冷拔内螺旋凸筋管变形区应力分布有限元分析

本文采用三维弹塑性有限元方法模拟了冷拔内螺旋凸筋管的成形过程,得到了此过程中管料在变形区的应力分布,揭示了冷拔内螺旋凸筋管的变形规律,为进一步优化模具设计提供了理论基础.     

冷拔残余应力应变对钢丝氢扩散过程的影响

利用有限元法对高强度珠光体钢丝冷拔残余应力应变进行有限元分析,在此基础上利用有限差分法计算应力应变同时诱导下的氢扩散浓度分布规律,并比较其与只考虑残余应力诱导氢扩散模型所得氢浓度分布规律的不同.结果表明,由于冷拔加工过程中钢丝表面和内部变形速率的差异,冷拔后在钢丝表面产生较大的残余拉应力和大量的塑性应变.残余应力应变的...     

十字形钢管拉拔成形的三维有限元模拟

异型钢管拉拔成形是一种高质量、高效率和低消耗的管材成形加工工艺.以十字形钢管为研究对象,采用有限元技术对拉拔成形过程进行数值模拟,得到了成形过程中管料的变形规律.研究发现：在应力分布上,轴向、周向和径向应力随管料在模具中位移增加而增大,三者最大值均出现在减径带与定径带连接处;沿壁厚方向,中心层应力分布较均匀.在应变分布上,塑性变形主要发生在管料与模具初始接触处及减径带与定径带连接处,周向应变沿拉拔轴向分布有较大变化,在模具入口端部分数值为负,在出口端部分数值为正.同时,模拟讨论了周向压缩系数η、拉拔速度v和摩擦系数μ对拉拔过程的影响,当η在1.05～1.14之间变化时,拉拔过程较稳定,应力-应变曲线分布平稳;拉拔应力随着μ的增加而增大;当v=250mm/s时,拉拔应力取得最小值.     

外螺纹铜管拉深成形过程的有限元模拟

利用非线性有限元仿真软件MARC,研究了外螺旋凸筋管成形过程的三维弹塑性有限元模拟技术.对外螺纹铜管的拉深成形过程进行了模拟,得到了成形过程中工件内部的应力和应变分布规律.结果表明,拉拔过程中,管料发生轴向延伸,但各部分延伸量不均匀,最大延伸变形发生在筋底中心部分.在周向,整体上管料发生压缩变形,但在筋底部分产生一定的延伸,应变为正;径向发生压缩变形.在定径区及铜管离开定径区后,轴向应力均为拉应力,但沿壁厚分布不均匀;同样,拉拔周向应力沿壁厚方向也呈不均匀分布,出定径区后在筋底区的外表面为负,内表面为正.     

影响高精度冷拔管内孔尺寸精度的因素分析

针对热轧管内孔椭圆度差、壁厚偏差大、材料硬度不均匀等问题,分析了热轧管料对高精度冷拔管内孔尺寸精度的影响.分析结果表明:热轧管料退火有利于控制冷拔管的内孔椭圆度,冷拔生产必须选择退火态或正火态的管料;热轧管料壁厚偏差越大,生产出的冷拔管内孔椭圆度和壁厚偏差就越大,通过冷拔无法消除其壁厚偏差;热轧管料内外径尺寸及椭圆度对...     

无缝钢管冷拔头的应力分析及结构优化

为了解决钢管冷拔生产过程中冷拔头开裂、断头问题,采用ANSYS/LS-DYNA软件对空拔钢管冷拔头进行数值模拟。建立短芯棒冷拔钢管的分析模型,计算成品规格为Φ385 mm×50 mm的4140无缝钢管的应力,发现冷拔头的应力集中在圆弧顶点两侧。根据分析结果,优化设计了3种冷拔头结构,通过模拟计算和生产验证确定相离冷拔头结构的应力最小,冷拔头不容易断裂。     

三通管复合胀形与轴向压缩胀形工艺研究

采用显示动力分析软件ANSYS／LS—DYNA建立复合胀形三维有限元模型,深入研究了三通管液压胀形过程中应力应变分布规律,系统比较了轴向压缩胀形和复合胀形过程中应力应变变化规律、胀形支管高度、壁厚分布的差异。研究表明：复合胀形较轴向压缩胀形应力应变分布更均匀、壁厚分布更均匀、更易获得较大的支管高度。     

逆法识别金属板材颈缩阶段应力应变曲线

金属板料成形过程的仿真需要定义材料在大应变处对应的流动应力曲线,即真应力-应变曲线。文章介绍了一种逆向识别方法,通过结合单向拉伸试验和有限元仿真分析来获得金属板料在大应变区间内的流动应力曲线。仿真分析过程中通过构建合适的有限元模型,正确模拟分散性失稳期间的各向异性塑性变形行为。在得出材料完整的直至颈缩阶段的流动应力曲线后,建立多个不同的硬化模型描述该曲线,并比较拟合结果,发现改进的Hockett-Sherby模型效果最好。     

一种钢管冷拔装置

<正>涉及一种钢管冷拔装置,包括模座、顶料机构,模座上设有芯杆,芯杆穿入后堵头、并支撑住后堵头,后堵头嵌入管坯一端,在管坯上、下位置设置有多个液压辊轮,多个液压辊轮用于对管坯径向限位。该实用新型在管料尾端加装后堵头,为过盈配合;在冷拔装置上下间隔安装液压辊轮机构。管料在拔制过程中,可以一边拔制一边自动矫直,使得成品尺寸精度     

通孔元件焊点的抗热疲劳性能预测Ⅱ.焊点内部力学响应特征的数值模拟

通过建立可靠性分析的力学模型，对温度循环载荷下通孔焊点内部应力应变场的分布特征进行了有限元数值模拟，结果表明，焊接方式的不同造成焊点形态的差异，进而应力应变的分布也不同；再流焊点的应力应变集中在钎料体及镀铜管处，而波峰焊点中线路板与镀铜层接触的拐角处是高应力集中区，这些位置容易引起裂纹产生和扩展．在热载荷过程中，应力-应变场的等值分布呈现出与温度历史相关的动态特性。     

Improving the Deformation Uniformity and Minimizing the Inner Surface Roughness in Rectangular Tube Drawing Process

This paper focuses on improving the quality of aluminum rectangular tube in the cold drawing process. The newly developed drawing tools (i.e., the drawing die and the plug) which are considered as one of the most significant factors influencing the final forming quality are proposed. The new-type drawing die is designed with the “convex hull” shape in sizing zone corner and the plug is featured with a “boss club” structure in sizing zone. The equivalent plastic strain, drawn tube’s dimensional accuracy, contact stress distribution, and drawing load have been analyzed for the conditions under which the original tools and the new-type ones have been used, respectively, based on finite element simulations. The simulation results show clearly that the discrepancy of plastic strain in the axial cross section and the tube axial elongation are smaller when the new-type die is employed, which indicates the more uniform metal deformation and steady material flow. Besides that, the fluctuation of wall thickness is also unobvious showing the new-type die is very helpful to improve the tube dimensional accuracy. The newly developed plug can cause higher compressive plastic strain and contact stress, which are crucial to guaranteeing the high surface quality. An experiment on the cold drawing process of the aluminum rectangular tube has been performed. The comparisons of the drawn tube dimensions, e.g., height/width and wall thickness, have been made between simulation results and practical production. Meanwhile, the surface finish has also been measured. The experimental result exhibits that the drawn tube can better fulfill the requirements of the design and usage when the new-type tool is adopted.     

薄壁深筒矩形件冲压工艺及级进模设计

通过分析薄壁深筒矩形件的结构特点和冲压工艺性,设计了制件冲压级进模。设计采用由圆形筒过渡到椭圆形筒,再从椭圆形筒过渡到矩形筒成形工艺。利用拉深与挤压相结合的方法以及合理选择制件材料和拉深系数,成功地解决了薄壁深筒矩形件成形、矩形筒小、过渡圆角起皱及矩形大、长宽比容易拉裂等问题。模具在连续生产中,制件质量稳定,模具寿命高。     

Fabrication of noncircular multicore microtubes by superplastic dieless drawing process

A superplastic dieless drawing process that requires no dies or tools is applied to the drawing of a Zn–22Al superplastic alloy for noncircular microtubes such as square, rectangular and noncircular multi core tubes having square inner and rectangular outer cross-sections. In this study, the effects of heating condition, such as heating length and the use or nonuse of cooling device, on deformation behavior are investigated. As a result, a square microtube with 0.58 mm side and a rectangular microtube of 0.75 mm × 1.3 mm were fabricated after 3-pass superplastic dieless drawing. In addition, the fundamental deformation behavior of noncircular tubes combined with square and rectangular tubes during the dieless drawing process has been clarified experimentally. The cross-sectional shape of the noncircular tubes after the superplastic dieless drawing process tends to be maintained on the basis of the similarity law in case of a wide heating length compared with a narrow heating length. Furthermore, a noncircular microtube, which has inner square tubes with a 335 μm side, and an outer rectangular tube of 533 μm × 923 μm were fabricated successfully after a 4-pass superplastic dieless drawing process. Consequently, it was found that the superplastic dieless drawing is effective for the fabrication of noncircular multicore microtubes.     

A study on the corner filling in the drawing of a rectangular rod from a round bar

An important characteristic of the shaped drawing process, unlike the wire drawing process, is the corner filling which influences the dimensional accuracy of the product. In this study, therefore, in order to investigate the effect of process variables, such as the reduction in area, the semi-die angle, and the rectangular ratio to the corner filling, the drawings of a rectangular rod from a round bar have been simulated by using the three-dimensional rigid-plastic finite element method (FEM) and an artificial neural network has been introduced to reduce the number of simulations. To verify the results of the study, the experimental investigations were also carried out on real industrial products. According to the results, in the case of the irregular-shaped drawing process the main process variable on the corner filling is the combination of the semi-die angle but for the regular-shaped drawing process, the reduction in area has a significant effect on the corner filling.     

薄壁盒形容器零件拉深起皱的原因分析与解决方法

各种薄壁盒形容器拉深零件在拉深过程中经常出现起皱现象,特别是对带有锥度的方形容器和带有阶梯的矩形容器等异型类零件的起皱现象,一直是在拉深模具设计中十分关注的问题.这些问题与拉深模具本身的设计参数有着直接的关系,也与拉深模具的制造参数与模具装配、调试有着直接的关系.     

铝合金矩形管拉拔成形质量因素分析优化

应用有限元模拟软件MARC对铝合金矩形管拉拔成形质量影响因素进行模拟仿真.对拉拔速度、模具人模角和摩擦因子三个工艺参数进行分析,通过比较等效塑性应变的分布、残余应力、拉拔载荷的影响规律以及成品管的尺寸精度,得到了较优的拉拔工艺方案.采用优化后的方案生产试制的成品管表面质量良好,尺寸合格,与模拟相吻合.     

坯料外形对镁合金矩形盒拉深成形的影响

用商业有限元软件模拟了在同一套模具和成形条件下不同毛坯外形的镁合金矩形盒拉深成形过程, 依据数值模拟结果,分析了不同坯料外形对镁合金矩形盒拉深成形的影响。结果表明:使用矩形圆角坯料比其他坯料的成形性能好。     

坯料外形对镁合金矩形盒拉深成形的影响

用商业有限元软件模拟了在同一套模具和成形条件下不同毛坯外形的镁合金矩形盒拉深成形过程．依据数值模拟结果，分析了不同坯料外形对镁合金矩形盒拉深成形的影响。结果表明：使用矩形圆角坯料比其他坯料的成形性能好。     

板料成形中拉延筋的模拟及应用

将拉延筋模型引入到板料成形动力显式有限元分析中,并以汽车前照灯矩形反光镜为应用实例,对其拉延成形过程进行了模拟。     

薄壁矩形管弯曲过程截面畸变的三维有限元分析

薄壁矩形管的弯曲成形是一个受材料性能和工艺参数等诸多因素交互作用的复杂成形过程,在弯曲过程中极易产生截面畸变等缺陷,导致成形质量难以达到要求。为此,文章提出了薄壁矩形管弯曲成形过程截面畸变的描述方法,并基于ABAQUS/Explicit软件平台,从截面形状变化、截面畸变量大小和弯曲过程中的能量变化等方面,研究了芯棒与管坯间隙和管坯与防皱块之间的摩擦对截面畸变的影响规律。该研究对薄壁矩形管弯曲过程工艺参数的选取,提供了理论依据。