Effects of die surface patterning on lubrication in strip drawing

Strip-drawing tests with annealed stainless steel samples involving small strains were used to investigate the effect of surface texturing in tribological applications involving mixed lubrication and plastic deformation. Dies were prepared with surface patterns composed of circular pockets and parallel grooves, and comparison tests were performed with highly polished dies. The effects of surface texturing were detected by friction force measurements and examination of the deformed strip surfaces, under conditions of oil lubrication. Surface patterns consisting of circular pockets with very low area coverage did not improve the tribological performance. For grooves with larger area coverage (≈25%), significant effects were observed on the friction between the dies and the strip, which were reflected in the drawing force. The performance was strongly influenced by the relative orientation between the grooves and the drawing direction. For grooves perpendicular to the drawing direction, the friction was greatly reduced; the grooves were believed to act as lubricant reservoirs and to induce microplastohydrodynamic lubrication. On the other hand, when the grooves were oriented parallel to the drawing direction, the friction was much greater and the strip surface finish became poorer; these grooves were believed to allow the lubricant to escape from the contact.     

微织构自润滑表面在油介质中的摩擦学性能

为探究不同表面处理方式对试样表面摩擦学性能的影响,分别对GCr15试样表面进行激光微织构加工,光滑表面涂抹润滑油,微织构表面填充固体润滑剂,微织构表面涂抹润滑油,微织构表面填充固体润滑剂并涂抹润滑油等不同表面处理方式,在MMW-1A摩擦磨损机上进行摩擦磨损试验。同时改变试验的载荷及转速,探究在不同转速和载荷工况下,不同表面处理方式对试样摩擦因数的影响。结果表明,在干摩擦条件下,试样表面采用微织构处理并填涂固体润滑剂可使摩擦因数较光滑表面降低47.6%;在油介质中,采用微织构处理可使摩擦因数较光滑表面降低4.8%,采用微织构处理并填充固体润滑剂可使摩擦因数较光滑表面降低17.7%。且在油介质中,采用织构化处理和固体润滑结合的表面处理方法,试样摩擦因数随载荷增大而减少且逐渐趋于稳定,但随转速增大而增大。     

激光微织构固体润滑表面高温摩擦学性能研究

目的 研究微织构纳米固体润滑剂及碳纳米管(CNTs)添加剂对微织构表面高温润滑性能的影响.方法 采用YLP-HP-1-100-100-100型光纤激光器在Cr4M04V高温轴承钢表面进行织构化处理,并填充二硫化钼(MoS2)-聚酰亚胺(PI)和不同碳纳米管添加含量的MoS2-PI-CNTs复合固体润滑剂.在环-盘接触的MMU-10G高温摩擦磨损试验机上进行了环境温度从室温到400℃的滑动摩擦性能试验.结果 填充含纳米MoS2的复合固体润滑剂的微织构表面的摩擦系数比填充含相同含量微米MoS2的低35％左右.微织构纳米MoS2-PI自润滑表面摩擦系数随碳纳米管含量的增加先减小后增大,当碳纳米管质量分数为6％时,其摩擦系数最小,且比无碳纳米管的低37％左右.在MoS2-PI纳米复合润滑剂中添加6％碳纳米管后,MoS2-PI-CNTs纳米复合润滑剂具有更高的使用温度和更低的摩擦系数.结论 纳米MoS2的润滑效果优于微米MoS2,碳纳米管有利于提高MoS2-PI复合固体润滑剂的耐热性能和润滑减摩性能.     

Lubrication for Micro Forming of Ultra Thin Metal Foil

The objective of the present investigation is to establish lubrication technique in micro forming operation. Conventional lubricant, in general, cannot be applied directly to micro forming process, since the lubricant thickness is similar to the dimensions of feature size in micro forming operations. In present investigation, the Octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) was chosen as a potential lubricant because it sticks to Si wafer die and can be applied to surface with uniform thickness of several nanometer thick. Friction coefficient and adhesion force were measured for OTS SAM coated wafer. It is shown that OTS SAM coated Si wafer offers substantially lower friction and lower adhesion than bare Si wafer. Micro channel wafer die was coated with OTS SAM and channel forming operation with 1μm thick copper foil was carried out. Experimental results show that OTS SAM coated wafer die improves forming characteristic of ultra thin copper foil substantially. These results show that SAM coating can be used as a lubricant in micro forming successfully.     

基于梳齿沟槽阵列的集油表面润滑特性

对限量供油条件下梳齿沟槽阵列表面的润滑特性及其集油性能进行了研究。 利用飞秒激光在摩擦表面制备了梳齿状沟槽阵列,形成了条状亲油区。 采用摩擦力及膜厚测量仪的往复运动模块对该条状自亲油区在限量供油条件下的润滑成膜特性和减摩降磨特性进行了研究。 同时,采用高速摄像机对梳齿沟槽阵列表面油滴的输运特性进行了观察。 结果表明,以梳齿状沟槽阵列为边界的润滑轨道对置于其上的润滑油有明显约束作用,限制其向润滑轨道之外的铺展。 在有限供油条件下,该类条状自集油表面具有较好的润滑能力、较小的摩擦因数和磨损。 相对于普通润滑表面, 集油表面摩擦因数减小了 30%左右,而往复运动行程中心位置最小膜厚增大了 20 nm。 油滴在梳齿沟槽阵列表面的输运产生明显差异,朝向润滑轨道的输运距离为远离润滑轨道输运距离的 1. 5 倍。     

铝箔冷轧工艺润滑状态与润滑效果研究

铝箔冷轧工艺润滑中,采用综合考虑变形区膜厚比、摩擦因数、轧后表面质量与轧制油添加剂影响性相结合的方法,综合评价润滑状态。结果表明:入口处的油膜厚度明显小于综合表面粗糙度,获得的轧后铝箔表面质量较好,轧后铝箔表面粗糙度都比仅加入基础油时的有所降低,添加剂已经发挥作用,润滑状态以边界润滑为主。     

基于Deform复合润滑剂镦粗试验和摩擦磨损研究

以聚四氟乙烯（PTFE）乳液为主要润滑成分,通过辅助添加剂制备了新型复合高分子水基润滑剂,并进行均匀设计试验获得最优的成分配比。基于Deform有限元模拟镦粗试验探究润滑剂的摩擦行为,通过SEM和EDS表征方法研究润滑机理,发现润滑性能的提高是由于PTFE在基体表面形成了一层转移膜,h-BN吸附在基底表面保护了PTFE膜而有效降低了基体表面阻力,提高了润滑剂的润滑性能,此润滑剂可用于冷挤压成形的润滑。     

Fabrication of curved micro structures on photoresist layer

A novel fabrication process for micro patterns with curvature was introduced. The curved structures were made by compensating rectangular micro structures with liquid photoresist layer. Because of the surface tension of the liquid in micro scale, various shapes of meniscus can be made on the micro channels. The micro channels were made on the silicon substrate in advance, and then the liquid layer was coated on the micro channels. From the nature of liquid behavior, the curved patterns with smooth surface are obtained, which cannot be made easily with the conventional mechanical machining, as well as with the microfabrication processes, such as wet and dry etching. With this principle, it is expected that the smooth and curved surfaces can be made by simple processes and the results can be applied widely, such as optical patterns.     

镁合金板料数控热渐进成形时的摩擦和润滑性能

利用数控实验机床和摩擦实验研究AZ31镁合金板料数控热渐进成形时的摩擦和润滑机理。结果表明:镁合金薄板在加热条件下可以实现单点渐进成形;固体润滑膜可分为粘结型和吸附陶瓷型两种;固体石墨和MoS2润滑剂的初始摩擦因数均小于0.12,均可保证热渐进成形件获得良好的内外表面质量,没有任何划痕和裂纹等缺陷;吸附多孔陶瓷型固体润滑膜具有润滑和自润滑作用,固体润滑剂颗粒大小对初始摩擦因数有一定影响;固体BN粉末没有起到润滑作用,不能单独作为热渐进成形用固体润滑剂;当温度小于500℃时,固体石墨和MoS2粉末按一定比例配置的润滑复合喷剂的初始摩擦因数均小于为0.2,且表现出一定的协同作用。     

基于热混合润滑的钢/橡胶接触表面水润滑增强调控

目的 增强钢/橡胶摩擦副的润滑性能,为提高混合润滑状态下水润滑轴承的性能提供参考。方法 建立水润滑条件下钢/橡胶摩擦副的热混合润滑模型,讨论热效应对润滑性能的影响,并在此基础上进一步研究表面粗糙度、水基润滑剂黏度和供水压力对水润滑增强调控的作用。结果 与等温解相比,热效应使Stribeck曲线发生了右移,摩擦因数和载荷比增大,膜厚比降低。最高水膜温度随着转速的增加而升高,热效应对混合润滑性能的影响显著。减小摩擦副表面粗糙度,Stribeck曲线向左移动。在相同转速下,载荷比随着表面粗糙度的减小而降低,膜厚比反之。表面粗糙度越大,水膜温度越高,最高温度位于出口区,且钢的表面温度低于水膜和橡胶的表面温度。当水基润滑剂的黏度增大时,膜厚比增大,载荷比和最高水膜温度降低,Stribeck曲线发生左移。增加供水压力可以改善水膜压力分布,使水膜承载区增大、压力减小,粗糙峰接触压力和承载区减小,导致载荷比减小、膜厚比增加,Stribeck曲线向左偏移,水膜最高温度降低。当接触区由边界润滑向混合润滑过渡时,水膜最高温度出现拐点,且水膜最高温度拐点随着供水压力的增加而左移。结论 热效应会降低摩擦副的混合润滑性能,因此在混合润滑中不能忽略。考虑热效应时,通过减小表面粗糙度,或增加水基润滑剂黏度和供水压力,均有利于增强钢/橡胶接触表面水润滑的混合润滑性能。     

Fabrication of curved micro structures on photoresist layer

A novel fabrication process for micro patterns with curvature was introduced. The curved structures were made by compensating rectangular micro structures with liquid photoresist layer. Because of the surface tension of the liquid in micro scale, various shapes of meniscus can be made on the micro channels. The micro channels were made on the silicon substrate in advance, and then the liquid layer was coated on the micro channels. From the nature of liquid behavior, the curved patterns with smooth surface are obtained, which cannot be made easily with the conventional mechanical machining, as well as with the microfabrication processes, such as wet and dry etching. With this principle, it is expected that the smooth and curved surfaces can be made by simple processes and the results can be applied widely, such as optical patterns.     

摩擦表面定域润滑研究进展及发展趋势

面向环境保护和资源节约使用的呼声,应用少量润滑剂实现摩擦表面定域可控润滑的研究越来越受到关注。基于润滑剂定域润滑效应,从定域润滑的形成机制、润滑层结构、润滑种类、润滑效果和定域与微观-宏观域关联等角度进行探索研究。概述了近年来国内外关于定域润滑的研究进展,从润滑约束角度概述了外力约束型、空间封闭约束型、表面形貌约束型和表面物化约束型等不同形式的定域润滑,同时对其成因及润滑机理进行了阐述,并对不同约束方式之间的耦合润滑效果研究,得出不同定域因素间会产生影响,且作用效果相似的约束方式之间耦合影响会明显增强。此外,系统性地阐述了定域润滑在数学模型理论研究、实验研究、仿真分析等方面研究的发展概况,并分析了定域润滑在摩擦过程中的润滑效应及其优势与不足。最后分析了目前定域润滑研究中存在的问题和拓展方向,并提出其可在多种影响因素耦合方面重点研究的建议。     

硅烷偶联剂对表面微坑复合PTFE的减摩及缓释性能影响研究

目的探究硅烷偶联剂对缸套表面微坑复合PTFE微粒的减摩和缓释性能的影响。方法利用激光刻蚀机在缸套表面加工不同参数的微坑,并依据摩擦系数对表面微坑参数进行优化。选取最佳表面微坑参数,进行加工,并机械涂覆经硅烷偶联剂修饰的PTFE,制备复合润滑结构。采取往复式摩擦磨损试验机对复合润滑结构的减摩性能进行分析。利用SEM和EDS研究摩擦副的表面形貌和成分,采用三维共聚焦显微镜研究微坑内PTFE的释放情况。结果在热压复合方法下,直径为0.4 mm、深度为120μm的微坑复合PTFE具有最佳的减摩效果。硅烷偶联剂的加入会进一步改善摩擦副之间的减摩性能,其摩擦系数为0.1248。与未处理缸套试样、微坑处理缸套试样、热压复合PTFE缸套试样进行对比,其摩擦系数分别降低了24.3%、18.8%和11.2%。另外,硅烷偶联剂还可以减缓表面微坑内PTFE的释放,延长作用时效,与热压复合方法相比,微坑内PTFE颗粒的释放速率约降低96.3%。结论复合润滑结构能够改善摩擦副之间的摩擦状况,其减摩和缓释机理是固体自润滑材料、表面微坑和硅烷偶联剂协同作用的结果。     

极地航行船舶防覆冰涂层研究进展

两极地区是未来重要的能源和资源基地。然而,极地长年低温多冰,极大限制了我国对两极地区的科学考察、商业航运和能源开发进程。因此,发展长效稳定的防覆冰技术是推进极地发展战略的关键。系统阐明了船舶在极地航行过程中面临的结冰困境,分析了船舶积冰的类型,总结了目前解决船舶覆冰问题的多种防除冰技术及发展现状,包括主动防除冰技术（机械除冰、超声导波除冰、加热除冰、化学熔融除冰等）和被动防覆冰涂层技术（气体润滑防覆冰涂层、液体润滑防覆冰涂层、“类液体”润滑防覆冰涂层、界面可控断裂防覆冰涂层等）,同时对各技术在极地船舶防冰应用中的优缺点和可行性进行了深入分析。展望了船舶装备对特种防冰涂层的关键需求,提出主、被动协同除冰技术是实现极地船舶防覆冰的重要策略。     

超滑表面(LIS/SLIPS)的设计与制备研究进展

仿生猪笼草结构的超滑表面(LIS/SLIPS)是一种通过将低表面能液体注入微纳孔而形成的固液复合结构,其具有优异的疏液、不粘附、自修复等特性,成为表界面领域的研究热点。综述了超滑表面制备过程中的经验、争议、误解与盲点,并讨论了超滑表面可能产生的失效。通过对比超滑表面与超疏水涂层结构的差异,分析了超滑涂层在滑动性、稳定性、自修复性等方面与超疏水的联系、区别以及超滑涂层表面四个相态间的作用关系,总结出超滑涂层设计的基本物理模型。从超滑涂层制备工艺,包括基底制备、基底修饰、润滑油选择、润滑油灌注等四个方面,详细梳理了超滑表面制备要点及选材标准,并讨论了超滑表面制备工艺存在的诸多争议。研究发现,超滑表面多孔结构的粗糙度对于形成稳定界面至关重要,有着其特殊的尺寸范围。为了追求疏液性能而选取表面能过低的润滑油不可取,过低表面能反而会引起cloak效应,最终导致油膜流失,而如何将润滑油完全填充到多孔结构中也被许多学者忽视,并且不合理的设计制备以及服役环境也将造成超滑表面的失效。最后展望了未来超滑表面制备应朝着工艺简化、性能稳定长效、多功能化、智能化方向发展。     

微坑分布位置对复合润滑结构缸套摩擦磨损性能的影响规律

采用电火花加工方法在FeNi合金镀铁缸套试样表面的止点、中点、全程位置刻蚀微坑织构,采用球磨法对微坑填充固体润滑剂MoS_2以制备复合润滑结构缸套。采用对置往复式摩擦磨损试验机,研究微坑分布位置对复合润滑结构缸套摩擦磨损性能的影响规律。采用SEM和EDS研究配副的磨损形貌。结果表明:复合润滑结构缸套能提高承载性能、降低摩擦因数,但不一定都能提高缸套的磨损性能和抗拉缸性能。唯有微坑分布在止点的复合润滑结构缸套相比未处理缸套,表现出良好的减摩耐磨和抗拉缸性能,摩擦因数降低了4.97%~6.26%,对磨环磨损量减少了58.3%,拉缸时间延长了10倍。随着往复运动的进行,微坑中的MoS_2逐渐向缸套表面转移,改善了止点区域的润滑性能,良好保护了摩擦界面。     

Lubrication using porous surface layer for cold drawing of steel wire

As a lubricant for steel cold working, metal soap on zinc phosphate coating is widely used. However the lubrication causes hazardous wastes, and hence an alternative system is demanded. The authors proposed to utilize porous layer on workpiece surface as a reservoir of liquid lubricant. In this study, 0.64%C steel wires were oxidized at 923 K under air and chemically reduced by pure hydrogen to form porous surface layer with pores 1–2 μm in diameter. In cold drawing with machine oil, the friction coefficient on the porous surface was 0.06, while that on normal surface was 0.11. The lubrication mechanism with porous surface is discussed.     

Analysis of surface topography changes in steel sheet strips during bending under tension friction test

In order to investigate the frictional behaviour and the change in surface roughness of different sheet topographies, a bending under tension friction test, BUT, was used. This test exposes the material to bulk-plastic deformation under conditions similar to those present in the drawing radius of a real tool. Each steel sheet material has been tested under different lubrication conditions. To measure the sheet surface topography a 3D stylus technique was used.For each steel strip the original surface, the area in contact with the tool and the resulting surface topography were measured. When comparing “standard” 3D surface roughness data for original and final surfaces, no correlation with friction data was obtained. However, with a special evaluation technique good correlation with oil retention volume and frictional behaviour was found for the surface in contact with the tool. By using measurements from the contact area, filtering the measured surface in two steps, firstly with a 5th degree polynom to get rid of the circular form and secondly with a ball filter to get rid of the waviness located in the topmost layer in the surface and then plotting the bearing area curve for the filtered surface on a probability paper, the real area of contact for each steel sheet surface can be determined, as well as the number of oil pockets and their mean area. The oil pockets were estimated by using a software in which areas of peaks were estimated, on a surface inverted at the level of the real area of contact.By plotting the mean area of the oil pockets versus the coefficient of friction for a sheet material with an excess amount of lubricant, a relationship is determined.     

A novel surface texture for magnetic fluid lubrication

Magnetic fluid has many advantages when serving as lubricant. With an appropriate magnetic field this lubricant can prevent leakage and increase the load capacity of lubricant film. It can also be fixed at the friction zone by applying an external magnetic field. A novel design of magnetic fluid lubrication with magnetic surface texture was proposed in this paper. A micro-scale dimple pattern was firstly fabricated on the surface of tribo-pair and then a permanent magnet material was electrodeposited into these dimples, so that there are both geometric surface texture and periodic distribution of magnetic field on the surface (magnetic surface texture). In this paper, CoNiMnP permanent magnetic film (about 25 μm thickness) was electrodeposited into micro-dimples (500 μm in diameter) on the surface of 316 stainless steel. The impact of magnetic surface texture on lubrication was investigated using a pin-on-disk test rig. The test results showed that magnetic surface texture was conducive to form effective lubrication at low sliding velocity when lubricated by magnetic fluids.     

Improvement of seizure resistance by roughening surface of stainless steel drawn cup in ironing using die having lubricant pockets

The seizure resistance in ironing of ferritic stainless steel drawn cups using a die having lubricant pockets was improved by roughening the sidewall of the cups. The effect of the surface roughness of the cup on the seizure resistance in ironing was investigated. The seizure resistance using the die having lubricant pockets was higher than that of a polished die, and was heightened by the surface roughness of the cup in the axial direction. To increase the surface roughness of the cup, deep drawing processes with a large clearance and a two-stage deep drawing process were developed. The ironing limits for the roughened cups by the two deep drawing processes were higher than that of the conventionally drawn cup. The thickness of the remaining lubricant film in the sidewall of the ironed cup increased with increasing surface roughness of the cup. It was found that the seizure resistance in ironing was improved by roughening the sidewall of the cup.