Performance evaluation of minimum quantity lubrication by vege-table oil in terms of cutting force,cutting zone temperature,tool wear,job dimension and surface finish in turning AISI-1060 steel

In all machining processes, tool wear is a natural phenomenon and it leads to tool failure. The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Metal cutting fluid changes the performance of machining operations because of their lubrication, cooling and chip flushing functions, but the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. The minimization of cutting fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. The concept of minimum quantity lubrication (MQL) has been suggested since a decade ago as a means of addressing the issues of environmental intru- siveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. This paper deals with experimental investigation on the role of MQL by vegetable oil on cutting temperature, tool wear, surface roughness and dimen- sional deviation in turning AISI-1060 steel at industrial speed-feed combinations by uncoated carbide insert. The encouraging results include significant reduction in tool wear rate, dimensional inaccuracy and surface roughness by MQL mainly through reduction in the cutting zone temperature and favorable change in the chip-tool and work-tool interaction.

DRAWING OF ALUMINUM-CLAD STEEL WIRE BY FORCE-FEED LUBRICATION

The force feed lubrication method is used for drawing aluminum clad steel wire. It is studied how deformation of wire and aspect of the lubricant film are influenced by the die angle, the reduction, the drawing speed and the gap between pressure die and wire. It has been concluded that when the factors above mentioned promote to thicken lubricant film, the drawing force is reduced and this favors the homogenous deformation of aluminum coating and steel core.

Dry Grinding of Titanium Alloy Using Brazed Monolayer cBN Wheels Coated with Graphite Lubricant

The purpose of this study is to investigate the effect of graphite lubricant on the dry grinding performance of Ti-6Al-4Valloy,using graphite-coated,brazed monolayer,cubic boron nitride(cBN)wheels.Brazed monolayer cBN wheels both with and without a coating of polymer-based graphite lubricant are fabricated and subsequently compared for grinding performance based on measurements of grinding temperature,surface microstructure and grinding.In terms of grinding temperature,considerable improvement in dry grinding performance of titanium alloy is achieved using coated brazed monolayer cBN wheels,with 42%—47%reduction in grinding temperature as opposed to uncoated wheels.The grinding force ratio with the coated wheels is observed to remain between 1.45to1.85despite material removal rates reaching up to 1 950mm3/mm.No tangible change in ground titanium surface microstructure is noted as a result of grinding with the graphite coated wheels as opposed to the uncoated ones.

Die wall lubricated warm compaction behavior of non-lubricant admixed iron powders

The phenomena of die wall lubricated warm compaction of non-lubricant admixed iron powders were researched, and its mechanism of densification was discussed. Water atomized powder obtained from the Wuhan Iron and Steel Corporation was used. With compacting and sintering, compared with cold compaction, the density of warm compacted samples increases by 0.07 - 0. 22 g/cm^3 at the same pressed pressure. The maximum achievable green density of warm compacted samples is 7.12 g/cm^3 at 120℃, and the maximum sintered density is 7.18 g/cm^3 at 80℃. Compared with cold compaction, the ejection force of warm compaction is smaller; the maximum discrep- ancy is about 7 kN. The warm compacted mechanism of densification of iron powders can be obtained： heating the powder contributes to improving plastic deformation of powder particles, and accelerating the mutual filling and rearrangement of powder particles.

ON THE TRACTION BEHAVIOR OF 4109 CHINESE AVIATION LUBRICANT

Based on improved test rig with cooling system, the traction experiments for 4109 Chinese aviation lubricant are tested under various simulated working conditions. Both the experimental data thanks to their accuracy and stability and the better cooling effect of the electric shafts has given the rationality of the experimental rig a strong support. An empirical equation for calculating the traction coefficient of 4109 lubricant, which may be conveniently used for engineering application,is obtained. Furthermore, the rheological properties of the lubricant are investigated.

Experimental Study on Grinding Force of Electrostatic Coated Grinding Wheel

In order to deal with the hard machining of TC4 alloy,coated graphite on grinding wheel surface by electrostatic device is proposed in this paper.This paper mainly completed the design of graphite electrostatic spraying grinding wheel device,force experimental analysis of grinding TC4 alloy with coated graphite grinding wheel,and summary of the influence of different grinding speeds and grinding depths on grinding force and grinding force ratio.The experimental results show that the lubrication coating can reduce the grinding force and grinding force ratio in the process of grinding TC4 alloy with graphite powder-coated wheel under electrostatic field force,compared to dry grinding with the uncoated wheel.

Improvement of Drill Performance in Metal Cutting Using MoST Solid Lubricant Coatings

Coated tools are widely used in today’s metal cutting industries and have significantly improved machining productivity through reducing operation costs and time. This paper presents the results of a systematic study of the performance of HSS drills coated with CrTiAIN and drills with a top solid lubricant coating of MoST?. The tests were performed on a Haas vertical machining centre under wet and dry cutting conditions to machine through holes in medium carbon steel workpieces. The feed force and torque were recorded throughout some of the tests using a force dynamometer, while the tool wear was monitored and measured. It was found that MoST? coatings even under accelerated conditions improve the tool life significantly based on their unique properties and very low friction.

润滑条件对TC4钛合金切削加工影响的实验研究

为了研究冷却润滑条件及切削参数对TC4钛合金的切削力和表面粗糙度的影响,分别开展CMQL、冷风、浇注式冷却润滑条件的TC4钛合金高速切削实验、四种不同润滑环境的粗/半精/精加工实验以及CMQL条件下TC4钛合金正交切削试验,通过单因素分析和正交试验法研究冷却润滑条件及切削参数对切削加工性的影响。研究表明:CMQL冷却润滑条件可在TC4钛合金高速切削时有效降低切削阻力和改善表面粗糙度,并在高速精车削阶段体现出降低切削阻力的优势。考虑CMQL条件下高速精车TC4钛合金加工效率,最佳参数组合为较高的切削速度、较小的精加工余量和合适范围内较大的进给量。

水液压泵柱塞副织构单元的润滑及承载特性分析

为研究水基轴向柱塞泵织构化柱塞副的润滑及承载特性,建立了轴向柱塞泵AMESim仿真模型,得出单柱塞往复速度、有效织构区长度与其腔内压力特性间的对应关系。建立织构化柱塞副的简化CFD润滑及承载力模型,分析了单周期内织构单元的压力云图、压力分布曲线及承载力特性曲线,研究了织构半径、深度及形貌对柱塞副润滑及承载特性的影响。结果表明:柱塞表面承载力曲线与柱塞腔压力脉动及压力梯度曲线的规律较为一致,在高压区柱塞承载力高,呈出与压力梯度曲线相应的波动式下降特征,而低压区柱塞承载力较低;仿真条件下,增大织构半径及深度均有助于提高柱塞表面承载力,且织构形貌对承载力影响较大,承载力由高到低的形貌依次为圆柱形、球冠形、菱形、方形和三角形。此外,织构收敛楔和发散楔开口大小分别对织构单元的正压核心和负压核心区的面积影响较大,且横截面为直角过渡的圆柱形织构比圆弧过渡的球冠形织构更利于压力集聚。

复合纳米自润滑金刚石砂轮磨削SiC陶瓷的试验研究

提出一种复合纳米自润滑金刚石砂轮的制备方法,并对制备的砂轮进行SiC陶瓷的磨削试验,分析砂轮表面不同质量分数的复合纳米颗粒对磨削性能的影响。使用MoS2、TiO2纳米颗粒作为自润滑砂轮基底的填充材料,采用复合纳米自润滑金刚石砂轮和传统金刚石砂轮进行磨削对比试验,研究复合纳米自润滑金刚石砂轮的润滑机制。研究结果表明,复合纳米自润滑金刚石砂轮自释放的纳米颗粒有效地参与了磨削区间的润滑,砂轮的法相力、切向力降低,提升了工件表面质量。在磨削深度为2~8μm内,复合纳米自润滑金刚石砂轮的具体表现为法向磨削力降低18.6%~38.7%、切向磨削力降低11.2%~28.6%,工件表面粗糙度降低13.9%~41.5%。根据本试验所得数据,当砂轮表面复合纳米颗粒质量分数为8%时,润滑性能和工件表面质量最佳。

复合润滑结构改善滑动导轨表面爬行现象研究

滑动导轨在低速重载时产生爬行现象,严重影响机床的加工精度。为了改善滑动导轨的爬行现象,对滑动导轨表面复合润滑结构的设计和摩擦力分阶段表征进行了研究。在激光烧蚀微织构的基础上,采用高温高压镶嵌法制备了复合润滑微织构,基于摩擦试验,提出了摩擦力分阶段表征方法,探索了不同复合润滑结构对各阶段摩擦力特征参数的影响规律,建立了复合润滑结构改善爬行现象的理论模型,找到抑制爬行现象性能最优的复合润滑结构。研究结果表明:表面微织构仅影响摩擦力的严重黏滑和爬升阶段,而复合润滑结构对整个启动阶段都有显著影响。填充二硫化钼(MoS 2)的正弦沟槽与六边形凹坑组合的多级复合润滑结构(SF-3)改善表面接触状态和抑制爬行现象的效果最好。与光滑表面(SS)试样相比,SF-3试样爬行时间缩短了72%,第Ⅰ阶段失稳力减小了69.83%,第Ⅱ阶段和第Ⅲ阶段的摩擦突跃力分别减小了75.91%和80.17%。

冷等离子体和微量润滑复合微铣削铝锂合金的表面性能研究

铝锂合金的延展性造成材料对刀具的粘附,会导致毛刺和积屑瘤等问题产生。为此,采用冷等离子体和微量润滑复合微铣削的方法加工铝锂合金,研究了工件的表面性能,并与单纯的干式、冷等离子体和微量润滑方法进行了对比。结果表明冷等离子体不仅改善了纳米流体在工件表面的浸润性,而且提高了材料的去除效率;相比于单纯的干式、冷等离子体和微量润滑方法,冷等离子体和微量润滑复合条件下的微铣削力分别降低了52.9%、42.9%和17.5%,而三维表面粗糙度Sa分别降低了67.3%、44.8%和33.3%。

钛合金铣削加工中MQL参数优化与切削性能研究

微量润滑(MQL)铣削过程中,系统工艺参数对刀具–切屑和刀具–工件间接触界面的冷却润滑效果影响显著。本文通过有限元仿真分析了铣刀高速旋转扰动的空气流场对MQL喷射角度的影响以及切削区压力影响下的切削液渗透机理。然后,以钛合金TC4为工件材料、油膜附水滴(OoW)为润滑介质,通过正交试验研究微量润滑系统喷射角度、喷射距离和润滑油流量对铣削力的影响规律,获得油膜附水滴微量润滑(OoWMQL)系统最佳工艺参数为:喷嘴俯角30°、喷射距离10 mm、润滑油流量135 mL/h。基于此,采用OoWMQL系统最优工艺参数,开展干式铣削和水基微量润滑(WMQL)铣削下切削速度、每齿进给量对钛合金切削性能的影响研究。结果表明,相比干式铣削,WMQL方法对铣削力的改善效果较弱,而OoWMQL方法在所有参数下均明显降低了铣削力,且降低幅度最高可达50%左右。此外,采用OoWMQL方法可显著降低表面粗糙度,抑制划痕和粘屑等表面缺陷的产生,有效提高钛合金的切削加工性。

磁场辅助纳米流体气雾渗透沉积特性及其加工性能

为了改善机加工过程中油基气雾润滑形成的高油雾质量浓度环境,提出磁场辅助纳米流体气雾润滑技术.该技术可以大幅降低作业环境的油雾质量浓度.搭建磁场辅助气雾装置,配制水基Fe3O4纳米流体切削液.研究磁场影响下纳米流体气雾的渗透和沉积特性.对比考察磁化气雾在铣削430不锈钢过程中的油雾质量浓度和加工性能.结果表明,磁场影响下的纳米流体气雾渗透能力提升,沉积量增多.当磁感应强度为60 mT时,纳米流体气雾润滑下的油雾质量浓度、刀具磨损量、切削力和粗糙度分别比植物油气雾润滑低66.3%、22.7%、14.6%和23.4%.磁场影响下的纳米流体易沉积且渗透进刀-屑接触界面的毛细微缝中发挥润滑冷却作用,抑制油雾的弥散.

The lubrication performance of water lubricated bearing with consideration of wall slip and inertial force

The lubrication mechanism and the performance parameters with consideration of wall slip and inertial force are studied in this paper. Based on the modified Reynolds equation, the finite difference method is used to study the lubrication mechanism and the performance. Effects of the wall slip and the inertial force on the performance parameters are obtained, and found in good agreement with the results of FLUENT. It is shown that the wall slip and the inertial force do not significantly change the distribution of the pressure, the load capacity and the friction force. The inertial force slightly increases the pressure and the load capacity by 1.2% and 4.8%, while the wall slip reduces them by 8.0% and 17.85%. The wall slip and the inertial force increase the friction by about 15.98%, 2.33%, respectively. Compared with the wall slip, the inertial force is smaller, but cannot be neglected.

软弹流状态下“脊-膜”织构化PDMS表面增摩特性的研究

润滑条件下,增加软质材料(如橡胶、凝胶等)表面摩擦效应是柔性电子、皮肤传感器和智能抓取等功能器件设计制造的1个重大需求.本文中采用激光加工与多次覆膜相结合工艺,在PDMS(Polydimethylsiloxane,聚二甲基硅氧烷)表面加工出不同间距的“脊-膜”织构,研究其在流体润滑状态下接触界面的摩擦学特性,并原位考察了接触界面内润滑介质的流动特征.结果表明:“脊-膜”织构在滑动界面内产生周期性弹性迟滞,引起润滑界面的能量耗散,从而显著提高了PDMS表面在软弹流状态下的滑动摩擦效应;当“脊”间距为3 mm时,织构化表面的平均摩擦力可达100.23 mN,与光滑表面相比,其摩擦效应提高了49.6倍.此外,PDMS表面摩擦效应随法向载荷的增加而增加,但在不同滑动速度下基本保持不变.

纳米粒子微量润滑磨削加工氧化锆研究

氧化锆陶瓷拥有高的强度、硬度、断裂韧度以及耐高温、耐腐蚀等性能,在3C电子、生物医疗、化工、机械、新能源等领域有着广泛的应用。但氧化锆陶瓷器件磨削加工效率低、工具磨损严重,难以获得高的表面质量。磨削加工过程中冷却润滑方式对氧化锆陶瓷加工效率和表面质量有着重要影响。文章研究了不同纳米粒子微量润滑条件下电镀金刚石工具磨削加工对氧化锆陶瓷的磨削力和表面质量。结果表明添加纳米金刚石、石墨烯、MoS2纳米冷却液的微量润滑条件下可以降低氧化锆陶瓷的磨削力,其中MoS2纳米冷却液的磨削力最小;而使用浇注式冷却条件下的法向磨削力最大,干式磨削条件下的切向磨削力最大;不同冷却方式加工的氧化锆陶瓷的表面粗糙度差异不大。

纳米润滑剂在不锈钢板冷轧过程中的润滑性能研究

分别在干轧、水包油润滑剂以及不同浓度TiO_(2)的水基纳米润滑剂条件下对不锈钢板材进行冷轧试验,对不同润滑条件下的轧制力以及轧件表面质量进行研究以揭示水基纳米润滑剂在不锈钢板轧制过程中的润滑机理。结果表明:使用水包油润滑剂和水基纳米润滑剂均可以显著降低轧制力,改善不锈钢轧件的表面质量。前者主要归因于在轧辊与钢板表面之间形成的油膜,后者主要归因于TiO_(2)纳米粒子改善了水基纳米润滑剂的润滑性能。当TiO_(2)纳米粒子的浓度为3.0%时,水基纳米润滑剂具有最佳的润滑效果。当TiO_(2)纳米粒子的浓度低于3.0%时,润滑剂的润滑效果不足;当TiO_(2)纳米粒子的浓度高于3.0%时,TiO_(2)纳米粒子发生团聚,显著影响不锈钢板的表面质量。

离心力作用下轴承滚道润滑剂流失与定量补油数值模拟

采用自由表面薄膜流动模型,数值模拟了高速轴承壁面润滑剂在离心力作用下的流动过程,并通过外部定量补油对壁面油层厚度和润滑状态进行了调控.结果表明:高速下离心力的作用可使轴承壁面的润滑剂呈现出非线性衰退,使轴承处于乏油润滑状态;与离心力相比,由表面张力引起的润滑剂回填几乎可以忽略,需依靠外部供油对轴承壁面油层进行增补;通过调整供油时间间隔,可实现轴承壁面润滑剂流动的供失平衡;采用多次微量供油,可将壁面油层厚度和接触区润滑状态调控在一定范围内,进而使轴承处于最佳的润滑状态.

载荷对油膜界面滑移及弹流润滑特性的影响研究

为探究恶劣工况下机械传动系统中摩擦副润滑失效的形成和演变机理,建立考虑油膜界面滑移的点接触弹流润滑模型,进行仿真计算,并开展双色光干涉弹流润滑试验,研究载荷对弹流润滑中油膜界面滑移的影响,进而研究界面滑移状态下卷吸速度、流体动压、油膜厚度、滑移参数等随载荷的变化特性。研究结果表明:随着载荷的增大,界面滑移幅度和滑移范围均显著增大,滑移区域卷吸速度明显下降,滑移区域动压分布趋于均匀,滑移区域产生膜厚堆积并出现入口凹陷特征,滑移区域形状逐渐呈“半月牙形”特征。