双粗糙面滑动过程摩擦因数的变化分析

采用W-M函数建立具有分形特征的三维双粗糙面接触模型,考虑了接触界面间的黏着效应,在滑动速度、法向载荷及界面剪切强度等参数变化下,运用有限元方法探讨了粗糙体在滑动过程中摩擦因数的变化情况。结果显示,滑动速度、法向载荷及界面剪切强度等参数对摩擦因数的变化有一定的影响,边界润滑工况下平均摩擦因数为0.28,无润滑工况下平均摩擦因数为0.713,最大界面剪切强度时的平均摩擦因数为0.73;随着界面剪切强度的减小、法向载荷的增大、滑动速度的增加,滑动摩擦因数有所减小。与相关文献结论或实验结果进行比较,证明了上述结果的正确性。分析结果可为摩擦学设计和摩擦材料的制备提供理论参考。     

双粗糙表面滑动过程不同条件对Z向速度的影响分析

采用W-M函数建立具有分形特征的三维双粗糙面接触模型,在滑动速度、法向载荷及界面剪切强度等各种因素的相互作用下,动态探讨了粗糙体在滑动过程中的摩擦磨损情况。运用有限元方法对滑动过程进行模拟仿真,对Z向速度在各种因素作用下的变化规律进行分析,结果显示滑动速度较小情况下,Z向速度振幅较小;较小法向载荷情况下,Z向速度的振幅较大;界面剪切强度较小情况下,Z向速度的振幅较大。从功率谱看,较小界面剪切强度下摩擦振动变化比较强烈,而相应的所需要能量比较小。将这些结果与相关文献或实验进行比较,得出模拟仿真的合理性,同时通过研究法向载荷、滑动速度、界面剪切强度等工况参数对摩擦振动的影响,以期为摩擦学设计和摩擦材料的制备提供理论参考。     

表面改性碳纤维对聚酰亚胺复合材料摩擦学行为的影响

采用硝酸氧化法和涂层复合改性法分别对碳纤维(CF)进行表面改性,并制备CF改性聚酰亚胺(PI)复合材料。考察材料在不同滑动速度和载荷下的摩擦磨损行为,利用扫描电子显微镜观察磨损表面形貌。结果表明:CF与PI基体的界面结合强度对PI复合材料在不同滑动速度下的摩擦磨损性能影响较大,涂层复合处理法比硝酸处理法能更有效提高CF与基体的界面结合强度,提高复合材料在高滑动速度下的摩擦磨损性能。CF的强度是影响复合材料在不同载荷下摩擦磨损性能的主要因素,CF经过表面处理后强度出现不同程度的下降,导致在高载荷条件下复合材料的摩擦磨损性能下较未处理的CF/PI复合材料相比有所下降。     

法向载荷和滑动速度对纳米摩擦的影响

由于尺度效应,纳米尺度摩擦机制与宏观尺度有很大差别。在原子力显微镜实验基础之上,探讨纳米尺度干摩擦中微摩擦力与法向载荷以及滑动速度之间的关系。当法向载荷较小时,摩擦力与法向载荷之间并非线性关系,而近似与法向载荷的2/3次方成正比。当滑动速度小于摩擦系统临界滑动速度时,摩擦力随速度的对数增长而增长,而当速度超过临界滑动速度时,摩擦力几乎不受滑动速度变化的影响。     

工业摩擦学 第二讲:摩擦与磨损

一、摩擦一个物体在外力作用下,相对于另一个物体运动或有运动趋势时,其公共界面上所生的切向阻力叫做摩擦力。两个物体相接触的表面在无润滑的干摩擦状态下,物体受力在刚足以开始作相对运动时,界面上的切向阻力为“极限静摩擦力”,比极限静摩擦力小的力所引起的切向阻力为“静摩擦力”;相对运动的两表面间的摩擦力为“动摩擦力”。1.摩擦定律、摩擦系数和表面性质摩擦定律是指:摩擦力与法向载荷成正比;摩擦力与表观接触面积无关;动摩擦力大体上与滑动速度     

考虑热诱导载荷和摩擦生热交互影响的高速角接触球轴承温度场分析

高速电主轴角接触球轴承内部的摩擦会使轴承温度升高,进而影响主轴的使用性能。为精确分析高速角接触球轴承的温度场,提出了一种考虑热诱导载荷和摩擦生热交互影响的轴承温度场分析方法。首先建立考虑差动滑动、自旋滑动、载荷以及润滑油黏性引起的摩擦的总摩擦生热量计算模型和热诱导载荷计算模型,然后分析两者之间的交互影响,最终基于有限元分析软件得到轴承稳态温度场,结果表明：稳态时轴承最高温度在球与内圈接触区域,球与外圈的接触区域温度较低;考虑热诱导载荷时差动滑动、自旋滑动以及载荷引起的摩擦生热量大于未考虑热诱导载荷,润滑油黏性引起的摩擦生热量无变化;考虑热诱导载荷时球与内圈的接触力及温升大于未考虑热诱导载荷。     

Inconel718与硬质合金摩擦磨损特性的实验研究

利用UMT-2多功能摩擦磨损试验机对镍基合金Inconel 718与硬质合金刀具对偶时的摩擦磨损特性进行研究,揭示法向载荷和滑动速度对摩擦副摩擦因数的影响,通过SEM观察试样摩擦形貌并分析磨损机制.研究结果表明:摩擦副的摩擦因数随着法向载荷的增大而减小,随滑动速度的增大而增大;Inconel 718镍基合金与硬质合金对偶时的磨损机制主要为黏着磨损、磨粒磨损和氧化磨损.     

滑动摩擦过程中接触力的研究

在接触面上接触力对材料的破坏起着决定性作用,有必要研究接触力的变化情况。研究了滑动摩擦过程中,不同的界面剪切强度、不同的法向载荷与不同滑动速度对粗糙面的接触力影响,研究表明随着界面剪切强度增加,粗糙表面间有向上的拉力,随着法向载荷的增大,平均切向接触力的增长速率加快。在润滑条件相同时,滑动速度存在最佳值使平均滑动阻力最小。     

二维粗糙表面滑动摩擦的研究

能源接近一半消耗在摩擦上,摩擦引起的磨损为主要的机械零件失效方式,通过对摩擦和磨损机理的研究能有效地延长机械零部件的使用寿命。通过对建立的二维双粗糙弹塑性分形模型的实例分析,分析界面剪切强度和法向载荷对磨损率和平均摩擦系数的影响。界面剪切强度增加,磨损率增加较快。随着界面剪切强度的增加平均摩擦系数增加;当界面剪切强度较小时,随着法向载荷的增加平均摩擦系数增加,当界面剪切强度较大时,随着法向载荷的增大,平均摩擦系数先减小后又逐渐增大。     

假肢材料与人体下肢皮肤界面的摩擦特性

采用UMT-II多功能摩擦磨损试验机,在往复摩擦模式下模拟假肢接收腔/残肢皮肤界面,研究了4种不同表面结构的硅胶内衬套材料与皮肤的摩擦学行为。结果表明:硅胶材料/皮肤界面、接收腔/硅胶材料界面在往复摩擦模式初期均会产生相对滑动,摩擦因数较大;随着界面间产生黏着,摩擦因数减小,逐渐趋于稳态。硅胶材料反面上的粗大微凸体,增加了与皮肤的粘结性,摩擦能耗减少;正面上的针织结构不但增加了往复摩擦过程中与接受腔之间的相对滑动量及摩擦能耗,而且减少了其反面与皮肤往复摩擦过程中皮肤协调位移时的变形,从而降低了与皮肤之间的摩擦因数和能量损耗,因此,有利于降低皮肤摩擦损伤的风险,提高残肢患者穿戴舒适性。     

Friction of rubber on ice: A new machine,influence of rubber properties and sliding parameters

Friction of rubber on ice and snow is important for performance of vehicle tyres in winter. We introduce a new linear tribometer that was designed for measuring the friction of rubber on ice. We present a systematic study of rubber sliding on ice, investigating speed, load, temperature and rubber properties. The friction was linked to behaviour at the interface, particularly melt–water formation and real area of contact. Friction tends to decrease with conditions that promote melt–water formation, and tends to increase as real area of contact increases. We observe stick-slip behaviour with high real area of contact and high load.     

Role of Rubber Stiffness and Surface Roughness in the Tribological Performance on Ice

The aim of this work is to investigate the effect of slider surface roughness and stiffness on the friction between rubber compounds and ice surfaces in order to provide insight into rubber–ice friction generation mechanisms. For this purpose, rubber compounds were designed to have different levels of macroscopic roughness and cured stiffness by modifying the filler system and plasticizer loading. In order to accurately evaluate the effects of surface and bulk rubber property on ice friction, linear friction tests were performed on laboratory ice with varied frictional heat buildup by modifying the friction test protocol. The results showed that the friction force was in general increased through the ploughing effect of a rough rubber block sliding on smooth ice. The increase in friction by ploughing was more pronounced when the contacting rubber block had sufficiently low stiffness and when the accumulation of frictional heat on ice was sufficiently high. It was also evidenced that a sufficiently hard rubber with test conditions leading to low heat buildup on ice could nevertheless lead to an opposite influence of roughness on rubber–ice friction; that is, lower friction force with a slider with a higher roughness.     

Comparison between rubber–ice and sand–ice friction and the effect of loose snow contamination

The application of sand particles is a common method to improve the friction of aircraft tires on snow or ice covered runways. Hence, an understanding of the prevailing rubber–ice and sand–ice friction mechanisms is of practical interest. Rubber–ice and sand–ice friction measurements were made with a British Pendulum Tester at temperatures between ?22 and 0 °C and the effect of loose snow contamination on top of the ice was investigated. The results (the response of the instrument) were expressed in a sliding length averaged friction coefficient μ_BP. Close to the melting point the friction of rubber on ice was low and increased with decreasing ice temperature. Below ?5 °C, reasonably high friction levels (0.2<μ_BP<0.5) were obtained between rubber and ice, but the friction level dropped drastically by the presence of a very thin layer of snow. The sand–ice friction level was less dependent on ice temperature and clearly not as much affected by the presence of snow, compared to rubber–ice friction. The micromechanisms involved in rubber–ice and sand–ice frictions were investigated by the application of etching and replicating technique (ERT) developed for the examinations of the dynamics of dislocations in ice during deformation.     

Method of Constructing a 3D Friction Map for a Rubber Tire Tread Sliding Over a Rough Surface

An experimental methodology for constructing a 3D friction map, which depends on normal pressure, sliding velocity, and temperature, for tire tread rubber has been presented. The methodology of constructing a 3D friction map is based on the principle of temperature–velocity superposition, which makes it possible to combine the obtained experimental data into one sculpted surface. Two types of the tread rubbers were investigated that are used in summer passenger tires and heavy-loaded all-metal tires. The results of analyzing the obtained 3D friction maps have been presented. The influence of normal pressure and sliding velocity to the amount and position of the values of coefficient of friction of the rubber sliding over the sandpaper surface with the specified abrasive grit has been considered.     

Method of evaluating the coefficient of friction of frost-resistant sealing rubbers

The results of an experimental study of the effect of the normal pressure in the range of 0.1–0.3MPa, a velocity of sliding of 1–100 mm/s, and a bulk temperature of 22 to–27°C on the coefficient of sliding friction of an elastomer–steel friction pair have been presented. Two types of elastomeric materials have been considered, i.e., frost-resistant rubber based on synthetic propylene oxide rubber and this rubber filled with the antifriction additive of ultrafine polytetrafluoroethylene powder in an amount of 1 weight part per 100 weight parts. The results have shown the efficiency of filling rubbers with ultrafine polytetrafluoroethylene; the coefficient of sliding friction at temperatures below–15°C decreases by more than two times.     

外界压力对粗糙表面摩擦与接触的影响研究

为研究外界压力对粗糙表面摩擦的影响,建立斜面滑块在不同真空度下的模型并进行试验测量在不同真空度下不同摩擦副配伍材料发生初始滑动时的斜面倾角。试验结果表明：随着外界压力增加,滑块发生初始滑动时的倾角增大,静摩擦力也增大。对于硬度小、重量轻以及接触面积大的摩擦副材料和零部件,其所受外界压力的影响更大。当外界压力从真空度-0.095 MPa增加到0 MPa,轴承钢/轴承钢的最大静摩擦力增大11%、轴承钢/聚碳酸酯增大12%,而聚碳酸酯/聚碳酸酯增大39%。由于通常情况下物体间的摩擦性能总是会受到外界压力的影响,因此真实摩擦角应在绝对真空环境下进行测量,而在大气中进行的测量都存在误差。同时可用文中方法测量两物体的实际接触面积。试验表明随着载荷增加实际接触面积增加,跟摩擦学的经验理论一致。     

Friction and Wear at High Sliding Speeds

Sliding tests have been carried out using a variety of soft metal and nonmetal pins on a rotating steel disk at speeds up to 150 m/s. A new high-speed friction apparatus in which the normal force, the friction force and the friction coefficient are recorded, was used. In general, the wear rate increased drastically, and the friction coefficient decreased moderately as the sliding speed was raised, these changes being especially pronounced when pin materials of low melting temperature were used. The friction data are in good agreement with those obtained by others using the pin-on-disk geometry. However, although in many cases the interface reached the melting temperature of the lower melting sliding material, the very low friction coefficient values of under 0.05 reported by some investigators were not reached.     

Dependence of polymer sliding friction on normal load and contact pressure

The sliding friction of bulk polymers was studied varying the normal load, contact pressure and sliding velocity. The variation of the area of apparent contact A with normal load W was also measured both under the sliding and unloaded conditions. For the sliding condition A ∝ W, while for the unloaded condition A ∝ Wⁿ where n is less than unity. The friction measurements were performed on a tribometer in the low load range and on a lathe using a strain gage dynamometer in the high load range. It was found that the coefficient of friction depends upon the velocity and pressure and the variation can be explained by the adhesion theory of friction in the light of the conditions at the interface. The measurement of sliding friction in an extrusion process shows that the coefficient of friction decreases with contact pressure and the interface friction shear stress is almost equal to the bulk shear strength of the material. All of these findings support the adhesion theory of friction for polymeric materials.     

Noise Effect on Ice Surface Softening During Friction

The ice surface softening by friction is investigated considering the additive non-correlated fluctuations of the shear strain and stress, and the temperature. The premelting is construed by the Kelvin–Voigt equation for shear strain and by the relaxation equations of Landau–Khalatnikov type for shear stress and temperature. Taking into account the noises in these equations, the Langevin and Fokker–Planck equations are derived. Their analysis is based on the investigation of extrema of the distribution function, i.e., steady-state values of the shear strain using the Stratonovich interpretation. The phase diagrams are constructed, where the noises intensities and thermostat temperature determine the regions of ice, softened ice and their mixture (stick–slip rubbing). We present that domain of ice friction is bounded by relatively small background sliding block temperatures and fluctuation intensities of the stress and temperature. The ice film softens with growth of the stress noise intensity even at small thermostat temperatures. The friction force time series for all rubbing modes are calculated and compared with experimentally observed ones.     

水润滑轴承材料弹流润滑性能比较研究

利用考虑惯性力的Reynolds方程,对水润滑条件下的实验橡胶滑块与钢环的弹流润滑问题进行了数值模拟,并分别与塑料、陶瓷材料的数值模拟结果进行了对比分析。结果表明,在水润滑条件下,惯性力对水膜压力的影响很小,而对水膜厚度及温度的影响很大。同样情况下,考虑惯性力时,最小膜厚增加,最高温度降低。橡胶/钢摩擦副中,惯性力对膜厚的影响是不可忽略的。陶瓷/钢摩擦副中,考虑惯性力时对温度影响更大。