管内液体压力对液压冲孔的影响

设计加工了管材液压冲孔试验装置,在该装置上开展了液压冲孔工艺试验.试验结果表明:液压冲孔过程中,管内液体压力越大,冲孔结束后塌陷尺寸越小,提高冲孔过程中管内液体压力,能够有效减小冲孔后的塌陷尺寸;冲孔过程中管内液体压力越大,冲孔结束后断口光亮带所占比例越高,断口质量越好;冲孔结束后的塌陷发生在一定区域内,长度对塌陷发展...     

如何强化小孔冲头

当使用细长的小冲头在抗剪强度较高、厚度较大的坯料上冲孔时,冲头承受了很大的压缩应力和弯曲应力。当冲头的长径比大于5时,在使用中就会产生种种麻烦,因此必须采用特殊的方法加以强化。 1.单件圆形冲头在下列情况下必须对小孔冲头采取强化措施: (1)冲孔直径小于0.100in; (2)板料抗剪强度较低,孔径:料厚<1.5; (3)板料抗剪强度较高,孔径;料厚<2。强化方法为:(1)加粗冲头杆部;(2)附加支承套管。首先可以采用较大直径的冲头杆部和较短的冲切部分。这类冲头常用的尺寸比例参见图     

冲压加工技巧[技巧篇]

第一章冲裁、剪切§1.1 避免塌角1.影响塌角变形的因素1)相对冲头直径的影响随着相对冲头直径的减小,被冲孔剪切断面的剪裂面及塌角部分随之减小,剪切面部分随之增加。特别是d/t<1.5时,这种现象更加显著。另一方面,废料的切口断面在 d/t=0.5的情况下急激减小。图1—1所示为冲孔废料剪切断面形状的变化曲线。所谓相对冲头直径是指冲头直径d 与被冲板厚 t 的比值 d/t。     

管材性能对液压冲孔质量的影响(英文)

通过对3种不同材料的管材液压冲孔的实验研究,分析管材材料性能对液压冲孔质量的影响。研究表明:不同材料对塌陷形成的影响不同,材料的屈服强度越高,液压冲孔后的塌陷越大。塌陷尺寸随着内压的降低而增大,在同一内压下,沿管长方向塌陷变化较慢,沿垂直管长方向塌陷变化快。不同材料对断口质量的影响不同,材料屈服强度越高,断面质量越好,材料较软时,撕裂现象更明显。     

渐进成形锥形件壁厚稳定区域影响因素的研究

基于ANSYS/LS-DYNA分析平台构建单道次渐进成形锥形件的有限元模型,利用数值模拟和实验方法研究单道次渐进成形锥形件减薄带出现后的壁厚稳定区域最大直径的影响因素.研究结果表明:壁厚稳定区域的最大直径随着成形角、锥形件口部直径的增大近似线性增大;轴向进给量和坯料厚度对壁厚稳定区域的最大直径影响较小,可以利用增加工艺余料的方法来获得壁厚均匀的锥形件.     

超塑性冲孔时金属宏观流动规律的计算机模拟

主要介绍了用上限元法(UBET)分析超塑性冲孔的基本理论与方法,并用UBET模拟了平冲头冲孔过程中金属的宏观流动,分析了变形体主要尺寸随冲头压入深度的变化和变形体原始尺寸变化对变形体初始变形的影响。     

螺杆钻具双等壁厚金属定子外高压成形方法研究

为了解决页岩气开采用螺杆钻具双等壁厚定子内螺旋曲面难加工的问题,建立双等壁厚定子的外高压成形数值模拟模型,研究管坯几何尺寸、液压力大小和回弹对定子成形质量的影响规律,通过实验和三维测量验证了数值模拟模型的准确性。结果表明：管坯几何尺寸与壁厚、等效塑性应变、位移、残余应力和间隙值成正比;成形液压力达到150 MPa及以上对等效塑性应变、壁厚几乎没有影响;定子胀型区域的回弹量大于过渡区域和接触区域;当成形液压力为210 MPa,管坯内径为88 mm,定子成形质量最优。     

基于疲劳失效的压药冲头结构参数优化研究

压药冲头疲劳损伤后会破坏均力压制,可能致使装药局部压力升高。应力的急剧升高,增加压装爆燃的概率。为提高压装的安全性,使用有限元方法研究压药冲头结构对疲劳寿命的影响,得出压药冲头止端部参数直径D、台高H以及肩部内圆角R设计与疲劳寿命相关的结论。在给出疲劳寿命随止端部几何尺寸参数的变化规律的同时,结合弹体尺寸和工艺要求,进而优化压药冲头止端部结构,提出满足疲劳寿命要求压药冲头尺寸。     

轴向加速度对单侧双排四通管内高压成形规律的影响

以单侧双排四通管为研究对象,应用有限元分析软件分析内压、平衡冲头速度和挤压冲头平均速度相同时,不同轴向加速度对单侧双排四通管内高压成形壁厚、支管高度和主管补料规律的影响。结果表明:随着挤压冲头加速度增大,最大壁厚和最小壁厚值变化较小,最大壁厚值变化略大于最小壁厚值变化;支管高度和主管端部轴向位移明显增加;挤压冲头加速度增大明显增加外侧主管补料,但是对内侧主管补料影响较小。这些规律为四通管加载路径的选择提供了参考。     

进给冲头对并列双支管成形性能的影响

采用有限元分析法与实验相结合的方式分析了五种不同进给冲头长度对内高压成形并列双支管高度与壁厚分布的影响。结果表明:随着冲头长度的增加,支管高度提高,支管顶部管壁壁厚增大,支管顶部壁厚减薄量逐渐减小。有限元分析结果与实验结果基本一致。     

Bulge forming of tubes with axial compressive force proportional to the hydraulic pressure

A device for applying an axial compressive force proportional to the internal hydraulic pressure in tube bulging was designed, constructed and tested. Using this device, copper tubes of diameter 25.4 mm were bulged. By varying the ratio of the axial compressive force to the hydraulic pressure, the largest ratio for maximum bulging was obtained. At lower values of the ratio, fracture occurred at lower circumferential expansions, whereas at higher values buckling of the tube resulted. The hydraulic pressure and the maximum strains at bursting were measured. Bulging in three stages, with interstage annealing, a circumferential expansion to a diameter of 48 mm was obtained. The maximum bulging possible in each stage was determined together with the hydraulic pressures necessary using the optimum ratio of axial load to the internal pressure. Meridional, circumferential, and thickness strains measured in each stage are presented.     

铝合金防碰撞吸能管液压成形加载路径研究

针对防碰撞吸能管成形需要,提出了对铝合金6061圆管液压胀形过程的轴向进给补偿-液压力加载路径控制过程.通过数值模拟方法,采用分析软件ABAQUS 6.10对铝合金6061管材液压胀形的加载路径进行了研究.以成形件不发生起皱、破裂两种失效方式以及最终成形壁厚分布为依据,分析了不同轴向进给和液压力加载路径对成形件质量的影...     

圆筒形件充液拉深成形精度

本文系统地研究了平底和球面圆筒形件充液拉深成形精度。充液拉深成形中，由于高压液体紧紧将毛坯贴向凸模表面，因而零件具有良好的贴模性并能获得很高的内径精度。同样，由于液压的施加在凸模圆角和压边圈之间产生与凸模运动方向相反的局部胀形，减小了凸模圆角处的弹复，提高了侧壁及球面件底部的形状冻结性。但是，平底零件的底面形状因液压的施加而使形状冻结性不好，平面度降低。     

高强度铝合金板材的温热介质充液成形研究

在温度20℃～300℃的范围内,对厚度1.2mm的7B04-T6高强度铝合金薄板在应变速率分别为0.0006s-1、0.006s-1和0.06s-1的条件下进行了单拉试验,并在此基础上利用MSC.Marc有限元软件进行了筒形件温热介质充液成形的差温热力耦合数值模拟,研究了成形温度、冲压速度和液室压力对于成形性能的影响。结果表明,在冲压速度15mm/min以及液室压力1MPa的情况下,零件的最大成形高度由常温下的20.5mm提高到了300℃时的31.6mm。     

基于MSC.MARC的TP2铜管材液压胀形数值模拟

利用有限元分析软件MSC.MARC,建立了变径铜管材模型,完成了管材液压胀形过程的模拟,对成形后的管材进行了壁厚和等效应变分析.得出了轴向进给和管内高压的较合理的匹配关系,得出了壁厚减薄率和应变的最大区域是在管材两端倒角和胀形最大区域的连接处.     

Deformation Behavior of a Thin-Walled Tube in Hydroforming with Radial Crushing Under Pulsating Hydraulic Pressure

Loading path plays a dominant role in tube hydroforming (THF), and the pulsating loading path has been reported capable of improving the formability of a tube in hydrobulging with axial feeding. As a new THF process, the tube hydroforming with radial crushing (THFRC) is receiving increasing attention; however, knowledge on the process still remains insufficient to extend its application to various other fields. In this study, the experiments of THFRC under both the pulsating and the linear hydraulic pressures were carried out to investigate the deformation behavior. The influences of the amplitude and the frequency of the pulsating hydraulic pressure on the shape precision, wall thickness, and the microstructures of the deformed parts were analyzed. Subsequently, metallographic examinations of the deformed specimens were conducted in an attempt to clarify the relationship between the microstructural evolution and deformation behavior. The mechanism of formability improvement in THFRC by the pulsating hydraulic pressure was explored from the perspective of microstructure. Compared with the linear hydraulic pressure, the pulsating hydraulic pressure could generate a higher shape precision, a more uniform wall thickness, as well as less martensites, and larger grain. The microstructural evolution induced by the pulsating loading path is supposed to contribute to the formability improvement of SUS304 stainless steel tubes.     

Factors affecting stretching limits of Aluminum sheet

The purpose of the present paper is to study methods to improve the stretching limit of metal sheet. The factors affecting the stretching limit were sheet thickness, blank diameter, blank holding pressure, and forming rate. Punch radius, die radius, and clearance between a punch and a die were retained constant. Tested materials were softened and half hardened types of aluminum sheet. The effect of lubrication was also studied. Lubricants used were a press working oil and graphite. Stretching by two types of punch shape, a spherical head punch and a truncated cone one, was tried in order to research the effect of punch shape. The half hardened aluminium, which has a larger n-value, showed the larger stretching limit. The larger thickness gave rise to the larger stretching limit. Flow characteristic of materials was poorer in larger diameter of a blank, so its stretching limit was lower. A bit lower holding pressure, which allows drawing of materials to some extent, yielded larger stretching limit than rigid holding. The forming rate did not so much affect stretching limit. Concerning the effect of lubrication, applied position of lubricants was important.     

Determination of optimal loading profiles in warm hydroforming of lightweight materials

In this study, a methodology is developed to determine proper profiles of the hydraulic pressure and the blank holder force under warm hydroforming conditions at different punch speeds. First, finite element models (2-D and 3-D) are developed and validated through comparisons with the experimental results from the literature. To determine the optimal hydraulic pressure and blank holder force profiles simultaneously, an adaptive FE analysis with fuzzy control algorithm was developed. Thinning, wrinkling, punch wall contact, die corner floating and conduction were used as criteria in the fuzzy control algorithm. The effects of the determined loading profiles are then presented in terms of thickness, strain and stress, and temperature distributions as well as success/failure of the forming process. The effect of punch speed was also investigated to reveal its impact on part formability. It was found that the optimal process conditions can be rapidly and accurately obtained with the developed adaptive FEA method coupled with fuzzy control algorithm.