Finite element modeling and experimental results of brass elliptic cups using a new deep drawing process through conical dies

This paper introduces a new technique for deep drawing of elliptic cups through a conical die without blank holder or draw beads. In this technique an elliptic-cup is produced by pushing a circular blank using a flat-headed elliptic punch through a conical die with an elliptic aperture in a single stroke. A 3D parametric finite element (FE) model was built using the commercial FE-package ANSYS/APDL. Effects of die and punch geometry including, half-cone angle, die fillet radius, die aperture length and punch fillet radius on limiting drawing ratio (LDR), drawing load and thickness strain of the cup have been investigated numerically for optimal process design. A die with half cone angle of 18° has shown the best drawability for the new technique. An experimental set-up has been designed, manufactured, and used for experimental production of elliptical shaped sheet-metal cups. A total of seven punches having aspect ratios ranging from 2 to 2.25 and a die with an aspect ratio of 2 have been manufactured and used. Tensile tests were carried out to obtain the stress–strain behavior for the formed sheet metal. Experiments were conducted on blanks of brass (CuZn33) with initial thicknesses of 1.5, 1.9, 2.4 and 3 mm at different clearance ratios (c/t). Effects of blank thickness and clearance ratio on limiting drawing ratio, drawing load and thickness strain were numerically and experimentally investigated. Finite element model results showed good agreement with experimental results. An elliptic cup with a limiting drawing ratio (LDR) of 2.28 has been successfully achieved using the proposed technique and set-up.     

Finite element simulation on the deep drawing of titanium thin-walled surface part

The deep drawing of titanium thin-walled surface part was simulated based on a self-developed three-dimensional finite element model. After an investigation on forming rules, a virtual orthogonal experimental design was adopted to determine the significance of processing parameters, such as die radius, blank holder force, and friction coefficient, on the forming process. The distributions of thickness and equivalent plastic strain of the drawn part were evaluated. The results show that die radius has a relative major influence on the deep drawing process, followed by friction coefficient and blank holder force.     

工艺参数对TA0半球件冷拉深成形的影响规律

以TA0薄壁半球形零件冷拉深成形为研究对象,采用数值模拟与试验研究相结合的手段,在研究该拉伸成形过程中零件的应变及壁厚分布规律及组织演变规律的基础上,对破裂、起皱缺陷位置进行了预测。同时,采用正交试验分析方法,研究了单位压边力、摩擦系数、凹模圆角半径和凸凹模间隙等工艺参数,对该拉深成形过程的影响规律。结果表明,单位压边力、摩擦系数、凹模圆角半径对拉深过程均有显著影响,其中贡献率分别为凹模圆角半径41.04%,摩擦系数30.27%,压边力24.68%。     

Numerical simulation and analysis on the deep drawing of LPG bottles

Deep drawing is one of the most used sheet metal forming processes in the production of automotive components, LPG bottles and household goods, among others. The formability of a blank depends on the process parameters such as blank holder force, lubrication, punch and die radii, die-punch clearance, in addition to material properties and thickness of the sheet metal. This paper presents a numerical study made on the deep drawing of LPG bottles. In particular, the application of both variable blank holder forces and contact friction conditions at specific location during deep drawing are considered. The numerical simulations were carried out with DD3IMP FE code. A variable blank holder force strategy was applied and the numerical results were compared with results from other blank holder force schemes. It is evident that the proposed variable blank holder force scheme reduces the blank thinning when compared to other schemes; the friction coefficient also has a significant influence on the stress–strain distribution.     

可控变压边力的盒形件拉深模具设计

压边结构及压边力对板料拉深成形质量有着重要影响。由于盒形件成形时具有应力分布不均匀、变形分布不均匀以及变形速度不均匀的特点，拉深模具压边结构采用了分区方式，将压边圈分为直边部分和圆角部分，各部分可以协调运动。拉深过程中压边力通过控制系统可以随拉深起皱规律而合理变化，有效地改善法兰区变形的不均匀性，提高盒形件的成形质量。     

板料拉深变压边力系统

结合型号为HHP28-120双动薄板拉深液压机的现状，对原有下顶出缸的液压油路控制系统进行一系列改进，采用高精度比例溢流阀控制下顶出缸的压力和高精度传感器采集顶出缸油压。使原有下顶出缸在工控机控制下能够提供可控变化的压边力大小，进一步结合可实时测量真实压边力大小和摩擦系数的探针式传感器，以不同的变化率变化该处的压边力大小，最后通过分析研究变压边力对不同拉深成形性能评估参数的影响显著性，来判断最优变压边力的加载模式。     

制动毂挡尘盖拉深成形过程的应力应变分析

在大型CAD软件Pro/E中建立了汽车车轴制动毂挡尘盖拉深成形的凸凹模模型,运用大型商用有限元软件MSC.Marc,对其拉深成形过程进行了数值模拟.分析金属材料在拉深时的流动情况及挡尘盖在拉深后的应力应变分布规律,重点研究了压边力和凸凹模间隙对板材成形性能的影响,分析了起皱和破裂产生的原因、特点、影响因素以及预防措施等.模拟及试验结果表明,工件在拉深时,凸缘部分材料易产生失稳起皱现象;凸、凹模之间的间隙是影响盒形部分产生破裂的主要原因.当刚性压边圈与凹模之间的间隙减小到1.2倍的料厚时,能获得表面质量光滑的合格件;当凸凹模及浮动凸凹模之间的间隙大于料厚时,能确保拉深过程顺利进行.     

基于神经网络的拉深力智能化预测系统

结合塑和学理论、正交试验法及神经网络技术建立了精确计算形件拉深力的智能化预测系统。根据Ｈｉｌｌ的各向异性理论导出了新的计算杯形件拉深过程中拉深力变化的理论公式,并坟出了最大拉深力,应用正交试验法分析了各工艺参数对最大拉深力的影响。针 对在应用ＢＰ网络时遇到的两个关键问题进行了讨论并提出了解决方案。应用人工神经网络技术把理论公式与试验数据结合在一起建立了智能化预测系统。     

基于载荷下降法的双相钢DP590拉深减薄率研究

采用载荷下降法研究了双相钢DP590在不同压边力下拉深成形的减薄率。采用BCS-50AR通用板材成形性试验机进行有无润滑条件的对比拉深试验,获得成形力-凸模位移关系曲线。试验结果发现,拉深件凸缘部位和凹模圆角处的润滑有利于拉深成形,而无润滑条件下的拉深容易破裂。拉深件凸缘部位增厚,凹模圆角处和筒壁部位均有不同程度的减薄。危险断面处的减薄率最大,破裂情况下的最小减薄率为28.6%,无破裂情况下的最大减薄率为19.3%,达到实际生产要求。     

Prediction of limiting drawing ratio considering the effective parameters of die arc region

In this paper an improved analytical method for estimating the limiting drawing ratio (LDR) for the first drawing stage is presented. In this method, the effects of parameters such as the geometry and the material properties of die arc region are taken into account for a more accurate determination of LDR. The results are compared to experiments and some other analytical methods reported in the literature. It is shown that the presented method is in good agreement with the experimental results and more accurate compared with other analytical methods. Using the presented method, the effect of some process parameters such as, coefficient of friction, strain hardening exponent, normal plastic anisotropy ratio, ratio of die arc radius to blank thickness and ratio of blank thickness to diameter on LDR is investigated.     

铝锂合金的温热拉深成形性能

在数值模拟研究压边力、毛料直径、凸凹模圆角半径、变形温度等对5A90铝锂合金板材拉深成形影响的基础上,采用正交试验设计方法对拉深成形工艺参数进行优化设计,并进行相应的拉深成形试验。研究表明,变形温度对拉深成形影响最显著,其次是毛料大小的影响,而变形速度和压边力的大小对拉深成形影响较小。通过对试验结果的计算、分析和总结,获得了5A90铝锂合金板材拉深成形的最佳工艺参数组合,在最佳工艺参数条件下,铝锂合金的极限拉深系数达到了0.45。     

Experimental and numerical investigation on micro deep drawing process of stainless steel 304 foil using flexible tools

Flexible forming technology provides significant application potential in various areas of manufacturing, particularly at a miniaturized level. Simplicity, versatility of process and feasibility of prototyping makes forming techniques by using flexible tools suitable for micro sheet metal forming. This paper reports the results of FE simulation and experimental research on micro deep drawing processes of stainless steel 304 sheets utilising a flexible die. The study presents a novel technique in which an initial gap (positive or negative) is adopted between an adjustment ring and a blank holder employed in the developed forming system. The blank holder is moveable part and supported by a particular spring that provides the required holding force. The forming parameters (anisotropy of SS 304 material, initial gap, friction conditions at various contact interfaces and initial sheet thickness) related with the forming process are in details investigated. The FE models are built using the commercial code Abaqus/Standard. The numerical predictions reveal the capability of the proposed technique on producing micro metallic cups with high quality and large aspect ratio. To verify these results, number of micro deep drawing experiments is conducted using a special set up developed for this purpose. As providing a fundamental understanding is required for the commercial development of this novel forming technique, hence the optimization of the initial gap in accordance with each sheet thickness, thickness distribution and punch force/stroke relationship are detected.     

汽车座椅外侧板单动拉延成形工艺分析及优化

以某型号汽车座椅外侧板为例,采用Auto Form软件对座椅外侧板拉延成形过程进行模拟分析,并根据分析结果预测出拉延过程中的拉裂风险。通过调整零件的圆角半径和修改局部结构,消除了开裂风险,降低了最大减薄率。为取得更好的成形效果,选取压边力、摩擦系数、冲压速度、凸凹模间隙4个重要成形工艺参数进行正交试验及参数优化,得出最优工艺方案为:压边力250 k N、摩擦系数0.13、冲压速度1000 mm·s-1和凸凹模间隙2.42 mm,最终零件的最大减薄率为24.33%,最大增厚率为6.54%。采用优化后方案进行实际拉深试模,得出零件的成形性能与有限元模拟结果一致,工件质量完全符合设计要求。     

A developed process for deep drawing of metal foil square cups

Deep drawing of non-axisymmetric cross-section cups from thin sheets or metal foils has become increasingly important, especially for miniaturization of mechanical components. However, with a thin sheet thickness, conventional deep drawing processes are not able to offer reasonable drawing ratios due to early formations of localized wrinkling and fractures at cup corners. In this paper, a friction aided deep drawing process has been developed to increase the deep drawability of thin sheets and metal foils. Productions of square cups have been chosen to verify the current proposed process since the shape provides recognizable non-homogeneous deformation, which can then be compared to conventional processes. In the proposed process, a circular blank holder of a square hole is divided into eight identical segments of 45°. During the deep drawing process, four of the eight segments will move radially inward while the other four segments will move radially outwards cyclically under a pre-determined blank holding pressure. A finite element model of the technique was used to simulate virtual experiments to evaluate and optimize the controlling parameters that influence the cup height and forming process. Taguchi and Pareto ANOVA statistical methods were subsequently used to determine the optimum conditions for best cup height. The results have shown that the new technique is capable of producing deep square cups from soft aluminum sheet (Al-O) of 0.5 mm thickness with a high drawing ratio of 3.3. In addition, it was also observed that the radial displacement was the most significant parameter in influencing the cup height.     

Enhancing formability in hydromechanical deep drawing process adding a shallow drawbead to the blank holder

In this paper, a new method was proposed in order to enhance the limiting drawing ratio (LDR) of AA5754-O in the hydromechanical deep drawing process (HDD). In the proposed method, a shallow drawbead was added to the blank holder to increase LDR so as to provide strain hardening of a large region on the flange of the sheet material in addition to pre-bulging process which affects particularly only the initial stage but not the later ongoing process. So the LDR of the AA5754-O was increased from 2.65 to 2.787 by enlarging the region of strain hardening in the flange and partially reducing wrinkling tendency due to occurred tensile stresses using the convenient pressure and blank holder force profiles. The importance levels and their convenient values for height of drawbead, pre-bulge height and pressure, surface roughness of the punch were determined with analysis of variance (ANOVA) is a statistical method. ANOVA analysis illustrated that adding a shallow drawbead to the blank holder is the most effective factor between the investigated factors for the HDD process. While the effects of the pre-bulging pressure and pre-bulging height were determined as quite small, the surface roughness of the punch was found unimportant compared to the effect of the shallow drawbead. The highest LDR value was obtained with 1 mm drawbead height, 5 mm pre-bulging height, 10 MPa pre-bulging pressure and 2.8 μm surface roughness of the punch.     

板材拉深成形过程中摩擦条件与压边力设定关系研究

利用“板料拉深成形摩擦系数测试系统”,研究不同种类的润滑剂在不同压边力值设定条件下,拉深过程中的摩擦系数与压边力、拉深力与压边力之间的关系。从两种实验用坯料物理模拟的结果得知：实验用的油基润滑剂其粘度值越大,拉深性能越好,受压边力数值设定的影响也越小;坯料尺寸的增加使拉深成形变得困难,但对摩擦系数的影响很小。该研究结果有助于生产现场中润滑剂的选用和最佳压边力数值的确定。     

AZ31镁合金铸轧板材热拉深工艺研究

用拉伸试验机测试了AZ31镁合金铸轧板材的高温力学性能和直角弯曲性能,并对镁合金铸轧板材进行了热拉深试验,研究了拉深温度、拉深速率、压边间隙、润滑方式等工艺参数对板材成形性能的影响。试验结果表明,AZ31镁合金铸轧板材适合于200℃以上拉深,且最小弯曲半径小于4mm,最佳拉深工艺条件为,拉深温度225℃～275℃,拉深速率50mm/min～100mm/min,压边间隙1.125t～1.15t,采用固体润滑剂PTFE,可以得到最大极限拉深比为2.95。     

Cold Deep Drawing of Commercial Magnesium Alloy Sheets

A cold deep drawing process for commercial AZ31 magnesium alloy sheets was developed. The commercial sheets were successfully formed into circular cups at room temperature by optimising the annealing temperature of the sheets, i.e. a limiting drawing ratio of 1.75 was attained for an annealing temperature of 500 °C. The increases in elongation, n-value and r-value, and the decrease in flow stress effective in the improvement of drawability were obtained for the annealing. The apparatus for cold deep drawing without heating becomes much simpler than that for the conventional warm deep drawing. The effects of the lubricant, the clearance between the die and the punch and the corner radius of the punch on the drawability were examined. The limiting drawing ratio was increased by applying force onto the edge of a blank through the die corner. In addition, cold deep drawing of magnesium alloy square cups was performed. It was found that comparatively shallow magnesium alloy cups are satisfactorily formed at room temperature without heating.     

基于压边力控制方盒形件拉深成形的数值模拟

板料拉深成形的起皱和破裂是拉深成形工件常出现的主要成形缺陷。通过压边圈对板料施加一定的压边力是控制板料塑性流动的有效方法。利用有限元数值模拟方法,在整体压边圈方式、不同的恒定压边力及变压边力加载模式下模拟方盒形件拉深成形材料流动情况。从模拟结果看出:在变压边力加载下,方盒形件拉深成形结果比恒定压边力下的理想。通过压边圈对板料施加变压边力是控制板料塑性流动的一种有效方法,可以抑制板料起皱和延缓破裂以及提高拉深件成形性能。     

大型板材拉深成形的磨擦特征

利用探针法探讨了St14钢板在拉深过程中凸缘处理的摩擦与润滑规律,根据实验结果分析了拉深成形过程中的摩擦特征,结果表明,随着压边力的增加,摩擦系数基本保持恒定：拉深坯料尺寸增加,拉深力将增加,加入粘度较小的润滑油可以在较小拉深力和压边力的工艺条件下完成拉深成形。