AZ80镁合金管材反挤压成形的数值模拟与试验研究

采用Deform-3D软件对AZ80镁合金厚壁管材的反挤压过程进行了数值模拟,模拟了不同挤压温度和挤压速度对反挤压成形过程的影响。结果表明,反挤压过程的等效应变主要集中在凸模与坯料接触处和管壁上,管材的内壁和外壁损伤值较大,容易产生损伤。挤压温度越高,管材成形的温差、等效应力和挤压载荷就越小,挤压变形越均匀。挤压速度越小,金属的流动速率峰值越小,金属流动越均匀,管材温差越小,挤压变形越均匀。通过镁合金管材的反挤压试验,验证了模拟结果的准确性。     

微反挤压数值模拟与实验研究

将退火后的T2紫铜圆柱坯料进行常温压缩实验,根据所得应力应变曲线,采用DEFORM-3D模拟杯壁厚度为0.5mm的杯形件的微反挤压成形过程。研究了凸模速度和摩擦系数对材料等效应变分布和凸模载荷的影响。结果表明,凸模速度越大,材料等效应变差值越大,变形越不均匀,但对凸模载荷无明显影响。摩擦系数越大,材料变形越不均匀,且凸模载荷明显增加。根据模拟结果选择合适的工艺参数进行微反挤压实验,实验所得杯形件晶粒变形较均匀,与模拟结果较吻合。     

旋转挤压裂纹萌生趋势的数值模拟

针对旋转挤压成形易产生裂纹的问题,利用Deform-3D有限元软件对AZ31镁合金旋转挤压过程进行了裂纹萌生的模拟,研究凸模在轴向-周向加载和径向-周向加载过程中,凸模圆角半径与摩擦系数对试样裂纹损伤分布的影响。结果显示,摩擦系数越大,裂纹损伤因子越大;凸模圆角半径越大,裂纹损伤因子越小,虽然凸模圆角半径R大于8 mm时裂纹损伤因子仍在减小,但是考虑工艺及材料利用,凸模圆角半径R为8 mm时最佳。通过单独径向、周向旋转挤压数值模拟,并与实验结果对比验证,得到轴向-周向加载下,筋部上区域损伤最大;径向-周向加载对试样的损伤影响较小。     

基于数值模拟的转向节挤压工艺优化

根据转向节的形状特点,分析并概述了其成形过程的金属流动特性和现有成形工艺存在的不足.将现有的自由锻制坯改进为挤压制坯.提出了一种新的成形方案为:下料—加热—摔杆—挤压制坯—预锻—终锻.应用三维有限元模拟软件Deform对转向节成形过程进行了数值模拟.针对杆部的折叠缺陷,分析其产生原因,提出增强法兰盘结构强度的解决方案,对挤压下模进行了改进.结果表明,所得终锻件各部位充填饱满、飞边均匀且无折叠缺陷.     

大口径厚壁钢管热模法离心铸造机的设计与应用

详细介绍了采用热模法离心铸造厚壁钢管坯的设计思路,以及该机主要机构(等量浇注装置、主机、推管机构等)的设计.     

大口径厚壁管道热挤压成形过程微观组织模拟及实验研究

针对某型核能发电用P91大口径厚壁无缝管道进行了不同挤压比条件下的垂直正挤压成形过程缩比数值模拟,研究了管道微观组织在挤压过程中的演变规律。研究表明:挤压过程中金属温度场变化和局部变形速率对管道晶粒组织演变具有重要影响。相同工艺因素条件下,平均晶粒尺寸在轴向上从变形区到挤出端逐渐递增,而在径向上从管道内侧到外侧逐渐递减;管道内侧的动态再结晶百分数高于外侧;管道金属在轴向比径向有更高的动态再结晶发生率,且动态再结晶晶粒尺寸比径向更小。管道的平均晶粒尺寸随着挤压比的增加呈减小的趋势,挤压比越大,动态再结晶发生的越充分,越利于晶粒细化。进行了与数值模拟相配套的缩比挤压成形实验,并针对获得的样件分别进行了金相实验和晶粒度评定,所测得的平均晶粒尺寸变化规律与数值模拟基本吻合,证明了数值模拟的正确性,同时验证了增大挤压比对管道晶粒细化具有重要的促进作用。     

一种热反挤压时坯料的定位方式

为解决热反挤压时坯料定位问题,采用外置定位钳的方式,将直径小于凹模内径的坯料放置在凹模中心,使反挤压过程中凸模的、坯料、凹模的中心在同一轴线上,保证金属均匀受力。运用Deform-3D软件,针对直径小于凹模内径时的坯料反挤压过程进行有限元数值模拟,分析了金属成形过程中的成形效果及应力分布,结果表明:模拟与工艺试验结果基本吻合,在热反挤压过程中,成形效果良好,金属等效应力分布均匀。经工艺试验验证,该定位方式操作简单,工件氧化皮较少,表面精度较高,适用于各类直径小于凹模内径的坯料定位,符合生产要求。     

火车车轮热成形金属流动规律数值模拟

借助商业有限元软件MSC/Superform,数值模拟了火车车轮锻压热成形过程.利用节点跟踪功能研究金属质点流动规律.研究结果表明,轮坯金属质点对应于钢坯中原始位置,轮坯压制辐板内外侧面金属来自钢坯上下端角部,钢坯柱形外侧面金属呈环状流向轮坯轮辋周边,轮坯辐板和轮辋心部金属来自钢坯径向正中部位,钢坯径向内环区域金属形成轮坯轮毂心部,钢坯轴心区域金属形成轮坯冲块.数值模拟结果与物理模拟相吻合.     

7075铝合金筒形件径向-反向挤压工艺的成形模拟研究

介绍了一种径向-反向挤压工艺。运用Deform-3D有限元分析软件对7075铝合金筒形件径向-反向挤压成形过程进行了模拟,重点分析了成形过程中的变形力和金属流动规律。结果表明,径向-反向挤压工艺可以有效地降低载荷,挤压过程中的金属流速平缓,筒体底部等效应力降低。     

铝型材挤压模芯早期磨损失效模拟与分析

运用Deform_3D有限元分析软件对框形截面铝型材挤压模芯的磨损失效进行数值模拟分析,结合Archard修正磨损模型,得到了模芯测试点挤压温度与磨损深度曲线、挤压温度与磨损系数曲线以及温度与硬度曲线。模拟分析结果表明,挤压压力越大,挤压温度越高,模芯硬度越低,磨损系数越大,磨损深度越大。可为制定铝型材挤压成型工艺提供参考。     

不同参数对铝合金枝杈类构件金属流线的影响及优化

通过有限元模拟软件,分析了不同参数对某铝合金枝杈类构件金属流线的影响,分析了该构件在成形过程中金属流线缺陷形成的原因.通过对坯料的高径比、挤压速度和摩擦因子3个参数进行优化,确定了最佳金属流线分布的成形方案.研究结果表明:适当增大坯料与模具之间的摩擦,可控制后期径向金属流动量和流动速度,从而有效地避免穿流缺陷的产生;较...     

组合摩擦对厚壁管件压弯成形的影响

在阐述了厚壁结构管件填充介质压弯成形工艺的基础上,建立了管件压弯成形过程有限元模型,研究了内外摩擦因数对管材弯曲成形过程中应力应变、成形载荷以及管壁厚度变化的影响。数值模拟结果显示:摩擦是影响管件成形的重要工艺参数。在管件的压弯成形过程中,摩擦力影响变形区的应力分布和金属流动,当选择适当的摩擦因数组合时,管件受到的应力与成形力均较小,壁厚均匀性较好。     

Influence of punch geometries on the divided material flow in a double cup extrusion process

This paper provides an analysis of the deformation patterns in a backward can extrusion combined simultaneously with a forward can extrusion process, which is known as a double cup extrusion process. The main objective of this study is to examine the divided material flow characteristics in DCEP. Analyses were conducted in a numerical manner by employing a rigid-plastic finite element method. Among many process parameters, the major design factors chosen for analysis include the reduction in area (RAB), the wall thickness ratio (TR), the punch nose radius (R), and the friction condition. The simulation results were summarized in terms of relationships between the process parameters and the ratios of extruded length and volume, and between the process parameters and force requirements, respectively. Comparisons between a multi-stage forming process in sequential operations and one-stage combined operation were also made in terms of the forming load and pressure exerted on the tool. The force requirement and self-regulating characteristics were more greatly influenced by the wall thickness ratio among the selected major design factors. And more severe load to form the same shape is expected in sequential operations than in a combined extrusion process.     

Research of Metal Flow Behavior during Extrusion with Active Friction

Using numerical simulation and experiment, the metal flow behavior mechanical mechanisms in the extrusion process with active friction were investigated. The characteristic variables, second invariant of the stress deviator J ₂ and the Lode’s coefficient μ were employed to partition the deformation region. It is shown that no metal flow interface occurred at the container bottom in the extrusion with active friction and the dead zone disappeared completely. The strain types of the material in the plastic deformation area decreased from three types into a single type of tension, and the homogeneity of metal deformation as well as metal flow was greatly improved. It was also indicted that the active friction was beneficial to the extrusion process and the promotion of product quality. After contrasting the result of experiment and the simulation, the displacement and the load were well correlated on both values and trends.     

空心坯料反挤压省力成形方法及应用研究

采用主应力法与数值模拟相结合的方法,研究分析空心坯料反挤压成形力变化规律。结果表明,空心坯料反挤压在减少接触面积的同时,减小了接触面上的单位变形力,大幅度降低了挤压成形力。经在重型车辆铝合金轮辋成形中验证和应用表明,该方法可行,为底部带中心孔的大型薄壁筒形零件的成形,提供了新思路。     

The friction modeling of different tribological interfaces in extrusion process

Friction and lubrication are of great importance in many important metal forming processes such as sheet metal forming, forging and extrusion. With the products being more complex, it may utilize different lubrication medium in different tool/workpiece interface in which the metal flow could be controlled more effectively. While there is a substantial body of published research on friction modeling in metal forming processes, there has been relatively little work on forming process in which different tribological interfaces such as lubricant/grease, lubricant/dry and dry/grease are existed. The objective of this research is to investigate the friction distribution in combined forward and backward extrusion process. A realistic model of friction is developed to determine the friction coefficient of lubricated tool/workpiece interface. The friction coefficient of the other interface in which grease or different lubricant may applied is then determined by a coupled FEM and experiment investigation. Both the simulation and experimental data will be presented.     

Numerical simulation of upsetting-extruding process of dispersion strengthened copper welding electrode

The simulation of the upsetting-extruding process ot dispersion strengthened copper welding electrode was carried out using Deform-2D finite element analysis software, and the characteristics of metal flow and the effect of different friction factors were analysed. The results show that the whole forming process consists of a forward extrusion and a backward extrusion. When the friction factor of the female die is 0.4, it is advantageous to the forward extrusion forming of the electrode work nose part, while the friction factor of the male die is only 0.1, it would be benefit to the backward extrusion forming of the electrode fit-up hole part. Addition of a scoop channel with 1.5 mm in depth and 4 mm in diameter at the bottom of the female die can avoid folds at the work nose. The rise in temperature is about 60℃ during the forming process.     

离合器外齿毂冷挤压成形工艺

对某汽车离合器外齿毂的结构特征进行了分析,针对其内花键成形困难的技术难点,提出了冷挤压成形的工艺方案。通过有限元软件DEFORM-3D对离合器外齿毂冷挤压成形过程进行数值模拟分析,研究了入模半角、毛坯壁厚和摩擦系数对成形载荷及成形质量的影响规律。研究结果表明:当入模半角为45°、毛坯壁厚为6. 0 mm、摩擦系数为0. 12时,离合器外齿毂内花键圆角填充饱满,成形载荷也相对较小。并采用离合器外齿毂冷挤压成形工艺方案进行试验,证明了该工艺方案的可行性及数值模拟结果的正确性。     

铝合金大型复杂薄壁壳体多道次旋压缺陷形成机理

铝合金大型复杂薄壁壳体旋压是多道次、多参数耦合作用下的复杂非线性过程,该过程中易出现反挤、鼓包、破裂等缺陷。采用实验和有限元模拟相结合的方法,分析这些缺陷的形成机理。结果表明,过大减薄率引起的旋轮前方金属隆起是导致反挤、鼓包、环状剥离及周向开裂的主因,过高的芯模转速会导致周向开裂和鳞状剥离等缺陷。提出了相应的缺陷防止措施,即采用24%以内的减薄率可以避免旋轮前方金属的严重隆起;限制芯模转速过高,以避免周向开裂和鳞状剥离等缺陷的发生。采用这些措施旋制出了合格的铝合金大型复杂薄壁壳体。     

空调联箱多通管内高压成形金属流动规律研究

以空调联箱多通管件为研究目标,运用有限元模拟方法对金属材料的变形过程进行模拟分析.通过分析工件壁厚的分布规律和典型节点的位移规律,由此揭示成形过程的金属流动的一般规律.结果表明:端部补料区金属沿水平方向流动较明显,成形区金属沿支管方向流动较明显,支管问的金属流动量很小,这些规律为成形工艺的选择提供了参考依据.