异形孔台阶齿轮冷挤压工艺与模具优化设计

在分析异形孔台阶齿轮结构基础上,确定异形孔台阶齿轮冷挤压工艺,设计了挤压模,在应力分析基础上,优化了挤压凸模、凹模结构参数,提高了模具使用寿命。     

Monte Carlo simulation of extrusion die life

Due to the high cost of metal forming tools (especially in hot extrusion), one of the major goals in tool design is a longer service life. Estimation and prediction of tool life thus becomes critically important for performance evaluation of the tools. The two most dominant failure mechanisms for extrusion dies (solid, hollow, and semi-hollow dies all taken together) are fracture and wear. In the first part of the paper, a fracture mechanics based fatigue life prediction model is described. A similar treatment is then presented for wear-related failures. Fracture and wear usually coexist as failure modes, and final die breakdown occurs due to the mechanism that becomes dominant. Therefore, a competing fracture–wear model has been later developed to represent the complete die failure situation. Attempt has been made to correlate the stochastic nature of various fatigue and wear related die parameters to die life. Monte Carlo simulation has been used to predict the life distribution of a die for a given set of manufacturing conditions and mechanical properties. In comparison with actual life data from the industry, the simulated life yields very realistic predictions.     

方花键轴开模冷挤压的模具设计及工艺实验研究

针对１２５ｃｃ摩托车变速箱的方花键主轴,讨论了花键开模挤压的模具结构特点和影响花键成形的模具回弹问题,提出在开模挤压的可成形性范围内选择入模角,可以避免挤压时出现的入模口局部镦粗现象的发生。     

DOE applied to optimization of aluminum alloy die castings

This paper discusses the application of a design of experiments (DOEs) experimental method for analysing the influence of three injection parameters (slow shot, fast shot and up set pressure) on the internal quality of die casting SAE 305 alloy parts. Initially, the experimental methods applied to the manufacturing process are described. An experimental design was followed: it employed different combinations of injection parameters and aimed to assess the presence of porosity in the die casting parts. The quality assessment of the die casting parts was based on density measurements and qualitative image analysis. Results were evaluated by means of variance analysis, which assessed how the variation in the three different injection parameters influenced the integrity of the components.     

航空座椅锁扣缸体冷挤压工艺及模具设计

通过研究航空座椅锁扣缸体的形状特点、零件的制造难度,确定了冷挤压成形零件的工艺方案,设计并制造冷挤压模具一套,生产出合格零件。演示并分析了零件的冷挤压变形过程;记录了冷挤压过程中与不同变形程度相对应的挤压力,绘制了冷挤压过程的连续挤压力曲线;对零件挤压方向的剖面进行了金属纤维组织观察,对零件流线分布进行了分析。     

反挤压凸模形状对挤压成形工艺的影响

通过数值模拟分析,比较了不同形状反挤压凸模对挤压过程中金属流动、挤压力以及凸模温升等方面的影响,进而得出凸模形状对反挤压成形工艺的影响,为挤压凸模及挤压件形状的优化设计提供一定的参考依据。     

Optimal extrusion die design to achieve flow balance

The design of a plane strain two-hole extrusion die is presented. This design example can be considered as a test case to judge the usefulness of the present method in the design of extrusion dies for uniform exit flow. Bearings for this die are to be designed so that the material exits both holes with parallel balanced flow. The finite-element method combined with techniques of mathematical programming is adopted. Derivatives of the objective function used during the optimization phase are efficiently computed using analytical sensitivity analysis and an optimal bearing length is reached after few iterations of the optimization procedure. Available experimental data for a two-out extrusion die with bearings have been used to validate the numerical results.     

活塞头挤压工艺模具设计与数值模拟优化

分析DFL350型活塞头的成形工艺，设计活塞头的温挤压模具。并以Deform-3D为平台，建立活塞头温挤压成形的三维塑性有限元模型，对其成形过程进行了数值模拟，主要分析温度、摩擦因子、拔模斜度以及型腔结构对成形力和模具充填情况的影响，优化成形工艺和模具结构，得出变形过程中挤压件破坏因子分布图和行程载荷曲线，给出了DFL350型活塞头的温挤压工艺参数的选择、模具设计以及设备选择。     

镁合金复合挤压工艺的有限元模拟

研究将普通挤压和等通道角挤压工艺结合而开发出的新型复合挤压工艺。采用有限元技术建立具有不同摩擦系数和不同转角的模型,模拟镁合金复合挤压过程,分析复合挤压力变化特征,以及挤压过程的应变累积情况。结果表明,摩擦系数增大或者通道角减小,复合挤压的挤压力和等效应变增加。摩擦和转角均会引起变形的不均匀性,摩擦因数越大,通道转角越小,其不均匀性越大。在摩擦因数为0.3,通道转角为120°时可以获得较大且均匀的等效应变。     

Parametric optimization of power in hydrostatic extrusion

The process of hydrostatic extrusion has gained great popularity in recent years because of its simplicity and low cost. The material to be extruded is in contact with the die only, whilst in conventional extrusion the material is in contact with three components, the ram, the chamber, and the die. Therefore, the power required to extrude the product is less in hydrostatic extrusion. Added to this, the frictional losses are kept to a minimum because of the hydrodynamic lubrication that takes effect at relatively high extrusion speeds, which prevents the product from coming into contact with the die.

In this study, an analytical model for studying hydrostatic extrusion is introduced. The model is used to investigate various parameters affecting extrusion, these parameters being: the die cone angle, the reduction ratio (the ratio of the billet diameter to the product diameter), the friction coefficient, the extrusion and back-pressure ratio, and the die shape. The model is extended to optimize the aforementioned parameters for securing a better product, and effecting minimum power requirement and small frictional losses. In order for it to gain recognition, the model was substantiated experimentally employing three commonly used engineering materials, the analytical and the experimental results being found to be in good agreement.     

引信上体热挤压工艺参数的多目标优化

基于回归正交试验,采用数值模拟代替传统物理试验的方法建立了以挤压力和平均晶粒尺寸为目标的单目标优化模型,通过加权和法构造了多目标优化的评价函数,利用改进的遗传算法得出引信上体较优的工艺参数组合用于指导生产。结果表明:该挤压工艺参数有助于企业短时间、低成本获得合格的零件。     

矩形花键冷挤压成形工艺参数多目标优化

针对矩形花键冷挤压成形中出现齿形充填不饱满和成形力过大的缺陷问题,以x1(坯料直径)、x2(坯料初始倒角)、x3(入模半角)为优化变量,采用响应面法结合有限元数值模拟对花键冷挤压成形工艺参数进行多目标优化。根据实验设计结果分别建立了两个目标函数的二阶响应面模型,方差分析结果表明,模型预测精度高并能够较好地描述两个目标函数关于设计变量的响应。在优化范围内得到矩形花键轴成形最优工艺参数为:x1=Ф48.5 mm,x2=20°,x3=15°。将优化后的工艺参数进行实际验证,结果表明:前端塌角量降至0.27 mm,最大成形力降至1300 k N。工艺试验证明了采用多目标优化得到的工艺参数可以获得合格的产品。     

挤压速度和摩擦状态对铝型材挤压过程的影响

挤压速度和摩擦状态是铝型材挤压过程中的重要工艺条件,对挤压产品的质量、挤压力、模具寿命和生产率等具有直接影响。文章以一异型铝型材挤压件为例,采取塑性剪切摩擦模型,使用3种挤压速度和6种摩擦因子的不同组合分别进行挤压过程数值模拟,得到不同参数下模具受力、挤压件温度分布变化及材料流动速度的变化等情况,研究讨论了挤压速度和摩擦状态对铝型材挤压过程的影响规律。研究结果为挤压生产实践提供了一定的理论指导与参考。     

法兰轴温挤压成形工艺分析与挤压凸、凹模参数优化

在分析法兰轴温挤压工艺的基础上,制定了法兰轴的温挤压工艺流程,采用正交试验法对挤压凸、凹模结构参数进行了优化,将优化的凸、凹模结构参数对法兰轴进行温挤压成形试制与验证,得到了合格零件,证明了法兰轴成形工艺方案的正确性。     

基于正交设计的神经网络训练样本的选择方法及其在冷挤压工艺设计中的应用研究

冷挤压件的形状是制定冷挤压工艺方案时需要考虑的最重要的因素之一,基于目的性和方便性原则,该文针对冷挤压件的形状特征进行分类,并在此基础上分别建立基于正交实验设计的人工神经网络训练样本子集,最后将所有子集进行整合,形成初始训练测试样本集。结合典型冷挤压件,分析了采用正交设计方法选取人工神经网络训练样本的过程,研究了基于正交设计的人工神经网络的训练、测试方法,实现了基于人工神经网络的冷挤压工艺设计。     

空心零件温挤数值模拟及工艺优化

本文基于粘塑性材料模型有限元数值模拟技术 ,对复杂多台阶空心零件温挤成形进行数值模拟 ,通过控制工艺参数和改变工艺条件发现 ,当凹模入口处圆角半径为 1mm ,且采用单面润滑即将凹模与坯料间的摩擦系数设为零时 ,可获得符合零件形状的正、反挤流动。根据优化结果进行实验 ,得到成形质量好的制件 ,这表明数值模拟技术是确定成形工艺参数的有效手段。     

椭圆异型挤压塑性成形及模腔映射优化

针对非轴对称金属异型挤压塑性流动及模腔研究的理论课题,借助于近代共形映射数学理论研究成果,利用法线收敛法,建立了映射函数解析方法。将三维金属异型材挤压塑性成形问题转化为二维轴对称成形问题,求解椭圆异型挤压金属塑性成形连续流动场和应变速度场的数学解析模型,并应用金属塑性成形理论,建立了精密挤压异型材优化模腔的数学模型,同时为精密快速地实现挤压模腔的CAD／CAM一体化目标提供了技术支持。     

冷挤压模具失效分析与提高模具寿命途径

本文系统分析了影响挤压模具寿命的各种因素,从设计选材、减少挤压件壁厚、模具表面强化处理等方面,阐述了提高挤压模具寿命的途径.     

挤压锻造模具形状的混合智能优化

数值仿真技术已成为挤压锻造模具设计中的重要评价手段，有助于设计人员更好的理解设计空间。然而，由于计算时问长，目标函数无法显式表述，搜索空间可能不连续等因素，很难直接基于数值仿真通过梯度法进行设计优化。非梯度的优化方法比如遗传算法、模拟退火法等由于需要更多的仿真次数，也很难实现。本文基于人工智能中的归纳学习方法，提出了一种针对挤压锻造工艺优化的基于数值仿真归纳知识的混合优化方法，并通过一个挤压锻造的实例验证了该方法的有效性。