MULTIPOINT BLANK HOLDER FORCE CONTROL IN HYDROFORMING OF FUEL TANK

The study of multipoint blank holder force（BHF） control is carried out for hydroforming a complicated shape motorcycle fuel tank. By finite element method （FEM） simulation, the configuration of multipoint blank holder cylinders and the setting of local BHF are optimized, and the influences of the multipoint BHF on the hydromechanical deep drawing and conventional hydroforming processes are studied. The desired fluid pressure and whole BHF are predicted for hydromechanical deep drawing process. Finally, simulation results are testified by forming experiment, and they are in agreement very well.

DETERMINATION OF BLANK HOLDER FORCE IN SHEET METAL DEEP DRAWING PROCESS

Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and wrinkle BHF curves are given. A close-loop control system is established to finish the forming process.

Effect of Variable Blank Holder Force on Rectangular Box Drawing Process of Hot-galvanized Sheet Steel

At first, a series of finite element method （FEM） simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force （VBHF） was as 1.9-2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.

WRINKLE LIMIT BLANK HOLDER FORCE MODELS IN SQUARE-BOX DEEP DRAWING WITH VARIABLE SEGMENT BLANK-HOLDERS

Constituting the reasonable control models of the wrinkle limit blank holder forces is the sticking point of the processes of the deep drawing with variable blank-holder forces, especially in the square-box forming. To begin with, a mode of segmenting flange of the square-box into eight zones is put forward according to the fact that the uniformity of flange deforming can be improved by control-ling segment blank-holders. Considering the integral influence of shear stress, a new concept, strain relaxation factor is defined. Hereby, the law of distribution of stress and stain in the deforming flange of square-box is achieved. Then based on these mechanical analysis models and the energy principle, the wrinkling flexivity functions of the straight flange and the circle flange are given, and the corresponding formulae of wrinkling limit blank-holder force in these two situations are also educed. In these processes, ply-anisotropy, strain hardening, thickness and friction are considered. In the end, a calculating example is designed to validate the rationality of the formulae of wrinkling limit blank-holder force, at the same time, the influences of the ply-anisotropy exponent and the strain hardening exponent on the wrinkle limit blank holder forces are also analyzed.

Novel algorithm for determining optimal blankholder forces in deep drawing of aluminum alloy sheet

Wrinkling and fracture are main defects in sheet metal forming of aluminum alloy sheet,which can be reduced or even eliminated by manipulating a suitable blank -holder forces (BHF). But,it is difficult to attain the optimum BHF during she et metal forming. A new optimization algorithm integrating the finite element me thod (FEM) and adaptive response surface method is presented to determinate the optimal BHFs in deep drawing of aluminum rectangular box. To assure convergence,the trust region modes management strategies are used to adjust the move limit of design spaces. Finally,the optimum results of rectangular box deep drawing a re given. Verification experiments are performed to verify the optimal result.

Blank Holder Force Control System Driven by Servo-Motor

Blank holder force (BHF) control is used to prevent wrinkles of sheet metal in deep drawing process. Based on a novel conception of BHF control technique driven by servo-motor, a new BHF device with six-bar linkage mechanism has been designed and manufactured. Whole control system of the new BHF technique was developed, and the basic structure of the hardware configuration of the system was given. Software analysis, implementation and division of the functional modules have been done. Also, the control software in data acquisition and processing module has been developed in the relevant technology of the BHF control system for the requirements of real-time, stability and accuracy. By the new BHF device combined with the hardware and the software system, the BHF can be regulated accurately variation with the predefined BHF profile in deep drawing process.

Multi-Objective Optimization of VBHF in Deep Drawing Based on the Improved QO-Jaya Algorithm

Blank holder force(BHF)is a crucial parameter in deep drawing,having close relation with the forming quality of sheet metal.However,there are different BHFs maintaining the best forming effect in different stages of deep drawing.The variable blank holder force(VBHF)varying with the drawing stage can overcome this problem at an extent.The optimization of VBHF is to determine the optimal BHF in every deep drawing stage.In this paper,a new heuristic optimization algorithm named Jaya is introduced to solve the optimization efficiently.An improved“Quasi-oppositional”strategy is added to Jaya algorithm for improving population diversity.Meanwhile,an innovated stop criterion is added for better convergence.Firstly,the quality evaluation criteria for wrinkling and tearing are built.Secondly,the Kriging models are developed to approximate and quantify the relation between VBHF and forming defects under random sampling.Finally,the optimization models are established and solved by the improved QO-Jaya algorithm.A VBHF optimization example of component with complicated shape and thin wall is studied to prove the effectiveness of the improved Jaya algorithm.The optimization results are compared with that obtained by other algorithms based on the TOPSIS method.

AZ91D镁合金筒形件拉深工艺研究

基于H1F60小松伺服压力机,采用电磁感应模内加热系统,对1 mm厚的AZ91D镁合金薄板在不同工艺参数条件下的拉深成形性能进行了研究。研究结果表明:在室温下,板料不能成形圆筒件,温度升高到100℃后,板料被成功拉深成圆筒件,板料的极限拉深比随温度先快速上升,后缓慢上升,最后下降,400℃时,极限拉深比达到最大值1.91,此温度下板料的拉深性能最好;而当压边力、冲压速度增大后,板料的拉深性能却随之降低。

基于GA-BP模型与NSGA-Ⅱ算法的冲压成形工艺参数优化方法

为了解决异形、薄壁特征零件在冲压成形过程中严重起皱、成形不足及能耗过高等问题,创新地建立了以压边力与摩擦因数为设计变量,以最大厚度、厚度减薄率和压边能耗为优化目标的GA-BP神经网络优化模型,并应用非支配排序遗传(NSGA-Ⅱ)算法求解,获得了冲压成形过程中的最优工艺参数组合。结果表明,通过有限元仿真获得了最优工艺参数组合下的最大厚度、厚度减薄率和压边能耗分别为0.269 mm、15.8%、8720 J,分别改善了0.74%、3.06%和11.32%,有效地改善了异形薄壁零件的严重起皱、成形不足及能耗过高此等问题。

基于VBHF的差厚激光拼焊圆筒件成形仿真研究

为研究变压边力对差厚拼焊板成形性能的影响,以差厚拼焊圆筒形件为例,设计2种随位置、行程不同的变压边力方案,得到了差厚激光拼焊圆筒形件的成形极限深度、焊缝移动量、破裂危险点处应变路径及焊缝两侧应变分布的变化情况.研究表明,薄、厚侧压边力的大小和分布对破裂危险点应变路径和安全裕度的影响很大,合理的变压边力分布可以调节焊缝两侧材料变形的均匀性,提高成形极限深度;通过变压边力技术可以控制薄侧破裂危险点的应变路径由拉压应变状态向双向拉伸应变状态过渡,从而调节破裂失效的位置,有效提高差厚激光拼焊圆筒件的冲压成形性能.

铝合金壳体精密成形回弹控制工艺优化

目的精确控制铝合金壳体成形回弹角度,对铝合金壳体成形工艺进行优化。方法针对影响回弹角度的多个成形工艺参数(保温成形温度、模具间隙、摩擦因数和压边力)进行单变量逐步优化研究。结果随着保温成形温度的升高,壳体回弹角度因流变应力的降低和校正力的升高而逐渐降低;随着模具间隙的增大,可变动模具的圆角半径增大,板材贴合模具程度降低,壳体回弹角度逐渐增大;随着摩擦因数的增大,板材加工的形状与模具更契合,成形后回弹的角度降低;随着压边力的增大,板材内/外表面间的应力差大大降低,回弹角度逐渐降低。结论通过多个参数的逐步优化,获得最终优化工艺参数如下:保温成形温度为310℃,摩擦因数为0.15,模具间隙为1.1 mm,压边力为12 kN,对应的回弹角度为7.027°。

Application of new VBHF optimization strategy to improve formability of automobile panels with aluminum alloy sheet

A VBHF(Variable Blank Holder Force) optimization strategy was employed to determine the optimal time-variable and spatial-variable BHF trajectories,aiming at improving the formability of automobile panels with aluminum alloy sheet.The strategy was implemented based on adaptive simulation to calculate the critical wrinkling BHF for each segmented binder of the Numisheet' 05 deck lid in a single round of simulation.The thickness comparison of the stamped part under optimal VBHF and constant BHF shows that the variance of the four sections is decreased by 70%,44%,64% and 61%,respectively,which indicates significant improvement in thickness distribution and variation control.The investigation through strain path comparison reveals the fundamental reason of formability improvement.The study proves the applicability of the new VBHF optimization strategy to complex parts with aluminum alloy sheet.

Deep drawing of 6A16 aluminum alloy for automobile body with various blank-holder forces

Based on the ABAQUS/explicit finite element method,the deep drawing of 6A16 alloy pre-aged and then storaged at room temperature for 1 week with various blank-holder forces(10,14,18 kN) was studied.The distribution and variation of stress and strain in deformation zones were investigated to drive the forming property and process of the alloy.Besides,the simulation result was verified combined with the deep drawing experiments.The results show that the stress and strain of the deformation zone have an incremental trend with the blank-holder force increasing while the deformation degree and grain size within a certain deformation zone have an obvious increase and an enlargement,respectively.After the deep drawing,the hardness of products also increases with the enhancement of blank-holder force.The blank-holder force of 18 kN is certified as the preferential one by the analysis of microstructure and simulation results.

航空发动机燃烧室帽罩变压边热成形技术

目的 提出帽罩零件真空环境变压边热成形新技术,解决航空发动机燃烧室帽罩零件冷成形回弹大、精度低、内部应力大,以及热成形壁厚不均、氧化严重等问题。方法 利用有限元仿真和工艺试验相结合的方法,选用GH3625高温合金板材研究变压边热成形过程中压边力加载路径对帽罩成形质量的影响,分析热成形模具热膨胀与回弹变形对帽罩尺寸精度的影响,建立考虑热成形、变压边力加载及模具补偿的成形方案。结果 在900℃条件下,帽罩热成形力相比室温下降低约70%,内外径回弹量分别降低约67%和59%。基于几何特征优化的压边力加载路径有助于减小零件型面的回弹。结合回弹变形和热膨胀变形补偿,确定模具总补偿量为内径-0.49mm,外径-0.62mm。工艺试验结果表明,采用模拟所确立的成形方案成形的帽罩质量较好,尺寸精度达到IT9级,型面精度在0.2 mm以内,切边后回弹量为0.1 mm,与有限元仿真结果吻合较好。结论 建立的有限元模型和变形补偿方案可以有效地优化帽罩的工艺成形过程,所提出的变压边热成形技术能够显著降低高温合金变形抗力和回弹,可以解决高精度帽罩零件成形制造难题。

后法兰盘翻孔翻边复合成形工艺研究

研究了汽车消声器后法兰盘内孔翻孔和外缘翻边采用复合模成形时的质量问题,首先利用Dynaform有限元软件分析各单一工艺参数对成形质量的影响,确定主要的影响因素,然后针对各主要因素进行正交试验设计,采用极差法分析各因素的影响顺序和显著性,以最小壁厚取值最大、内孔翻孔高度和外缘翻边高度分别满足(15.2±0.5)mm和14.2-1.0+0.5mm要求选取最优工艺参数组合。最终将选取最优工艺参数组合进行试模,获得的法兰盘最小壁厚为2.187 mm,内孔翻边高度为14.9 mm,外缘成形高度为13.8 mm,零件成形质量良好,没有出现开裂与起皱。应用基于正交试验设计方法预测和控制成形质量,减少了试模次数,降低了生产成本,为此类零件的研究提供了参考。

考虑磁场区影响的电控永磁压边方法

电控永磁压边方法具有独立加载、传动链短、节能、易于控制等优点。针对铁磁性板材成形,提出了一种新的成形区和磁场区重合的电控永磁压边方法。以圆筒形件的拉深成形为例,采用新设计的压边装置对不同压边力加载条件下的结构变形进行了磁力耦合有限元模拟,分析了板坯磁性对磁场和压边力分布的影响。由分析结果可知,新设计的压边力加载装置的刚度明显提高,新压边方法具有更好的压边效果,模具结构更紧凑。根据模拟和理论分析结果设计制作了拉深试验装置。实验结果表明,将成形区和磁场区重合的电控永磁压边方法是完全可行的。

基于变压边力的汽车翼子板冷冲压成形模拟分析

针对汽车零件冷冲压成形过程中易出现的起皱、回弹以及拉延不足等质量问题,以某品牌汽车的翼子板为例对其进行了变压边力成形分析.首先,以零件成形极限为评价目标,通过分析整体恒压边力成形确定零件的临界压边力值;其次,利用整体变压边力成形方法分析9种常用变压边力加载形式的优劣,以此确定最佳的变压边力加载形式;最后,根据拉延后板料的应变分布给出分区变压边力成形的方法,并对汽车翼子板进行分区变压边力仿真成形分析.仿真分析表明:整体变压边力成形方法能够有效降低零件的最大减薄率、最大增厚率和最大回弹量以及改善零件的成形极限;分区变压边力成形方法不仅能够有效提升零件的成形极限,而且还可减少最大减薄率和有效控制回弹量.该研究结果可为选取汽车零件的冲压成形工艺提供参考.

6061铝合金飞机溢油口拉深成形研究

目的掌握深腔薄壁溢油口拉深成形工艺,解决拉深成形过程中起皱和破裂问题,研究各参数对拉深成形的影响规律,最终成形出合格产品。方法以6061铝合金飞机溢油口为主要研究对象,采用Dynaform有限元数值模拟软件建立有限元模型,分析成对拉深成形对材料流动的影响并与单一拉深成形进行对比,通过改变毛坯外形尺寸、凹凸模间隙和压边力等参数进行拉深成形模拟试验研究,最终通过拉深成形试验验证成形方法及各参数设置的合理性。结果成对拉深成形能限制单一拉深成形圆弧开口位置材料收缩,改善开口处起皱和变形缺料的现象。随着凹凸模间隙的增大,最大减薄率逐渐降低而后升高,最佳成形凹凸模间隙为1.05t;随着压边力的增大,最大减薄率逐渐升高,最大增厚率逐渐降低,最佳成形压边力为50 kN;凹模圆角半径小于7 mm时,板料最大减薄率逐渐减小,半径为4 mm时,最大减薄率下降最快,半径在7~8 mm范围内,板料最大减薄率趋于平稳,最佳成形凹模圆角半径为7 mm。结论模拟得到了毛坯外形尺寸、凹凸模间隙和压边力等参数对拉深成形的影响规律,最终制造出了满足设计要求的产品,验证了各参数设置的合理性。

基于分区压边技术的铝合金方盒形件拉深技术研究

提出了一种适用于盒型件等非轴对称结构的径向分区压边方法,可对法兰不同径向区域独立加载压边力。首先,采用理论方法建立了法兰区皱纹模型,并推导出相对于传统压边方法,新方法只需要更小的压边力即可以抑制起皱,初步验证了径向分区压边方法的理论可行性。然后,采用有限元方法对成形效果进行了数值模拟。结果表明,径向分块压边圈对控制材料的流动更有效,可有效地抑制起皱并且提高成形极限。最后进行了板材拉深成形实验。同样施加5.9 kN的压边力,径向分区压边方法作用下的盒型件具有更好的成形效果,验证了所提出的新压边方法用于板材成形是切实可行的。

压边力对电磁钢板圆盘剪分切的影响研究

实验选用0.50 mm厚的电磁钢板进行圆盘剪分切加工,从板材剪切断面形貌、边缘加工硬化及剪切力三个方面研究了压边力的影响,以深入理解圆盘剪分切塑性变形及断裂机理。实验结果表明,压边力对电磁钢板剪切断面特征、加工硬化程度及剪切力大小有直接影响。采用Deform-2D有限元软件进行了剪切过程等效应变的仿真,模拟结果也证实了压边力对板材变形的影响。在此基础上,建立了板材在分切过程的力学模型,探讨了压边力的作用机理。