基于显著性的薄壁铝合金管小弯曲半径数控弯曲工艺参数优化(英文)

薄壁铝合金管小弯曲半径数控弯曲是个多因素耦合、多模具约束下的复杂过程。提出以有限元模拟为基础,基于显著性的工艺参数优化方法,即采用析因因子设计分析工艺参数对成形质量,即最大壁厚减薄率和最大截面畸变变化率影响的显著性,获得影响显著的参数,即管与防皱模间间隙的最优值,并确定其他影响不显著的参数值,包括管与模具间的间隙和摩擦、芯棒伸出量和助推速度。结果应用于规格为d50mm×1mm×75mm和d70mm×1.5mm×105mm(管外径D0×管壁厚t0×弯曲半径R)的铝合金管弯曲,获得了合格的管件。     

Effect of mandrel on cross section quality of thin-walled tube numerical controlled bending

The effect of mandrel with the structure of ball and socket on the cross section quality of thin-walled tube numerical controlled （NC） bending was studied by numerical simulation method, combined with theoretical analysis and experiment. Influencing factors of the mandrel include the count of mandrel heads, the diameter of mandrel and its position. According to the principle of NC tube bending, quality defects possibly produced in thinwalled tube NC bending process were analyzed and two parameters were proposed in order to describe the cross section quality of thin-walled tube NC bending. According to the geometrical dimension of tube and dies, the range of mandrel protrusion was derived. The finite element model of thin-walled tube NC bending was established based on the DYNAFORM platform, and key technological problems were solved. The model was verified by experiment. The effect of the number of mandrel heads, the diameter of mandrel and the protrusion length of mandrel on the cross section quality of thin-walled tube NC bending was revealed and how to choose mandrel parameters was presented.     

基于数值模拟的薄壁管冷弯成形工艺研究

薄壁管冷弯成形过程中最常见的缺陷有管坯内侧失稳起皱、外侧减薄破裂,为获得质量良好的某车用水冷管接头冷弯件,采用数值模拟方法分别研究了芯棒伸出量e、防皱块与管坯间隙c以及芯棒直径d等工艺参数对冷弯成形质量的影响.结果表明:随着芯棒伸出量e增大,管坯外侧壁厚减薄率γ增大,管坯内侧起皱趋势先减小再增大;随着管坯与防皱块的间隙...     

模具间隙对薄壁管绕弯成形的影响规律

详细分析了薄壁管绕弯成形过程及其变形特点,基于有限元法对绕弯成形模具芯棒与管坯间隙,压块与管坯间隙,防皱块与管坯间隙以及弯曲凹模与管坯间隙等4个因素与薄壁管成形质量、回弹量的影响显著程度进行了四因素三水平的正交试验分析。结果表明：芯棒与管坯的间隙对成形后薄壁管壁厚及回弹的影响最显著,弯曲凹模与管坯间隙对回弹影响也较显著。     

薄壁管数控弯曲截面畸变的实验研究

截面畸变是薄壁管小弯曲半径数控弯曲成形容易出现的成形缺陷之一。文章采用实验法,研究了芯头个数、芯棒伸出量、弯曲角度、压块润滑状态、相对弯曲半径、材料等因素对截面畸变的影响;并提出了减小截面畸变的有效措施。结果表明,增加芯头个数与芯棒伸长量都能减小弯管的截面畸变,但两者都导致弯管壁厚减薄量增大;随着弯曲角度的增加,截面畸变越严重,相对弯曲半径越小,无芯棒与芯头支撑段弯管的截面畸变愈严重;在压块无润滑情况下,弯管的截面畸变和壁厚减薄量都小,并且在同等弯曲条件下,1Cr18Ni9Ti弯管的截面畸变小于LF2M弯管。     

圆管压扁-压弯连续变形过程有限元模型的建立及截面畸变研究

为研究圆管压扁-压弯连续变形过程中的截面畸变,基于有限元软件ABAQUS建立了该过程的三维有限元模型,并实验验证了其可靠性。分析了圆管压扁过程中的截面变化规律及弯曲下模圆角半径、模具与管材间的摩擦系数对成形过程截面畸变的影响。结果表明,圆管压扁过程中形成扁管直壁部分的材料在外层周向压应力、内层周向拉应力的合力作用下出现塌陷。形成扁管圆弧部分的材料在外层周向拉应力、内层周向压应力的合力作用下出现扁化。在无芯轴、有芯轴压扁成形前期,圆弧部分均出现扁化,且无芯轴压扁成形中期,直壁部分出现塌陷。但有芯轴压扁过程中芯轴的支撑作用不但抑制了直壁部分的塌陷,而且还矫正了成形后期圆弧部分的扁化。由于圆管压扁-压弯过程中模具与管材的接触区域始终不大,因此成形过程中弯曲下模圆角半径,及模具与管材间的摩擦系数,对截面畸变影响不显著。     

芯管间隙对JAC590Y高强钢矩形管绕弯成形质量的影响

为了判断JAC590Y高强钢矩形管180°绕弯时芯棒与管坯之间的间隙大小对弯管成形质量的影响,基于Dynaform软件对4种芯管间隙下JAC590Y高强钢薄壁矩形管的绕弯成形分别进行了模拟,得出了不同芯管间隙值下弯管的主要畸变参数。结果表明:在芯管间隙处于一定范围内时,弯管的宽度扩展率受芯管间隙值的影响很小,而中面高度缩减率会随着芯管间隙的增大而变大;弯管上最大的壁厚减薄率出现于紧邻距芯棒最远芯头的横截面上顶板与两侧板的交角处,选取较大的芯管间隙有助于降低弯管的最大壁厚减薄率;JAC590Y高强钢薄壁矩形管180°绕弯成形时芯管间隙率的合理范围为0. 01~0. 025。     

铝合金大口径薄壁管数控弯曲实验研究

铝合金大口径薄壁管小弯曲半径数控弯曲成形过程中更容易发生起皱、截面畸变和壁厚减薄等缺陷。文章根据成形缺陷产生的原因对弯管模具结构和设备装置进行了改进,包括模具内锁设计、紧凑型柔性芯棒、模具并紧杆和长内衬顶推。在此基础上,采用实验研究方法,对Φ70mm×1.5mm×105mm(外径×壁厚×弯曲半径)的大口径薄壁铝合金管数控弯曲成形质量及应变规律进行了分析,并研究了顶推装置在大口径薄壁铝合金管数控弯曲成形中的效用。     

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。     

薄壁管小弯曲半径数控绕弯成形芯模效用的实验研究

薄壁管数控弯曲中带芯头的柔性芯模是提高薄壁管件成形极限和成形精度的关键因素。文章建立了绕弯过程芯模(包括芯棒和芯头)的理论解析模型,包括了芯模直径d、芯棒伸出量e、芯头个数n、芯头厚度k、芯棒/芯头孔心间距p及芯棒圆角半径r等参数的选取公式的推导,获得了不同弯曲规格下的芯模参数取值范围,验证了解析模型的合理性;实验研究了芯模参数对管材失稳起皱、壁厚减薄和截面畸变的影响规律。通过分段抽芯的工艺方法,完成了38mm×1mm×38mm(1D)高难度不锈钢管件的弯曲。     

助推作用对大口径铝合金薄壁管数控弯曲壁厚减薄和回弹的影响

以有限元软件Dynaform为平台,建立了大口径薄壁管数控弯曲及回弹的有限元模型,分析了压块助推速度和压块与管子之间的摩擦系数对壁厚减薄和回弹角的影响规律。结果表明,压块与管子之间没有摩擦或者压块的助推速度为0.9、助推速度为1.0且压块和管子间摩擦系数为0.1的条件下,管子壁厚减薄超过航空标准中允许的最大减薄量0.4375mm。在压块的助推速度不变的条件下,压块与管子之间摩擦系数从0.1增加到0.3,能够有效地降低管外侧的壁厚减薄,但是回弹角也会明显增大。当压块与管子之间的摩擦系数为定值时,助推速度从1.0增加到1.2,对管外侧壁厚减薄的改善作用不大,回弹角没有明显变化。     

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.     

Role of mandrel in NC precision bending process of thin-walled tube

The thin-walled tube NC bending process is a much complex physical process with multi-factors coupling interactive effects. The mandrel is the key to improve bending limit and to achieve high quality. In this study, one analytical model of the mandrel (including mandrel shank and balls) has been established and some reference formulas have been deduced in order to select the mandrel parameters preliminarily, i.e. mandrel diameter d, mandrel extension e, number of balls n, thickness of balls k, space length between balls p and nose radius r. The experiment has been carried out to verify the analytical model. Based on the above analysis, a 3D elastic–plastic FEM model of the NC bending process is established using the dynamic explicit FEM code ABAQUS/Explicit. Thus, the influences of mandrel on stress distribution during the bending process have been investigated, and then the role of the mandrel in the NC precision bending process such as wrinkling prevention has been revealed. The results show the following: (1) Wrinkling in the tube NC bending process is conditional on membrane biaxial compressive stress state; the smaller the difference between the biaxial membrane stresses is, the more possibility of wrinkling occurs. (2) If the mandrels of larger sizes are used, it will cause the neutral axial to move outward and the difference between the in-plane compressive stresses to become more obvious, which may increase minimum wrinkling energy and anti-wrinkling ability. But the larger mandrel sizes make outside tube over-thinning. (3) When the mandrel extension length increases, the neutral axial will move outward and the difference between the biaxial compressive stresses becomes larger, but the significance is less than that of the mandrel diameter. The excessive extension will cause tube to over thin or even crack. (4) The significance of ball number's effect on the neutral axial position and difference between biaxial compressive stresses is between ones of mandrel diameter and mandrel extension. Increasing the ball number will enhance the thinning degree and manufacturing cost. The results may help to better understanding of mandrel role on the improvement of forming limit and forming quality in the process.     

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%.     

Springback of thin-walled tube NC precision bending and its numerical simulation

The springback is one of the key factors which affect the forming quality of thin-walled tube NC precision bending. The elastic-plastic finite element method was proposed to study the springback process of thin-walled tube NC precision bending and the combination of dynamic explicit algorithm and the static implicit algorithm was proposed to solve the whole process of thin-walled tube NC precision bending. Then, the 3D elastic-plastic finite element model was established based on the DYNAFORM platform, and the model was verified to be reasonable. At last, the springback rule of thin-walled tube NC precision bending and the effect of geometry and material parameters on the springback rule of thin-walled tube NC precision bending were studied, which is useful to controlling the springback of thin-walled tube NC precision bending, and the numerical simulation method can be used to study other effect of parameters on the forming quality of thin-walled tube NC precision bending.     

基于数据库的薄壁管数控弯曲知识库的构建

针对薄壁管数控弯曲生产过程中容易出现各种质量缺陷,需要进行反复调模的问题,文章总结该领域的专家知识,并根据薄壁弯管质量标准、有限元模拟结果和实验结果等大量信息数据,采用基于数据库的技术,研究开发了薄壁管数控弯曲知识库系统。结果表明,该系统可以全程指导数控弯管实际生产过程,迅速有效地供给操作人员专家的建议。     

厚壁结构管件刚模塑性成形过程的数值模拟与工艺研究

基于刚塑性有限元法,忽略了回弹和管坯与模具、芯轴的间隙的影响,建立了简化的有限元模型,对厚壁管压弯、压扁成形过程进行了数值模拟,得到了各场量的分布。根据应力分布结果,对起皱和破裂等缺陷进行分析预测,并根据截面变化情况,研究了芯轴对截面畸变的作用与影响。该研究对厚壁管件弯曲和扁化过程的工艺方法提供了依据。     

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。     

模具与管材不同配合条件下中强TA18厚壁钛管数控弯曲变形行为

采用基于ABAQUS建立的中强TA18钛合金厚壁管数控弯曲有限元模型,研究了不同配合参数条件下中强TA18钛合金厚壁管数控弯曲过程中的壁厚变化和截面扁化行为,确定了适合于中强TA18厚壁管数控弯曲的压力模、弯曲模与管材间隙和摩擦的选取原则。结果表明,压力模和弯曲模与管材的间隙,对壁厚增厚率的影响较减薄率的影响显著,过大的压力模与管坯间隙会造成内侧小凸包缺陷,过大的弯曲模与管材间隙会造成外侧壁的严重塌陷。因此,弯曲模和压力模与管材的间隙应取较小的值;压力模和弯曲模与管材间的摩擦,对壁厚变化和截面扁化影响不大,因此,压力模和弯曲模与管材间可选用航空润滑油或拉深油进行润滑。     

Roles of Surface Booster System on Bending of Thin-Walled Copper Tube

Thin-walled C12200 circular copper tube has been widely used in HVAC (heating, ventilation, air conditioning, and refrigeration) industry. Rotary draw bending is a versatile and precise method in forming of thin-walled copper tubes. Wall thinning and sectional fattening are the two main defects that affect tube quality in industrial applications. With traditional die settings, such as adjusting position or type of the mandrel, one factor usually decreases at the expense of increasing the other. An assistant equipment, surface booster system, has been recently developed to relieve both defects at the same time. In the present study, the role of the booster system in the bending process is investigated with finite element simulation. A basic model of copper tube rotary draw bending is established and validated by experiments. Then, cases of different sets of main parameters of the booster system are studied. The relationship between loading force, lower displacement, speed of the booster, and forming characteristics of tube is obtained based on which suggestions about process parameters settings are given. The results provide a better understanding of the role of the booster system in the improvement of forming quality.