Numerical and Experimental Studies on Tribological Behaviors of Cu-Based Friction Pairs from Hydrodynamic to Boundary Lubrication

When studying the tribological behaviors of a Cu-based friction pair in different lubrication regimes, calculation of the real contact area of asperity contacts is crucial but difficult. In this work, a mixed lubrication model in plane contacts is developed, and pin-on-disc tests are carried out. The real contact area ratio, load sharing ratio, and friction coefficient are investigated. Effects of sliding velocity, temperature, and pressure are considered. The results show that when the maximum contact area ratio is about 14.6%, the load sharing ratio of asperity contacts is about 95%. The friction coefficient obviously increases from less than 0.04 to about 0.15 as the regime changes from hydrodynamic to boundary lubrication. Asperities have a significant influence on the local lubrication of a Cu-based friction pair, and the action of hydrodynamic pressure cannot be ignored.     

脂润滑条件下闸门底枢摩擦副磨损失效评价

采用摩擦磨损试验机,获得了QAL9-4/40Cr和ZCuAl8Mn13Fe3/40Cr两种闸门底枢摩擦副在不同接触应力的脂润滑条件下的摩擦学特性,并运用灰色系统理论GM（1,1）模型对其达到许用磨损量的磨损失效进行了评价。低速重载条件下,两种摩擦副的实际接触应力在许用应力之下时,其磨损形式均以犁切为主,且磨损量随接触应力的增大而增大,摩擦因数随着接触应力的增大而减小;反之,其磨损形式均以黏着为主,且磨损速度、摩擦因数均会急剧增加。受同一接触应力作用时,QAL9-4/40Cr具有更好的耐磨性。理论模型对磨损失效的预测结果与实测值吻合度达到95%。     

不同润湿组合配流副的摩擦磨损试验研究

为调控配流副表面润湿性以提高摩擦学性能,采用低面能修饰法制备具有不同润湿性的上试样超级双相不锈钢SAF2507和下试样碳纤维增强聚醚醚酮(CFRPEEK)组成配流副,利用MMD-5A标准摩擦磨损试验机测试并分析其在蒸馏水、海水、L-HM46抗磨液压油3种润滑条件下的摩擦磨损特性。结果表明：低面能修饰使配流副上试样与下试样由亲水表面转变为疏水表面,上下试样表面虽仍保持亲油性但其油接触角明显增大;同种配流副在油、海水、水介质中摩擦因数依次减小;在水、海水、油介质下双疏水表面配流副较双亲水表面配流副摩擦因数分别减小8.2%、38.2%、24.4%;同种配流副在水、海水、油介质中磨痕深度依次减小。配流副的摩擦主要以犁沟效应和黏着磨损为主,双低表面能组合配流副能有效减小摩擦过程中的黏着磨损,从而表现出较好的摩擦学性能。     

钢铜摩擦副摩擦磨损特性的试验研究

本文试验分析了ＺＱＡ１９－４和ＺＱＺｎ６－６－３两种铜合金材料在不同的表面粗糙度下对摩擦系数和出口区油温的影响，以及改变载荷和相对滑动速度时，摩擦系数的变化状况。结果表明；铜合金成分不同时具有不同的硬度。     

摩擦副表面沟槽型织构润滑性能的数值仿真

从目前的研究来看,织构的深度和载荷对油膜的润滑性能具有显著的影响,然而,在载荷变化的情况下,润滑膜的最小膜厚和黏性阻力是一个动态变化的过程。因此不同载荷下,最佳织构深度的选取还需系统地进行分析。通过建立沟槽型织构流体润滑模型,分析了织构的深度以及承载力对摩擦副的油膜厚度、压力、剪切力、以及摩擦因数的影响。结果表明：在承载力一定时,油膜厚度随织构深度的增加呈先增大后减小的趋势。在89 N载荷下时,存在最佳油膜厚度6.4184μm,此时织构深度为2.97μm,摩擦因数为0.0162。     

Effects of Friction on the Contact and Deformation Behavior in Sliding Asperity Contacts

Finite-element analyses are carried out to study the effects of friction on the contact and deformation behavior of sliding asperity contacts. In the analysis, on elastic-perfectly-plastic asperity is brought in contact with a rigid flat at a given normal approach. Two critical values of the normal approach are used to describe the asperity deformation. One is the approach corresponding to the point of initial plastic yielding, and the other at the point of full plastic flow. Additional variables used to characterize the deformation behavior include the shape and size of the plastic zone and the asperity contact size, pressure, and load capacity. Results from the finite-element analysis show that the two values of critical normal approach decrease significantly as the friction in the contact increases, particularly the approach that causes plastic flow of the asperity. The size of the plastically deformed zone is reduced by the friction when the contact becomes fully plastic. The reduction is very considerable with a high friction coefficient, and the plastic deformation is largely confined to a small thin surface layer. For a low friction coefficient, the contact size, pressure and load capacity of the asperity are not very sensitive to the friction coefficient. For a moderate friction coefficient, the contact pressure is reduced and the junction size increased; the load capacity of the asperity is not significantly affected due to the compensating effects of the pressure reduction and the junction growth. For a high friction coefficient, the pressure-junction compensation is not longer sufficient and the asperity load capacity is reduced. The degree of the friction effects on these contact variables depends on the applied force or the normal approach. Although the analyses are conducted using a line-contact model, the authors believe that the effects of friction in sliding asperity contacts of three-dimensional geometry are essentially the same and the same conclusions would have been reached. These results may provide some guidance to the modeling of rough surfaces in boundary lubrication, in which the asperity friction coefficient can be high and vary significantly both in time and from one micro-contact to another.     

室温及气氛条件下铜基自润滑复合材料的摩擦磨损性能研究

采用粉末冶金法制备了3种铜基自润滑复合材料,分别考察了它们在室温及气氛条件下的摩擦磨损性能,通过对复合材料的力学性能和磨痕表面形貌、成分的分析,探讨其摩擦磨损机制.结果表明:Cu-9%石墨、Cu-4.5%石墨-4.5%MoS2、Cu-9%MoS2复合材料的密度、硬度和抗弯强度值都依次增大;室温条件下,因石墨与Cu的硫化物协同润滑作用,Cu-4.5%石墨-4.5%MoS2复合材料的摩擦磨损性能最好;气氛条件下,因Cu的硫化物发挥了其自润滑作用,Cu-9%MoS2复合材料表现出最佳的减摩耐磨性能,而Cu-4.5%石墨-4.5%MoS2复合材料次之;铜基自润滑材料的基体强度与固体润滑膜的覆盖率,是影响摩擦磨损机制转变的关键因素.     

混合型轴承摩擦机理的研究

采用Timken摩擦试验机在空气中,水、润滑油及合成油脂润滑状态下对M50钢、热静等压氮化硅陶瓷轴承元件的摩擦机理进行了研究.对各种参数包括速度、滑动距离和润滑剂进行了比较.     

纯水柱塞泵摩擦副材料磨损试验研究

纯水液压用纯水作为工作介质，克服了液压技术中矿物油易燃烧、污染环境的缺点。纯水的理化性能和纯水柱塞泵中摩擦副的工况特征，决定了筛选低成本的摩擦副材料是研制纯水柱塞泵的重要工作。针对酏水柱塞泵工况，在滴水润滑条件下，研究了5种陶瓷涂层和氧化铝配对的摩擦磨损情况，考察了摩擦系数和磨损量随时间的变化曲线，以期为纯水柱塞泵的材料选择提供依据。     

聚合物填充聚四氟乙烯复合材料的摩擦磨损性能

采用机械共混-冷压成型-烧结的工艺制备了PEEK、PPS填充PTFE基粘弹．摩擦型阻尼材料,用环-块式磨损试验机研究了在干摩擦条件下的摩擦磨损性能;用扫描电子显微镜观察磨损表面形貌和内部组织结构。结果表明：混合填充PEEK和PPS时,2种填充物的比例对材料的摩擦因数影响不大,当二者含量相近时,摩擦因数最大;填充物对磨损性能的影响与对摩擦因数的相同;随着PEEK含量的增加和PPS含量的减少,材料的磨损方式由疲劳剥落磨损为主转变为犁削、粘着磨损;PTFE含量的增加,使得复合材料的摩擦因数减小,而磨损有所增大。综合考虑认为,PTFE与适当比例的PEEK／PPS混合填充,具有合适的摩擦因数和较好的耐磨性,能够满足特殊工况下阻尼材料的需要。     

生物摩擦磨损润滑剂的润滑特性

关节转换已广泛应用于关节炎晚期治疗,外伤致残和滑瘤切除手术中。关节转换材料的耐磨性能会直接影响转换关节的使用寿命和使用质量。蒸馏水、盐水、血浆、血清等均被用作生物摩擦磨损研究的润滑剂,但是对这些润滑剂的润滑特性并未认真考察。本文应用ＴＬＴ－１型弹流试验台对血浆在内的几种生物摩擦磨损润滑剂的润滑特性进行了研究,结果表明血浆的润滑性能最好。     

水润滑塑料轴承的摩擦性能研究

用MPV—200型摩擦磨损试验机测定了超高分子量聚乙烯(简称UHMW—PE)塑料合金轴承水润滑条件下的摩擦学性能，考察了载荷、速度、运行时间等因素对轴承摩擦系数和磨损率的影响，得出了摩擦学性能随各种因素的变化规律。并对作用机理进行了系统的分析，为水润滑超高分子量聚乙烯塑料合金轴承的实际应用提供理论依据。     

ZrN涂层刀具的滑动磨损特性研究

山东大学摘要:采用电弧离子镀法在硬质合金刀具表面制备了厚度为2.19~5.23μm的ZrN系列涂层,测定了涂层的显微硬度,并通过划痕试验和摩擦磨损试验考察了涂层与基体的结合强度及其摩擦磨损性能。在扫描电镜下观察磨损表面形貌,结果表明:ZrN系列涂层能够显著提高硬质合金刀具的表面硬度;涂层与基体的结合强度较高,划痕临界载荷高于60N;与此同时,电弧离子镀法ZrN系列涂层可以显著改善硬质合金刀具的耐磨性能。磨损机理主要是磨粒磨损和涂层的微剥落。     

Friction and Wear on Single-Layer Epitaxial Graphene in Multi-Asperity Contacts

Friction and wear of single layers of graphene have been studied at the micrometer scale. Epitaxial graphene grown by thermal decomposition on SiC-6H(0001) is found to have an initial friction coefficient of 0.02, significantly lower than graphite under the same experimental conditions. During reciprocal sliding the graphene layer is damaged. The evolving friction coefficient of 0.08 for the carbon-rich interface layer terminating the SiC layer is still lower than that of graphite and five times lower than that of the hydrogen-etched SiC substrate. Micrometer-sized patches within the sliding track retain the low friction coefficient of graphene even after hundred sliding cycles.     

轴向柱塞泵摩擦副润滑膜性能动态试验系统分析

为了进行供油压力高、输出流量大的轴向柱塞泵配流副、滑靴副等关键摩擦副润滑膜性能试验,基于试验供油油路与加载油路分离原则,研制了轴向柱塞泵摩擦副润滑性能试验系统。论述了轴向柱塞泵摩擦副润滑特性研究的必要性及目前试验研究存在的主要问题,根据润滑理论模型分析了试验研究的主要内容,针对其难点提出了基于精密位置反馈的新型电液控制润滑膜动态试验系统组成、特点及关键技术等。通过在研制的试验系统上进行实际的油膜平衡、密封带多点膜厚实测及泄漏流量与膜厚等试验的数据分析表明,该试验系统稳定、可靠,能够完成预期设计的试验对系统的要求,亦可开展相关摩擦副润滑特性试验研究。     

试验参数对人工滑液边界润滑条件下超高分子量聚乙烯/Ti6Al4V往复摩擦磨损行为的影响

采用自行研制的往复摩擦磨损试验机,在法向载荷50 N、往复频率1 Hz、摩擦副接触形式为圆环外圆周/平面、初始线接触长度为6 mm、相对湿度为80%的试验条件下,研究了钛合金表面粗糙度、试验环境温度、试验延续时间、滑液成分等试验参数对UHMWPE/Ti6A14V摩擦副的往复摩擦磨损行为的影响.结果表明,这些试验参数均显著影响UHMWPE/Ti6A14V摩擦副的往复摩擦磨损行为;在环境温度20℃、25%小牛血清去离子水溶液边界润滑、180 min往复摩擦磨损试验条件下,当钛合金表面粗糙度由Ra0.04 μm增加至Ra0.06μm时,摩擦副的平均摩擦因数由0.033增加至0.096,UHMWPE试样磨损量由0.131 mm3,增加至0.149 mm3;在钛合金表面粗糙度为Ra0.06μm、25%小牛血清去离子水溶液边界润滑、180 min往复摩擦磨损试验条件下,当试验环境温度由10℃上升至37℃时,摩擦副的平均摩擦因数由0.135减少至0.077,UHMWPE试样磨损量由0.188 mm3减少至0.134 mm3.     

油润滑下MoSi2材料的摩擦磨损性能

运用M-200型摩擦磨损试验机测定了油润滑条件下MoSi2与45调质钢、45淬火钢和CrWMn钢配对时的摩擦磨损性能，采用扫描电镜和微探针分析了摩擦副表面的形貌，探讨了磨损机理：结果表明：采用20号机械油润滑可有效地降低MoSi2材料的磨损率及摩擦因数；与低硬度的45调质钢和45淬火钢对摩时，MoSi2材料的主要磨损机制为晶间断裂、疲劳断裂、轻微粘着磨损和磨粒磨损；MoSi2材料与高硬度的CrWMn钢对摩时，主要磨损机制表现为粘着磨损、微犁削式磨粒磨损，并在偶件表面材料凸点的前端形成楔块。     

Thermodynamic Differences of Different Friction Pairs in a Multidisc Clutch Caused by Spline Friction: Numerical Simulation and Experimental Verification

Abstract

Considering the spline friction, the dynamic model of a multidisc clutch is established that permits the calculation of the contact pressure and friction torque acting at each friction surface; the thermal model is then developed to investigate the temperature difference between different friction pairs. The corresponding test bench is established, where the effect of inertia on the torque error is analyzed in detail. The simulated and measured results are compared to validate the numerical model and confirm the existence of spline friction. The results indicate that spline friction can lead to the attenuation of contact pressure on friction pairs along the axial direction. Therefore, there exists a significant temperature gradient in the axial direction, and the maximum temperature appears in the second separate plate near the piston. Moreover, the friction torque of a single pair decreases along the axial direction. Thus, as the number of friction pair increases, the total friction torque increases nonlinearly, and the average torque of single friction pair decreases gradually.     

水压柱塞摩擦副的润滑特性研究

基于静压支承的思想，提出双阻尼效应柱塞副来提高其抗卡紧能力。该结构在柱塞的圆周表面上设置了几组支承腔室和阻尼小孔，构成的静压支承结构具有间隙中压力可随间隙变化的调节刚度，保证间隙大小的均匀性，避免卡紧。对双阻尼效应柱塞副进行了抗卡紧特性的理论推导和计算流体力学（computational fluid dynamics，CFD）研究。同时，综合考虑了水的流动惯性和表面粗糙度的影响，研究了水压柱塞副的泄漏特性，并进行了样机试验，对两种柱塞副结构的润滑特性进行了对比分析。     

钢在磁场环境中的摩擦磨损行为

以45#钢为研究对象,在自制的销-环式摩擦磨损试验机上对其在磁场条件下的摩擦磨损性能进行研究。采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对磨损表面形貌进行表征。试验结果表明:施加磁场后,试样的摩擦因数和磨损率均显著降低;磨屑在接触表面的堆积及氧化是磁场改善钢铁材料摩擦磨损性能的主要原因。