管坯结构对小半径薄壁弯头内胀冷推弯成形的影响

针对Ф40 mm×1 mm铝合金管材且弯曲半径为1倍管径的L形弯管成形,以数值模拟技术为平台,建立了内胀冷推弯有限元模型,研究了管坯端头不同补偿角度对弯管成形质量的影响。结果表明:补偿角度过大时,弯管内侧易产生压缩起皱,降低补偿角度则能有效防止弯管产生压缩起皱,且随着角度的降低,成形弯管减薄区域不断扩大,同时弯管弯曲内侧有效长度不断降低,易造成成形不足;补偿角度为45°时,起皱现象消失,外侧壁厚最大减薄率为7. 1%,整体成形质量较佳。以45°补偿角度进行内胀冷推弯试验,成形出符合要求的1倍弯曲半径弯管,且试验结果与模拟结果整体较吻合。     

缠绕式弯管工艺对管壁厚度影响的数值分析

采用大型通用有限元分析软件ANSYS对缠绕式弯管制造工艺进行数值模拟分析，计算出弯管在弯制成形后的外壁减薄率和内壁增厚率、弯管的应力应变分布等相关工艺参数，并比较了不同的相对弯曲半径对壁厚减薄的影响。     

碳钢弯管的热推制成形过程数值模拟

在实验研究结果基础上,采用软件MSC.Marc对90°碳钢弯管热推制成形过程进行了数值模拟,研究了成形过程中弯管轴向典型特征边及环向典型特征层的应变分布,并对弯曲成形过程中管壁壁厚变化进行了分析。数值模拟结果与实际生产要求相符,能为研究热推弯管成形机理起到积极作用。     

低碳钢/铝合金双层管充液弯曲变形规律

为解决传统技术无法制造大径厚比、小弯曲半径铝合金薄壁弯管的难题,提出采用双层管充液弯曲新方法。运用数值模拟研究厚度比和内压对低碳钢/铝合金双层管充液弯曲过程中起皱行为和壁厚分布的影响。结果表明,随着厚度比的增加,起皱的现象得到缓解直至消除,内层弯管外侧减薄率逐渐减小,壁厚分布更为均匀;随着内压的增加,起皱现象逐渐延缓,内层管壁厚最大减薄率增加,因此增加厚度比和内压均有助于提高双层管弯曲成形的稳定性。通过实验成功研制出径厚比为63的铝合金薄壁弯管件,外侧最大减薄率为24%。     

五边形横截面零件旋压成形壁厚变化规律研究

为探讨非圆截面零件旋压成形时壁厚变化规律,采用MSC.Marc有限元软件对五边形横截面锥形件旋压过程进行数值模拟,获得了工件厚度减薄率沿圆周及母线方向的分布规律;通过分析对比几种不同截面形状的五边形及圆形横截面锥形旋压件的厚度减薄率变化,获得了不同工件截面形状对厚度减薄率的影响规律。结果表明,厚度减薄率沿圆周方向的分布大小与截面圆周方向的轮廓曲率有关,曲率越大的位置厚度减薄率越大,反之亦然。     

管材弯曲中外侧壁厚变化的数值模拟

回转牵引式弯曲成形是一种高质量、高效率的管材弯曲成形方式,能够有效地防止起皱、管壁的过分减薄和截面的椭圆化等成形缺陷.以圆形钢管为研究对象,采用有限元软件DEFORM-3D对弯曲成形过程进行数值模拟,找出管壁最大减薄处所在的位置,并获得滚珠与管壁的间隙、滚珠角速度及压力模速度对弯管外侧壁厚变化的影响规律.结果表明,随着滚珠与管壁间隙的增大,管壁受滚珠的影响变小,即壁厚变化较小;随着滚珠角速度的增大,壁厚变化先减小后增大,当滚珠角速度与弯曲模角速度大小相同时,壁厚变化最小;随着压力模速度的增大,壁厚变化渐渐变小,当压力模速度为64.28 mm·s-1时,壁厚变化最小.采用数值模拟后的优化参数在弯管机上进行试制,生产出合格件,模拟结果与实验结果基本吻合.     

间隙对0Cr21Ni6Mn9N不锈钢管材数控弯曲截面质量的影响

基于ABAQUS/Explicit,建立了0Cr21Ni6Mn9N(21-6-9)不锈钢管材数控弯曲成形的三维弹塑性有限元模型,模拟分析了管模间隙对管材弯曲成形截面质量的影响规律。结果表明:壁厚减薄和截面畸变程度在中间部位严重,在弯曲平面和初始弯曲平面附近较小;随着芯棒与管材间隙的增大,壁厚减薄率减小,截面畸变程度先减小后增大;随着弯曲模与管材间隙的增大,壁厚减薄率和截面畸变程度增大;随着防皱块与管材间隙的增大,壁厚减薄率和截面畸变程度先减小后基本不变;压块与管材间隙对弯管截面质量的影响不显著。     

基于数值模拟的翻边带筋肋板弯曲成形工艺研究

对飞机翻边带筋肋板零件弯曲成形开裂问题进行研究,以危险区域减薄率为指标,基于数值模拟并结合试验研究了翻边加强筋处凹模结构形式、凸模与凹模间隙、坯料形状对弯曲成形的影响。结果表明,平口式凹模结构较斜坡式能有效抑制翻边加强筋根部的快速减薄;随着凸、凹模间隙增大,危险区域减薄率减小;坯料上设置的缺口有利于材料由加强筋顶部向根部转移,抑制了根部破裂但同时顶部缺口边缘破裂风险加剧。     

间隙对0Cr18Ni9不锈钢管大曲率无芯弯曲成形性的影响

基于Abaqus有限元平台建立了0Cr18Ni9不锈钢管大曲率无芯弯曲有限元模型,分析了管材与模具间隙对管材弯曲成形性的影响,同时验证了模型可靠性。结果表明:弯管外凸侧壁厚减薄率与管-弯曲模间隙、管-压力模间隙呈正相关关系,而与管-防皱模间隙呈负相关关系;弯管内凹侧壁厚增厚率与管-弯曲模间隙、管-防皱模间隙呈正相关关系,而与管-压力模间隙呈负相关关系;弯管横截面椭圆度与管-弯曲模间隙、管-压力模间隙呈正相关关系,而与管-防皱模间隙呈负相关关系;管材与模具间隙对壁厚减薄率及横截面椭圆度影响的趋势一致。     

管材数控弯曲中的起皱分析与控制

针对内高压成形过程中,对弯曲件质量的严格要求,研究了低碳钢管材的数控弯管过程。采用数值模拟和实验,分析了不同弯曲半径、芯棒和管坯的间隙、芯棒位置和有无防皱块等参数对起皱的影响。结果表明,随着弯曲半径、芯棒直径、芯棒伸出量的增大及采用防皱块的情况下,管材弯曲起皱的趋势减小;在数值模拟的基础上进行了试验研究,试验结果和数值模拟结果吻合较好。采用二倍管径的弯曲半径,芯棒和管材间隙0.015D的情况下,能够有效地避免了弯曲内侧的起皱和外侧的减薄,成形出合格的副车架弯曲件,满足后续的内高压成形。     

On a new concept of rotary draw bend-die adaptable for bending tubes with multiple outer diameters under non-mandrel condition

A traditional rotary draw bending die on the numerically controlled (NC) tube benders or other benders can bend tubes with only one kind of outer diameter. It is difficult for such a situation to meet the requirement of modern manufacturing with characters of much varieties and small batch. The present study proposed a new concept of rotary draw bending die called MDB-Die (Multiple-diameter Bending Die), on which tubes with different outer diameters within a definite range can be bent using the same die by only adjusting the pads inside the die set. Numerical and experimental approaches were employed to investigate the forming process of tubes with different outer diameters when bent on the MDB-Die, especially on the characters of force and elastic-plastic deformation of tube wall, and the effects of groove shapes and bending parameters on the cross-section distortion and wall thinning in the process. Analytical expressions in simple tube bending based on plastic theories given by Tang (2000) for calculating the magnitude of stresses, together with the wall thickness change, deviation of the neutral axis, and section flattening, were also used for comparison. The result proved that tubes with different outer diameters (from 18 to 25 mm in the study) can be bent successfully on MDB-Die without degrading the bending quality, i.e., the aspect ratios of section distortion of less than 5% and wall thinning of less than 7.8%.     

G115钢热压弯成形工艺试验研究

分析了电站典型管件热压弯头、热压三通及热压封头的变形特点,其中热压三通的变形率最大,可达38％.并对G115钢热压弯成形进行了仿真模拟,结果可涵盖变形最为严重的情况.进而设计了热压弯工艺试验,研究了不同成形温度、道次和冷却方式对成形的影响,并对试样进行了外观检验、渗透检验、硬度检验和微观组织观察.通过热压弯工艺试验研究...     

Ti-6Al-4V钛合金的激光弯曲成形特性

以Ti-6Al-4V薄板材料为研究对象,研究了激光弯曲成形技术在钛合金上的应用特征.通过实验描述了不同扫描参数对弯曲角的影响规律,并对多次扫描下的板材弯曲动态特性进行了研究.结果表明:弯曲角随扫描次数呈近似的线性增加关系;在扫描次数一定的情况下,存在一个最优的累积线能量使弯曲角达到最大;不同的材料状态在加热和冷却过程呈现出不同的弯曲动态特性.此外,对激光弯曲后的材料微观组织、力学性能进行了测量和分析.结果表明:扫描参数的选择对发生相变的区域形状与相变区组织有较大影响;多次扫描后,加热区材料的强度与硬度均增加,塑性降低.     

Numerical and experimental study on in-plane bending of microchannel aluminum flat tube

Microchannel aluminum flat tubes have attracted more and more attention in recent years, especially in ACR (air conditioning and refrigeration) industry. Rotary-draw bending is a versatile and precise method in forming of tubes. Compared with traditional out-of-plane bending method, in-plane bending can cause different forming defects. During the process, wall thinning, sectional distortion, wrinkling, and channel shape degradation are the main defects that affect tube quality in industrial applications. In this paper, an experimental apparatus for flat tube in-plane bending is manufactured, and experiments are performed to examine the forming quality of tubes. Considering the characteristics of the bending process, based on the LS-DYNA software environment, a 3D elastic–plastic finite element model is established and validated by experiment. Using the validated FE model, the forming quality of microchannel flat tube bending process is evaluated quantitively. Furthermore, the influence mechanism of process parameters, such as bending radius, tool–tube clearance, and channel diameter, has been revealed. The results indicate that the degradation of the tube channels is relatively small under common process conditions; bending radius is the main factor which influences the forming quality of the flat tube; the tool–tube clearance mainly affects the wrinkling of the flat tubes; channel diameter has little effect on the formability of tube.     

对冷弯成形过程真实实验研究的探索

以攀钢汽车纵横梁用P510L为试样,在分析比较冷弯成形过程的实验方法的基础上,提出了1种新的适合冷弯成形过程真实实验的方法——网格法,通过试验找出了适合将钢板与网格打印材料土工膜连接在一起的KS胶粘剂.试验表明,实验结果与已有的理论分析结果相似,表明了试验方法的可靠性.     

大型复杂薄壁壳体多道次旋压过程中的壁厚变化

基于ABAQUS/Explicit和Standard建立的包含回弹与退火的大型复杂薄壁壳体多道次旋压全过程模拟模型,分析了该过程中壁厚的分布与变化及工艺参数对壁厚的影响规律。结果表明,壁厚减薄经历了剪切减薄和拉薄两个阶段,壁厚剧烈减薄部位位于旋轮后方的环带并向工件口部移动,而且其值逐渐减小;壁厚沿工件母线方向分布不均匀,沿周向分布较均匀;回弹对壁厚的分布影响不大。摩擦系数在一定范围内的增大,可以有效地抑制第一道次旋压过程中壁厚过度减薄的发生,使壁厚分布更均匀;而旋轮进给比对工件壁厚的影响与摩擦系数的作用相反。在后续道次旋压过程中,工件壁厚差随着摩擦系数的增大先减小后增大,随着旋轮进给比的增大逐渐减小。这些结果可为大型复杂薄壁壳体多道次旋压成形参数的确定和优化设计提供理论依据。     

Effects of process parameters on numerical control bending process for large diameter thin-walled aluminum alloy tubes

Numerical control(NC) bending experiments with different process parameters were carried out for 5052O aluminum alloy tubes with outer diameter of 70 mm, wall thickness of 1.5 mm, and centerline bending radius of 105 mm. And the effects of process parameters on tube wall thinning and cross section distortion were investigated. Meanwhile, acceptable bending of the 5052O aluminum tubes was accomplished based on the above experiments. The results show that the effects of process parameters on bending process for large diameter thin-walled aluminum alloy tubes are similar to those for small diameter thin-walled tubes, but the forming quality of the large diameter thin-walled aluminum alloy tubes is much more sensitive to the process parameters and thus it is more difficult to form.     

支架模拟分析及其弯曲模设计

运用DYNAFORM有限元数值模拟分析软件,对汽车转向柱后支架的弯曲成形进行了数值模拟.结果表明,一次成形在弯曲处有严重的变薄现象,两次成形无论是应力分布还是厚度分布都优于一次成形,所以采用两步弯曲成形的工艺方案.同时,设计了多工位弯曲模具,即将支架的两套弯曲模安装在同一模架上,在冲床的一次行程中完成支架的弯曲成形.这样避免了在一套弯曲模上一次成形产生的缺陷,同时解决了用两套模具单工序成形效率低的问题.     

Influence of initial texture on formability of AZ31B magnesium alloy sheets at different temperatures

Repeated unidirectional bending (RUB) process was carried out to improve the texture of AZ31B magnesium alloy sheets. Influence of initial texture on formability of AZ31B magnesium alloy sheets at different temperatures was investigated. Compared with the as-received sheets, the limiting drawing ratio of the RUB processed sheets increased to 1.3 at room temperature, 1.5 at 50 °C and 1.7 at 100 °C, respectively. The improvement of the press formability at lower temperatures can be attributed to the texture modification, which led to a smaller Lankford value and a larger strain hardening exponent. However, the press formability of the sheet with a weakened basal texture has no advantage at higher temperature. This is due to much smaller r-value that results in severe thinning in thickness direction during the stamping process which is unfavorable to forming. Anyhow it is likely that the texture control has more effect on the press formability at lower temperature.     

阳极板多道次辊弯成形过程数值模拟

利用有限元软件MAC.MARC,根据按辊弯成形工艺建立的辊花图,对阳极板多道次辊弯成形过程进行了数值模拟。基于动力显示算法,采用刚性辊轮沿板材长度方向运动的方式建立了阳极板多道次辊弯成形有限元模型。分析了成形过程中阳极板的Y向位移、等效应力与等效塑性应变的变化,重点研究了板材成形时等效塑性应变在弯曲角处的变化。结果表明,等效塑性应变的极值主要出现在当前道次所成形的弯曲角位置,且随成形弯曲角度的增大而增大。