DEFORM金属挤压成形工艺数值模拟技术

金属挤压成形是用压力机和模具对放置在模具腔内的金属坯料施加强大的压力使金属坯料产生定向塑性变形,从挤压模的模孔中挤出而获得所需断面形状、尺寸且具有一定力学性能的零件或半成品的塑性加工方法。挤压成形的种类很多,例如按照金属塑变流动方向可分为正挤压、反挤压、复合挤压及径向挤压。按照金属坯料温度分冷挤压、温挤压和热挤压等。     

DEFORM金属挤压成形工艺数值模拟技术

金属挤压成形是用压力机和模具对放置在模具腔内的金属坯料施加强大的压力使金属坯料产生定向塑性变形，从挤压模的模孔中挤出而获得所需断面形状、尺寸且具有一定力学性能的零件或半成品的塑性加工方法。挤压成形的种类很多，例如按照金属塑变流动方向可分为正挤压、反挤压、复合挤压及径向挤压。按照金属坯料温度分冷挤压、温挤压和热挤压等。     

填充对钢管脐带缆截面力学性能影响分析

基于平面应变模型,建立无填充、部分填充和密实填充等3种情况下的钢管脐带缆截面有限元模型．考虑单元间的挤压接触和摩擦等非线性因素,给出径向载荷下脐带缆内核结构力学性能的数值模拟结果．通过对关键构件极值应力、构件间挤压力以及截面整体变形的分析比较,发现填充对脐带缆截面力学性能的影响显著．在进行脐带缆截面设计分析时,必须考虑填充对截面各单元的影响．     

注塑模CAE流动模拟技术概述

注塑模CAE软件根据塑料成型流变学、热传学和数值计算方法的基本理论,建立熔体在模具型腔内的流动、热传的物理数学模型,利用计算机图形学技术在计算机上形象,直观地模拟出在实际成型过程中熔体在模腔中的动态填充过程、保压过程和冷却过程,定量地给出成型过程的状态参数.     

双丝共熔池GMAW焊接熔池流场和温度场的计算机模拟

利用之前所建立的准稳态数值模型以及焊接热输入模型,对双丝共熔池GMAW焊接过程熔池成型、流场和温度场进行计算机模拟,并对模拟结果给予实验验证。     

注塑模CAE流动模拟技术概述

注塑模CAE软件根据塑料成型流变学、热传学和数值计算方法的基本理论,建立熔体在模具型腔内的流动、热传的物理数学模型,利用计算机图形学技术在计算机上形象,直观地模拟出在实际成型过程中熔体在模腔中的动态填充过程、保压过程和冷却过程,定量地给出成型过程的状态参数.……     

基于刚粘塑性有限元法的定子挤压工艺仿真

该文讨论了油泵定子传统成形方法的局限性,提出了采用温挤压工艺成形油泵定子的新工艺,为验证新工艺的可行性以及降低产品开发周期与模具成本,对油泵定子温挤成形过程的有限元仿真分析,优化了成形工艺及模具参数,通过与物理试验比较,验证了数值模拟分析的准确性。研究结果表明：①采用新工艺可以成形出机械性能好、材料利用率高的油泵定子;②采用数值模拟优化后的坯料,可以成形出锻件质量好,综合机械性能高的产品;③生产试验表明,有限元数值模拟是分析金属塑性成形问题的一种先进的、有效的方法,采用数值模拟优化后的方案对锻件进行生产试制,可以获得成形质量好的锻件,且模拟结果与生产试制结果一致。     

气辅成型首次气体穿透的无网格模拟

基于气体穿透机理的研究分析,精确描述气辅成型中气体穿透推进过程,将三明治成型理论应用到气辅成型中。以矩形平板型腔为例,结合Hele-Shaw流动模型,引入合理简化和假设,建立气体辅助注射成型首次气体充填过程的压力控制方程和气/液交界面运动方程,并应用无网格Galerkin法做数值模拟。得到了不同时刻气体的穿透情况以及不同节点的压力随时间的变化曲线。数值表明:三明治成型理论应用于气辅成型所建的数学模型能准确反应气体穿透推进过程,无网格Galerkin法能较好的追踪气/液界面的动态演化过程。     

基于TDR的多孔介质中含水/水合物饱和度测量方法仿真研究

为了优化设计时域反射技术（TDR）中的探针结构,建立基于TDR响应的含水/水合物测量模型,利用有限元数值模拟方法建立了TDR测量过程数值仿真模型。分别以空气、不同浓度氯化钠溶液以及不同水合物含量的石英砂为被测介质验证了模型的正确性、研究了被测介质电导率和介电常数对反射波形的影响规律。通过改变被测介质的介电常数来模拟含水/水合物饱和度不同的石英砂,随着石英砂中水合物含量的增加,含水量逐渐降低,表观介电常数随之减小,电磁波传播速度随之以非线性形式增加;与理论值相比较,仿真计算所得到的传播速度最大误差处于5%以内。下一步需要在数值模型中的被测区域中填充各相异性材料来更加真实地模拟含水合物沉积物被测介质。     

Pro/ENGINEER二次开发教程(4)

五、实例三：齿轮参数修改程序在本例中，我们要首先在Pro/ENGINEER系统中建立一齿轮模型，然后输入三个参数：齿数、分度圆直径和压力角。在建模过程中，加入若干关系式来控制生成不同参数的齿轮模型（这部分内容不是本文的重点，所以在此省略）。这样，我们就建好了一个可以由参数驱动的齿轮模型，即通过改变参数，可以生成不同齿数、分度圆直径、压力角度数的直齿轮模型。我们要建立一个程序，该程序能够接受我们所输入的参数数值，并传给Pro/ENGINEER系统中的参数，通过零件的再生（Regenerate），便可以生成不同的齿轮。下面对…     

Three Dimensional Numerical Simulation of Cup-Shaped Thin-Walled Inner Gear Spin-Forming

The cyclic symmetry and local fine-mesh technology were adopted in the establishment of numerical simulation model for inner gear spin-forming. And the processing experiment was proceeded to verify the reliability of the established model. The simulation result indicates that besides radial and axial flows, there also exists rather large tangential flow, which results in an increase of forming force in tangential direction. Furthermore, the un-uniform deformation of metal during spin-forming would cause for...     

Predictions of the minimum relative depth of die cavity and the minimum amount of preforming in the radial extrusion of tubular components

In this study, both the minimum relative depth of die cavity and the minimum amount required in preforming are determined to produce a defect-free product of tubular component in the preforming technique of radial extrusion. This scheme is based on the least amount of material dissipation in radial extrusion of tubular component. A finite element based code is utilized to investigate the effects of various amount of relative deformation and different relative depths of die cavity on the material flow characteristics resulting in the movements of the defects locations. An algorithm is thus developed for the determination of minimum relative depth of die cavity and the minimum amount required in preforming, and the abductive network is also applied to synthesize the data sets obtained from the numerical simulations through the algorithm proposed in this study. Consequently, a prediction model is established for organizing the minimum relative depth of die cavity and the related minimum amount of preforming of the tubular component that the locations of induced defects are just coincided with the inner surface of the tube at the end stroke of deformation.     

Pseudo-interference stiffness estimation, a highly efficient numerical method for force evaluation in contact problems

This paper presents a novel method, Pseudo-Interference Stiffness Estimation (PISE), for evaluating the contact compliance and the contact load in the contacting elastic solids. The PISE method is based on the evaluation of the geometric overlap of two assumedly rigid bodies and estimation of the contact force based on this artificial overlap area (or volume). In this paper, an example of the dynamic simulation of two disk collision problem is solved both by PISE method and finite element contact model. The contact force and velocity changes during impact from both methods are shown to be in good agreement. However, PISE method is, computationally, orders of magnitude (about 3000 times in our numerical simulations) faster than finite element contact analysis. The proposed method will be of practical use in contact force approximation of contacting bodies, such as meshing of spur gear teeth, cam analysis and synthesis, robotic grabbing, and numerous other applications.     

混合齿轮行星系分插机构的设计与仿真

将偏心齿轮-非圆齿轮行星系应用于插秧机分插机构中,研制出混合齿轮行星系分 插机构。建立偏心齿轮与非圆齿轮的节曲线数学模型,获取齿轮节曲线方程,并结合KISSSOFT 和MATLAB 软件对非圆齿轮进行设计。建立分插机构运动数学模型,利用MATLAB 开发优化 辅助软件,对分插机构的参数进行优化。完成了分插机构的三维CAD 设计,并在ADAMS 中 对分插机构进行了运动学虚拟仿真,获取了秧针尖点的静态轨迹和动态轨迹,将其与理论分析 得到的轨迹曲线进行对比,验证了混合齿轮行星系应用于插秧机分插机构上的可行性。     

Three-dimensional non-Newtonian computations of extrudate swell with the finite element method

Numerical simulations have been carried out for the extrudate swell problem in three-dimensional domains. The finite element method is used with streamline elements, which render the calculations fast and efficient for flows through long extrusion dies (no reservoir present). The method is first tested against purely viscous (Newtonian), viscoplastic (Bingham), and slightly viscoelastic (CEF model) results for the determination of extrudate swell from circular dies, which have a two-dimensional counterpart. Full three-dimensional die designs are also studied, such as extrusion from a square and a cross-shaped die.     

应用逆向数值模拟分析覆盖件成形性能

研究了逆向数值模拟技术原理,针对覆盖件模型不规则而导致传统成形分析求解困难的问题,提出采用改进膜单元构造板料网格,以准确地描述毛坯变形行为;为提高边界条件定义的可信度,根据摩擦性质差异对非平面压料圈分类处理,凹凸模作用由冲压力和摩擦力的合力求解,开放式拉延筋则建立包含弯曲和摩擦效应的等效阻力模型;分析计算数据,并结合成形缺陷形成机理,完成产品成形性能评估．实验结果表明,经改进的算法能快速求解展开料参数、预测复杂产品破坏特征分布,适合用于覆盖件冲压设计。     

A multi-mesh MPM for simulating the meshing process of spur gears

A numerical scheme is presented to simulate the meshing process of spur gears, based on the material point method (MPM). To allow engagements at successive contact points and subsequent separation between neighboring gear teeth, a contact/sliding/separation procedure in a multi-mesh environment without using master/slave nodes is proposed so that the no-slip contact constraint inherent in the existing MPM can be released. Individual drive members rotate around corresponding axes, through which simulated angular velocity transmission is in good agreement with the analytical solution. It appears from the simulation results presented here that the multi-mesh MPM could become a robust spatial discretization tool for gear design problems that involve large rotation, contact/sliding and separation.     

基于拓扑重构的流线特征跟踪算法

地下水流线的构造与可视化有助于提高数值模拟后处理的效率。以研究区地下水渗流场的连续流线仿真模拟为目标,建立了核心拓扑结构和动态重构时所需要的拓展拓扑结构,基于有限元数值计算理论方法,结合地下水渗流场的实际运移情况,探讨了在流线模拟过程中的特征提取问题。在此基础上,提出了一个快速、健壮的流线自动跟踪算法,可用于流线和流经时间的计算。并以北京市平原区地下水渗流场为例,实现了虚拟开采井条件下和实际复杂流场的地下水流动仿真模拟。     

An elasto-plastic rate-dependent finite element analysis of the metal forming process

An elasto-plastic rate-dependent finite element formulation is developed into the solution of the large strain and deformation problem. The formation is based on the power form constitutive equation for the stress-strain-strain rate relation of the material. A simple one-step Euler's time integration scheme is adopted to automatically control the time increment. After incorporating a force rate term which is due to the effect of the strain rate, the simulation is completed by modifying the updated Lagrangian formulation. The numerical results can be used as options in the selection of the adequate tool speed, die geometry, and die material.