小规格TiNiNb管材的反向挤压成形工艺参数

针对44 mm×10.5 mm小规格Ti Ni Nb管材反挤压成形试验的工艺参数确定和模具设计问题,采用有限元热力耦合数值模拟和单因素轮换法,分析在满足制件成形质量(挤出温度低于共晶熔点)的前提下,挤压力与凹模模角和定径带长度、凹模和挤压筒温度、毛坯初始温度、挤压速度及摩擦因子等工艺参数和模具结构参数之间的关系,确定影响挤压力的主要工艺参数和模具结构参数分别为凹模模角、初始坯料温度、挤压速度和摩擦因子,并给出上述参数的取值范围。通过基于数值模拟的正交试验方法,得到了主要工艺参数和模具结构参数的最佳组合,即在保证润滑效果的前提下,取凹模模角110°、毛坯初始温度为950℃、挤压速度为50 mm/s。利用铅和45号钢毛坯在6.5 MN多向模锻挤压液压机上进行了验证实验。     

基于有限元法的铝合金四通阀多向加载成形过程中的变形特征分析(英文)

采用数值模拟方法,研究7075铝合金四通阀体类零件在多向加载成形条件下成形过程中的材料变形特征。结果表明:四通阀多向加载成形过程中存在正挤、反挤、正挤和侧挤复合、反挤和侧挤复合等4种变形模式。在不同成形阶段,表现出的变形模式依赖于加载路径。一般在变形初期会发生正挤或反挤的变形行为;在变形中期以反挤变形模式为主;在变形终期一般会发生反挤、正挤和侧挤复合变形模式。为提高型腔填充稳定性和减少成形缺陷,在变形初期和中期,应增加侧挤变形行为;在变形终期应减少或避免正挤变形行为。     

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...     

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.     

金属塑性加工的物理模拟

物理模拟是进行体积成形工艺研究和生产设计的重要工具方法 ,这种方法简捷、直观 ,还可以预测材料流动情况、填充情况和工艺缺陷形成过程。本文介绍了利用北欧新型模拟材料“菲蜡” ( Filia)进行体积成形物理模拟实验的方法、原理、设备装置、模具和模拟材料的特性。对圆柱坯料的自由镦粗、正挤、反挤、管件变薄挤压、平板坯料平面应变镦粗进行了物理模拟 ,分析讨论了物理模拟实验结果 ,并与上限模拟软件的结果进行了对比。     

An upper bound method for computing loads and flow patterns in plane strain forging process

This paper describes a general method for predicting metal flow developed from the basis approach defined by Kudo in 1960 [1]. He proposed to divide the cross section of the part being into a numer of rectangular regions and calculated the forging loads by using a list of relations valid for several types of unitary rectangular regions. Two different friction conditions were considered: no friction and sticking.The authors have first defined a new list of relations valid with any friction condition. The calculus was obtained by using a programme which was able to run on a 32-K bytes minicomputer. Then new trapezoidal unitary regions were described and flow patterns obtained.Calculations of the loads and geometry are very easily programmed, e.g. those referring to forging-extrusion processes, forging of square bars on one of their diagonals and forging of rollers. Examples of flow pattern plotting related to upsetting, backward and forward extrusion processes are given. When compared with the published ones, the results are found to be rather accurate. The method can be used in the industry for predicting the optimum geometry of the work-piece and the steps in the deformation processes.     

微型零件半固态反挤压数据采集装置的设计

介绍了微型零件半固态反挤压成形工艺特点,设计了一套微型零件半固态反挤压数据采集装置,并对其工作原理进行了阐述。微型零件半固态反挤压数据采集装置实现了凸模载荷和位移数据的实时采集和温度的精确控制,经使用该装置对ZL101铝合金坯料进行半固态反挤压试验研究,验证了该数据采集装置的可行性。     

铝材长方形空心管挤压过程数值模拟与模具结构优化设计

对AA1100铝材长方形空心管的挤压过程使用数值分析软件SuperForge进行数值模拟。在挤压生产中,金属流出工作带时的流速均匀性是得到高质量型材的关键。在挤压生产中通常采用几种方法修改模具,消除流速不均,例如修改分流孔的大小、形状和位置分布,修改工作带长度和焊合室形状尺寸等。本文通过数值模拟发现在长方形空心管挤压的初始模具设计中型材截面流速不均匀,造成端面不平。对此,提出了三种模具修改方案,并分别对其进行了数值模拟,经过分析比较确定了最佳模具设计方案,由此方案可以生产出合格的挤压件。     

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。     

Effect of EDT surface texturing on tribological behavior of aluminum sheet

Surface texturing, which fabricates micro dimples or micro channels on the surface of parts, is a growing technique for improving tribological characteristics of materials. Currently, electrical discharge texturing (EDT) technique, one surface texturing method suitable for mass production, is being used to texture aluminum sheets for the applications in automotive industry. It has been widely accepted in industry that EDT improves the forming behavior of aluminum sheets due to better friction behavior. However, how the textures on the surface of sheet metal change the friction behavior has not been investigated. In this paper, the influence of EDT on the friction behavior of aluminum automotive sheet at different contact pressures and sliding speeds is investigated based on both experimental studies and numerical simulations. To fully investigate the tribological behaviors, a flat-on-flat friction test device was built and a numerical code based on mixed lubrication theory was developed. It was found that EDT texturing can reduce the friction coefficient of contacting pair at high contact pressure, however, increase friction coefficient at low contact pressure. Numerical simulations confirmed this finding. Furthermore, the model provides valuable information for the prediction of friction behavior of EDT sheets and helps to optimize processing parameters for various forming processes using EDT aluminum sheets.     

热反挤压过程中金属不稳定流动状态的研究

利用有限元软件Deform-3D对厚壁钢管热反挤压制坯过程进行数值模拟,分析了摩擦系数和壁厚对金属流动状态的影响.结果表明:反挤压件管壁内侧的金属在向上平移的同时还伴有径向移动,摩擦系数越大、管壁越厚,径向移动的程度越大,越容易造成凸模抱模的现象.根据模拟结果,提出了一种新增径向塑性变形区的大型厚壁钢管热反挤制坯的变形...     

Process Parameter Investigations of Backward Extrusion for Various Aluminum Shaped Section Tubes Using FEM Analysis

In this article, a FEM investigation has been carried out to analyze the backward extrusion of aluminum tubes which have internally and externally shaped sections. ABAQUS/Explicit finite element method was used to solve the problem. As a result, the distribution of stress, strain, and spatial velocity in the deformation region were obtained. Grid deformation patterns were also studied using the FE simulation to observe the material flow during the process. Initial billets with various cross sections such as rectangular, elliptical, hexagonal, octagonal, and square shapes were utilized in the simulations. Also various shaped punches such as circular and elliptical sections were employed for this analysis. In this article, the influence of the process parameters such as friction factor and reduction in area on the extrusion pressure was studied. The effects of reduction of area and friction factor on the configuration of free surface and velocity field have been investigated too. The results obtained from the present study were compared with analytical and experimental works and acceptable agreements were observed.     

Experimental and numerical analysis of friction in high aspect ratio combined forward-backward extrusion with retreat and advance pulse ram motion on a servo press

A method for maintaining lubrication in the backward extrusion of deep holes for lightweight structural components is proposed utilizing a servo press and a punch with an internal channel for liquid lubricant supply. In this forming method, the punch is pushed into the specimen with a servo press in a manner that combines pulsed and stepwise modes. Sufficient liquid lubricant is periodically supplied to the deformation zone through the internal channel upon the retreat of the punch. This forming method with pulse punch ram motion was tested in combined forward-backward extrusion process with a high aspect ratio (height/diameter) in this study. The material flow of the aluminum specimen during the extrusion with pulse punch ram motion was investigated to determine the coefficient of shear friction at the specimen–punch interface. The punch wear was assessed by a finite element analysis of the material flow of the specimen during the extrusion with pulse punch ram motion.     

有限体积法模拟铝型材挤压成形过程

研究了有限体积法模拟金属塑性成形的基本理论和关键技术，得到了适用于塑性成形的有限体积控制方程，给出了模拟过程中有限体积网格体系的建立、成形过程中金属流动的跟踪描述和时间增量步长的确定等技术处理方法。然后采用该数值模拟方法，对铝合金门窗型材的挤压成形过程进行了仿真。详细地分析了该零件在挤压成形过程中金属的流动情况，给出了成形各阶段等效应变、温度和速度等物理场量的分布情况以及整个成形过程中模具载荷／行程曲线的变化情况。研究结果证明有限体积法是一种行之有效的铝型材挤压数值模拟方法，它可以为铝型材新产品的开发设计提供理论指导。     

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.     

型材拉弯数值模拟夹钳边界条件的一种等效模型

拉弯是一种重要的型材弯曲工艺,被广泛应用于汽车和飞机制造业。有效应用该工艺必须了解不同工艺参数如何影响工艺过程和零件最终形状。当前数值模拟是研究这些问题的一种有效手段。然而准确模拟成形过程的前提是准确描述毛料的边界条件。张臂式拉弯夹钳力矩边界条件复杂,在数值模拟中处理困难,为此该文提出了一种位移加载等效模型。利用该模型对矩形中空截面铝合金型材张臂式拉弯过程进行了模拟和试验验证。切向应变、截面畸变和回弹模拟结果与试验结果基本吻合,说明上述夹钳等效模型可行,为后续工艺参数优化提供了基础。     

铝合金FSJ接头弧纹形成过程及主要影响因素分析

轴肩的偏心挤压在铝合金搅拌摩擦接头弧纹形成过程中起到了决定性作用.搅拌摩擦连接弧纹形成的过程是搅拌头偏心产生的长轴挤压软化的金属材料的过程,在长轴挤压下将产生弧纹的弧峰,两次弧峰间将产生弧谷,并且弧纹的产生可以进行数值表征.利用数值仿真对无针搅拌头进行连接过程的模拟可以得到弧纹,并利用试验方法进行了有针和无针搅拌摩擦焊接的对比.结果表明,无针的搅拌头也能产生弧纹,且弧纹的轮廓与有针时相同;弧纹的形成主要是搅拌头轴肩挤压的作用;搅拌头的前进速度越大,搅拌头的旋转频率越慢,则接头的弧纹间距将会越大;弧纹在后退侧形成的夹角比前进侧形成的夹角大.     

T-shape upsetting–extruding test for evaluating friction conditions during rib–web part forming

Since the deformation features of existing friction testing methods are not as similar as those of the closed die forging process of rib–web parts, the friction conditions evaluated by these methods are not consistent with the actual situation. In this paper, a new friction testing method, the T-shape upsetting–extruding process employing a rectangular blank, is proposed for evaluating the friction conditions during rib–web part forming process. It was found that rib height and the web width are both sensitive to friction conditions. Therefore, the ratio of rib height to web width was chosen as a criterion for friction evaluation. With the utilization of a commercial FEM program, DEFORM, the effects of the geometrical parameters and testing variables on the friction sensitivity were investigated, and the friction conditions between different interfaces were analyzed. In order to verify the proposed method, friction factors of a water-based graphite lubricant measured by three different methods (the proposed one, the ring compression test and the double-cup extrusion test) at 723 K were used to simulate the isothermal deformation process of a cross-rib part. The experimental results suggest that the proposed method is more accurate than the other two methods for rib–web part forming process.