有限元和弹塑性有限元的原理;综述了金属体积成形过程中锻造、挤压和轧制工艺有限元模拟的国内外最新应用进展,并分析了有限元法在不同工艺中应用的未来发展方向。最后总结了塑性有限元法在金属体积成形领域未来发展的难点和趋势。     

齿轮坯模锻成形过程的数值模拟及优化

以齿轮组锻压件为研究对象,采用金属体积成形过程模拟软件DEFORM为工具,基于刚塑性有限元与热力耦合的思路,分析了齿轮坯在锻压中的成形过程,以及各种外界因素对成形情况的影响,得出合理因素下的成形结果。     

金属体积塑性成形过程数值模拟技术与仿真系统

介绍了金属体积塑性成形过程数值模拟方法、关键应用技术及其仿真系统的构成和国内外相关软件系统,对二维、三维有限元网格自动生成技术进行了较为详细的论述,综述了金属塑性成形过程优化设计方法、有限体积法以及无网格方法的国内外现状.最后给出了目前存在的问题及其将来应努力的方向.     

金属体积塑性成形过程数值模拟技术与仿真系统

介绍了金属体积塑性成形过程数值模拟方法、关键应用技术及其仿真系统的构成和国内外相关软件系统,对二维、三维有限元网格自动生成技术进行了较为详细的论述,综述了金属塑性成形过程优化设计方法、有限体积法以及无网格方法的国内外现状.最后给出了目前存在的问题及其将来应努力的方向.     

金属体积成形的无网格Galerkin模拟

为避免金属体积成形有限元法模拟中网格畸变造成网格重划和模拟精度降低,采用无网格法模拟金属体积成形.利用无网格法近似位移场,建立金属体积成形的无网格法连续性控制方程,采用罚函数法施加本征边界条件和体积不变条件,基于Markov变分原理推导了金属体积成形的无网格Galerkin求解列式.用数值计算法求解该列式,实现金属体积成形的无网格模拟.数值结果表明,无网格法能有效处理金属体积成形中出现的大变形,避免了网格畸变和重划,具有较高的模拟精度.     

热冲盂成形过程的刚粘塑性有限元模拟

采用刚粘塑性有限元法对热冲盂成形过程进行了数值模拟.讨论了刚粘塑性有限元法,并分析了热冲盂成形工艺的模拟结果.     

基于流线型凹模型腔的直齿圆柱齿轮冷挤压数值模拟分析

齿轮挤压属于体积成形,它是一个三维非稳态塑性成形过程,变形机制十分复杂。基于NURBS曲面构造流线型凹模型腔,用大变形刚塑性有限元数值模拟软件对圆柱直齿轮挤压过程进行了模拟。结果表明,采用流线型凹模型腔的连续性挤压成形,在改善角隅部分金属的充填性、减少变形突变以及提高变形分布均匀性等方面十分有效。这一结论可以作为齿轮挤压工艺设计的参考。     

热锻过程中动态再结晶的数值模拟

在热锻过程中,由动态再结晶引起的微观组织演化是决定锻件最终性能的重要因素之一。基于更新的拉格朗日格式刚塑性有限元和考虑动态再结晶的粘塑性模型,建立了能够模拟变形过程、温度变化过程和动态再结晶过程的有限元方法,研制了轴对称有限元软件,并用该软件模拟26Cr2Ni4MoV小圆柱试样镦粗过程中由动态再结晶引起的微观组织演化。在软件中应用网格重新划分技术降低由于网格畸变引起的计算误差。模拟结果和实验结果符合良好。     

金属体积成形过程有限元模拟中六面体网格重划技术的研究

针对金属体积成形过程有限元模拟中的网格重划问题,提出了基于边界构形的有限元网格重划技术,并对其中的一系列技术处理进行了详尽的讨论。将该技术应用于矩形块体镦粗过程的有限元模拟中,较好地解决了六面体网格重划问题。     

The dimension splitting reproducing kernel particle method for three-dimensional potential problems

In this paper, the dimension splitting reproducing kernel particle method (DSRKPM) for three-dimensional (3D) potential problems is presented. In the DSRKPM, a 3D potential problem can be transformed into a series of two-dimensional (2D) ones in the dimension splitting direction. The reproducing kernel particle method (RKPM) is used to solve each 2D problem, the essential boundary conditions are imposed by penalty method, and the discretized equation is obtained from Galerkin weak form of potential problems. Finite difference method is used in the dimension splitting direction. Then, by combining a series of the equations of the RKPM for solving 2D problems, the final equation of the DSRKPM for 3D potential problems is obtained. Five example problems on regular or irregular domains are selected to show that the DSRKPM has higher computational efficiency than the RKPM and the improved element-free Galerkin method for 3D potential problems.     

A point collocation method based on reproducing kernel approximations

A reproducing kernel particle method with built‐in multiresolution features in a very attractive meshfree method for numerical solution of partial differential equations. The design and implementation of a Galerkin‐based reproducing kernel particle method, however, faces several challenges such as the issue of nodal volumes and accurate and efficient implementation of boundary conditions. In this paper we present a point collocation method based on reproducing kernel approximations. We show that, in a point collocation approach, the assignment of nodal volumes and implementation of boundary conditions are not critical issues and points can be sprinkled randomly making the point collocation method a true meshless approach. The point collocation method based on reproducing kernel approximations, however, requires the calculation of higher‐order derivatives that would typically not be required in a Galerkin method, A correction function and reproducing conditions that enable consistency of the point collocation method are derived. The point collocation method is shown to be accurate for several one and two‐dimensional problems and the convergence rate of the point collocation method is addressed. Copyright © 2000 John Wiley & Sons, Ltd.     

基于重构核的最小二乘配点法求解封闭声腔响应

基于重构核思想,应用无网格配点法构造近似函数,并利用最小二乘方法的原理解决边界问题,离散控制微分方程,建立求解的代数方程.并将此方法应用于封闭声腔响应的求解,即对亥姆霍兹方程进行离散,建立其最小二乘无网格配点格式.该方法的系数矩阵是对称正定的,因而保证了解的稳定性.通过数值算例分别验证了配点均匀分布与随机分布时此方法的...     

多联通封闭空间声场响应的基于核重构的最小二乘无网格解法

针对多通域封闭空间声场响应的亥姆霍兹方程的求解问题,本文基于核重构思想,应用无网格配点法构造近似函数,并利用最小二乘方法的原理解决边界问题,离散控制微分方程,建立求解的代数方程。边界问题以及稳定性问题一直是无网格法的难点,该方法的系数矩阵是对称正定的,因此结果具有较好的稳定性。通过数值算例分析多联通域二维问题中配点均匀分布与随机分布时此方法的精确性以及稳定性,利用典型算例对比无网格方法数值解与解析解,结果证明此方法不需要进行网格划分,节点可随机分布,精度较高且具有良好的收敛性。     

Elasto‐plasticity revisited: numerical analysis via reproducing kernel particle method and parametric quadratic programming

Aiming to simplify the solution process of elasto‐plastic problems, this paper proposes a reproducing kernel particle algorithm based on principles of parametric quadratic programming for elasto‐plasticity. The parametric quadratic programming theory is useful and effective for the assessment of certain features of structural elasto‐plastic behaviour and can also be exploited for numerical iteration. Examples are presented to illustrate the essential aspects of the behaviour of the model proposed and the flexibility of the coupled parametric quadratic programming formulations with the reproducing kernel particle method. Copyright © 2002 John Wiley & Sons, Ltd.     

The reproducing kernel particle method for two-dimensional unsteady heat conduction problems

The numerical solution to two-dimensional unsteady heat conduction problem is obtained using the reproducing kernel particle method (RKPM). A variational method is employed to furnish the discrete equations, and the essential boundary conditions are enforced by the penalty method. Convergence analysis and error estimation are discussed. Compared with the numerical methods based on mesh, the RKPM needs only the scattered nodes instead of meshing the domain of the problem. The effectiveness of the RKPM for two-dimensional unsteady heat conduction problems is examined by two numerical examples.     

Reproducing Kernel Particle Method in Plasticity of Pressure-Sensitive Material with Reference to Powder Forming Process

In this paper, an application of the reproducing kernel particle method (RKPM) is presented in plasticity behavior of pressure-sensitive material. The RKPM technique is implemented in large deformation analysis of powder compaction process. The RKPM shape function and its derivatives are constructed by imposing the consistency conditions. The essential boundary conditions are enforced by the use of the penalty approach. The support of the RKPM shape function covers the same set of particles during powder compaction, hence no instability is encountered in the large deformation computation. A double-surface plasticity model is developed in numerical simulation of pressure-sensitive material. The plasticity model includes a failure surface and an elliptical cap, which closes the open space between the failure surface and hydrostatic axis. The moving cap expands in the stress space according to a specified hardening rule. The cap model is presented within the framework of large deformation RKPM analysis in order to predict the non-uniform relative density distribution during powder die pressing. Numerical computations are performed to demonstrate the applicability of the algorithm in modeling of powder forming processes and the results are compared to those obtained from finite element simulation to demonstrate the accuracy of the proposed model.     

A meshless analysis of three-dimensional transient heat conduction problems

In this paper, we consider a numerical modeling of a three-dimensional transient heat conduction problem. The modeling is carried out using a meshless reproducing kernel particle (RKPM) method. In the mathematical formulation, a variational method is employed to derive the discrete equations. The essential boundary conditions of the formulated problems are enforced by the penalty method. Compared with numerical methods based on meshes, the RKPM needs only scattered nodes, rather than having to mesh the domain of the problem. An error analysis of the RKPM for three-dimensional transient heat conduction problem is also presented in this paper. In order to demonstrate the applicability of the proposed solution procedures, numerical experiments are carried out for a few selected three-dimensional transient heat conduction problems.     

A Lagrangian reproducing kernel particle method for metal forming analysis

A Meshless approach based on a Reproducing Kernel Particle Method is developed for metal forming analysis. In this approach, the displacement shape functions are constructed using the reproducing kernel approximation that satisfies consistency conditions. The variational equation of materials with loading-path dependent behavior and contact conditions is formulated with reference to the current configuration. A Lagrangian kernel function, and its corresponding reproducing kernel shape function, are constructed using material coordinates for the Lagrangian discretization of the variational equation. The spatial derivatives of the Lagrangian reproducing kernel shape functions involved in the stress computation of path-dependent materials are performed by an inverse mapping that requires the inversion of the deformation gradient. A collocation formulation is used in the discretization of the boundary integral of the contact constraint equations formulated by a penalty method. By the use of a transformation method, the contact constraints are imposed directly on the contact nodes, and consequently the contact forces and their associated stiffness matrices are formulated at the nodal coordinate. Numerical examples are given to verify the accuracy of the proposed meshless method for metal forming analysis.     

板材成形无网格法模拟中的关键技术处理

针对有限元法费时的网格划分/网格重划问题,提出采用无网格法模拟板材成形.采用约束型再生核子法描述板材成形力学方程,仅用一层节点离散板材,同时对形函数进行改造,所得动可容形函数具有插值性,避免了大变形所导致的不稳定形函数及频繁构造形函数,提出了稀疏矩阵数据结构加快接触搜索方法.基于上述措施建立了板材冲压成形无网格数值模拟...