TA1板料数控渐进成形时摩擦与润滑的研究

为研究TA1板料数控渐进成形时的摩擦与润滑机理,提出了黏着摩擦、边界摩擦和流体润滑摩擦三分区原则。为了提高TA1板料数控渐进成形的表面质量,选用硬度足够的高速钢成形工具头;使用质量比为4∶1的MoS2与凡士林混合物作为润滑剂;在纯钛板表面用微弧氧化工艺覆盖氧化膜。实验结果表明：经过处理后的成形工具头和纯钛板料涂覆润滑剂后,加工出的零件表面光滑,表面粗糙度达到0.92μm。     

润滑对板料胀形和拉深性能的影响

胀形和拉深是板料成形中重要的工序,摩擦状况直接关系到成形效果.在胀形和拉深实验中其他条件不变的情况下,通过采用6种不同的润滑剂、液压成形和无润滑剂,对同样形状的板料进行胀形和拉深实验,比较润滑剂对钢和铝板料成形性能的影响.实验结果表明:在板料成形中,干润滑剂润滑效果好于湿润滑剂润滑效果;润滑剂对钢和铝板两组试件成形性能的影响基本一致,并对结果进行了分析.     

纳米石墨颗粒在矩形件拉深成形过程中的摩擦特性研究

以石墨颗粒作为固体润滑剂及液体润滑剂的添加剂,在不同的润滑状态下进行了板料拉深成形物理试验,运用探针测试技术实时测试了矩形件的不同变形部位在拉深成形过程中所产牛的摩擦冈数大小及分布状况,评估纳米石墨颗粒作为润滑添加剂在矩形件拉深成形中的实际摩擦特性及润滑效果.研究表明纳米石墨颗粒作为润滑添加剂对板料拉深成形性能的影响显著.     

B1500HS硼钢800℃冲压界面粉末润滑特性研究

高强钢热冲压成形件由于其高比强度广泛应用于汽车零部件制造,但高温冲压成形界面的摩擦磨损非常严重,对产品质量有着重要影响。以石墨、氮化硼粉末为固体润滑剂,在800℃高温下对硼钢B1500HS进行了冲压成形实验,结合干摩擦和润滑条件下的成形件表面宏微观形貌的对比分析,对热冲压界面粉末润滑机制进行了研究。结果表明:使用这两种润滑剂均可以有效地提高B1500HS钢成形件表面质量,冲压后润滑膜会均匀或离散地附着于成行件表面;六方氮化硼润滑效果较石墨更高效,并在一定程度上抑制热冲压件表面的氧化;热作模具的加载作用会使粉末润滑层产生滑移,润滑膜延展,从而提高成形件表面质量。     

板料渐进成形件表面质量的影响因素分析

表面质量控制是板料渐进成形领域的热点研究内容。以典型锥形零件为研究对象,推导不同残余波峰区域形状时残余波峰高度和垂直进给量的转化关系式,提出渐进成形工具对板料的接触频次与残余波峰高度、成形角和工具半径之间关系的数学模型,以此评价成形工具对板料的研磨效应。通过不同的预设残余波峰高度、原始板料表面粗糙度和摩擦类型,对倒锥形零件成形开展全因子试验,分析成形零件表面轮廓曲线与粗糙度值,揭示不同因素对表面质量的影响程度和机理。试验结果表明,在不同轨迹间距条件下,影响渐进成形件表面质量的主要因素是犁沟效应和研磨效应,采用滚动摩擦的方式可以有效地降低该效应。     

一种新型摩擦材料在水润滑下的摩擦学性能研究

采用环块式摩擦磨损实验研究了一种新型摩擦材料在水润滑状态下不同载荷与转速对试样摩擦学性能的影响,并对比干摩擦条件下的摩擦学性能变化,借助磨损表面形貌观察分析其磨损机理。实验结果表明:水润滑条件下,摩擦系数随着载荷的增大而减小,随着转速的提高先增加后减小;磨损率随着载荷与转速的提高都减小。相同载荷与转速下,干摩擦时磨损机理以磨粒磨损和黏着磨损为主,而水润滑条件下水形成边界润滑,磨损机理以磨粒磨损和轻微的黏着磨损为主;水润滑条件下摩擦系数和磨损率均低于干摩擦,主要是由于水起到了润滑和冷却的作用,阻止了转移膜的形成,并在材料表面形成水膜起到了边界润滑的作用。     

金属加工中的摩擦化学反应与节能润滑技术

论述了金属加工中的表面摩擦化学反应、润滑剂浓度和反应活性与腐蚀磨损的关系及其边界极压润滑效果。提出了金属切削加工和成形加工中的一些节能润滑技术。     

数控渐进成形中摩擦致热分析

为了进一步认识数控渐进成形提高板料可成形性的机理,使用Abaqus有限元分析软件,以冷轧板为对象,在分析成形过程中能量转换的基础上,探讨了板料发生的摩擦致热机理.研究发现:塑性变形和摩擦导致的耗散能都会使板料在成形过程中温度升高;成形工具移动过程中,与板料之间的滑动摩擦产生的热量最多,对板料温升的贡献最大,其后,依次为成形工具自转时与板料发生的摩擦以及板料的塑性变形耗散能.     

金属微弯曲成形方法的研究

介绍微弯曲成形方法——激光微弯曲成形以及塑性微成形方法。并提出了激光辅助加热微弯曲成形方法。即激光辅助加热待加工件使其达到合适的温度范围后进行微弯曲成形的方法，提高难成形材料的微塑性成形能力和质量。     

数控渐进成形工艺参数对表面质量的影响

应用数控渐进成形设备,针对铝合金锥形件进行了试验研究。通过改变成形中的润滑方式、工具头形状、工具头直径、进给量等工艺参数,并对成形后的试验件表面粗糙度和表面形貌进行测量和分析,研究成形参数对零件表面质量的影响。实验结果如下:球头工具头成形的零件表面质量优于圆柱形工具头,大直径的工具头成形零件的表面质量要好于小直径的工具头,层进给量越小,零件表面质量越好,固体润滑剂相比于液体润滑剂对5754铝合金成形的零件表面质量影响较小。     

Numerical simulation and experimental investigation to improve the dimensional accuracy in electric hot incremental forming of Ti–6Al–4V titanium sheet

Electric hot incremental forming is feasible and easy to control to form hard-to-form sheet metals, but the limited accuracy is a major deficiency. In order to find methods to improve precision, single-point electric hot incremental of Ti–6Al–4V titanium sheet was numerically simulated using MSC.Marc, and experimental investigations were also carried out in this paper. Through numerical analysis, distributing laws of temperature, thermal strain, stress, and equivalent strain were revealed, and impacts of cold contract and thermal strain on forming were also revealed. Analysis showed that electric hot incremental forming is a complex pyroplastic deformation, and there is a large internal stress in single-point electric hot incremental forming. The incremental sheet forming region can be divided into three parts: bending deformation at the beginning, shear forming at middle, and reverse bending at last; it is important to enhance the accuracy of the bending part and the reverse bending part, and adequate support must be provided in the beginning to reduce the bending part. In order to form a workpiece with small angle, two-point incremental forming was adopted at first because the gravity of clamp can reduce the reverse bending, then single-point electric hot incremental forming was adopted to enhance the accuracy and reduce internal stress of workpiece.     

Electric hot incremental forming of Ti-6Al-4V titanium sheet

Electric hot incremental forming of metal sheet is a new technique that is feasible and easy to control to form hard-to-form sheet metals. In the present study, Ti-6Al-4V titanium sheet was studied because it was wildly used in the aeronautics and astronautics industries. Although Ti-6Al-4V titanium can be well-formed in high temperature, the surface quality is a problem. In order to enhance the surface quality, it is very important to select the proper lubricant. At the same time, because Ti-6Al-4V titanium has a lively chemical property, it is very important to choose a processing temperature range in order to acquire excellent plastic property and to prevent oxidation. Various lubricants were selected in processing to compare the effect, and some workpieces were formed at different temperatures to find the best forming temperature. The results show that using the lubricant film of nickel matrix with MoS₂ self-lubricating material, Ti-6Al-4V titanium workpiece was formed with high surface quality, and the optimum thickness of composite coating is 20 μm for Ti-6Al-4V titanium sheet of 1.0-mm thickness. In fact, the lubricant film also does help to prevent oxidation of Ti-6Al-4V titanium sheet. The appropriate temperature range of Ti-6Al-4V forming with slightly oxidized is 500–600°C in processing, and the maximum draw angle formed in this range was 72°.     

Tribological behaviour and lubrication performance of hexagonal boron nitride (h-BN) as a replacement for graphite in aluminium forming

In metal-forming processes friction leads to the generation of heat, adhesion and the pick-up of work material, tool wear, inhomogeneous deformations, defects and a poor surface quality. Therefore, the use of suitable lubricants is required, especially in the case of aluminium and aluminium alloys. With the increased complexity of the parts being formed, higher strength requirements and the introduction of new alloys, the forming lubricants are also being subjected to ever-increasing demands in terms of temperature stability, reduced friction, galling prevention and surface protection. Graphite is a well-known, solid lubricant that is successfully used in the cold and hot forming of aluminium. However, it leaves dark stains on the surface of the formed part, which means that additional grinding or polishing is required. One of the possible substitutes for graphite is hexagonal boron nitride (h-BN), also known as white graphite.In this work the possibility of replacing graphite with h-BN in Al-forming lubricants was investigated, including the influence of h-BN powder size and concentration on its tribological performance and the aluminium’s surface quality. The results of the investigation show that h-BN, as a solid lubricant, is capable of successfully replacing graphite in Al-forming processes, while at the same time maintaining a clean surface without staining. The study has shown that the tribological performance, including the friction and wear, the lubrication-film stability and the surface quality, very much depend on the powder size and the concentration. Under the investigated contact conditions, the best performance was obtained for 30-µm h-BN powder when added to the grease in a concentration between 10 and 20%.     

铝材轧制工艺润滑与表面质量

本文用系统方法进行了铝材润滑轧制过程的摩擦学分析，论述了铝材热轧与冷轧过程的工艺润滑机理及润滑剂评价，最后，提出了铝材轧制表面质量控制系统。     

铝板数控单点渐进成形的成形极限曲线研究

对薄壁复杂构件进行数控单点渐进成形时，板料易发生破裂、起皱等缺陷，且材料变形机制演化复杂，对加载条件极为敏感，使得板料在数控单点渐进成形时的破裂预测和控制变得极难。为此，选取1060铝板作为研究材料，通过试验研究了数控单点渐进成形技术中板料的成形性能，以实现对破裂的预测和控制。利用拓印法将制件的空间变形问题转化为平面变形问题，采用数码显微镜对拓印的制件网格数据进行测量和提取，选用插值法和多项式拟合法对数据进行拟合处理，最终得到了1060铝板料在数控单点渐进成形技术下的成形极限曲线（FLC）。通过对FLC进行分析研究，得到了制件破裂区和安全区域的应变分布，实现了制件破裂的预测和控制。为进一步提高1060铝板的成形极限，将超声振动引入到单点渐进成形中，通过试验对比研究了超声振动辅助渐进成形的FLC和传统渐进成形的FLC，试验结果表明：当振动功率为120 W、振动频率为25 kHz时，1060铝板料的成形极限提高了11%。     

Mechanical property of Ti-6Al-4V sheet in one-sided electric hot incremental forming

Although Ti-6Al-4V titanium can be quickly and easily formed by electric hot incremental forming, the material property is the key factor for industrial application. In the current work, mechanical properties of Ti-6Al-4V sheet in one-sided electric hot incremental forming, such as microstructure, hardness, and tensile strength, were investigated. The results show that the current is obviously the most important factor to elevate temperature, so a higher feed rate can be adopted if the current is increased. In order to keep a constant processing temperature, an online temperature detector and current feedback system should be adopted. After observation and analysis of the microstructure of forming workpieces, the electric hot incremental forming is an integrated process, which involves plastic hardening and annealing. The temperature of the tool–workpiece contact side reached the β-transus one, α phase disappeared, and the basket weave structure was formed because of the fast air-cool. A composite organization with superior property which includes elongated α phase grains and basket weave structure can be acquired by one-sided electric hot incremental forming. If a uniform metal structure is obtained, special heat treatment must be adopted. Micro-hardness analysis shows that electric hot incremental forming is an enhanced processing. In order to improve the tensile strength, the oxidation of sheet must be prevented and inert gas protection should be adopted in future research.     

Un nouvel outil pour l'étude des interactions tôle–outil–lubrificant: Le test en cadence

In order to obtain a formed part, free from any defect such as necking, failure, galling marks or bad surface appearance, it is increasingly important to control the deep interactions between the steel sheet, the lubricant and the tooling. Another fundamental requirement for the industry is an ever growing productivity which implies a better stability of the process, also allowing an increase in the number of parts drawn per minute. Recently, RDCS has developed a new friction set-up able to study the behaviour of the steel sheet, coated or not, during its short contact with the tooling in the presence of a lubricant. Series of hundreds of samples are successively drawn. First results are interpreted.     

Influence of Surface Topography on the Tribological Behaviour of Aluminium Alloy 5182 with EDT Surface

Friction is one of the most important parameters in sheet metal forming. Friction conditions are influenced by the texture of the sheet surface, by the surface or coating of the tools and by the lubrication. The aluminium alloy AA 5182 with EDT surface has been studied and tested at various angles between rolling and sliding direction. The friction behaviour observed in experiments at different normal pressures based on Coulomb’s friction law are shown and discussed in this article. Moreover, local surface topography and lubricant distribution in the contact area are described.     

[成形质量的闭环与自适应控制技术]具有开放几何特征钣金件渐进成形的回弹控制与补偿

实现了具有开放几何特征钣金件的渐进成形。提出采用工艺参数优化、多道次渐进成形和轨迹补偿等方法提高钣金件的几何精度。设计了多道次渐进成形方法的中间构型，目的在于增大材料塑性变形并减小几何偏差。采用层切法轮廓轨迹形成两道次成形中第一道次的构型，为了防止第一道次成形时出现破裂，将非固定方向的成形角度设定为75°，第二道次将非固定方向的板料完全成形。采用基于几何补偿的两道次渐进成形方法可以将开放几何特征钣金件的几何偏差控制在0.5 mm左右。