6061铝合金曲线翻边零件橡皮成形回弹补偿与试验验证.pdf

第43卷第2期Vol． 43 No． 2FORGING 2.中航工业南京机电液压工程研究中心,江苏南京211106; 3.空军航空大学飞行训练基地,辽宁锦州121000)摘要:橡皮成形是飞机钣金零件制造的一种重要的成形工艺,为提高典型零件橡皮成形的效率,对6061铝合金橡皮成形过程中产生的回弹问题进行了研究。首先对新淬火状态下6061铝合金板料进行拉伸试验,获得基本材料参数,为有限元模拟提供材料本构关系与模型;然后对6061铝合金进行材料成形极限试验,绘制出成形极限图;为得到曲线翻边零件橡皮成形回弹角度,采用Pamstamp 2G有限元软件进行模拟,通过基于理论回弹算法二次开发的回弹补偿模块进行模具回弹补偿。结果表明,补偿后零件所有部位偏差均在1°以内。最后通过实际成形试验,验证了有限元模拟的可行性和回弹补偿的可靠性。关键词:橡皮成形; 6061铝合金;新淬火状态;回弹;回弹补偿;成形极限DOI: 10． 13330/j． issn． 1000-3940． 2018． 02． 009中图分类号: V261． 2; TG146． 2 +1 文献标识码: A 文章编号: 1000-3940 (2018) 02-0044-06Experimental verification and springback compensation on rubber forming ofcurve flanging parts for aluminum alloy 6061Zhang Lingyun1, Wang Jun1, Liu Huan2, Zhou Shuai1, Piao Xiaodong3(1. Key Lab of Fundamental for National Defense of Aeronautical Digital Manufacturing Process, Shenyang Aerospace University,Shenyang 110136, China; 2. AVIC Nanjing Electromechanical Hydraulic Engineering Research Center, Nanjing 211106, China;3. Air Force University Aviation Training Base, Jinzhou 121000, China)Abstract: Rubber forming is one of the most important forming process in the manufacture of aircraft sheet metal parts. In order to im-prove the efficiency of rubber forming for typical parts, the springback problem produced in the rubber forming process aluminum alloy6061 was researched. Firstly, the tensile test of aluminum alloy 6061 sheet in the new quenching state was carried out, and the basic ma-terial parameters were obtained as a reference for the constitutive relation and model of the material for the finite element simulation.Then, the forming limit tests of aluminum alloy 6061 were conducted, and the forming limit diagram was drawn. In order to obtain thespringback angle of the curve flanging part, its forming process was simulated by finite element software Pamstamp 2G, and the spring-back compensation of die was conducted by the secondary developed springback compensation module based on theoretical springback al-gorithm. The results show that all the partial deviations are within 1°. Finally, through the actual forming test, the feasibility of finite ele-ment simulation and the reliability of springback compensation are verified.Key words: rubber forming; aluminum alloy 6061; new quenching state; springback; springback compensation; forming limit收稿日期: 2017 -08 -04;修订日期: 2017 -11 -21作者简介:张凌云(1963 - ),男,博士,教授E-mail: zhangly79@163． com通信作者:王 俊(1988 - ),女,硕士研究生E-mail: hrbwj8520@163． com橡皮成形是利用橡皮作为弹性凹模(或凸模),用液体作为传压介质使金属板料随刚性凸模(或凹模)变形的软模成形方法[1],与传统工艺相比,该方法大幅度降低了生产准备时间及生产成本。板料成形后不可避免地会出现回弹现象,当回弹量超过允许容差后,成为成形缺陷,影响零件几何精度。回弹补偿有助于解决板料在成形过程中的回弹问题[2],提高钣金件生产质量和生产效率。目前,国内外学者对回弹问题的研究已经进行了很多研究。 Gil I等[3]通过对高强度钢进行回弹数值模拟,得出了不同摩擦因数对回弹的影响; Mar-retta L等[4]提出了多目标优化问题,考虑润滑条件和应变硬化指数,通过改变变量来减小回弹; ChenL等[5]研究了模具圆角半径与板料厚度的比值即r/ t对回弹的影响,得出r/ t <2时可以消除回弹;付明杰等[6]研究TNW700钛合金在较低温度条件下的变形,断口附近因应变速率高以及变形温度低的双重万方数据作用,在晶界三角区产生应力集中使晶界滑移变得困难,并导致有孔洞产生。韩志仁等[7]通过试验与有限元模拟,研究了带下陷钣金件的回弹规律;杨伟俊等[8]提出一种考虑回弹误差修正的模面设计方法,建立了针对曲弯边的回弹分布函数,并对模具进行回弹补偿;宋灏等[9]利用位移回弹补偿原理对拉延型面和整形型面进行回弹补偿,验证了回弹补偿结果满足设计产品的精度要求。均没有在6061铝合金板材曲线翻边方面进行针对性研究和探讨。本文采用Pamstamp 2G软件对6061铝合金曲线翻边零件进行数值模拟,通过理论回弹算法二次开发回弹补偿模块进行模具回弹补偿,并用实际成形试验进行验证。1 试验1． 1 6061铝合金拉伸试验1． 1． 1 试验材料热处理过程中,时效温度对合金抗拉强度的影响显著,而时效温度、固溶时间及固溶温度对合金屈服强度的影响显著[10]。新淬火态铝合金是处于热处理的中间状态(完成淬火处理后的一段时间里尚未发生或完成时效硬化的一种不稳定状态)的铝合金,具有塑性好、硬度低、易成形等特点[11],其主要化学成分见表1。表1 6061铝合金的化学成分(% ,质量分数)Table 1 Chemical compositions of aluminium alloy 6061(% , mass fraction)Mg Si Fe Mn Cr Zn Cu Ti Al0． 9 0． 62 0． 33 0． 06 0． 17 0． 02 0． 28 0． 02 Bal．1． 1． 2 试验方案根据GB/ T 228． 1— 2010[12]相关要求,设计如图1所示的拉伸试件。对于6061铝合金,由于固溶处理后组织变化的不稳定性,制定其失效时间见表2。图1 单向拉伸试件Fig． 1 Uniaxial tensile specimen表2 铝合金6061试件轧制方向和时效时间Table 2 Rolling directions and aging time of aluminiumalloy 6061 test pieces参数方向/ (°)时效时间/ min数值0/45/90 20/40/60将淬火之后的试件放入到低温试验箱,整个过程需在10 min内完成,采用MTS材料试验机进行试验,试验机通过伺服电机驱动系统传动横梁上下移动来实现对试件施加载荷,并保证尺寸精度控制在±0． 3%。将不同板料轧制方向和不同时效时间的试件夹持到试验机上,连接电子传感器进行试验,试件的变形量由系统实时记录。1． 1． 3 试验结果试验结束后,由单拉试验测得结果,并经公式计算得到6061铝合金材料力学性能参数,见表3。最终得到的应力-应变曲线如图2所示。表3 6061铝合金的力学性能参数Table 3 Mechanical property parameters of aluminum alloy 6061参数弹性模量/ GPa泊松比屈服强度/ MPa强度系数/ MPa硬化指数各向异性指数伸长率/ %数值65 0． 33 105 155 0． 25 0． 63 20图2 6061铝合金真实应力-应变曲线Fig． 2 True stress-strain curve of aluminum alloy 60611． 2 6061铝合金成形极限试验根据GB/ T 15825． 8— 2008[13],制定了9种尺寸的试验件,尺寸分别为20 mm × 180 mm, 40 mm ×180 mm, 60 mm ×180 mm, 80 mm ×180 mm, 100 ×180 mm, 120 × 180 mm, 140 × 180 mm, 160 ×180 mm, 180 mm × 180 mm。采用电腐蚀法对板料进行网格印制,试验采用刚性冲头胀形方案[14],其54第2期张凌云等: 6061铝合金曲线翻边零件橡皮成形回弹补偿与试验验证 万方数据原理如图3所示。试验时,将板料放在凹模与压边圈中部区域,施加压边力压住板料,板料中心区域在凸模载荷压力下发生胀形变形,板料表面的方形网格出现了畸变,当板料突出的部位上某个小区域出现颈缩或拉裂时,试验结束。图3 胀形试验原理图Fig． 3 Principle of bulging test试验采用SP-150多功能成形试验机,试验过程中用AutoGrid网格应变自动测量分析系统实时监测板料变形过程, 4个摄像头分别位于试验机顶端,呈四边形分布监测,若拍照不全可相互拼接图像得出变形后完整图像用于分析板料FLD,记录下板料最终变形结果如图4所示。图4 4方位高速抓拍摄像图像(a)方位1 (b)方位2 (c)方位3 (d)方位4Fig． 4 Four-way high-speed capture images(a) Position 1 (b) Position 2 (c) Position 3 (d) Position4试验得到的新淬火态6061铝合金成形极限图如图5所示。2 曲线翻边零件橡皮成形及回弹补偿2． 1 曲线翻边零件橡皮成形橡皮成形是一种利用橡皮作为弹性凸模(或者图5 6061铝合金成形极限图Fig． 5 Forming limit diagram of aluminum alloy 6061凹模),另一半模具为刚性模的成形方法。根据橡皮“一步法”成形工艺的要求,从设计的盖板、模具、零件上提取相应的曲面,导入PAMSTAMP 2G软件中,划分网格并赋予相应的材料,建立橡皮与工作台。成形时,载荷作用在橡皮上,随着橡皮向下运动,包裹板料并与工作台接触,从而使板料与模具贴合,成形出合格的钣金零件。飞机的框肋零件大多为曲线翻边零件,有凸凹之分,凸翻边成形缺陷为起皱,凹翻边成形缺陷为拉裂,其共同的缺陷是回弹,为了研究凸曲线翻边,选择图6所示的典型零件来分析。图6 曲线翻边典型零件Fig． 6 Typical part of curve flange图7a、图7b、图7c和图7d分别为曲线翻边零件橡皮成形后的位移、厚度、主应力和主应变的分布情况。由图7a可知,在翻边部位1处翘曲严重,卸载后最大位移为13． 6 mm,导致翘曲的原因为卸载后残余应力释放;从图7b可以看出,在交界处,下陷端材料减薄,末端材料增厚,厚度减薄最大值为0． 08 mm,而下端厚度增大最大值为0． 05 mm;由图7c和图7d可知,在圆角位置,下陷端均受拉应力,部位4受切向压应力,出现了起皱,在部位3与4的交界处, 4与5交界处起皱明显,部位4翻边部分出现了小皱。对部位1, 2, 3进行回弹分析,结果见表4。由表4可知,随着弯曲角度的减小与64锻 压 技 术 第43卷万方数据曲率半径的增大,回弹增大,其中回弹最大值为2． 3°,最小值为1． 5°。图7 有限元模拟结果(a)位移分布 (b)厚度分布 (c)主应力分布 (d)主应变分布Fig． 7 Finite element simulation results(a) Displacement distribution (b) Thickness distribution (c) Main stress distribution (d) Main strain distribution表4 曲线翻边零件不同翻边部位的回弹Table 4 Springback of different flanging areas forcurve flanging parts参数部位1 2 3弯曲角度/ (°) 25． 7 25． 4 18． 8曲率半径/ mm 102 282 189回弹角/ (°) 2． 3 2． 1 1． 52． 2 回弹补偿采用基于理论回弹算法的二次开发回弹补偿模块对原始零件型面进行回弹补偿,进而生成补偿后的型面,用新的型面设计补偿模具,如图8所示。图8 模具回弹补偿前后的型面对比Fig．8 Comparison of profile before and after mold springback compensation采用补偿模具成形后的曲线翻边零件位移分布如图9所示,选择未起皱部位1, 2, 3,测量回弹后角度与原始角度进行对比,结果见表5。结合表4和表5可知,回弹和起皱现象已明显小于补偿之前。由表5可知,基于回弹理论算法设计的曲线翻边零件补偿模具成形后,回弹后角度偏差最小为0． 1°,所有部位偏差均在1°以内,曲线翻边零件补偿模具设计得到了良好的效果。图9 采用补偿模具成形零件的位移分布Fig． 9 Displacement distribution of part formed by compensation die表5 补偿模具后曲线翻边零件成形的回弹结果Table 5 Springback results of formed curve flanging partsafter die compensation参数部位1 2 3原翻边角/ (°) 25． 7 25． 4 18． 8回弹后/ (°) 26． 5 25． 5 19． 4差值/ (°) +0． 8 +0． 1 +0． 63 实际成形试验橡皮成形试验采用ABB公司生产的QFC 1． 4 ×74第2期张凌云等: 6061铝合金曲线翻边零件橡皮成形回弹补偿与试验验证 万方数据4-1000橡皮囊液压机,其工作效率高,使用方便,省时高效。试验过程中补偿模具和验证模具如图10所示,材料为Q235钢。图10 原始模具与补偿模具Fig． 10 Original die and compensation die采用补偿模具进行橡皮成形试验,本次试验选用板料成形专用SDL水基润滑剂,由于化学吸附的选择倾向性,在润滑剂中添加一定量的油酸钠,使微粒均匀分布,成形后零件如图11所示。发现零件成形后质量良好,无明显的回弹及起皱,且回弹后的零件满足了尺寸设计要求,达到了预期的目的。验证了补偿模具设计正确。图11 补偿后成形零件Fig． 11 Forming parts after compensation4 结论(1)对新淬火状态下6061铝合金板料进行单向拉伸及FLD试验,得出材料基本参数及成形极限,为橡皮成形材料选择及钣金零件成形提供依据。(2)采用二次开发回弹补偿模块对模具进行回弹补偿,对补偿后的模具进行有限元模拟,回弹后角度偏差最小为0． 1°,偏差均在1°范围内,曲线翻边零件补偿模具的设计具有良好的效果。(3)在数值模拟的基础上,利用实际成形试验获得合格的钣金零件,验证了数值模拟的可行性和回弹补偿方法的可靠性。参考文献:[1] 王福东,陈明和,熊杰.大曲率凸弯边零件橡皮囊液压成形工艺的数值模拟[J].机械工程材料, 2011, 35 (12): 107 -111.Wang F D, Chen M H, Xiong J. 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Research on the springback com-pensation of automotive reinforcing plate based on displacementspringback compensation principle [ J ]. Heavy Machinery,2015, (1): 49 -52.[10]陈佳,闫晓东,沈健,等.热处理工艺对6A02合金管材组织性能的影响[J].稀有金属, 2016, 40 (3): 193 -200.Chen J, Yan X D, Shen J, et al. Effect of heat treatment processon microstructure and properties of 6A02 alloy pipe [J]. Chinese84锻 压 技 术 第43卷万方数据第43卷第2期Vol． 43 No． 2FORGING 强力旋压;变薄拉深;锡青铜;筒形件; SimufactDOI: 10． 13330/j． issn． 1000-3940． 2018． 02． 010中图分类号: TG376 文献标识码: A 文章编号: 1000-3940 (2018) 02-0049-06Quality research on power spinning and ironing for cylindrical partbased on SimufactYang Feng, Fan Wenxin, Tang Chuanyao, Wang Ruirui, Kong Weijing(College of Mechanical Engineering, North University of China, Taiyuan 030051, China)Abstract: In order to get high forming quality of cylindrical part, cylindrical part forming processes of power spinning and ironing were an-alyzed by finite element numerical simulation. For tin-bronze cup part, two different forming technologies of the same blank were simulatedby software Simufact. The inner diameter expansion amount, external roundness error, straightness error of outer axis, straightness error ofinner axis and length of bell mouth of formed connecting rod bushing were regarded as evaluation indexes of forming quality, and the relia-bility of simulation was verified by test through selecting the best forming process. The results show that comparing with the power spin-ning with three rotating wheels and three times consecutive ironing of tin-bronze parts, the size accuracy of ironing process is slightly high-er than that of the power spinning process, and the bell mouth formed by the ironing process is shorter. Thus, the ironing process hashigher material utilization and is suitable for mass production of single-type connecting rod bushing.Key words: connecting rod bushing; power spinning; ironing; tin-bronze; cylindrical part; simufact连杆衬套作为连接发动机活塞销和连杆小头的收稿日期: 2017 -11 -01;修订日期: 2017 -12 -22基金项目:山西省自然科学基金资助项目(2012011023 -2)作者简介:杨 锋(1993 - ),男,硕士研究生E-mail: 122297706@ qq． com通讯作者:樊文欣(1964 - ),男,博士,教授E-mail: fanwx@ nuc． edu． cn关键零部件,它避免了活塞与连杆小头直接接触,降低连杆小端应力集中,从而有效地保护了连杆小端,因此,要求具有良好的力学性能,同时还要具有良好的表面精度与经济性。目前,连杆衬套多采用强力旋压或变薄拉深成形工艺加工,这两种成形工艺都属于无切削等体积塑性成形工艺,常用来加工一些整体无缝空心的回转体零件,且经过强力■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■Journal of Rare Metals, 2016, 40 (3): 193 -200.[11]高宏志,周贤宾.新淬火状态硬铝合金板的成形性能及数值模拟[J].航空材料学报, 2008, 28 (5): 27 -31.Gao H Z, Zhou X B. Formability and numerical simulation for as-quenched aluminum alloy sheet [J]. Journal of Aeronautical Ma-terials, 2008, 28 (5): 27 -31.[12] GB/ T 228． 1— 2010,金属材料 拉伸实验 第1部分:室温试验方法[S].GB/ T 228． 1— 2010, Tensile test of metallic materials— Part 1—Room temperature test method [S].[13] GB/ T 15825． 8— 2008,金属薄板成形性能与试验方法[S].GB/ T 15825． 8— 2008, Sheet metal forming performance and testmethods [S].[14]王峥.基于PAMSTAMP2G的板料冲压成形区域与成形性能划分的研究[D].长春:吉林大学, 2014.Wang Z. Study on the Stamping Forming Zone and Forming Per-formance Based on PAMSTAMP2G [D]. Changchun: Jilin Uni-versity, 2014.万方数据