面接触条件下织构表面摩擦特性研究

为研究织构表面对面接触摩擦副摩擦特性的影响,设计和制造4个表面高度算术平均值相同、表面微凹坑面积占有率分别为7%、14%、21%、28% 的试件,选用HDM20端面摩擦磨损试验机,针对油润滑和脂润滑两种润滑剂,在不同载荷、转速等工况和不同摩擦副配对材料等条件下进行了试验研究,探讨表面形貌对摩擦特性的影响规律,并使用Talysurf CCI Lite 非接触式三维光学轮廓仪对试样进行三维表面测量,采用ISO25178定义的体积参数和连通性系数对三维表面形貌进行表征,从而得出表面体积参数及连通性系数与摩擦因数的关系。结果表明：在油润滑条件下表面形貌的微观结构特性对摩擦的影响要比脂润滑条件下的更显著;在钢对铜摩擦副条件下织构表面的摩擦因数变化比较复杂,在钢对钢摩擦副条件下织构表面的摩擦因数变化相对平稳;在不同的条件下,最优的表面微观结构特性也不同;将连通性系数和体积参数结合起来对表面形貌进行表征将更有利于表面微观结构特性的摩擦学设计。     

滑滚比对钢/钢配副表面摩擦特性的影响

采用三点接触式摩擦机对钢/钢配副在不同滑滚比(SRR)以及边界润滑条件下的表面摩擦特性进行了研究,使用光学显微镜和扫描电子显微镜(SEM)对摩擦副表面不同疲劳磨损阶段的损伤形貌进行表征,并利用X射线电子光谱仪(XPS)对摩擦副表面进行了化学分析。结果表明:提高滑滚比可以减少摩擦副表面微点蚀的数量,磨损量也随之上升,而摩擦系数没有明显的变化。同时,XPS结果表明:随着滑滚比的提高,摩擦副表面所含氧化物含量上升,而润滑油膜随之变厚。因此,滑滚比影响摩擦副在边界润滑条件下的摩擦学性能不仅与摩擦系数和磨损量有关,也与其中的摩擦化学有紧密联系。     

表面微凹坑和纹理方向对界面摩擦的耦合影响

选取三种不同纹理的铝合金试样,并在试样上加工不同面积占有率的规则圆形微凹坑,利用自制的摩擦试验装置,在油润滑条件下以不同接触压力进行摩擦试验,试验过程中滑动方向与表面纹理方向的夹角分别为0°、45°、90°。利用非接触式三维轮廓仪测量试验前后试样的三维表面形貌,并选取Sa、Str、Vvv、Vvc等表面表征参数来分析滑动接触界面表面形貌的变化。结果表明：表面纹理方向的差异导致铝合金表面在滑动接触摩擦过程中表现出各向异性,而在其表面加工不同面积占有率的微凹坑,减弱了铝合金表面纹理方向性对界面摩擦的影响,反映出表面微凹坑和纹理对界面摩擦的耦合作用。同时界面摩擦对试件的表面形貌也有明显的影响,Str、Vvv、Vvc在试验后发生了规律性的变化。     

表面织构化对活塞环-缸套滑动副摩擦系数的影响

活塞环-缸套滑动副的摩擦学性能对内燃机的使用效率、使用寿命等有显著影响。通过激光表面织构化技术在试件表面加工不同参数的微凹坑织构,并进行摩擦学实验,由实验结果可知:表面织构可以有效减小摩擦副的摩擦系数;微凹坑直径、微凹坑深度、微凹坑织构面积占比对摩擦系数减小有影响。     

化工机械设备轴承合金表面微造型对摩擦磨损性能的影响

为了研究表面微凹坑造型对化工机械设备中轴承合金润滑摩擦性能的影响,利用UMT-2型多功能摩擦磨损试验机,对不同工艺参数表面微凹坑轴承合金进行油润滑条件下摩擦磨损试验。研究了微凹坑面积密度、深度对摩擦因数的影响规律,同时探讨了工况条件对摩擦性能的影响。试验结果表明:微凹坑面积密度和微凹坑深度对摩擦性能的影响均存在最优值,微凹坑面积密度为10%,深度为25μm时,表面微凹坑造型减摩效果最佳;微凹坑面积密度、深度不变时,表面微凹坑造型试样摩擦因数随加载载荷增大而增加,说明高载荷工况下利用微凹坑造型改善耐磨性能效果不明显。磨痕形貌分析表明,低载荷工况下,合金表面微凹坑造型抗磨损效果明显。     

复合工艺制备的表面微凹坑织构的摩擦性能研究

在构建的激光电化学复合微加工系统上,采用皮秒脉冲激光辐照与电解刻蚀复合加工方法在7075铝合金表面制备出不同尺寸的阵列凹坑微织构。采用共聚焦显微镜观测复合加工织构试样表面形貌,采用MFT-5000型RTEC摩擦磨损试验机研究润滑条件下凹坑织构的摩擦学性能,并探讨直径、深度、面积密度对减摩性能的影响。结果表明:复合加工工艺制备的表面微织构具有良好的表面形貌;润滑条件下材料表面的凹坑型织构能显著改善其摩擦学性能,相比光滑表面最高可降低摩擦因数30%;在实验参数范围内,凹坑的直径与面积密度对材料表面摩擦性能影响较大,凹坑深度对摩擦性能影响较小。     

摩擦副表面圆形微凹坑特种加工工艺设计与试验

摩擦副表面一定规则形貌的微凹坑可以改善表面摩擦学特性,提高润滑耐磨性能.根据摩擦学理论,设计圆形微凹坑;用组合电加工方法制作阵列微细轴工具电极;采用多种微细特种加工方法加工出微凹坑,并进行微凹坑加工工艺分析.     

表面微织构影响点接触润滑摩擦性能的实验研究

针对球-盘高副点接触开展微织构表面摩擦学性能实验研究。采用激光工艺在试样表面上加工出具有一定形状、深度和面积比的矩形微织构,采用三维表面形貌仪测量微织构的形貌特征,在摩擦磨损实验机上进行摩擦学实验,研究往复运动模式下微织构深度、间距等参数对球-盘点接触润滑摩擦性能的影响。结果表明:较浅的微织构具有相对较小的摩擦因数;较高频率下微织构表现出较好的润滑和减摩效果;沿运动方向的微织构间距增大,摩擦因数逐渐降低,超过Hertz接触直径之后,摩擦因数变化不明显;垂直于运动方向微织构边长增大,摩擦因数呈现先减小后增大的变化趋势。     

人工髋关节球形凹坑微织构表面摩擦学性能研究*

为改善人工髋关节表面的摩擦学性能,在人工髋关节表面设计球形凹坑微织构;建立人工髋关节微织构表面的流体动压润滑模型,利用CFD软件ANSYS Fluent对微织构表面流体动压进行数值分析,得到摩擦副表面相对滑动时产生的油膜平均承载力以及摩擦因数,并分析表面微织构参数对摩擦学性能的影响。结果表明:在给定的织构参数范围内,平均承载力随深径比的增加呈现出先降低后升高再降低的趋势,随面积密度的增加呈先升高再降低的趋势;摩擦因数随深径比和面积密度增加的变化趋势与平均承载力相反;织构的最优参数分别为深径比0.06,面积密度25%。因此,在人工髋关节表面设置合适参数的球形凹坑微织构可以提高油膜平均承载力和降低摩擦因数,从而起到减小关节的摩擦磨损提高人工关节使用寿命的作用。     

线接触摩擦副织构化表面动压润滑性能

为研究线接触摩擦副织构化表面动压润滑性能,建立其理论模型,并运用多重网格法进行数值分析,探讨工况参数(载荷、转速)和微织构参数(面积占有率、深径比)对表面油膜压力的影响;在MMW-1A摩擦磨损试验机上研究微织构面积占有率与摩擦因数的关系。结果表明,线接触条件下微织构化表面的油膜平均压力随着载荷和转速的增大而增大,随着微织构面积占有率的增大而先增大后减小,随着深径比的增大而减小;而摩擦因数随着微织构面积占有率的增大而先减小后增大再减小;存在最优的微织构面积占有率,使得油膜平均压力最大和摩擦因数最小。试验结果较好地验证了数值模拟结果,表明线接触摩擦副织构化表面具有较好的减摩特性。     

Tribological characteristics of antifriction alloys and mass transfer processes during operation of contact pairs in sliding bearings

The process of the formation of protective films on a contact surface after tribotesting is studied. The following three sliding pairs are tested: babbit-cast iron, aluminum antifriction alloy-cast iron, and bronze-steel. Metallographic methods implemented on a scanning electron microscope and local X-ray analysis are applied to examine the structure and relief of the protective film on the contact surface. The relationship between mass transfer and the tribological characteristics of the friction pairs is found. It is shown that the central process of the formation of secondary structure films evolves on the counterface.     

Tribological behaviour of steel‐alumina sliding pairs under boundary lubrication conditions

The tribological behaviour of oil‐lubricated steel‐alumina sliding pairs was investigated using a ball‐on‐disc tribometer at room temperature. Commercial bearing balls of 10 mm diameter were mated to 99.7% Al₂O₃ discs, and additive‐free mineral oil was fed into the contact area. The sliding speed and the applied normal load were varied, and the initial surface roughness of the Al₂O₃ disc was altered using different polishing and grinding procedures. The results showed that the surface roughness of the ceramic discs dominated the tribological behaviour under the given experimental conditions. The sliding speed as well as the normal load showed less effect on the friction behaviour, but the amount of wear depended strongly on the normal load. From the results it was concluded that improvement of the surface roughness and optimised surface machining of the ceramic material can be essential for improving the tribological performance for boundary‐lubricated steel‐ceramic sliding pairs.     

The development of a feasible method for the tribological characterization of gear teeth surface treatments

In this investigation, an experimental campaign, dedicated to the tribological characterization of surface treatments for gears, is presented. Wear in gears is herein simulated by means of a Ring-on-Ring test machine, where the ring and the cylinder are chosen in such a way that the kinematic and dynamic conditions are as much as possible similar to those presented in the teeth contact, in one of the two extreme points of the action line. The dynamics is simulated by imposing the same contact stress, while the kinematic conditions are applied by assuming in the two systems the same ratio of the specific slide rather than the same sliding speed. The latter choice is justified by the results shown in a preliminary test phase, which have shown the importance of the specific slide for the prediction of wear in gear profiles. The apparatus has shown a fair prediction capacity and has been used to compare the different wear resistances and typologies of gear pairs having different surface treatments. Results are herein presented and briefly discussed.     

A Wear Model of Plane Sliding Pairs Based on Fatigue Contact Analysis of Asperities

Wear modeling is essential to predict and improve wear resistance of machine parts. This article presents a fatigue wear model of plane sliding pairs under dry friction. The wear model is constructed through developing a dynamic contact model of surfaces and proposing a mean fatigue damage constant of asperities. It is simpler and more practical than existing fatigue wear models because it describes the quantitative relationship between the wear behaviors of the plane sliding pairs and the main factors including the load and sliding speed, material property, friction property, and surface topography of the pairs. Furthermore, the wear model can predict the wear of each component of the sliding pairs. Reasonability and applicability of the wear model are validated via pin-on-disc wear tests. The wear model is applicable to predict the wear of the plane sliding pairs, which is characterized by friction fatigue of contact surfaces. The wear model can also be used to guide the tribological design of sliding pairs in machinery.     

沟槽型织构表面对界面摩擦学行为的作用机制

在球-盘接触状态下,研究具有不同宽度的沟槽型织构表面对界面摩擦学特性的影响,并揭示沟槽型织构表面对界面摩擦学行为的作用机制。试验结果表明:沟槽型织构表面显著地改变界面的摩擦学行为,特定尺寸参数的沟槽型织构表面能有效改善界面的摩擦磨损特性;沟槽的存在改变摩擦界面的接触状态,从而引起界面的法向位移和法向力信号产生突变;具有合理尺寸参数的沟槽型织构表面,能充分捕获界面的磨屑,避免对摩试样之间产生强烈的撞击作用,从而有效地改善界面摩擦学行为。     

Contact friction in lead and lead-bismuth coolants

Analytical and experimental data are presented for the tribological characteristics of contact pairs in heavy-metal liquid coolant.     

小尺度摩擦副润滑特性数值模拟研究

与一般大型机械设备中的摩擦副不同,小尺度摩擦副润滑油膜在表面张力的作用下不再是水平形状,从而影响到摩擦副的摩擦学特性。在考虑到表面张力作用的基础上,对小尺度摩擦副进行摩擦学理论分析,建立了二维模型并求解了雷诺方程,以研究小尺度下表面张力对摩擦副摩擦学特性的影响。研究结果显示,由于表面张力的影响,摩擦副的油膜压力分布和承载能力有较大幅度的变化。宏观状态下的摩擦学设计与小尺度摩擦副的实际情况相去甚远,对小尺度摩擦副表面张力作用下的摩擦学特性进行研究是十分必要的。     

Investigating the Effect of Surface Finish on Mixed EHL in Rolling and Rolling-Sliding Contacts

Surface finish may significantly affect the lubrication performance of a tribological interface through the influence of topography on micro/nanoscale fluid flows around localized contacts at surface asperities. This paper aims to study the mixed lubrication performance of a group of engineered surfaces, including turned, isotropically finished, ground, and dimpled surfaces, under different operation conditions by means of a deterministic mixed elastohydrodynamic lubrication (EHL) model. The honed surface was used to mate with other surfaces. The results indicate that a longitudinal contact ellipse favors longitudinally oriented mating surface roughness and that a transverse contact ellipse, as well as a line contact, prefers a transversely orientated mating surface roughness for lubrication enhancement.     

Tribological properties of lubricant additives of Fe,Cu and Co nanoparticles

Tribological investigations were performed on mineral oil containing Fe, Cu and Co nanoparticles and their combinations. The tribological tests showed that each set of nanoparticles significantly reduced the friction coefficient and wear (up to 1.5 times) of friction pairs. The use of Cu nanoparticles provides the most effective reduction of friction and wear in each combination of nanoparticles. Surface analysis shows that the constituent elements of nanoparticles precipitated on the contact surface during the use of the oils with nano-additives. Different structures formed on the friction surface are observed in the contact zone and over the remainder of the ball surface. The SEM micrographs and EDX chemical analysis confirm the formation of a tribo-layer composed of the elements from the nanoparticles.     

表面粗糙度对纳米润滑添加剂摩擦学性能影响的研究

摩擦学系统的复杂性及多变性增加了对材料在摩擦试验过程的预见性的难度，通过XP销盘摩擦磨损试验机分别考察了钢／钢摩擦副住不同润滑介质中不同的表面粗糙度对其摩擦系数和磨损量的影响。试验结果表明：表面粗糙度对摩擦副的摩擦学影响是复杂的，在特定的润滑条件下，不同的表面粗糙度表现出不同的摩擦学性能。