轴颈表面粗糙度对橡胶材料干摩擦特性的影响

当船舶艉轴承供水系统出现故障或轴承过载时,金属轴颈与橡胶轴承之间会发生局部接触而处于干摩擦状态下。为研究金属轴颈表面粗糙度对水润滑橡胶轴承干摩擦特性的影响,采用TIME3230表面粗糙度测量仪对金属轴颈表面微凸体进行测量,得到金属轴颈表面微凸体的位置参数分布曲线,并对其进行去噪处理;利用傅立叶变换重新构造去噪后的金属轴颈表面粗糙度分布,并依据理论计算金属轴颈-橡胶轴承摩擦副的摩擦因数。金属轴颈-橡胶轴承摩擦副的摩擦因数计算结果与实际情况吻合,说明建立的轴颈表面粗糙度分布模型合理。分析结果表明:在干摩擦状态下,金属轴颈-橡胶轴承摩擦副的摩擦因数随着表面粗糙度函数波幅的增大呈线性增大趋势,随着粗糙度分布函数的特征波长系数的增大呈非线性增大;润滑流动方向顺着加工纹理方向时,摩擦因数比垂直加工纹理方向和与加工纹理呈45°时的摩擦因数都小。因此,选择合理的轴承表面粗糙度的幅值和波长可以提高金属轴颈-橡胶轴承摩擦副的摩擦润滑性能;沿加工纹理加工、装配金属轴颈-橡胶轴承摩擦副,可降低摩擦因数。     

表面粗糙度理论发展研究

简述了表面粗糙度理论与标准的历史 ,分析了精密加工表面性能评价对表面粗糙度理论及参数的新要求 ,对表面形貌评定的分形法、Motif法、特定功能参数集法进行了论述 ,指出了表面粗糙度理论的发展趋势     

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。     

三维表面粗糙度的等方性评定

基于分形几何理论,通过分析机加工随机表面的轮廓谱矩和表面谱矩的特性,提出了一种各向异性表面的三维形貌的等方性评定参数。实例计算表明,精车加工表面是不等方性的,而平面磨削工件表面形貌的等方性较好。     

盘形凸轮表面粗糙度对其动态特性的影响

以前的研究已经表明盘形凸轮的制造方法和凸轮从动件性能的动态质量之间在统计学上的重要关系。本文设计和制造的凸轮动态试验装置(CDTF)在调速和负载控制的条件下运行,可以采用各种技术加工而成的凸轮。动态试验的内容有:从动件的切向和法向加速度,从动件的切向和法向力,滚子的滑移也可以精确的测量。在凸轮试件运行之前,凸轮表面粗糙度可以由霍曼尔(Hommel)T—20S表面粗糙度测试计进行测量。跑合期后,在测量力、速度和加速度的情况下又可得到表面参数。加速度和力的数据可转换到频域。所有的试验均是随机的,数据要进行方差分析,以求得加速度有效功率谱和凸轮试件表面粗糙度参数之间的相关性。研究的凸轮试件是由连续数控制造技术采用1/°、1/2°、和1°的数值步长加工而成。试验结果表明:铣削和磨削的凸轮的动态性能具有很大的差异,但没有由于数值步长的不同而引起差异。一种可以替代铣削凸轮整体淬硬的热处理方法(离子氮化)已经显示出在动态性能方面有很大的改进。     

轴承表面粗糙度对使用寿命的影响

本文对轴承表面不同粗糙度在台架试验及使用试验中,应用人工测量基准法中的刻痕法,研究轴承在润滑油膜中出现的磨损过程,能获得较为理想的试验结果。     

虚拟数控车削表面形貌的仿真与表面粗糙度预测

在国内外各种研究工作的基础上,综合考虑影响表面轮廓形成的各种相关因素,提出矢量叠加和参数动态修正两种方法相结合而建立加工表面轮廓的模型,从而解决了全方位、真实预测数控车削表面粗糙度这一技术难题。阐述了应用VC 6.0和OpenGL建立其不规则表面轮廓的关键技术。     

超声辅助磨削工艺对微晶玻璃表面粗糙度的影响研究

微晶玻璃的高脆硬性会导致其在磨削过程中出现崩碎和裂纹等问题,从而影响其使用性能和寿命。文章针对微晶玻璃,开展了其超声辅助磨削加工试验研究,探究了磨削微晶玻璃的工艺参数（主轴转速、磨削深度及进给速度）和烧结磨头粒度号差异对其表面粗糙度和表面形貌的影响规律。研究结果表明：超声磨削可显著减小微晶玻璃的表面粗糙度值,在研究的主轴转速段内降幅2.03%～36.03%,磨削深度段内降幅9.76%～17.99%,进给速度段内降幅6.98%～36.23%;相比于非超声磨削,超声磨削在较小主轴转速、磨削深度及进给速度条件下更能发挥其对微晶玻璃表面粗糙度的提升作用;较小的磨头粒径能减小微晶玻璃的表面粗糙度值并改善表面质量。     

干摩擦条件下载荷动特性对摩擦面粗糙度的影响

在自行研制的环 -块磨损试验装置上研究了干摩擦状态下矩形波载荷特性对摩擦面粗糙度的影响 ,结果表明 :1随着磨程的进行 ,摩擦面粗糙度将达到一个稳定值—平衡粗糙度 ,其大小与摩擦面初始形貌无关 ;2当载荷波形占空比 φ较小时 ,平衡粗糙度 Rsq 对φ的变化敏感 ,且随 φ的增加而增加。当 φ足够大时 ,Rsq 几乎不随 φ而变化     

表面粗糙度对悬臂梁小试样蠕变性能评价的影响研究

小试样试验方法在材料蠕变性能评估中具有节省材料、快捷等优点.但在小试样蠕变试验过程中,加载压头与试样接触产生的摩擦会对试验结果产生影响.悬臂梁小试样因载荷点位置偏置,压头与试样之间容易发生相对滑移,进而受到接触摩擦的影响,目前尚未有相关试验研究表面粗糙度对悬臂梁小试样蠕变性能评价的影响.通过选取不同表面粗糙度的悬臂梁小...     

Effect of surface treatment by ceramic conversion on the fretting behavior of NiTi shape memory alloy

Three types of surface-treated NiTi samples, M-1 (700 °C/0.5 h), M-2 (650 °C/1 h) and M-3 (400 °C/50 h), were prepared by ceramic conversion treatment under different conditions. The effect of the surface treatment on the fretting behavior of NiTi alloy was investigated in the Ringer’s solution by using a horizontal servo-hydraulic fretting apparatus. The experimental results indicated that the surface layer of the low temperature (400 °C) treated samples M-3 was dominated by a single TiO₂ layer, while the high temperature (650 and 700 °C) treated samples M-1 and M-2 consisted of surface TiO₂ layer followed by a TiNi₃ layer. These surface layers were found to have a strong effect on the fretting behavior of the NiTi alloy in terms of changes in the shape of the curves of the tangential force (F _t) versus displacement (d), the fretting regimes and the damage mechanisms involved. The stress-induced reorientation of martensite bands in the NiTi alloy could decrease the slope of the F _t–d curve and thus increase the elastic accommodation ability of the NiTi plate against 1Cr13 steel ball pair. However, since the surface-treated layers could suppress the martensite reorientation in the NiTi substrate and thus decrease the elastic accommodation ability of NiTi, the gross slip started at a smaller displacement amplitude for the surface-treated NiTi samples than for the untreated one. The main wear mechanism of the as-received NiTi alloy in slip regime was adhesion and delamination, while the major damage to the high temperature treated NiTi samples M-1 and M-2 was determined as the spallation of surface-treated layers. Due to the high bonding strength of the surface-treated layer with NiTi substrate, the low temperature treated NiTi samples M-3 showed the best fretting wear resistance in all samples tested.     

Laboratory fretting tests with thin wire specimens

Wire ropes, due to their construction and application, are prone to fretting damages. In order to know the wear behaviour of individual wires under fretting conditions, laboratory tests are required. The present work describes the preliminary fretting tests accomplished with thin steel wires to optimise the testing procedure. The tests were carried out with ‘crossed‐cylinders’ configuration varying the stroke and normal load. Afterwards, the fretted surfaces were characterised by means of an optical and scanning electron microscope, and a diamond stylus. No significant influence of selected parameters was detected and a good correlation was proved for on‐line measured parameters and off‐line obtained values. Copyright © 2007 John Wiley & Sons, Ltd.     

润滑接触摩擦力的往复式实验研究

在往复式试验机上研究实际加工表面球-盘式接触混合润滑摩擦特性,比较采用不同黏度润滑油光滑接触摩擦力的大小。针对表面粗糙度幅值和纹理对摩擦行为的影响进行研究,结果表明,混合润滑时较高黏度润滑油的摩擦力较小;表面粗糙度幅值在混合润滑时对摩擦力影响较大,且随速度增加而增强,边界润滑时影响很小。与纵向纹理相比,横向纹理表面的摩擦力较小且稳定,低速时这种差别更加明显。     

Design effects on the fretting wear behaviour of ball bearings

A change in design of a ball bearing is described based on the results of numerical and experimental analysis to reduce fretting wear. Increasing the radii of curvature of the inner and outer races by a small amount reduces the product of the relative slip δ and the tangential traction τ at the contact region, both of which are caused by Heathcote slip. This results in the consequent reduction in fretting wear because there is a good correlation between the amount of fretting wear and τδ. This prediction is confirmed experimentally by increasing the groove radius of the inner race from 4.02 to 4.21 mm for a ball of radius 3.97 mm.     

An experimental investigation on composite fretting mode

An apparatus for composite fretting tests on a steel ball opposite to the inclined steel flat with different inclined angles (60° and 45°) have been carried out. During the tests, the maximum imposed loads were varied from 200 N to 400 N and 800 N at a constant loading speed of 12 mm/min. Dynamic analysis in combination with microscopic examinations through optical microscopy, profilometery, and SEM have been performed. Composite fretting behaviour has been analyzed and compared with the conventional fretting.     

Effect of a combined machining/burnishing tool on the roughness and mechanical properties

Burnishing is a cold working surface treatment process in which plastic deformation of surface irregularities occurs by exerting pressure through a very hard and a very smooth roller or ball on a surface to generate a uniform and work‐hardened surface. This treatment occurs generally after the machining process. In this study, a new combined machining/burnishing tool is designed and is fabricated. This tool allows for generating simultaneously the machining (turning) and the burnishing of the cylindrical surface using a turning machine. First, turned surfaces at different conditions, sketches, finishing and half finishing were performed using only the cutting tool. The evolutions of a surface roughness parameter and the technological time relative to every test condition have been investigated. Second, using the combined machining/burnishing tool at coarse conditions, the evolutions of the surface roughness and the technological time have been also investigated. A comparison among the parameters obtained under different machining conditions and those obtained using the combined machining/burnishing tool has been carried out. Moreover, the analyses of the layers obtained on the combined machined/burnished surface have shown that the burnishing process induces compressive residual stresses on the subsurface treated specimens. Copyright © 2013 John Wiley & Sons, Ltd.     

The influence of water vapour in air on the friction behaviour of pure metals during fretting

An investigation was conducted to determine the effect of water vapour content in air on the frictional behaviour during fretting of pure metals: iron, aluminium, copper, silver, chromium, titanium and nickel. The fretting experiments were carried out under various humidity levels, ranging from dry air to 50% relative humidity at 23°C. During the experiment the frictional force between fretting surfaces was measured. Pure metals, except iron, were found to have a maximum value of the coefficient of friction during the steady-fretting stage (μ_s) at a specific humidity (RH_max). Iron showed a rapid decrease in μ_s with increasing humidity at RH_max. Each pure metal also exhibited maximum fretting wear at RH_max. The value of μ_s at RH_max for each metal was strongly related to the heat of formation of the lower metal oxide, indicating that the adhesive contact area was larger at RH_max for the fretting of metals with less chemical activity. At high humidity levels water vapour generally reduced the coefficient of friction, μ_s.     

Effect of the dynamic response of fretting devices on test results

The dynamic response of equipment and measurement systems can have a significant influence on results. These effects have a particular importance in experimental fretting studies owing to the frequency levels usual for these kinds of test. In the present work the measuring systems used in fretting rigs to measure friction force are modelled using a lumped mass system with a single degree of freedom. Correction factors are calculated for application to the amplitude and the phase of the measured friction force. The application of these factors to a case study is demonstrated. The distortion of the phase introduced by some filtration techniques is also discussed.     

Comparison between radial fretting and dual-motion fretting features of cortical bone

Fretting tests were carried out to compare the effect of radial and dual-motion modes on wear of cortical bone. A titanium ball was rubbed against fresh human cortical bone under controlled load and motion test conditions. Dual-motion fretting mode produced more severe damage than radial fretting, with more debris occurring at the worn surface. Cracks were abundant in radial fretting and they were significantly affected by the microstructure of cortical bone; this effect was not obvious in the case of the dual-motion fretting mode. Radial fretting test could be used to evaluate the anisotropy of material and crack propagation of brittle cortical bone.     

On the mechanisms of various fretting wear modes

According to relative motion directions for a ball-on-flat contact, there are four fundamental fretting wear modes, e.g., tangential, radial, torsional and rotational modes. In this paper, the mechanisms of these four fundamental fretting wear modes, particularly for the later three modes, have been reviewed from results obtained by the authors in combination with results from literature. Some general features have been reported. Differences both in running and degradation behavior have been discussed in detail. Results showed that some similar laws for three fretting regimes (partial slip regime, mixed regime and slip regime), fretting maps (running condition fretting map and material response fretting map), wear and cracking mechanisms obtained from the classic mode (i.e. tangential fretting) were also identified and useful to characterize the other modes. Nevertheless, the occurrence of relative slip for the radial fretting, the formation of mixed regime for the torsional fretting, the evolution of surface morphology for the rotational fretting were quite different compared to that of the classical fretting mode.