An investigation on the tribological behaviors of steel/copper and steel/steel friction pairs via lubrication with a graphene additive

In this study,the tribological behaviors of graphene as a lubricant additive for steel/copper and steel/steel friction pairs were compared.For the steel/copper friction pair,the graphene sheets remarkably decreased the coefficient of friction and wear scar depth under low loads,but these slightly increased under high loads.The steel/steel friction pair showed excellent tribological properties even under high loads.Severe plastic deformation on the copper surface reduced the stability of the graphene tribofilm because of a rough copper transfer film on the steel during the running-in period.The results provide a better understanding of the mechanism of graphene as a lubricant additive.

Study on the characterization of the surface topography of friction pairs during wear process with fractal theory

Wear of machine parts is an important problem in operating life of machines. Rationalwear and running-in procedures are able to machine parts improve in conformity, surface topog-raphy and frictional compatibility during usage, therefore improving machine reliability and pro-longing its operating life. Hence, it is necessary to study the topography characterization of thesurfaces of friction pairs and its change laws in wear or running-in process. This paper appliesfractal theory to study the characterization of the worn surface topographies of friction pairs duringthe initial stage of wear process. Experimental researches show that the fractal parameters of thesurface topographies of friction pairs will reach their steady-state values, respectively, with thewear process going on. And the variations of the fractal parameters have corresponding laws fortwo samples of friction pairs.

The Friction and Wear of Sleeve-ring Pair Lubricated by Active Lubricants in the Presence of Magnetic Field

The effect of magnetic field on the tribological process of sleeve-ring pair lubricated by WRL lubricants was investigated by means of a NG-x wear tester and a PS5013 video microscope. The friction coefficient(f) and the wear weight(W) in lubricating test with WRL lubricant were decreased with the increase in the magnetic field vertical to the rubbing surface, and an almost zero wear lubricating situation was gained in a magnetic field of 1000A/m. The captured wear micro particles on the rubbing surface were observed in the testing process, and the theoretical analysis of magnetic effects was completed. It is indicated that the magnetic field has not only a capturing action of wear micro particles on the worn surface, but also a inducing polarization of magnetic anisotropy of lubricant molecular. The actions promote the absorption of WRL lubricant into the wear surface as well as wear micro-particles, so that a good tribological effect is obtained when both magnetic field and WRL present.

Analysis of composite material interface crack face contact and friction effects using a new node-pairs contact algorithm

A new node-pairs contact algorithm is proposed to deal with a composite material or bi-material interface crack face contact and friction problem （e.g., resistant coating and thermal barrier coatings） subjected to complicated load conditions. To decrease the calculation scale and calculation errors, the local Lagrange multipliers are solved only on a pair of contact nodes using the Jacobi iteration method, and the constraint modification of the tangential multipliers are required. After the calculation of the present node-pairs Lagrange multiplier, it is turned to next contact node-pairs until all node-pairs have finished. Compared with an ordinary contact algorithm, the new local node-pairs contact algorithm is allowed a more precise element on the contact face without the stiffness matrix singularity. The stress intensity factors （SIFs） and the contact region of an infinite plate central crack are calculated and show good agreement with those in the literature. The contact zone near the crack tip as well as its influence on singularity of stress fields are studied. Furthermore, the frictional contacts are also considered and found to have a significant influence on the SIFs. The normalized mode-II stress intensity factors KII for the friction coefficient decrease by 16% when f changes from 1 to 0.

微织构对挖掘机铲斗关节摩擦副表面耐磨性能研究

为了改善挖掘机铲斗关节摩擦副的磨损问题,以特定的挖掘机模型为例,通过模拟挖掘机铲斗关节摩擦副的典型工况确定其相应的载荷,采用有限元法对此加载条件下各种形貌微织构表面的应力分布进行了研究。采用GY-LC-01型飞秒激光打标机对1Cr13基体表面加工一定尺寸的微织构,在有油润滑条件下,使用端面摩擦磨损试验机进行摩擦磨损试验,利用三维扫描深度显微镜观察磨损表面,研究了不同微织构的摩擦机理以及润滑条件下摩擦副的减摩效果。研究结果表明,织构表面的摩擦性能优于非织构表面,应力集中在织构边缘,圆形织构表面应力最小、减摩耐磨特性最好,具有最低的平均摩擦因数。

Characteristics of Magnetic Tribology on High Flux Pair of Magnetic Driving Mechanism

The rectangle-like pulsed magnetic field acted on the rubbing pair was presented through analyzing the exciting property in the reciprocating travel. The test of wear in NG-x tester shows that the wear between the electromagnetic core and down magnetic board distributes in the high velocity slip region of reciprocating travel, and the adhesive wear in the low velocity slip region nearby up and down dead points is depressed owing to the presence of high flux magnetic field. The lubrication by magnetic fluid with high permeability effectively reduces the friction and wear of high flux rubbing pair, and improves the conducting property of magnetic circuit constructed by the rubbing pair, which is beneficial to increase the operation performance of magnetic driving mechanism.

滑动摩擦副表面非对称微织构空化效应数值分析

为探究滑动摩擦副表面非对称微织构空化效应及其影响因素,基于N-S方程建立了表面织构化滑动摩擦副数值计算模型并进行求解,讨论了凹槽型非对称微织构的结构参数、运动速度和润滑油黏度对凹槽内的气相分布、空化面积率、油膜承载力和摩擦系数等的影响.结果表明:凹槽型非对称微织构的承载力大于对称微织构,而其摩擦系数小于对称微织构;在考虑空化效应时,凹槽型非对称微织构比对称微织构能更显著地改善摩擦学性能,并且非对称微织构凹槽离入口距离越远,空化效应越显著;滑动摩擦副运动速度和润滑油黏度对空化效应有重要影响,运动速度越高、润滑油黏度越大,凹槽型非对称微织构的空化效应越明显,且提升承载力的能力明显优于对称微织构,该研究对滑动摩擦副表面微织构的设计和分析有一定的参考意义.

织构化盘式摩擦副性能及优化设计研究

为探索提高盘式摩擦副抗摩擦磨损性能的有效途径,以斜盘柱塞泵配流副为研究对象,综合运用仿真分析及试验研究方法对比分析了面积织构率和截深形状相同条件下,椭圆开口和圆形开口离散凹坑微织构及沟槽形微织构配流副的摩擦因数随织构形貌、转速和压力的变化规律。研究结果表明:摩擦因数随转速的增大而显著降低,随压力的增大而降低,椭圆开口离散凹坑微织构为三种微织构中提高配流副性能最优者。对椭圆开口离散凹坑微织构进行多目标参数优化,得出的最优参数为:椭圆开口长轴半径为452μm、短半轴为187μm、径向中心距为0.7 mm。试验结果表明,优化后的织构在不同工况下较优化前摩擦因数和磨损量均有不同程度的降低。

Distribution Performance Analysis and Experimental Research on the Port Plate Pairs of Low Speed High Torque Seawater Hydraulic Motor

The current research of seawater hydraulic motor mainly focused on piston motor and vane motor, but seldom regarded low speed high torque seawater hydraulic motor. Low speed high torque seawater hydraulic motor as a kind of energy conversion device and actuator plays an important role in seawater hydraulic transmission system. However, the physical and chemical properties of seawater, such as low viscosity, high causticity and poor lubrication, result in numerous problems. In this paper, the flow distribution characteristics of port plate pairs for the seawater hydraulic motor are investigated, and the leakage flow and power loss models of port plate pairs are established. Numerical simulations are carried out to examine the effects of water film, inlet pressure and rotating speed on the pressure distribution and leakage flow. And the friction and wear tests of port plate pairs are also carried out. Moreover, the test system of the seawater hydraulic motor is constructed and the performance of prototype with no-load or loading is conducted. The results indicate that the clearance of port plate pairs and inlet pressure have a significant effect on distribution characteristics, but the effect of rotating speed is not very obvious. The experimental results show that the minimum error rate can be maintained within 0.3% by the proposed flow model and the counter materials of 316 L against carbon-fiber-reinforced polyetheretherketone(CFRPEEK) are suitable for the port plate pairs of seawater hydraulic motor. Finally, based on the seawater hydraulic experiment platform, the volumetric efficiency of no-load and loading are obtained that the maximum can achieve 94.71% and 90.14%, respectively. This research work may improve the flow distribution performance, lubrication and the friction and wear properties, enhance energy converting efficiency of port plate pair and provide theoretical and technical support for the design of highperformance water hydraulic components.

机体振动信号时频特性与燃烧压力相关性分析

为了探明机体振动信号与缸内燃烧状态间的相关性,本文通过改变转速、转矩、润滑油温度及配缸间隙形成不同的燃烧状态,利用连续小波变换算法得到了振动信号时频域特性,并与燃烧压力峰值进行对比分析。结果表明:随转速增加,燃烧压力峰值出现波动,8 kHz以上成分的能量总体呈增加的趋势;随转矩增加,燃烧压力峰值及振动信号的能量均增加;随润滑油温度升高,20 kHz以上主要频率成分的能量增加;随配缸间隙增加,10kHz以上频率成分的能量总体呈增加的趋势。

多锥形摩擦副接合过程摩擦转矩特性研究

多锥形摩擦副是新型湿式离合器的关键部件,具有体积小、转矩传递性能好等优点.针对多锥形摩擦副的特殊构型,考虑油膜承载力、微凸体接触以及摩擦元件温升等因素,建立了接合过程中摩擦转矩的多物理场耦合数学模型并进行数值求解.计算得到的摩擦转矩与试验数据相比误差小于10%,仿真模型具有较高的准确性.基于该模型对不同加载压力和相对转速下的摩擦转矩特性进行了研究.此外,采用Box-Behnken Design试验设计,通过响应面分析得到锥面数量、锥形角度、锥形高度等锥形参数对摩擦转矩的影响规律.结果表明:摩擦转矩与加载压力呈正相关关系,当加载压力从0.1 MPa增加到0.2 MPa时,摩擦转矩峰值增大了102.2%;减小锥形角度的同时增大锥形数量可更有效地提高摩擦副的转矩传递能力,缩短同步时间.研究结果可为新型多锥形摩擦副的优化设计提供参考依据.

点接触弹流摩擦副动特性研究

弹流油膜具有显著的弹簧、阻尼特性,对高副机械零件和系统的动特性具有重要影响。研究弹流摩擦副的动特性,揭示弹流摩擦副动力学特性的变化规律,对改进和提升整个机械系统的动力学设计具有重要意义。基于弹流润滑理论和机械振动学,建立点接触弹流摩擦副的摩擦学-动力学耦合模型,采用数值方法求解弹流摩擦副在简谐激励下的振动响应;通过简谐激励下弹流摩擦副的阻尼环识别出弹流摩擦副的刚度和阻尼,用参数控制的方法研究载荷、速度、材料参数及椭圆度等对弹流摩擦副刚度和阻尼的影响。结果表明:在研究的速度和载荷范围内,摩擦副的刚度和阻尼随载荷和椭圆度的增大而增大,随速度和材料参数的增大而减小,其中载荷对点接触EHL摩擦副的刚度和阻尼的影响最为显著,相比阻尼,摩擦副的刚度随载荷、速度和材料参数的变化幅度要大得多。在数值算例的基础上,给出弹流摩擦副的刚度和阻尼关于载荷、速度和材料参数的拟合公式。数值比较结果表明,给出的拟合公式具有满意的精度,可快速计算弹流状态下点接触摩擦副的刚度和阻尼。

线接触弹流润滑摩擦副刚度阻尼拟合公式

弹流润滑油膜具有显著的弹簧阻尼作用,对齿轮、滚动轴承、凸轮等高副接触零件的动力学性能具有重要影响,然而目前关于弹流摩擦副刚度阻尼的认识还不统一。运用数值方法求解线接触弹流润滑摩擦副的摩擦学-动力学耦合模型,获得线接触弹流润滑摩擦副在简谐激励下的阻尼环,通过阻尼环识别出线接触弹流润滑摩擦副的刚度和阻尼;用变量控制的方法研究载荷、卷吸速度、材料参数等对线接触弹流润滑摩擦副刚度和阻尼的影响,并分析载荷、卷吸速度影响线接触弹流润滑摩擦副刚度阻尼的机制。结果表明,线接触弹流润滑摩擦副刚度阻尼随载荷增加而变大,随速度增加而减小。在数值解的基础上,拟合出线接触弹流润滑摩擦副刚度和阻尼公式,结果显示,载荷对弹流润滑摩擦副的刚度和阻尼影响最显著,而且弹流润滑摩擦副的刚度随载荷、速度和材料参数的变化幅度比阻尼的大。对拟合公式精度的检验表明,在很宽的参数范围内,拟合公式计算结果与数值解的相对误差小于10%,所提出的刚度和阻尼拟合公式具有很高的精确性。

基于分形理论的静压支承滑靴系统摩擦自适应特性分析

静压支承滑靴副比一般的滑动摩擦副具有更好的摩擦自适应特性,对滑靴的早期磨损有一定的修复效果,但其摩擦自适应机理目前尚不明确。为此,基于分形理论,采用分形维数、尺度系数等分形参数描述滑靴表面形貌,对摩擦自适应过程进行理论分析,开展磨损试验并以分时段更换试件的试验方法观察分形参数的变化情况,得到分形参数对摩擦学特性的影响规律,揭示滑靴摩擦自适应机理。结果表明,滑靴副在发生早期磨损后,分形维数呈增大-减小-再增大-再减小的变化过程,尺度系数和摩擦系数呈减小-增大-再减小-再增大的变化过程,滑靴在早期磨损阶段呈现出显著的摩擦自适应特性,其表面性能表现出劣化-修复-再劣化-再修复的变化特征。

表面织构对径向柱塞泵滑靴副摩擦磨损性能的影响

高压大排量径向柱塞泵的承载力较大,而滑靴副是影响该类泵摩擦特性的关键因素之一。开展织构对滑靴副摩擦特性影响的研究,对提升高压大排量径向柱塞泵滑靴副润滑与摩擦特性具有重要意义。为此,以高压大排量径向柱塞泵滑靴副为研究对象,计算了不同形状、面积率、深径比织构的滑靴磨损量。首先,选取了正方形、圆形和三角形共3种形状的织构表面,对织构的深度、形状、面积率进行了定义,构建了滑靴织构形貌影响因素和正交试验样本;然后,开展了10组样本数据的试件摩擦磨损试验,分别以摩擦系数和磨损量为因变量,得到了多因素方差分析检验结果;最后,基于显著性小的因素确定了研究参数,开展了不同形状织构表面的摩擦仿真与试件试验。研究结果表明:织构的面积率对摩擦系数和磨损量影响最大;面积率为9.66%、深度为120μm的三角形织构表面的摩擦系数最小,相比无织构表面下降16%;摩擦仿真所得三种形状织构表面的磨损量排序与试验结果一致;面积率为9.66%、深度为120μm的正方形织构表面的减摩效果最好、磨损量最小,磨损量较无织构表面下降35%,摩擦系数相对无织构下降15.86%。该研究结果可以为高压大排量径向柱塞泵滑靴副设计,改善滑靴副的摩擦磨损特性,延长柱塞泵的使用寿命提供一定的参考。

B_(4)C&H-DLC薄膜在过氧化氢溶液中的摩擦学行为研究

采用闭合场非平衡磁控溅射技术在316L不锈钢表面沉积硼、氢掺杂类金刚石碳(B_(4)C&H-DLC)薄膜,利用扫描电镜(SEM)、Raman、X射线光电子能谱仪(XPS)、纳米压痕和线性往复摩擦试验机等系统分析了B_(4)C&H-DLC薄膜的结构、力学性能及过氧化氢水溶液中与不同对偶球的摩擦学行为.结果表明:B_(4)C&H-DLC薄膜在过氧化氢环境中与Al_(2)O_(3)球相对摩擦时,有严重的磨粒磨损行为,摩擦系数与磨损率较高.此外,B_(4)C&H-DLC薄膜在过氧化氢环境中与Si_(3)N_(4)和SiC球相对摩擦时发生了复杂的摩擦化学反应,形成了硅胶和硼酸的摩擦化学产物,发挥了减摩抗磨作用[磨损率较低分别为0.8×10^(-7)和1.0×10^(-7)mm^(3)/(N·m)].因此,本研究为碳基薄膜在氧化条件下摩擦副的合理设计和应用提供了试验依据,同时也为保护在苛刻环境工作的机械部件提供了1种可行方法.

水润滑陶瓷滑动轴承材料配副摩擦学性能的研究

陶瓷滑动轴承由于材料化学性能稳定,适合在各种与水直接接触的场合下运行。为找到边界水润滑条件下摩擦学性能较优良的陶瓷轴承材料配副及其适合的运行工况,对Al_(2)O_(3),ZrO_(2)陶瓷分别与不同陶瓷材料组成的配副开展了摩擦学性能试验。结果表明:1)Al_(2)O_(3)系列配副的磨损机制为从前期的机械磨损为主逐步过渡到以摩擦化学磨损为主;Al_(2)O_(3)/Si_(3)N_(4)配副的摩擦系数最小,耐磨性好且摩擦接触面较光滑;在选取的4种速度条件下,当摩擦副相对滑动速度为0.157 m/s时,润滑效果最好。2)ZrO_(2)系列配副的磨损机制以磨粒磨损为主,ZrO_(2)/Si_(3)N_(4)配副的摩擦系数和磨损体积最小;在选取的4种速度条件下,当摩擦副相对滑动速度为0.136 m/s时,摩擦系数最小,但其摩擦系数曲线不稳定。

基于硬质WC涂层的不同摩擦副间的摩擦磨损特性及损伤机制研究

目的探究硬质WC-12Co涂层与摩擦副间的力学性能、摩擦磨损特性的对应关系。方法采用超音速火焰喷涂(HVOF)技术制备WC-12Co硬质涂层,利用SEM、XRD、EDS等分析涂层的微观形貌、物相组成和元素分布规律等,研究该涂层与不同对偶配副的摩擦学性能及摩擦磨损机理等。结果采用HVOF技术制备的WC-12Co涂层中各元素及物相分布均匀,涂层的显微硬度约为1103.8HV0.3,纳米硬度约为20.47GPa。涂层和不同对偶配副的干摩擦因数均在0.80以上,磨损率在10^(-6)mm^(3/)(N·m)量级,其中与Al_(2)O_(3)对偶球配副时摩擦因数(约0.81)最低,与WC-6Co对偶球配副时摩擦因数(约0.85)最大,在与Al_(2)O_(3)配副时磨损率最大,约为11.09×10^(-6)mm^(3)/(N·m),与GCr15配副时磨损率最小,约为1.60×10^(-6)mm^(3)/(N·m)。结论硬质WC-12Co涂层致密均匀,其力学性能优异,与不同材质对偶球配副时其磨损机制有所不同,导致摩擦副间的摩擦因数和磨损率略有差异,但其耐磨性均良好,可以根据实际应用工况特点选择不同的摩擦副,以保证硬质碳化钨涂层的安全稳定长效服役。

银/聚多巴胺改性氧化石墨烯改善陶瓷摩擦副摩擦性能的研究

目的提高润滑油在陶瓷摩擦副中的润滑性能。方法通过一步法制备银/聚多巴胺改性氧化石墨烯(Ag/PGO)纳米复合粒子,并作为润滑油的添加剂,通过摩擦试验研究含Ag/PGO润滑油的润滑性能。通过重力沉降法测试Ag/PGO在润滑油中的分散稳定性。观察磨痕微观形貌,通过分子动力学模拟方法,揭示含Ag/PGO润滑油的润滑机理。结果聚多巴胺改性氧化石墨烯(PGO)在润滑油中可以稳定分散25 d,Ag/PGO在润滑油中可以稳定分散10 d。含Ag/PGO润滑油在Si_(3)N_(4)/Si_(3)N_(4)、Si_(3)N_(4)/GCr15两种摩擦副中均表现出良好的润滑性能,含Ag/PGO润滑油在Si_(3)N_(4)/Si_(3)N_(4)摩擦副中的最佳质量分数为0.05%,与基础油相比,其摩擦因数和磨痕宽度分别降低了16.8%、17.6%;在Si_(3)N_(4)/GCr15摩擦副中的最佳质量分数为0.2%,其摩擦因数和磨痕宽度分别降低了53.6%、22.7%。表明含添加剂润滑油的磨痕表面质量得到提升。结论聚多巴胺经改性,可以有效提高氧化石墨烯在润滑油中的分散性能。与Si_(3)N_(4)壁面相比,含Ag/PGO的润滑油易于吸附在GCr15壁面。在剪切过程中,Ag/PGO与润滑油分子的相互作用减小了润滑油分子与摩擦壁面的相互作用能,减小了摩擦阻力,因此含Ag/PGO的润滑油在Si_(3)N_(4)/GCr15摩擦副中表现出更好的润滑性能。

机体表面振动信号影响因素关联性分析

为了研究机体表面振动信号各影响因素的影响规律,在不同转速、转矩、润滑油温度及配缸间隙下,对比分析振动信号的峰值、方差、标准差及均方根等4个时域参数以及小波包分解得到的各频段能量的变化趋势。结果表明:随着转速的升高,燃烧压力峰值出现波动,在活塞惯性力的主导作用下,振动信号时域特征参数及频段5以上频率成分的能量呈增加的趋势;燃烧压力峰值随着转矩的增加而增大,振动信号时域特征参数及各频段能量均呈增加的趋势;随着润滑油温度的升高,在润滑油阻尼及燃烧压力的双重作用下,振动信号时域特征参数幅值整体呈降低的趋势,频段12以上频率成分的能量呈增加的趋势;随着配缸间隙的增加,密封性降低导致燃烧压力峰值减小,但由于活塞二次运动加剧,导致振动信号时域特征参数及频段5以上频率成分的能量呈现增加的趋势。