连续挤压塑变区速度场分析及功率计算

在分析轮腔间隙区和轮槽区金属流动规律以及溢余几何形态的基础上,建立质点流动速度场。由该速度场导出溢余量与单位挤压力、轮腔间隙和轮速等工艺参数之间的关系式;在对变形区进行受力分析的基础上,给出挤压型腔几何参数、单位挤压力、轮腔间隙以及轮槽尺寸之间的关系式,推导出挤压轮上的驱动功率和摩擦功率的计算公式。连续挤压实验和力学性能测试证明数学模型正确,可以作为工程实践的指导。     

基于神经网络与遗传算法的关节轴承挤压模具优化

针对实际生产中关节轴承内外圈间隙分布不均问题,以GEW12关节轴承为例,应用ABAQUS软件对关节轴承挤压装配过程进行了数值模拟。采用BP神经网络建立了挤压模具形状与内外圈最大间隙与最小间隙之差的映射关系。以关节轴承内外圈间隙均匀分布为目标,结合遗传算法,提出了一种集数值仿真、人工神经网络和遗传算法为一体的关节轴承挤压模具型腔优化设计方法。实验结果表明,模具型腔经过优化后,轴承内外圈间隙均匀性得到了很大的改善,轴承金属流动速度更加均匀。     

模孔偏置位置参数对型材挤压成形影响的数值研究

通过引进流速均方差作为评价塑形变形时金属流动速度不均衡性指标，来有效地控制型材挤压成形时金属流动的不均匀性。通过采用有限变形弹塑性有限元方法，对不同模孔偏置位置参数下型材挤压过程进行了数值模拟研究，获得了挤压力、流速均方差和型材件内部应力应变场随其变化的规律，为进一步实现型材挤压工艺参数优化提供了理论参考。     

基于Fluent的超薄连续铸轧三维流场仿真分析

基于计算流体软件Fluent,比较全面地分析双辊超薄连续铸轧的流场,特别是铸嘴型腔三维流动现象及其特点.分析铸轧区对流场的作用.铸轧区有利于铸嘴出口速度的均匀流动,有利于速度均匀混合,但不能彻底消除速度梯度.把计算的铸嘴出口处的流体速度与实验结果相比较,两者基本吻合,并得出结论:分流块的形状与位置是影响铸轧流场的主要原因之一,常规铸轧常用铸嘴熔体出口速度相对误差达38%,不能满足超薄连续铸轧技术的需要.     

斜轧穿孔过程金属流动的有限元模拟

应用刚塑性有限元法对热轧穿孔过程中的变形、几何构形以及变形区内速度场、应变场和温度场等进行了模拟计算。在确定的工艺条件下,如辊型、送进角、孔喉尺寸、顶头前伸量及毛管的椭圆度等,解决了斜轧金属流动有限元模拟中的边界条件、网格自动划分等相关问题。由变形速度场的分布可明确穿孔中顶头前的金属流动状况,其计算结果通过变形区轧卡试件进行了比较,认为该模拟对斜轧变形过程是可行合理的,且可用于其他斜轧过程的有限元模拟分析。     

锥形螺母冷镦挤数值模拟及模具设计

提出了锥形螺母一次冷镦挤复合成形新工艺,设计了采用管坯冷镦挤成形锥形螺母的模具结构,运用Deform-3D有限元软件,模拟分析了锥形螺母冷镦挤成形过程中坯料填充凹模型腔的流动速度场和等效应力场。结果表明:管坯各处的流动应力值均不超过其材料的流动应力极限,金属坯料可以流动到型腔的各个部位,此工艺能够获得形状完整的锥形螺母。     

口模压缩段对塑料挤出流动影响的有限元分析

在塑料挤出成形过程中，压缩段是调节模头流道各部分流量(流速)的主要区段，对熔体的流动具有重要影响。本文采用有限元数值分析方法，计算了熔体在口模内流动的速度场和压力场，定量分析了压缩比和压缩角等压缩段模具结构参数对挤出速度分布、挤出流量和挤出流动均匀性等的影响规律，为优化流道结构参数，提高挤出流动均匀性的研究提供了基础。     

柱塞体变形模式转换的成形工艺分析与研究

在柱塞体复合挤压成形过程中,金属的流动方式为过渡方式,其金属的流动规律非常复杂,对柱塞体零件成形的三种不同工艺方案进行了数值模拟分析.并运用滑移线场理论对其流动规律进行了讨论,给出了塑性变形的滑移线场和速端图,预测了金属的流动方向、流动速度等.指出了成形工艺缺陷产生的原因,确定了正确的工艺方案.     

压铸模具浇排系统的研究

<正>压铸是有色金属成型的一个重要手段之一。在压铸过程中,由于型腔内的金属液流动状态不同,可能产生冷隔、花纹、气孔、偏析等不良现象。为了防止这些不良现象,控制型腔内的金属液流动状态是相当必要的。而控制型腔内的金属液流动状态,关键就在于压铸模具浇排系统的研究与设计。     

注塑成形流动模拟技术的新进展——从中面流到双面流再到实体流

1.概述 注塑成形流动模拟技术旨在预测塑料熔体流经流道、浇口并填充模具型腔的过程,计算浇注系统及模具型腔的压力场、温度场、速度场、剪切应变速率场和剪切应力场的分布,并将分析结果以图表、等值线图和真实感图的方式直观地反映在计算     

基于流函数法的铝型材挤压导流模合理设计

采用模拟试验法和理论分析法研究了导流模内型材挤压的流动机理;提出了确定导流腔最小深度的理论依据;用基于流函数的上限分析法确定了实心薄壁铝型材挤压变形的流线方程、动可容速度场、应变速率场及上限功率;讨论了变形程度等参数对导流模最小理论深度的影响,得出实心薄壁铝型材导流腔深度的理论最小值为导流腔半宽的0.7～0.8倍。理论结果得到了试验证实,为导流模合理设计提供了可靠的依据。     

涡旋压缩腔径向泄漏对内部流场影响的分析

为了揭示泄漏对涡旋压缩机压缩腔内部流场的影响,应用CFD技术对不同间隙尺寸下的涡旋压缩机内部流场的定常流动进行数值计算,通过改变轴向间隙,追踪一个选定的月牙形压缩腔,在一个循环周期内流场的变化,进而分析泄漏对涡旋压缩机压缩腔内部流场的压力场、温度场、速度场的影响,得到压缩腔的泄漏规律及最佳泄漏间隙,并将模拟结果与理论绝热过程进行比较,验证所采用数值技术方法的正确可行性。     

金属橡胶高压精密流量阀流场分析

为确保阀出口处输出流量和压力的稳定性,提出了采用压电陶瓷和金属橡胶两种材料设计的一种金属橡胶高压精密流量阀,利用压电陶瓷驱动流量阀的主阀芯实现对阀芯与阀体开口间位移的精密控制,利用金属橡胶材料的多孔性以及减压、节流和过滤等特点实现对阀出口处流体脉动的平纹波处理。运用Fluent仿真分析了阀出口处的平纹波特性和金属橡胶参数对阀腔内流体湍动能分布的影响规律。分析结果表明:在阀进、出口处安装金属橡胶环后,阀出口处流体速度变化平缓、方向趋于一致,流动更为平缓,一定程度上确保了阀输出流量和压力的稳定性;阀腔内流体的湍动能明显减小,阀腔内的流场更趋于平稳,从而提高了阀的使用寿命和启闭可靠性。     

An analysis of hemispherical punch stretching by the energy method

An approach using the energy method in which the total deforming region is divided into several sections of different geometric shapes is suggested for the analysis of axisymmetric sheet metal forming with friction boundary condition. The corresponding solutions are found through optimization of the total energy dissipation with respect to some parameters assumed in the velocity field as well as in the corresponding geometric profile. Computations are carried out for hemispherical punch stretching of normal anisotropic work-hardening materials for several lubrication conditions. The punch load vs stroke relation, geometric configuration and strain components are determined from the computation. The comparison of the computed results with finite element solutions and corresponding experiments shows good agreements of solutions in load vs stroke, deformed profiles and strain distribution for various lubrication conditions. It is thus shown that the present simple approach can be effectively employed for the analysis of axisymmetric sheet metal working processes.     

Modeling and simulation of polymer melts flow in the extrusion process of plastic profile with metal insert

The extrusion technology of plastic profile with metal insert is recently an advanced plastic processing method whose products keeps rising today for their excellent performance. However, the related fundamental research on polymer forming mechanism in the extrusion process of plastic profile with metal insert is lagging behind. With the development of computational fluid dynamics (CFD) theory, numerical method becomes an effective way to investigate such complex material forming problems as in the polymer extrusion process. In the present study, the mathematical model for three-dimensional non-isothermal viscous flow of the polymer melts obeying a Carreau model is developed based on the CFD theory. The Williams–Landel–Ferry equation is employed to involve the temperature dependence of material parameters. A decoupled numerical algorithm based on the penalty finite element method is conducted to predict the rheological behaviors of polymer melts within the complex flow channel. The streamline upwind/Petrov–Galerkin scheme is employed to improve the computational stability for the calculation of temperature field. Based on the theoretical model, the essential flow characteristics of polymer melts in the extrusion process of plastic profile with metal insert is investigated. The distributions of principal field variables like flow velocity, melt temperature, flow stress and pressure drop are predicted. The effects of die structure parameters including the intake angle and the distribution section length upon the melts flow patterns are further discussed. The variations of melt rheological properties versus different processing conditions like the volume flow rate and the metal insert moving velocity are also investigated. Some advice on practical processing operations of the extrusion process of plastic profile with metal insert is accordingly put forward based on the numerical results.     

Research on the cathode design and experiments of electrochemical machining a closed impeller internal flow channel

In order to improve the electrochemical machining (ECM) precision and efficiency of a closed impeller internal flow channel, the internal flow channel cathode shape and structure were optimized by gap flow field simulation. Firstly, the theoretical model and three-dimensional gap flow field simulation geometric model were set up. Next, the inter-electrode gap flow field simulation results were draw from the streamline, velocity, and pressure cloud picture. Secondly, the cathode and the frock clamp were designed according to the simulation results. Finally, the verification experiment was carried out to evaluate the cathode structure and the ECM process parameters, and the experimental results were consistent with the simulation results. The whole process is stable and no short-circuit phenomenon with the forward flow field machining pattern. The results show that the method of gap flow field simulation-assisted ECM cathode design is useful and economical for machining closed impeller internal flow channel.     

鼠笼式搅拌磨机性能研究及参数优化

对新型鼠笼式搅拌磨机磨腔内的流体场建立了数学模型，用有限元流体动力分析软件对磨腔圆截面内的流体场进行计算分析，得到磨腔内浆液具有高速度梯度值的两个环形区域，该区域内磨机的功效最为显著。建立了磨介在磨腔内随浆液运动的数学模型，用龙格一库塔法迭代求解得到磨介的运动轨迹。通过对不同工况条件下磨介轨迹的计算分析，得到使磨介能在高速度梯度区保持较稳定运动的工况参数优化值。分析结果与实验结果一致。     

涡旋压缩机非定常流动的三维数值模拟

针对涡旋压缩机工作过程中运动部件公转平动的运动方式使得工作腔内流场难以测试的问题,提出了带有移动边界、啮合间隙和封闭工作腔的涡旋压缩机非定常流动的三维数值计算方法。以齿头双圆弧修正型线为例,建立了三维几何模型。解决了带有啮合点的动边界在动网格中容易出现的负体积问题以及排气口遮挡问题,实现了三维数值模拟。得到了任意曲轴转角下的各工作腔内各截面的气体流动的压力和速度的动态分布规律,揭示了增压过程中腔内流动状态的变化机理。模拟结果表明:压力在各工作腔分布均匀,最大与最小压力之差不超过5%。沿着涡旋齿型线齿尾到齿头,内外侧的压差逐渐增大。速度分布不均匀,单个工作腔内最大最小速度之差可达到180m/s。径向泄漏沿啮合线呈对称分布,速度呈跳跃式分布,最大泄漏速度为200m/s,切向泄漏最大泄漏速度可达450m/s。     

Roll System and Stock’s Multi-parameter Coupling Dynamic Modeling Based on the Shape Control of Steel Strip

The existence of rolling deformation area in the rolling mill system is the main characteristic which distinguishes the other machinery. In order to analyze the dynamic property of roll system’s flexural deformation, it is necessary to consider the transverse periodic movement of stock in the rolling deformation area which is caused by the flexural deformation movement of roll system simultaneously. Therefore, the displacement field of roll system and flow of metal in the deformation area is described by kinematic analysis in the dynamic system. Through introducing the lateral displacement function of metal in the deformation area, the dynamic variation of per unit width rolling force can be determined at the same time. Then the coupling law caused by the co-effect of rigid movement and flexural deformation of the system structural elements is determined. Furthermore, a multi-parameter coupling dynamic model of the roll system and stock is established by the principle of virtual work. More explicitly, the coupled motion modal analysis was made for the roll system. Meanwhile, the analytical solutions for the flexural deformation movement’s mode shape functions of rolls are discussed. In addition, the dynamic characteristic of the lateral flow of metal in the rolling deformation area has been analyzed at the same time. The establishment of dynamic lateral displacement function of metal in the deformation area makes the foundation for analyzing the coupling law between roll system and rolling deformation area, and provides a theoretical basis for the realization of the dynamic shape control of steel strip.