微凹坑织构表面对脂润滑关节轴承摩擦特性的影响

为研究脂润滑下表面织构对关节轴承摩擦特性的影响,设计和制造了4组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%、10%、15%和21%的关节轴承内圈表面形貌.使用Talysurf CCI Lite非接触式三维轮廓仪对试件表面进行测量,采用ISO25178定义的表面参数对试件表面形貌进行表征.在改造的HDM-20端面摩擦磨损试验机上,采用2#锂基脂润滑在不同载荷、转速条件下进行了一系列摩擦磨损试验,研究了表面形貌参数与摩擦系数的关系.在本试验中,选取表面高度算术平均值Sa和表面峰态Sku等表面高度参数、表面峰区平均材料体积Vmp、表面中心区平均空体体积Vvc和表面谷区平均空体体积Vvv等表面功能参数以及平均谷体积Sdv等表面特征参数对关节轴承表面形貌进行表征.结果表明:各表面参数对摩擦系数的影响不同,将表面高度参数、功能参数和特征参数这几种表面形貌参数结合对关节轴承表面形貌进行表征,更有利于脂润滑下关节轴承表面形貌的摩擦学设计.     

谐波减速器黏着磨损失效加速寿命模型研究

针对空间润滑谐波减速器黏着磨损失效的加速寿命试验方法问题,首先基于Johnson-Williamson的粗糙表面接触模型建立了混合润滑状态下的黏着磨损模型,模型表明磨损速率主要由粗糙表面微凸体接触承担的载荷比例决定.然后,对磨损部位进行考虑粗糙表面真实形貌与润滑剂流变特性的混合润滑数值分析表明,转速与载荷对微观界面接触与润滑分布状态的影响显著,温度的影响有限,因此传统提高转速并升高温度以保持油膜厚度一致的加速寿命试验方法已不适用.最后以增大转速、载荷并保持或增大混合润滑状态下微凸体接触承担的载荷为加速寿命试验准则,以微凸体承担载荷为加速应力建立了黏着磨损的加速寿命模型,并以不同工况的加速寿命试验与寿命分布统计对其准确性进行了验证.     

蛇纹石润滑油添加剂摩擦反应膜的力学特征与摩擦学性能

文中考察了变载、变速条件下表面修饰蛇纹石超细粉体作为矿物基础油添加剂的摩擦学性能,利用扫描电镜、能谱仪、纳米压痕仪等对比分析了蛇纹石添加剂形成的摩擦反应膜和基础油润滑下的磨损表面微观形貌、元素分布及微观力学性能.在此基础上,通过改变旋转滑动试验过程中的载荷/速度比,建立了基础油/摩擦反应膜和基础油/普通磨损表面润滑体系的Stribeck曲线.结果表明:蛇纹石超细粉体作为润滑油添加剂形成的摩擦反应膜具有较高的硬度和近似于金属材料的弹性模量,氧化物颗粒的嵌入进一步改善了摩擦反应膜的微区纳米力学性能,同时膜层的多孔结构可起到储油和捕获磨粒的双重作用,从而使摩擦反应膜在边界和混合润滑状态下表现出优异的摩擦学性能.     

润滑剂中微纳米润滑材料的研究现状

随着纳米技术的发展,微纳米润滑材料在润滑剂中已得到广泛的应用。本文对润滑剂中微纳米润滑材料进行分类,通过分析润滑剂承载能力变化,对偶件磨损表面的修复情况,评价了不同类型微纳米润滑材料的摩擦学性能,总结了微纳米润滑材料在润滑剂中的特点,并根据微纳米润滑材料自身的理化性能,提出主要的减摩、抗磨和自修复机理,即光滑或超光滑表面滚动摩擦作用机理、沉积膜机理、嵌入渗透层/摩擦化学反应膜机理。最后,提出了微纳米润滑材料应用于润滑剂中存在问题的和今后关于该研究发展的一些建议。     

润滑条件下金刚石薄膜及石墨／金刚石复合薄膜的摩擦学性能

利用SRV摩擦磨损试验机对比考察了液体石蜡润滑时硬质合金基体上金刚石薄膜和石墨 /金刚石复合薄膜的摩擦学性能 ,采用扫描电子显微镜对试样和磨痕表面形貌进行了观察分析 ,并进而探讨了磨损机理 .结果表明 ,在润滑条件下 ,石墨 /金刚石复合薄膜的摩擦系数和磨损体积损失均较金刚石薄膜的小 ,金刚石薄膜和石墨 /金刚石复合薄膜的主要磨损机理均为亚微断裂磨损 ,而石墨膜可以有效地减轻亚微断裂磨损     

接触式机械密封混合润滑状态摩擦演化规律研究

接触式机械密封在运转中主要处于混合润滑状态,为探究其混合润滑状态下摩擦机理,结合粗糙面弹塑性模型,求解考虑密封端面粗糙度效应的雷诺方程,探究了转速和介质压力等工况条件对密封混合润滑状态密封摩擦参数的影响,推导了密封声发射波能量公式,将密封混合润滑状态分为磨损期和稳定期,应用1.5维谱理论提取密封特征频率,探究混合润滑状态摩擦演化规律.研究结果表明摩擦参数影响密封声发射波能量幅值且密封摩擦形式随混合润滑状态发生变化：在磨损期,微凸体接触特征频率幅值较大,密封端面间摩擦以微凸体接触为主;在稳定期,流体膜黏性剪切摩擦特征频率幅值变大,黏性剪切效应增强,密封端面只存在局部微凸体接触.所得结论对接触式机械密封混合润滑状态摩擦机理的研究具有一定的理论指导意义.     

介观双粗糙弹塑性流体动力润滑界面法向接触刚度模型

弹性流体动力润滑状态通常出现在机械高副零部件的点/线接触部位,如齿轮、轴承和蜗轮蜗杆等.宏观上点/线接触在介观层面表现为两粗糙表面的接触,在微观层面上则又表现为微凸体间的接触.由于在中/重载荷作用下,粗糙表面上的微凸体发生接触后会产生弹塑性/塑性变形,从而使得两粗糙表面的弹流润滑接触转变为弹塑性流体动力润滑接触.此外,界面的接触刚度决定了机械装备的整机刚度.为了精确获得弹性流体动力润滑状态下界面法向接触刚度及其主要影响因素,基于界面的法向接触刚度由固体接触刚度和润滑油膜刚度两部分构成的思想,根据固体弹塑性理论和流体动力学理论,分别对界面间微凸体侧接触及部分膜流体动力润滑进行分析,从微观入手揭示双粗糙表面弹塑性流体动力润滑接触机理,进而建立考虑微凸体侧接触弹塑性变形的流体动力润滑界面法向接触刚度模型.通过仿真分析,揭示了法向载荷、卷吸速度、表面粗糙度及润滑介质特性等因素对润滑界面法向接触刚度的影响规律.研究表明：在相同速度、粗糙度及润滑油黏度的工况下,固体接触刚度和油膜接触刚度均随着法向接触载荷的增加呈非线性增大;在相同载荷、速度及润滑油黏度的工况下,接触表面粗糙度越大,表面形貌对于润滑...     

点接触润滑粗糙表面滑动摩擦力的预测研究

在整个润滑区域内基于统一Reynolds方程的混合润滑模型,根据流变模型计算流体摩擦力,根据边界膜极限剪应力模型计算微突体接触摩擦力,二者相加得到混合润滑摩擦力.分析了粗糙度幅值和纹理对摩擦系数的影响以及非牛顿流变模型对流体摩擦系数的影响.模拟跨越整个润滑区,即弹流润滑、混合润滑和边界润滑,得到完整的Stribeck曲线.结果表明,表面越粗糙,混合润滑的摩擦系数越大,弹流润滑和边界润滑时粗糙度幅值影响很小.交叉斜纹的润滑效果优于横向纹理.不同极限剪应力流变模型计算的摩擦系数相差不大.     

尼龙自润滑性与表面织构协同作用对HDPE基水润滑轴承摩擦磨损性能的影响

传统的船舶尾轴油润滑轴承的润滑油泄露造成了严重的海洋污染,逐渐被水润滑轴承取代,但水较差的承载能力要求水润滑轴承具有良好的减磨耐磨性能. 通过HDPE与PA66的共混材料研究尼龙润滑填料和表面织构协同作用对水润滑轴承摩擦磨损性能的影响,利用超景深三维显微系统测量共混材料试样浸泡后的表面纹理结构,利用CBZ-1摩擦磨损试验机对试样进行摩擦试验并记录摩擦系数,利用表面轮廓仪和扫描电镜(SEM)观察试样磨损形貌并分析其磨损机理. 试验表明:PA66的添加能优化共混材料的摩擦学性能. PA66的水溶胀性使共混材料表面形成微凸织构,降低摩擦系数和减轻表面磨损;PA66的存在可使共混材料在摩擦过程中在对摩铜盘表面形成转移膜,有效保护摩擦副表面,减轻磨损.      

缅甸蟒蛇腹鳞表面的摩擦机理及摩擦各向异性研究

采用原子力显微镜观察缅甸蟒蛇腹鳞表面的微观结构,采用UMT-2型摩擦磨损试验机研究不同载荷及运动方向的腹鳞表面的宏观摩擦各向异性,建立了摩擦运动的接触模型,分析了腹鳞表面的磨损机理.结果表明:腹鳞表面的微观结构由指状微突体和板结构部分周期排列而成,其结构可用9个特征参数定量描述;腹鳞表面摩擦力由分子作用力、表面微突体的犁沟力、楔形作用力以及材料弹性滞后共同引起;腹鳞表面的摩擦系数在0.07左右并与运动方向有关,摩擦系数随载荷增加而减小;后向运动及左、右侧向运动时摩擦系数基本相等,比前向运动时高33%左右;腹鳞表面微突体不同方向上倾斜角度的差异是引起摩擦各向异性的主要原因.研究结果对仿生制造摩擦各向异性表面提供实验依据.     

磨合过程中液体润滑实现超低摩擦的混合模型研究

针对球-盘滑动试验,在磨合过程中获得超低摩擦的液体润滑状态,建立耦合流体润滑、粗糙接触力学、Archard磨损方程和相关物理参数(液体黏度、表面粗糙度和磨损系数)时变函数的混合模型,研究磨合过程中液体润滑的摩擦系数演化.通过数值模拟结果可知：在磨合过程中,润滑介质等效黏度增大,形成流体动压润滑薄膜,有效隔开粗糙表面;其次在磨合过程中,新生成的表面粗糙度降低,减少粗糙峰承载比,实现超低摩擦润滑状态;最后在适当的液体黏度和提高表界面效应减少边界摩擦系数,可进一步实现液体超低摩擦润滑状态.为磨合过程宏观液体润滑性能演化所建立的混合数值模型对提高液体润滑超低摩擦设计效率具有重要价值意义.     

轿车钢板表面形貌特征参数的提取

通过对典型轿车钢板表面形貌的分析,以形貌与其摩擦学性能的关系为出发点,对粗糙表面、粗糙峰和粗糙谷的分布特性进行了统计分析。结果表明：粗糙表面、粗糙峰和粗糙谷数的统计分布特性与润滑及接触等性能密切相关;针对轿车钢板表面、粗糙峰和粗糙谷数在高度方向概率分布曲线的非Gauss特性,提出采用Weibull概率密度函数的非线性曲线拟合对分布特征进行分析处理。所得拟合参数具有非常明确的物理意义,所此可以采用少量参数来较全面地描述其对应的轿车钢板表面形貌特征分布。     

A slip-line plasticity analysis of abrasive wear of a smooth and soft surface sliding against a rough (fractal) and hard surface

Abrasive wear of a soft and smooth surface sliding against a rough (fractal) and hard surface was analyzed by the slip-line theory of plasticity. The analysis is based on a slip-line model of a rigid spherical asperity (wear particle) plowing through a soft surface and removing material by microcutting. Integration of this single-contact model into a three-dimensional contact mechanics analysis of an abrasive surface exhibiting multi-scale roughness described by fractal geometry yielded relationships of the abrasive wear rate and wear coefficient in terms of the interfacial shear strength (adhesion), topography (fractal) parameters of the hard/rough surface, elastic–plastic material properties of the soft/smooth surface, and total normal load. Analytical results from the single-contact analysis provide insight into the deformation of a perfectly plastic material caused by the abrasive action of a rigid asperity/wear particle under different normal load and interfacial friction (adhesion) conditions. The dependence of the abrasive wear rate and wear coefficient on normal load (global interference), roughness of the abrasive surface, elastic–plastic material properties of the abraded surface, and interfacial shear strength (lubrication effect) is interpreted in the context of numerical results obtained for representative ceramic/ceramic, ceramic/metallic, and metal/metal sliding systems.     

Elasto-plastic contact of rough surfaces: a mixed-lubrication model for the textured surface analysis

An improved asperity contact model for two rough surfaces with misalignment is presented in this study. The contact model is statistical and can account for the elasto-plastic behavior of interacting asperities. By combining the improved asperity contact model and the average flow Reynolds equation together, a mixed-lubrication model is developed to understand the effect of surface texturing. By comparing with the results of the purely elastic asperity contact model, it is found that the improved asperity contact model can predict the contact force and actual contact area more accurately, particularly under high load conditions. Moreover, comparing with the elasto-plastic model with an equivalent rough surface against a plane, the improved contact model can consider the effect of permitting misalignment of two rough surfaces. This is beneficial for analyzing the performance of the textured piston ring/liner system, especially when asperities contact and wear happen.     

Modeling of directional friction on a fully lubricated surface with regular anisotropic asperities

The modern surface technology now promises to fabricate surfaces with regular asperities. The regular asperity means that asperities, which are related to surface roughness in a conventional tribology, have similar shape and size, and their distribution over the surface is controllable. The regular asperity surface technology may have transformative impact to contemporary tribology. In this paper, we present a study of friction on the surface with regular anisotropic asperities (RAA) in a fully lubrication status. By anisotropic asperity, it is meant that the geometry of the asperity presents different to different motion directions, which is further speculated to have different friction behaviors along different motion directions. The primary goal of the study was to develop a model of friction force on the RAA surface in a fully lubrication status. The secondary goal was to exhibit the directional friction behavior based on our model. We employed Computational Fluid Dynamics (CFD) software to assist in the modeling and used the published data in the literature to validate our model. As a result, accuracy of our model was shown much better than that of the model reported in the current literature. With our model, we successfully demonstrated several interesting directional friction behaviors on the fully lubricated RAA surface.     

An adhesive wear model of fractal surfaces in normal contact

A generalized adhesive wear analysis that takes into account the effect of interfacial adhesion on the total load was developed for three-dimensional fractal surfaces in normal contact. A wear criterion based on the critical contact area for fully-plastic deformation of the asperity contacts was used to model the removal of material from the contact interface. The fraction of fully-plastic asperity contacts, wear rate, and wear coefficient are expressed in terms of the total normal load (global interference), fractal (topography) parameters, elastic–plastic material properties, surface energy, material compatibility, and interfacial adhesion characteristics controlled by the environment of the interacting surfaces. Numerical results are presented for representative ceramic–ceramic, ceramic–metallic, and metal–metal contact systems to illustrate the dependence of asperity plastic deformation, wear rate, and wear coefficient on global interference, surface roughness, material properties, and work of adhesion (affected by the material compatibility and the environment of the contacting surfaces). The analysis yields insight into the effects of surface material properties and interfacial adhesion on the adhesive wear of rough surfaces in normal contact.     

粗糙峰微接触及其对润滑的影响

根据椭圆弹塑性接触模型,提出了流量因子影响模型,给出了几个该模型的应用计算实例．计算结果表明,该模型与粗糙表面的实际润滑状况有较好的一致性．通过算例分析,发现粗糙峰弹塑性变形对流量因子的影响主要决定于表面综合属性、弹性和塑性变形量．     

Finite element analysis of large contact deformation of an elastic–plastic sinusoidal asperity and a rigid flat

Normal contact deformation of an asperity and a rigid flat is studied within an axisymmetric finite element model. The asperity features a sinusoidal profile and is elastic–plastic with linear strain hardening. Influences of geometrical (asperity height and width) and loading (the maximum interference) parameters on frictionless contact responses are explored for both loading and unloading. Dimensionless expressions for contact size and pressures covering a large range of interference and asperity ratio values are obtained in power-law forms. Results show the mean contact pressure after fully-plastic contact reaches a plateau only for small asperity ratios, while it continues increasing for large asperity ratios. The residual depth is found to be associated with plastically dissipated energy.