AZ31B镁合金板材快速气压胀形行为

对板厚1.0 mm的细晶AZ31B镁合金板材进行快速气压胀形研究,在300~400℃的温度范围内进行了各种气压下300 s的快速气压胀形试验,研究温度和气压对AZ31B板材快速气压胀形能力的影响。结果表明:在不同温度下,胀形高度均随着气压的升高而增大,但气压升高到一定程度时,胀形时间不到300 s即产生破裂;胀形高度在胀形温度400℃时出现峰值为45 mm。在400℃和0.6 MPa条件下,胀形5 min时相对胀形高度达到1.13。胀形件壁厚分布不均匀,温度越高,壁厚分布不均匀度越高。最后,研究了不同温度下快速气压胀形时胀形件微观组织的演变规律。     

半球形件粘性压力成形的实验研究

本文对半球形件的粘性介质胀形进行了实验研究。充分利用实验设备的特点 ,分析了背压、介质排放口等粘性压力成形中的工艺参数对板材成形性能的影响。实验结果表明 ,粘性压力成形中背压及介质排放口分布的变化可以引起模腔中介质压力场的变化 ,在板材表面形成不同的压力分布 ,进而改变了板料的流动模式及应力状态 ,选取合适的背压及介质排放口的分布可以改善板材的成形性能     

Ti-22Al-25Nb合金板材气压胀形实验及数值模拟

通过气压胀形实验和数值模拟研究了Ti-22Al-25Nb合金板材在高温下的热成形行为,并分析了在930和970℃下的胀形球壳形状和壁厚分布,讨论了胀形部分的微观结构和力学性能。结果表明,在胀形初期,胀形球壳接近球面,随胀形高度的增加逐渐椭球化。在930和970℃下,最终胀形高度分别达到46.25和49.85 mm,壳顶的曲率半径分别达到49.33和49.19 mm。胀形部分壁厚不均匀,从底部至顶部逐渐减小。变形温度对球壳形状影响较大,在930℃时胀形局部形状更加不均。在相同的胀形高度下,930℃下的胀形球壳曲率半径较小且壁厚减薄率较高。此外,在930℃胀形过程中,O相析出并球化,导致O型、V型空洞的产生且硬度下降。而在970℃胀形后,微观组织分布均匀,O相在冷却过程中以层片形式析出,强化了胀形件。     

AZ31镁合金板材超塑性气胀成形研究

研究了AZ31镁合金板材不同工艺条件下的气胀成形性能。实验表明,胀形高度随温度的升高而增大,且应变速率敏感指数值均大于0．3。在673 K,0．7 MPa下胀形25 min所得的胀形件胀形高度达23．34 mm,高径比为0．67。由金相及SEM电镜观察可知,在胀形件的顶端晶界处聚集了大量空洞。通过动态再结晶,晶粒得到了很大细化。并且随变形程度的增大,晶粒细化更明显。AZ31镁合金板材的超塑性胀形主要由晶界滑移控制,动态再结晶则为重要的辅助机制。     

AZ31镁合金板材超塑性气胀成形研究

研究了AZ31镁合金板材不同工艺条件下的气胀成形性能。实验表明，胀形高度随温度的升高而增大，且应变速率敏感指数值均大于0.3。在673K,0．7MPa下胀形25min所得的胀形件胀形高度达23．34mm，高径比为0．67。由金相及SEM电镜观察可知，在胀形件的顶端晶界处聚集了大量空洞。通过动态再结晶，晶粒得到了很大细化。并且随变形程度的增大，晶粒细化更明显。AZ31镁合金板材的超塑性胀形主要由晶界滑移控制，动态再结晶则为重要的辅助机制。     

LZ91镁锂合金板材的超塑性气胀成形研究

本文利用热拉伸实验、气胀成形实验、金相分析和扫描电镜观察,研究LZ91镁锂合金板材的超塑性、气胀成形性能及其组织结构。结果表明:在热拉伸变形温度为573 K、应变速率为0.001 s-1时,其伸长率可达343.7 %,应变速率敏感指数为0.697,轧制态的LZ91合金板材表现出优良的超塑性;在胀形温度573 K,胀形气压0.06 MPa条件下,板材成形高度为51.14 mm,高径比达1.279,说明该镁锂合金板材具有良好的超塑性成形潜力;在热拉伸变形和超塑性气胀成形过程中,均有动态再结晶现象产生,可有效提高该合金的塑性成形能力;在拉伸断口和胀形件破裂处断口均存在典型的超塑性空洞形貌特征,说明两者的主要变形机制均为晶界滑移,且合金超塑性失效的主要原因是空洞的长大和连接。     

5A06铝合金板材热态快速气压胀形的变形形为(英文)

通过热态气压胀形实验测试5A06铝合金板材在不同温度、保压时间和气压下的成形性能。测量不同成形条件下(温度:325~500°C;压力2.5,4.0MPa;保压时间:8~120s)圆底杯形件的轮廓、圆角半径和壁厚分布,分析各因素对板材热态气压胀形行为的影响。结果表明:温度越高,压力越大,保压时间越长,板材贴靠模具程度越大。圆底杯形件圆角半径最小仅为2.0mm。最小壁厚值出现在圆角与底部过渡区域。在400~500°C温度范围内,提高气体压力可以缩短保压时间,实现板材的快速气压成形。     

AZ91D镁合金板材的快速气压胀形行为研究

对板厚1.0mm、晶粒尺寸6.0μm的细晶AZ91D镁合金板材进行了快速气压胀形行为的研究.在250～400℃的温度内进行了各种气压的300 s的半球件快速气压胀形试验,研究温度和气压对快速气压胀形能力的影响.试验结果表明,在400℃、0.5 MPa气压下可以得到最大胀形高度为33.0mm的半球件.以上述结果为基础,进行了300 s的筒形件快速气压胀形试验,采用两阶段加载快速气压胀形出了20 mm高而且表面质量好、圆角半径符合要求的筒形件.对胀形件不同位置取样进行金相观察,变形量越大,晶粒越细小.     

关键参数对薄壁筒形件充液成形的影响规律

为了研究初始反胀高度(IRBH)、反胀压力(IRBP)和液室压力加载路径3个工艺参数对板料充液成形的影响规律,以不锈钢321材料为研究对象,进行板材充液成形工艺过程的分析。首先,利用数值模拟的方法,在有初始反胀(IRB)的充液成形基础上,研究了初始反胀高度与初始反胀压力的组合形式以及液室压力加载路径对制件成形的影响规律,然后分别研究了有无初始反胀的充液成形过程。最后,通过实验的方法进行验证。结果表明:当初始反胀高度为3.75 mm、初始反胀压力为2 MPa时,充液结束时板料的最大减薄率为4.803%,在所有结果中最小;无初始反胀时,零件壁厚最大减薄率为5%;当在充液拉深后期继续加大液室压力时,板料底部发生波动,出现二次变形,与此同时,板料最大减薄率增大。从而验证了合适的初始反胀高度和反胀压力可以减小制件壁厚的最大减薄率,液室压力加载路径不同,零件的壁厚分布也不同。     

汽车桥壳胀—压复合成形工艺预制坯胀形模拟研究

以某型汽车桥壳为例,结合汽车桥壳胀—压复合成形工艺预制坯的设计方法,确定了预制坯形状与尺寸。根据预制坯的设计尺寸,确定采用两次胀形工艺与有益褶皱相结合的方式进行胀形。通过ABAQUS有限元模拟软件模拟了预制坯两次胀形过程中不同加载曲线对胀形件成形质量的影响,其中:一次胀形3种加载曲线最大胀形压强分别为10MPa、20MPa、30MPa;二次胀形3种加载曲线最大胀形压强分别为10MPa、20MPa、30MPa,分析了理想胀形件的壁厚分布情况。模拟分析表明:通过一次胀形加载曲线2可得到理想有益褶皱,进而增压得到成形质量较好的一次胀形管坯;通过二次胀形加载曲线2最终得壁厚减薄小且所需进给力小的理想预制坯。理想预制坯的壁厚最大减薄为20%,最大增厚为50%,满足汽车桥壳胀—压复合成形工艺压制过程的需要。     

Research on sheet-metal flexible-die forming using a magnetorheological fluid

Related studies showed that viscosity has a great effect on the formability of sheet metal in viscous pressure forming. However, the viscosity of viscous medium keeps constant in VPF. In this paper, a new flexible-die forming method for sheet metal using magnetorheological (MR) fluids, magnetorheological pressure forming (MRPF), is proposed, which enables the viscosity of flexible-die medium adjustable by changing the magnetic fields during the forming process. Squeezing tests of MR fluid show that its rheological behavior can be changed greatly under different magnetic fields. Magnetorheological pressure bulging tests of Al1060 sheet are conducted on the self-designed experimental apparatus. Experimental results show that MR fluids can be used effectively as a flexible-die medium to form the parts and its rheological behavior can be adjusted during bulging process. Variation of MR fluid's rheological behavior can lead to different forming pressure load paths and have an effect on sheet metal formability. For the same piston stroke of 8.0 mm, when the magnetic flux density is 0.180 T and 0.318 T, average dome height of bulging specimen is 8.71 mm and 10.61 mm, respectively. The value increases significantly by 21.8%. At the same time, the maximum thickness strain increases from −9.2% to −23.0%.     

镁合金板材正反向快速气压胀形实验

采用两种不同轮廓的反向预成形模具进行高应变速率气压胀形实验,结果表明,内外凹圆弧预成形模的成形效果好于半圆弧预成形模,反向胀形的时间可控制在10s,表面和微观组织均无明显缺陷。利用上述预成形模进行半球件正反向气压自由胀形实验,研究正反向胀形的效果,正反向胀形可以显著提高AZ31B镁合金板料的成形能力,使胀形件高径比从0.344提高到0.522,并使壁厚均匀度从19.4%提高到半圆弧预成形模具的32.3%,内外凹圆弧预成形模具的45.5%。在400℃温度下胀形300s,可以成形出高径比为0.522的完好半球件。     

Bulging in incremental sheet forming of cold bonded multi-layered Cu clad sheet: Influence of forming conditions and bending

Bulge is a defect that causes geometrical inaccuracy and premature failure in the innovative incremental sheet forming (ISF) process. This study has two-fold objectives: (1) knowing the bulging behavior of a Cu clad tri-layered steel sheet as a function of forming conditions, and (2) analyzing the bending effect on bulging in an attempt to identify the associated mechanism. A series of ISF tests and bending analysis are performed to realize these objectives. From the cause-effect analysis, it is found that bulge formation in the layered sheet is sensitive to forming conditions in a way that bulging can be minimized utilizing annealed material and performing ISF with larger tool diameter and step size. The bending under tension analysis reveals that the formation of bulge is an outgrowth of bending moment that the forming tool applies on the sheet during ISF. Furthermore, the magnitude of bending moment depending upon the forming conditions varies from 0.046 to 10.24 N·m/m and causes a corresponding change in the mean bulge height from 0.07 to 0.91 mm. The bending moment governs bulging in layered sheet through a linear law. These findings lead to a conclusion that the bulge defect can be overcome by controlling the bending moment and the formula proposed can be helpful in this regards.     

Effects of process parameters on warm and electromagnetic hybrid forming of magnesium alloy sheets

As the lightest structural metal, magnesium (Mg) is attracting increasing interest from both the industrial and academic fields. Magnesium alloy parts are mainly processed by die casting due to their poor sheet formability at room temperature. Warm forming is a popular method of forming; Mg alloy sheets produced in this manner show excellent formability around 200-400 °C. Electromagnetic forming (EMF) can improve the formability of metal sheets without the need for lubricants. In this paper, a new approach, called warm and electromagnetic hybrid forming (WEMF), is presented. The effects of voltage, capacity, and temperature on the bulging height of Mg alloy sheets are investigated. Results show that the bulging height of Mg sheets increases with moderate discharging energies. Enhancing the discharging voltage is also a more efficient method for increasing bulging height compared to simply increasing the capacity. When the discharging energy is kept constant, the bulging height first decreases (<150 °C) and then increases (>150 °C) from room temperature to 230 °C. The formability of Mg alloy sheets improves with increasing temperature, while the forming efficiency of WEMF decreases under similar conditions.     

Cavitation behavior in superplastic 5083 Al alloy during multiaxial gas blow forming with lubrication

Despite its importance for industrial applications, the effect of lubrication on the cavitation behavior of superplastic materials has been given little attention. In this paper, a series of experiments were performed regarding bulging superplastic 5083 Al alloy sheet into dies with a cylindrical (cup) and rectangular (pan) die cavity for forming with and without lubrication, the formed parts were then evaluated to determine the effect of lubrication on the cavitation level evolution, thickness distribution, and void distribution. It was found that void shrinkage took place in the overlaid region for both forming with and without lubrication. The maximum void volume fraction could be effectively reduced for forming with lubrication; however, reductions in the maximum void volume fractions for cup forming were less significant than those for pan forming.     

TA2纯钛板的成形极限

为了探究TA2纯钛板的成形极限,通过电化学腐蚀方法印制网格,在室温下使用BCS-50AR板材试验机分别对厚度为0.5和0.8 mm的TA2纯钛板进行了Nakizima胀形试验.通过网格分析系统采集网格的畸变,获得材料的主、次应变,并绘制了TA2纯钛板在室温下的成形极限图.根据单位体积塑性功相等的原理改进了Hill48屈...     

DC04钢板胀形-渐进复合成形锥形件成形能力的实验研究

为了提高渐进成形过程中板料的成形极限和加工效率,提出了胀形-渐进成形的复合成形方法,通过胀形-渐进成形复合成形锥形件实验,研究了DC04钢板胀形-渐进成形复合成形锥形件和纯渐进成形锥形件的成形极限角和应变变化以及壁厚分布规律。结果表明:预成形高度为h=15 mm和h=25 mm时,复合成形零件的成形极限角分别为α极=66°和α极=69°;采用胀形-渐进成形复合成形锥形件,当胀形的最大减薄量发生在局部渐进成形区内,并且胀形和渐进成形的最大减薄量位置方向相反时,锥形件壁厚趋于均匀,提高了胀形-渐进成形的复合成形能力。     

粘性介质反向压力胀形对5A02铝合金板成形性的影响

粘性介质压力成形(ViscousPressureForming,VPF)是一种适合于难变形材料板金零件制造的软模成形工艺。采用粘性介质胀形实验研究了反向压力对5A02铝合金板料成形性能的影响,结果表明在一定范围内的反向压力有利于抑制板料的平面各向异性,而在更高的反向压力条件下板料具有更好的成形性。